Paper Summaries List
Meshi I, Breiman U, Haj-Ali R. The Parametric High-Fidelity-Generalized-Method-of-Cells with phase-field damage micromechanical model for heterogeneous composites. Composite Structures. 2023;320:117199.
This study presents a novel micromechanical modeling framework that integrates the Parametric High-Fidelity Generalized Method of Cells with phase-field damage theory to analyze heterogeneous composites. The model captures complex damage mechanisms, including crack initiation and propagation, at the microstructural level with high precision. Its parametric design enhances computational efficiency while maintaining the accuracy needed for simulating nonlinear material behavior under mechanical stress. Benchmark validations demonstrate its capability to predict damage evolution across various composite configurations. This approach significantly advances the tools available for designing and optimizing composite materials in engineering applications.
Hochster H, Bernikov Y, Meshi I, Lin S, Ranatunga V, Waas AM, et al. Refined nonlinear micromechanical models using artificial neural networks for multiscale analysis of laminated composites subject to low-velocity impact. International Journal of Solids and Structures. 2023;264:112123
This study introduces refined nonlinear micromechanical models enhanced by artificial neural networks (ANNs) for multiscale analysis of laminated composites under low-velocity impact. The integration of ANNs improves the predictive accuracy and computational efficiency of traditional micromechanical models, enabling precise characterization of complex impact responses. The approach captures nonlinear deformation, damage progression, and interlaminar effects with high fidelity, addressing limitations of conventional methods. Validation against experimental and numerical data confirms its capability to predict damage evolution and mechanical behavior across scales. This work represents a significant breakthrough in applying machine learning to advanced composite material analysis, offering new opportunities for optimizing impact-resistant composite designs.
Morany A, Lavon K, Gomez Bardon R, Kovarovic B, Hamdan A, Bluestein D, et al. Fluid–structure interaction modeling of compliant aortic valves using the lattice Boltzmann CFD and FEM methods. Biomechanics and Modeling in Mechanobiology. 2023;22:837-50.
This paper develops a fluid–structure interaction (FSI) framework for modeling compliant aortic valves by combining lattice Boltzmann computational fluid dynamics (CFD) with finite element methods (FEM). The hybrid approach enables accurate simulation of the complex interplay between blood flow and valve deformation under physiological conditions. By leveraging the strengths of both methods, the model captures detailed hemodynamic phenomena, such as vortex formation and flow-induced stresses, while accounting for the mechanical behavior of the valve tissue. Validation with experimental data demonstrates the framework’s ability to replicate realistic valve dynamics and fluid flow patterns. This work advances FSI modeling capabilities, providing a powerful tool for studying valve mechanics and optimizing designs for improved cardiovascular treatments.
Morany A, Lavon K, Halevi R, Haj-Ali N, Bluestein D, Raanani E, et al. Fragmentation of Different Calcification Growth Patterns in Bicuspid Valves During Balloon Valvuloplasty Procedure. Annals of Biomedical Engineering. 2023;51:1014-27.
This study investigates the fragmentation behavior of various calcification growth patterns in bicuspid aortic valves during balloon valvuloplasty using computational and experimental approaches. The research models calcified valve leaflets with distinct growth patterns to evaluate their mechanical responses under the procedure's dynamic loading conditions. Results highlight the critical influence of calcification morphology on fragmentation patterns and potential embolic risks. The findings are validated through in-vitro experiments, providing insights into the mechanical failure of calcified tissues during intervention. This work enhances the understanding of valve biomechanics and offers valuable guidance for improving the safety and efficacy of balloon valvuloplasty procedures.
Helbock RT, Anam SB, Kovarovic BJ, Slepian MJ, Hamdan A, Haj-Ali R, et al. Designing a Novel Asymmetric Transcatheter Aortic Valve for Stenotic Bicuspid Aortic Valves Using Patient-Specific Computational Modeling. Annals of Biomedical Engineering. 2023;51:58-70.
This research presents the design of a novel asymmetric transcatheter aortic valve tailored for stenotic bicuspid aortic valves using patient-specific computational modeling. The approach integrates advanced simulations to account for the unique asymmetry and biomechanics of bicuspid valves, enabling optimal valve alignment and performance. Computational analysis evaluates the valve's hemodynamic properties and its interaction with native tissues, addressing challenges such as paravalvular leakage and structural stresses. The results demonstrate improved fit and function compared to conventional symmetric designs. This work highlights the potential of patient-specific modeling to innovate transcatheter valve designs, enhancing outcomes for patients with complex valve anatomies.
Breiman U, Meshi I, Aboudi J, Haj-Ali R. Finite strain PHFGMC micromechanics with damage and failure. Acta Mechanica. 2022;233:2615-51.
The study advances the micromechanical modeling of heterogeneous materials by extending the Periodic Homogenization Finite Generalized Method of Cells (PHFGMC) to account for finite strain behavior with damage and failure. This framework enables the detailed simulation of nonlinear material responses, capturing interactions between matrix and fiber components at the microstructural level. The incorporation of damage models provides a powerful tool for predicting failure initiation and progression, making it suitable for analyzing composite materials under extreme conditions. The researchers validated their approach through benchmark problems and comparisons with experimental and numerical data, demonstrating its accuracy and reliability. This enhanced PHFGMC model offers significant potential for applications in engineering and material design, particularly in scenarios where understanding the complex mechanics of failure is crucial. Overall, the study contributes to the development of predictive tools for advanced material systems.
Karnibad M, Sharabi M, Lavon K, Morany A, Hamdan A, Haj-Ali R. The effect of the fibrocalcific pathological process on aortic valve stenosis in female patients: a finite element study. Biomedical Physics & Engineering Express. 2022;8:025017.
This paper examines the impact of fibrocalcific pathological processes on aortic valve stenosis in female patients using finite element modeling. The research focuses on the distinct biomechanical and structural characteristics of stenotic valves affected by fibrocalcific changes, emphasizing their influence on valve function and stress distribution. Computational simulations reveal gender-specific differences in valve biomechanics, highlighting the unique challenges posed by the fibrocalcific process in female patients. The findings provide valuable insights into the progression of valve pathology and its implications for personalized treatment strategies. This work advances the understanding of gender-specific aortic valve biomechanics, supporting the development of targeted therapeutic approaches.
Reza S, Bianchi M, Kovarovic B, Anam S, Slepian MJ, Hamdan A, Haj-Ali R, Bluestein D. A computational framework for post-TAVR cardiac conduction abnormality (CCA) risk assessment in patient-specific anatomy. Artif Organs. 2022 Jan 26. doi: 10.1111/aor.14189. Epub ahead of print. PMID: 35083748.
The research introduces a computational framework to assess the risk of cardiac conduction abnormalities (CCA) following transcatheter aortic valve replacement (TAVR) in patient-specific anatomies. The framework integrates patient-specific imaging and modeling to simulate the mechanical interactions between the implanted valve and surrounding cardiac conduction pathways. By evaluating the deformation and stress distributions in critical regions, the model predicts the likelihood of CCA development post-TAVR. Validation with clinical cases demonstrates its potential for improving pre-procedural planning and reducing CCA-related complications. This work provides a novel tool for personalized risk assessment, contributing to safer and more effective TAVR outcomes.
Anam SB, Kovarovic BJ, Ghosh RP, Bianchi M, Hamdan A, Haj-Ali R, et al. Validating In Silico and In Vitro Patient-Specific Structural and Flow Models with Transcatheter Bicuspid Aortic Valve Replacement Procedure. Cardiovascular Engineering and Technology. 2022;13:840-56.
This study validates patient-specific structural and flow models for transcatheter bicuspid aortic valve replacement (TAVR) procedures using both in silico and in vitro approaches. The research integrates computational simulations with experimental testing to replicate the mechanical and hemodynamic behavior of bicuspid aortic valves during TAVR. Validation results confirm the models' ability to predict valve deformation, stress distribution, and flow dynamics with high accuracy. The study emphasizes the importance of patient-specific modeling in understanding the unique challenges posed by bicuspid valves, such as asymmetric anatomy and calcification patterns. This work provides a robust framework for improving pre-procedural planning and optimizing TAVR outcomes in patients with bicuspid aortic valve disease.
Anam SB, Kovarovic BJ, Ghosh RP, Bianchi M, Hamdan A, Haj-Ali R, et al. Assessment of Paravalvular Leak Severity and Thrombogenic Potential in Transcatheter Bicuspid Aortic Valve Replacements Using Patient-Specific Computational Modeling. Journal of Cardiovascular Translational Research. 2022;15:834-44.
This study employs patient-specific computational modeling to assess paravalvular leak (PVL) severity and thrombogenic potential in transcatheter bicuspid aortic valve replacements (TAVR). The models simulate the interaction between the transcatheter valve and the bicuspid aortic anatomy, capturing the effects of calcification and anatomical asymmetry on PVL occurrence. Additionally, the framework evaluates the risk of thrombosis by analyzing blood flow patterns and shear stress distributions. Validation against clinical observations demonstrates the model's accuracy in predicting PVL and thrombogenic risk. This work enhances the understanding of complications associated with TAVR in bicuspid valves, providing a valuable tool for personalized treatment planning and improving procedural outcomes.
Lavon K, Morany A, Halevi R, Hamdan A, Raanani E, Bluestein D, Haj-Ali R. Progressive Calcification in Bicuspid Valves: A Coupled Hemodynamics and Multiscale Structural Computations. Ann Biomed Eng. 2021 Dec;49(12):3310-3322. doi: 10.1007/s10439-021-02877-x. Epub 2021 Oct 27. PMID: 34708308.
This study investigates the progressive calcification in bicuspid aortic valves using a coupled hemodynamic and multiscale structural computational framework. The model integrates blood flow dynamics with tissue-level mechanical behavior to simulate calcification growth and its effects on valve function. Results demonstrate how calcification patterns influence hemodynamic performance, valve deformation, and stress distribution. The multiscale approach provides insights into the interplay between mechanical forces and pathological calcification progression. Validation against clinical data confirms the framework's predictive accuracy. This work enhances the understanding of calcification mechanisms in bicuspid valves, contributing to improved diagnostic and therapeutic strategies.
Wertheimer S, Sharabi M, Shelah O, Lesman A, Haj-Ali R. Bio-composites reinforced with unique coral collagen fibers: Towards biomimetic-based small diameter vascular grafts. Journal of the Mechanical Behavior of Biomedical Materials. 2021;119:104526.
The research explores bio-composites reinforced with coral-derived collagen fibers as a novel material for biomimetic small-diameter vascular grafts. The research focuses on the mechanical and structural properties of the bio-composite, aiming to mimic the strength and flexibility of natural blood vessels. Unique collagen fibers derived from coral provide enhanced reinforcement, contributing to improved mechanical performance and durability under physiological conditions. Experimental evaluations demonstrate the potential of these bio-composites to maintain integrity and functionality in vascular applications. This work advances the development of biomimetic graft materials, offering promising solutions for small-diameter vascular reconstruction.
Chricker R, Mustacchi S, Massarwa E, Eliasi R, Aboudi J, Haj-Ali R. Ballistic Penetration Analysis of Soft Laminated Composites Using Sublaminate Mesoscale Modeling. Journal of Composites Science. 2021;5(1):21.
This study presents a ballistic penetration analysis of soft laminated composites using a sublaminate mesoscale modeling approach. The framework captures the complex interactions between individual laminate layers and their mesoscale structures during high-velocity impacts. The model provides detailed insights into deformation, energy absorption, and failure mechanisms, enhancing the understanding of ballistic performance. Validation against experimental data confirms its predictive accuracy for damage patterns and penetration resistance. This approach offers a robust tool for optimizing the design of laminated composites in applications requiring high-impact resilience, such as personal and structural protection systems.
Massarwa E, Aronis Ze, Eliasy R, Einav S, Haj-Ali R. Nonlinear multiscale analysis of coronary atherosclerotic vulnerable plaque artery: fluid-structural modeling with micromechanics. Biomechanics and Modeling in Mechanobiology. 2021. doi.org/10.1007/s10237-021-01483-z
The paper discusses the develpoment a nonlinear multiscale fluid-structural modeling framework to analyze coronary arteries with atherosclerotic vulnerable plaques. The model integrates micromechanical principles with fluid-structure interaction to simulate the biomechanical behavior of plaques under physiological loading conditions. It captures key phenomena, including plaque deformation, stress distribution, and hemodynamic forces contributing to plaque vulnerability. The approach enables detailed insights into the mechanical factors underlying plaque rupture, a leading cause of acute cardiovascular events. Validation with clinical and experimental data supports the framework's accuracy. This work advances the understanding of plaque biomechanics, providing a foundation for improved diagnostics and treatment strategies.
Meshi I, Breiman U, Aboudi J, Haj-Ali R. The cohesive parametric high-fidelity-generalized-method-of-cells micromechanical model. International Journal of Solids and Structures. 2020;206:183-97.
The paper introduces the cohesive parametric high-fidelity generalized method of cells (PHFGMC) micromechanical model for analyzing the behavior of heterogeneous materials. The model incorporates cohesive interfaces to simulate damage initiation and progression at the microstructural level, providing a detailed representation of material failure mechanisms. By combining high-resolution parametric capabilities with cohesive zone modeling, the framework accurately captures interactions between phases and damage evolution. Validation against experimental and numerical benchmarks demonstrates its predictive accuracy for complex loading scenarios. This work advances micromechanical modeling, offering a robust tool for studying failure processes in composite and multi-phase materials.
Svetlizky, David; Zheng, Baolong; Buta, Tali; Zhou, Yizhang; Golan, Oz; Breiman, Uri; Haj-Ali, Rami; Schoenung, Julie M.; Lavernia, Enrique J.; Eliaz, Noam, “Directed energy deposition of Al 5xxx alloy using Laser Engineered Net Shaping (LENS (R)),” MATERIALS & DESIGN, 10.1016/j.matdes.2020.108763
This study explores the use of Laser Engineered Net Shaping (LENS®), a directed energy deposition technique, for processing Al 5xxx aluminum alloys. The research investigates the microstructural evolution, mechanical properties, and performance of the deposited material under varying process parameters. Results highlight the ability of LENS® to produce components with fine microstructures, improved mechanical properties, and minimal defects. The study also identifies optimal deposition conditions to enhance the material's strength and durability while mitigating challenges such as porosity and residual stress. This work advances the understanding of additive manufacturing for aluminum alloys, demonstrating its potential for high-performance applications in aerospace and automotive industries.
Shelah, Ortal; Wertheimer, Shir; Haj-Ali, Rami; Lesman, Ayelet (2020), “Coral-Derived Collagen Fibers for Engineering Aligned Tissues,” TISSUE ENGINEERING PART A, 10.1089/ten.tea.2020.0116
This study investigates the use of coral-derived collagen fibers for engineering aligned tissues, focusing on their structural and mechanical properties. The research demonstrates that these unique collagen fibers provide a natural scaffold for creating highly organized and mechanically robust tissue constructs. Experimental results highlight their ability to promote cell alignment and enhance tissue regeneration under physiological conditions. The biocompatibility and structural integrity of coral-derived fibers make them a promising material for various biomedical applications. This work advances the field of tissue engineering by introducing a novel biomaterial that supports the development of functional, aligned tissue systems.
Morany, Adi; Lavon, Karin; Bluestein, Danny; Hamdan, Ashraf; Haj-Ali, Rami (2020) “Structural Responses of Integrated Parametric Aortic Valve in an Electro-Mechanical Full Heart Model, Annals of Biomedical Engineering, 10.1007/s10439-020-02575-0
This study presents a comprehensive analysis of the structural responses of a parametric aortic valve integrated within an electro-mechanical full heart model. The framework combines advanced structural modeling with electrical and mechanical simulations to capture the valve's behavior under realistic physiological conditions. Results highlight the interplay between hemodynamic forces, valve deformation, and cardiac dynamics, providing insights into stress distribution and functional performance. Validation against experimental and clinical data demonstrates the model's accuracy and robustness. This work advances the understanding of aortic valve mechanics and offers a powerful tool for optimizing valve designs and improving patient-specific treatment strategies.
Breiman, Uri; Meshi, Ido; Aboudi, Jacob; Haj-Ali, Rami (2020) “Finite strain parametric HFGMC micromechanics of soft tissues,” Biomechanics and Modeling in Mechanobiology, 10.1007/s10237-020-01348-x
This study develops a finite strain parametric high-fidelity generalized method of cells (HFGMC) micromechanics model to analyze the behavior of soft tissues. The framework captures the nonlinear mechanical responses of soft tissues under large deformations, accounting for their heterogeneous microstructural characteristics. By integrating parametric capabilities, the model enables detailed simulations of tissue mechanics and provides insights into stress distribution and deformation patterns. Validation with experimental data confirms its accuracy and applicability. This work enhances the understanding of soft tissue mechanics, offering a robust tool for advancing research in biomechanics and improving medical applications.
Meshi, I., A. Levi-Sasson, U. Breiman and R. Haj-Ali (2020). "The parametric HFGMC micromechanical model for soft UHMWPE laminated composites." Mechanics of Materials 141: 103223.
This study introduces a parametric high-fidelity generalized method of cells (HFGMC) micromechanical model for analyzing soft ultra-high molecular weight polyethylene (UHMWPE) laminated composites. The model captures the nonlinear behavior and complex interactions within the composite microstructure under various loading conditions. By incorporating parametric capabilities, it provides detailed insights into stress distribution, deformation mechanisms, and the effects of material heterogeneity. Validation against experimental data confirms the model's accuracy and reliability. This work advances the understanding of UHMWPE composites, offering a powerful tool for optimizing their design and performance in engineering and biomedical applications.
Massarwa, E., J. Aboudi and R. Haj-Ali (2019). "A multiscale modeling for failure predictions of fiber reinforced composite laminates." Composites Part B: Engineering 175: 107166.
This study develops a multiscale modeling framework for predicting failure in fiber-reinforced composite laminates. The approach integrates microscale and mesoscale analyses to capture the progressive damage mechanisms within the composite structure under various loading conditions. The model accounts for fiber-matrix interactions and the nonlinear behavior of individual components, enabling accurate predictions of damage initiation and propagation. Validation against experimental data demonstrates the framework's reliability in assessing failure patterns and structural integrity. This work advances the predictive capabilities for composite materials, supporting their optimized design and application in high-performance engineering systems.
Mirit Sharabi, Aviad Levi-Sasson, Roza Wolfson, Kelly R. Wade, Fabio Galbusera, Dafna Benayahu, Hans-Joachim Wilke, Rami Haj-Ali (2019). "The Mechanical Role of the Radial Fibers Network Within the Annulus Fibrosus of the Lumbar Intervertebral Disc: A Finite Elements Study (vol 14, 021006, 2018)." Journal of biomechanical engineering. 141(4).
Researchers in this study explore the mechanical role of the radial fiber network within the annulus fibrosus of the lumbar intervertebral disc using finite element modeling. The analysis investigates how the radial fibers contribute to the structural integrity and load distribution of the intervertebral disc under physiological conditions. Results reveal the critical role of these fibers in maintaining disc stability and mitigating stress concentrations, particularly during complex loading scenarios. The findings provide insights into the biomechanical behavior of the lumbar spine, highlighting the importance of fiber network architecture in disc functionality. This work enhances the understanding of spinal mechanics, supporting the development of improved therapeutic strategies and disc repair techniques.
Lavon, K., G. Marom, M. Bianchi, R. Halevi, A. Hamdan, A. Morany, E. Raanani, D. Bluestein and R. Haj-Ali (2019). "Biomechanical modeling of transcatheter aortic valve replacement in a stenotic bicuspid aortic valve: deployments and paravalvular leakage." Medical & Biological Engineering & Computing 57(10): 2129-2143.
This research focuses on biomechanical modeling of transcatheter aortic valve replacement (TAVR) in stenotic bicuspid aortic valves, examining deployment dynamics and the occurrence of paravalvular leakage (PVL). The study employs advanced computational techniques to simulate valve-tissue interactions and evaluate how anatomical asymmetries and calcifications influence deployment outcomes. Results highlight key factors contributing to PVL and provide insights into optimizing valve positioning and design. Comparison with clinical observations supports the model's accuracy in predicting complications and guiding procedural strategies. This work advances the understanding of TAVR biomechanics, offering valuable tools for improving patient-specific treatments and outcomes in bicuspid valve cases.
Ingram, E., O. Golan, R. Haj-Ali and N. Eliaz (2019). "The Effect of Localized Vibration during Welding on the Microstructure and Mechanical Behavior of Steel Welds." Materials 12(16).
This study investigates the influence of localized vibration during welding on the microstructure and mechanical properties of steel welds. The application of vibration is shown to refine the microstructure in the weld zone, improving grain uniformity and reducing residual stresses. These changes enhance the mechanical performance of the welds, including increased strength and ductility. Experimental analysis highlights how vibration modifies the solidification process, leading to improved metallurgical properties. The findings provide valuable insights into optimizing welding techniques for steel, with potential applications in industries requiring high-performance welded structures. This work offers a novel approach to improving weld quality through controlled mechanical intervention.
Haj-Ali, R., R. Wolfson and Y. Masharawi (2019). "A patient specific computational biomechanical model for the entire lumbosacral spinal unit with imposed spondylolysis." Clinical Biomechanics 68: 37-44.
This study develops a patient-specific computational biomechanical model of the entire lumbosacral spinal unit, incorporating the condition of spondylolysis. The model captures the unique anatomical and mechanical characteristics of the spine to simulate the effects of this condition on spinal stability and load distribution. Results reveal critical insights into how spondylolysis alters stress patterns and joint mechanics, contributing to a better understanding of its biomechanical impact. The approach allows for personalized analysis, offering potential applications in diagnosis and treatment planning. By addressing patient-specific factors, this research advances biomechanical modeling and its role in improving spinal healthcare strategies.
Sharabi, M., S. Wertheimer, K. R. Wade, F. Galbusera, D. Benayahu, H.-J. Wilke and R. Haj-Ali (2019). "Towards intervertebral disc engineering: Bio-mimetics of form and function of the annulus fibrosus lamellae." Journal of the Mechanical Behavior of Biomedical Materials 94: 298-307.
This study explores the bio-mimetic design of intervertebral disc engineering, focusing on replicating the form and function of the annulus fibrosus lamellae. The research investigates structural and mechanical properties, aiming to create engineered constructs that mimic the natural lamellar architecture and biomechanical behavior of the disc. Experimental findings demonstrate the potential of bio-mimetic approaches to achieve functional properties similar to native tissues, such as load distribution and flexibility. The study highlights the importance of structural fidelity in tissue engineering for replicating complex biological systems. This work provides valuable insights for advancing intervertebral disc repair and regeneration, contributing to the development of effective therapeutic strategies.
Sharabi M., Wade K. R., Galbusera F., Rasche V., Haj-Ali R. and Wilke H-J. Three- dimensional microstructural reconstruction of the intervertebral disc using ultra-high field MRI. The spine journal, 18 (11),2119-2127, 2018.
This research employs ultra-high field MRI to achieve a three-dimensional microstructural reconstruction of the intervertebral disc. The advanced imaging technique provides detailed insights into the internal architecture of the disc, including the intricate organization of its fibers and lamellae. The reconstructed models offer a highly accurate representation of the disc’s microstructure, enabling a better understanding of its biomechanical function. This approach enhances the ability to study pathological changes and their effects on disc mechanics. The findings contribute to advancements in diagnostic imaging and the development of more effective treatments for intervertebral disc disorders. This study demonstrates the potential of cutting-edge MRI technology in capturing complex biological structures.
Rotem Halevi, Ashraf Hamdan, Gil Marom, Karin Lavon, Sagit Ben-Zekry, Ehud Raanani and Rami Haj-Ali, A New Growth Model for Aortic Valve Calcification,” ASME Journal of Biomechanical Engineering, Vol. 140, 2018. DOI: 10.1115/1.4040338
This paper presents an innovative approach to modeling the growth of calcification in aortic valves, focusing on the progression of this condition and its mechanical implications. The model incorporates both biomechanical and biological influences to simulate the accumulation of calcific deposits and their effects on valve performance. It provides a detailed understanding of how calcification evolves in response to hemodynamic forces and structural changes over time. The model’s predictions align closely with experimental and clinical observations, demonstrating its reliability in capturing complex disease mechanisms. This research offers valuable insights into the dynamics of valve calcification, paving the way for improved diagnostic methods and treatment strategies.
Uri Breiman, Jacob Aboudi, Rami Haj-Ali, “Semi-analytical compressive strength criteria for unidirectional composites,” Journal of Reinforced Plastics and Composites, Vol. 37(4) 238–246, 2018.
This research proposes a semi-analytical framework to evaluate the compressive strength of unidirectional composites. By integrating micromechanical analysis with simplified analytical methods, the study offers a detailed understanding of the failure mechanisms that occur under compressive loads. The model considers fiber-matrix interactions and microstructural characteristics, enabling precise strength assessments across various composite systems. Comparisons with experimental results confirm the accuracy and practical utility of the criteria. This work provides a valuable resource for advancing composite material design and optimizing their performance in structural applications.
Benayahu D., Sharabi M., Pomeraniec L., Awad L. Haj-Ali R. and Benayahu Y., Unique collagen fibers for biomedical applications. Marine drugs Journal, 16(4), 102, 2018.
This study explores the potential of unique collagen fibers derived from marine sources for various biomedical applications. The research highlights the structural and biochemical properties of these fibers, emphasizing their suitability for use in tissue engineering, regenerative medicine, and other medical fields. Experimental analyses demonstrate their biocompatibility, mechanical strength, and ability to support cellular activity, making them an attractive alternative to traditional collagen sources. The findings underscore the versatility and effectiveness of marine-derived collagen for developing innovative medical solutions. This work opens new pathways for utilizing marine biomaterials in advanced healthcare technologies.
Eyass Massarwa, Jacob Aboudi, and Rami Haj-Ali, “A Multiscale Progressive Damage Analysis for Laminated Composite Structures using the Parametric HFGMC Micromechanics,” Journal of Composite Structures, Vol. 188, pp. 159-172, 2018.
This study introduces a multiscale progressive damage analysis framework for laminated composite structures using the parametric high-fidelity generalized method of cells (HFGMC). The model combines microscale and macroscale analyses to simulate damage initiation and propagation in composite laminates under various loading conditions. By incorporating the parametric HFGMC approach, the framework captures detailed material behavior, including fiber-matrix interactions and failure mechanisms. The analysis is validated against experimental data, demonstrating its effectiveness in predicting damage progression and structural performance. This research offers a robust tool for optimizing the design and reliability of composite materials in engineering applications..
Lavon, K., Halevi, R., Marom, G., Ben Zekry, S., Hamdan, A., Schäfers, H-J, Raanani, E., and Haj-Ali, R.,” Fluid-Structure Interaction Models of Bicuspid Aortic Valves: The Effects of Non-Fused Cusp Angles,” J Biomech Eng 140(3), 2018. doi: 10.1115/1.4038329.
This study examines the fluid-structure interaction (FSI) behavior of bicuspid aortic valves, focusing on the effects of non-fused cusp angles. Using advanced computational models, the research analyzes how varying cusp angles influence valve mechanics, hemodynamics, and stress distribution during the cardiac cycle. The findings reveal that non-fused cusp angles significantly affect flow patterns, leaflet deformation, and the overall performance of the valve. These insights provide a deeper understanding of the biomechanical challenges associated with bicuspid valves and their role in disease progression. This work contributes to improving diagnostic and therapeutic approaches for patients with bicuspid aortic valve conditions.
Eyass Massarwa, Jacob Aboudi, Fabio Galbusera, Hans-Joachim Wilke, and Rami Haj-Ali, “A nonlinear micromechanical model for progressive damage of vertebral trabecular bones,” Journal of Mechanics of Materials and Structures, Vol. 12 No. 4, pp. 407-424, 2017.
This study presents a nonlinear micromechanical model for analyzing the progressive damage of vertebral trabecular bones. The model captures the intricate microstructural behavior of trabecular bone under various loading conditions, simulating damage initiation and progression at the microscale. By incorporating nonlinear material behavior, the framework provides detailed insights into the mechanical response and failure mechanisms of vertebral bone. Comparisons with experimental data validate the model’s accuracy and effectiveness in predicting damage evolution. This research enhances the understanding of bone mechanics, offering valuable tools for studying bone health and improving strategies for diagnosing and treating vertebral disorders.
Haj-Ali, R., Massarwa, E., Aboudi, J., Galbusera, F., Wolfram, U., and Wilke, H-J, “A New Multiscale Micromechanical Model of Vertebral Trabecular Bones ,” Biomechanics and Modeling in Mechanobiology, Vol. 16 (3), pp. 933–946, 2017.
Researchers present a novel multiscale micromechanical model to investigate the mechanical behavior of vertebral trabecular bones. The framework integrates microscale and macroscale analyses to accurately capture structural and mechanical interactions within the bone tissue. It offers detailed insights into stress distribution, deformation, and failure mechanisms under various loading conditions. The model demonstrates strong agreement with experimental data, confirming its reliability and precision. This work advances the understanding of vertebral biomechanics and contributes to improved treatment strategies and orthopedic biomaterial design.
Sharabi M., Varssano D., Eliasy R., Benayahu Y., Benayahu D., and Haj-Ali R., Mechanical flexure behavior of bio-inspired collagen-reinforced thin composites, Composite Structures, 153, 392-400, 2016.
This study investigates the mechanical flexure behavior of bio-inspired thin composites reinforced with collagen fibers. The research examines how the unique properties of collagen contribute to the structural performance of these composites under bending loads. By mimicking natural reinforcement strategies, the composites demonstrate enhanced mechanical strength and flexibility. Experimental testing validates the effectiveness of the bio-inspired design, highlighting its potential for advanced engineering and biomedical applications. This work provides valuable insights into leveraging natural materials to develop innovative composite structures with improved mechanical properties.
Meshi, I., Amarilio, I., Benes, D., and Haj-Ali, R., "Delamination behavior of UHMWPE soft layered composites," Composites-B Eng., 98, pp. 166-175, 2016.
This study explores the delamination behavior of ultra-high molecular weight polyethylene (UHMWPE) soft layered composites. The research focuses on understanding how the unique layered structure of these composites influences their resistance to delamination under various loading conditions. Experimental and computational analyses reveal critical factors affecting interlayer performance, including the material's mechanical properties and the applied stress states. The findings demonstrate the composites' ability to maintain structural integrity while highlighting potential improvements in their design. This work contributes to advancing the application of UHMWPE composites in fields requiring high durability and resistance to delamination.
Haj-Ali, R., and Aboudi, J.,” Integrated Microplane Model with the HFGMC Micromechanics for Nonlinear Analysis of Composite Materials with Evolving Damage” Int. J. Solids and Structures, Vol 90, pp. 129–143, 2016.
This article introduces an integrated microplane model combined with the high-fidelity generalized method of cells (HFGMC) for analyzing the nonlinear behavior of composite materials with evolving damage. The framework captures the complex interactions between microstructural components, enabling accurate simulation of progressive damage under various loading conditions. By integrating microplane theory with micromechanics, the model provides detailed insights into the material's response at multiple scales. Validation with experimental data confirms its reliability in predicting nonlinear behavior and damage evolution. This research advances the understanding and modeling of composite materials, offering a robust tool for their design and analysis in engineering applications.
Halevi, R., Hamdan, A., Marom, G., Lavon, K., BenZekry, S., Raanani, E., Bluestein, D., and Haj-Ali, R., Fluid–structure interaction modeling of calcific aortic valve disease using patientspecific threedimensional calcification scans, Med. Biol. Eng. Comput., pp 1-12, 2016.
The paper addresses the development of a fluid-structure interaction (FSI) model to analyze calcific aortic valve disease using patient-specific three-dimensional calcification scans. The framework integrates detailed imaging data with computational modeling to simulate the interplay between blood flow dynamics and valve deformation in diseased states. Results highlight the effects of calcification on valve function, including altered flow patterns, stress distribution, and mechanical behavior. The patient-specific approach provides valuable insights into the progression of the disease and its impact on valve performance. This work enhances the understanding of calcific aortic valve disease and supports the development of improved diagnostic and therapeutic strategies tailored to individual patients.
Levi-Sassona, A., Aboudi, J., Matzenmiller, A., and Haj-Ali, R. Failure Envelopes for Laminated Composites by the Parametric HFGMC Micromechanical Framework. Composite Structures. Vol. 140:15,pp. 378–389, 2016.
This research develops a parametric high-fidelity generalized method of cells (HFGMC) framework for determining failure envelopes of laminated composites. The model effectively captures the detailed interactions between fibers and the matrix, as well as progressive damage mechanisms, under various loading conditions. Using a parametric approach, the framework provides in-depth insights into the failure characteristics of composites. Validation with experimental data highlights its accuracy in predicting stress responses and failure behavior. This study offers a powerful tool for enhancing the analysis and design of laminated composites in structural engineering applications.
Haj-Ali, R., Eliasi, R., Fourman, V., Tzur, C., Bar, G., Grossman, E., Verker, R., Gvishi, R., Gouzman, I., and Eliaz, N. Mechanical characterization of aerogel materials with digital image correlation. Microporous and Mesoporous Materials 226, 44-52, 2016.
This study focuses on the mechanical characterization of aerogel materials using digital image correlation (DIC) techniques. The research highlights the unique properties of aerogels, such as their low density and high porosity, while addressing challenges in accurately measuring their mechanical behavior. By applying DIC, the study provides precise insights into strain distribution and deformation patterns under various loading conditions. The methodology enables a detailed understanding of the aerogels' structural performance, offering improved accuracy compared to conventional techniques. The findings contribute to advancing the use of aerogels in engineering applications, where their lightweight and insulating properties are critical.
Aboudi, J. and Haj-Ali, R.M., A fully coupled thermal-electrical-mechanical micromodel for multi-phase periodic thermoelectrical composite materials and devices, Int. J. Solids and Structures, 80, pp. 84–95, 2016.
This study introduces a fully coupled thermal-electrical-mechanical micromodel for analyzing multi-phase periodic thermoelectrical composite materials and devices. The model integrates the interactions between thermal, electrical, and mechanical fields to capture the complex behavior of these materials under various conditions. By considering the microstructural characteristics of the composites, the framework provides detailed insights into their coupled responses and performance. The results demonstrate the model's capability to predict the behavior of thermoelectrical composites accurately, enabling the optimization of their design for advanced applications. This work contributes to the development of efficient and multifunctional composite materials and devices in engineering and technology.
Mega M, Marom G, Halevi R, Hamdan A, Bluestein D, and Haj-Ali R. Imaging analysis of collagen fiber networks in cusps of porcine aortic valves: effect of their local distribution and alignment on valve functionality. Computer Methods in Biomechanics and Biomedical Engineering. 25, 1-7, 2015.
This study analyzes the collagen fiber networks in the cusps of porcine aortic valves, focusing on how their local distribution and alignment affect valve functionality. Using advanced imaging techniques, the research provides detailed insights into the structural organization of collagen fibers and their role in maintaining valve mechanics under physiological conditions. The findings highlight the critical impact of fiber orientation and density on valve deformation, stress distribution, and overall performance. By correlating structural characteristics with functionality, this work enhances the understanding of valve biomechanics. The results offer valuable guidance for designing improved biomimetic and prosthetic valve solutions.
Sharabi M., Benayahu D., Benayahu Y., Issacs J., and Haj-Ali R., Laminated Collagen-based bio-composites for tailor designed soft tissue mimetics. Composites Science and Technology, 117, 268-276, 2015
This study investigates laminated collagen-based bio-composites designed to mimic the properties of soft tissues. By tailoring the structural and mechanical characteristics, the research demonstrates how these bio-composites can replicate the flexibility, strength, and behavior of natural soft tissues. Experimental analysis highlights the potential for customizing the composites to match specific tissue requirements, making them highly versatile for biomedical applications. The findings emphasize the effectiveness of collagen as a primary material for creating functional tissue mimetics. This work contributes to advancements in tissue engineering, offering innovative solutions for regenerative medicine and soft tissue repair.
Halevi, R., Hamdan, A., Marom, G., Mega, M., Raanani, E., and Haj-Ali, R.,” Progressive Aortic Valve Calcification: Three-Dimensional Visualization and Biomechanical Analysis,” J. of Biomechanics, Volume 48, Issue 3, pp. 489–497, 2015.
This study examines the progression of aortic valve calcification using three-dimensional visualization and biomechanical analysis. Through advanced imaging and computational modeling, the research investigates how calcification alters valve mechanics, including stress distribution, deformation, and hemodynamic performance. The results provide key insights into the biomechanical effects of calcification growth and its role in disease progression. By linking structural changes to functional outcomes, this work enhances the understanding of aortic valve pathology. The findings support the development of improved diagnostic methods and more effective treatments for calcific aortic valve disease.
El-Hajjar, R. and Haj-Ali, R, “An Infrared Thermoelastic Stress Analysis Investigation for Detecting Fiber Waviness in Composite Structures,” Polymer-Plastics Technology and Engineering, 53: 1251–1258, 2014.
This study investigates the use of infrared thermoelastic stress analysis (TSA) for detecting fiber waviness in composite structures. The research explores how TSA can identify stress concentrations caused by fiber misalignments, which are critical to understanding and predicting composite performance under loading. Experimental results demonstrate the effectiveness of TSA in revealing fiber waviness and its associated mechanical implications. The findings highlight the potential of this non-invasive technique for evaluating structural integrity and quality in composite materials. This work advances the application of thermoelastic analysis for improving the reliability and performance of composite structures in engineering applications.
Sharabi M., Mandelberg Y., Benayahu D., Benayahu Y., Azem A. and Haj-Ali R., A new class of bio-composite materials of unique collagen fibers. Journal of the mechanical behavior of biomedical materials, 36, 71-81, 2014
In this paper researchers introduce a novel class of bio-composite materials incorporating unique collagen fibers to improve structural and mechanical properties. The work investigates the behavior of these collagen-based composites, emphasizing their potential in biomedical and tissue engineering applications. Experimental analyses reveal their remarkable strength, flexibility, and biocompatibility, demonstrating their suitability for mimicking natural tissue behavior. Results underscore the versatility of collagen fibers in creating advanced bio-composites tailored for specific biomedical requirements. This research advances the development of innovative materials for applications in regenerative medicine and healthcare.
Haj-Ali, R., Zemer, H., El-Hajjar, R., and Aboudi, J., Piezoresistive Fiber-Reinforced Composites: A Coupled Nonlinear Micromechanical-Microelectrical Modeling Approach, Int. J. Solids and Structures, Vol. 51(2), Pp. 491-503, 2014.
This research presents a coupled nonlinear micromechanical-microelectrical modeling approach to analyze the behavior of piezoresistive fiber-reinforced composites. The study focuses on the interaction between mechanical deformation and electrical resistance changes at the microscale, providing insights into the material's piezoresistive properties. Results demonstrate how fiber and matrix interactions contribute to the overall electromechanical response, enabling accurate predictions of material performance under various loading conditions. The work highlights the potential of these composites for applications requiring integrated sensing and structural functionality. This advancement supports the development of smart materials with enhanced performance for engineering and technological applications.
Sasson Levi, A., Meshi, I., Mustacchi, S., Amarilio, I., Benes, D., Favorsky, V., Eliasy, R., Aboudi, J., and Haj-Ali, R., “Experimental Determination of Linear and Nonlinear Mechanical Properties of a Soft Laminated Composite Material System”, Composites Part B: Engineering, Vol 57, pp. 96-104, 2014.
The study examines the linear and nonlinear mechanical properties of a soft laminated composite material system through comprehensive experimental testing. Detailed analyses provide insights into the material’s behavior under different loading scenarios, emphasizing its distinct mechanical features. The layered structure’s impact on flexibility and strength is a key focus, offering valuable data for predicting performance in real-world applications. These observations contribute to the development and optimization of soft laminated composites for use in engineering and biomedical industries.
Haj-Ali, R. and El-Hajjar, R., An Infrared Thermoelastic Stress Analysis Investigation of Single Lap Shear Joints in Continuous and Woven Carbon-Fiber/Epoxy Composites. Int. J. Adhesion and Adhesives, Vol. 48, Pp. 210-216, 2014.
The study investigates the stress behavior of single lap shear joints in continuous and woven carbon-fiber/epoxy composites using infrared thermoelastic stress analysis (TSA). This advanced technique provides detailed insights into stress distribution and concentration within the joint under shear loading. The analysis highlights differences in mechanical performance between continuous and woven composite configurations, offering a deeper understanding of their structural behavior. These findings support the optimization of composite joint designs for improved durability and performance. The research contributes to the advancement of TSA as a non-invasive method for evaluating stress in composite materials and joints.
Shoham N, Sasson AL, Lin FH, Benayahu D, Haj-Ali R, Gefen A.,” The mechanics of hyaluronic acid/adipic acid dihydrazide hydrogel: Towards developing a vessel for delivery of preadipocytes to native tissues.” J Mech Behav Biomed Mater. 22;28C:320-331, 2013.
This study examines the mechanical properties of hyaluronic acid/adipic acid dihydrazide hydrogels with a focus on their potential use as a delivery vessel for preadipocytes to native tissues. Through mechanical testing, the research highlights the hydrogel's structural integrity, elasticity, and ability to withstand physiological loading conditions. The findings provide valuable insights into the material's suitability for cell delivery and tissue engineering applications. The study emphasizes the hydrogel's potential to support cell viability and integration within native tissue environments. This work contributes to the advancement of biomaterials for regenerative medicine and therapeutic delivery systems.
Marom G., Peleg M., Halevi R., Rosenfeld M., Raanani E., Hamdan A. and Haj-Ali R., “Fluid-structure interaction model of aortic valve with porcine-specific collagen fiber alignment in the cusps.” J. Biomech. Eng., 135(10) , 2013.
This article presents a fluid-structure interaction (FSI) model of the aortic valve, incorporating porcine-specific collagen fiber alignment in the cusps. The model simulates the dynamic interplay between blood flow and valve deformation, emphasizing the influence of collagen fiber orientation on valve mechanics. Analysis reveals how fiber alignment affects stress distribution, deformation patterns, and overall valve functionality under physiological conditions. These insights highlight the critical role of collagen structure in maintaining valve performance and durability. The research advances the understanding of aortic valve biomechanics, offering valuable guidance for designing improved prosthetic valves and enhancing treatments for valve-related conditions.
Marom, Gil, Kim, Hee-Sun, Rosenfeld, Moshe, Raanani, Ehud, and Haj-Ali, Rami. Fully Coupled Fluid-Structure Interaction Model of Congenital Bicuspid Aortic Valves: Effect of Asymmetry on Hemodynamics. Medical & Biological Engineering & Computing, 51(8): 839-848, 2013.
The paper develops a fully coupled fluid-structure interaction (FSI) model to investigate the hemodynamics of congenital bicuspid aortic valves, focusing on the effects of valve asymmetry. The model integrates blood flow dynamics with valve deformation, providing detailed insights into how asymmetry influences stress distribution, flow patterns, and overall valve performance. Results demonstrate that valve asymmetry significantly alters hemodynamic behavior, contributing to abnormal flow characteristics and potential complications. These findings offer a deeper understanding of the biomechanical challenges associated with bicuspid valves. The research provides valuable guidance for improving diagnostic methods and therapeutic strategies for congenital valve abnormalities.
Marom G., Halevi, R., Haj-Ali R., Rosenfeld, M., Schäfers H.J. and Raanani E. Numerical model of the aortic root and valve: Optimization of graft size and sinotubular junction to annulus ratio. The Journal of Thoracic and Cardiovascular Surgery, 146(5), 1227-1231, 2013.
This study presents a numerical model of the aortic root and valve, focusing on optimizing graft size and the sinotubular junction-to-annulus ratio. The model simulates the mechanical and hemodynamic behavior of the aortic root to evaluate how graft sizing impacts valve function and stress distribution. The findings demonstrate the importance of maintaining an optimal ratio to ensure proper valve performance and reduce mechanical stress on the surrounding tissues. Insights from the study provide critical guidance for improving surgical outcomes in aortic root reconstruction. This research contributes to the development of patient-specific approaches for aortic valve repair and replacement procedures.
Haj-Ali, R., and Aboudi, J.,” A New and General Formulation of the Parametric HFGMC Micromechanical Method for Two and Three-Dimensional Multi-Phase Composites” Int. J. Solids and Structures, Vol. 50 (6), pp. 907–919, 2013.
This study introduces a new and comprehensive formulation of the parametric high-fidelity generalized method of cells (HFGMC) for analyzing two- and three-dimensional multi-phase composites. The advanced micromechanical framework provides detailed modeling of composite materials, accounting for interactions between multiple phases and microstructural heterogeneity. The methodology is versatile and applicable to a wide range of composite systems, enabling accurate predictions of mechanical behavior under various loading conditions. The work demonstrates the model's effectiveness in capturing stress-strain responses and material performance. This research offers significant advancements in micromechanical analysis, supporting the design and optimization of multi-phase composite materials for engineering applications.
Marom, G., Haj-Ali,R., Rosenfeld, M., Schäfers, H-J, and Raanani, E., “Aortic root numerical model: Annulus diameter prediction of effective height and coaptation in post aortic valve repair,” Journal of Thoracic and Cardiovascular Surgery Vol. 145(2), pp. 406-411, 2013.
The paper develops a numerical model of the aortic root to examine the influence of annulus diameter on effective height and leaflet coaptation after aortic valve repair. The analysis explores how changes in annulus size affect valve mechanics, including stress distribution and coaptation efficiency. Results emphasize the critical connection between annulus dimensions and valve functionality, offering valuable insights for improving surgical outcomes. The findings highlight the importance of precise annulus sizing to ensure optimal repair results and long-term performance. This contribution enhances the understanding of aortic valve mechanics, supporting the advancement of patient-specific surgical strategies.
Marom G., Haj-Ali R., Rosenfeld M., Schäfers H.J. and Raanani E. Aortic root numerical model: Correlation between intra-operative effective height and diastolic coaptation. J. Thorac. Cardiovasc. Surg. Vol 145(1), pp. 303–304, 2013.
The study focuses on the design and analysis of sandwich panels with advanced core materials for marine applications. The authors evaluate the structural performance of panels under static and dynamic loading conditions, identifying optimal configurations for enhanced durability. The findings contribute to the development of lightweight, high-strength materials for marine engineering.
Haj-Ali R., Marom G., Ben Zekry S., Rosenfeld M. and Raanani E., “A general three-dimensional parametric geometry of the native aortic valve and root for biomechanical modeling,” J. Biomech., Volume 45(14), pp. 2392–2397, 2012.
This study develops a general three-dimensional parametric geometry for modeling the native aortic valve and root, aimed at advancing biomechanical simulations. The framework defines the complex anatomy of the aortic valve and root, including cusp geometry, sinuses, and the sinotubular junction, through a flexible parametric approach. This model enables accurate representation of patient-specific and generalized geometries, facilitating simulations of mechanical behavior under physiological conditions. The study highlights its utility in analyzing valve function, stress distribution, and potential pathological changes. This work provides a robust tool for improving biomechanical modeling, supporting advancements in aortic valve research, diagnostics, and treatment strategies.
Choi, J., Haj-Ali, R., and Kim, H-S,”Integrated fire dynamic and thermo-mechanical modeling of a bridge under fire,” Structural Engineering and Mechanics, Vol. 42, 6, 2012.
This study presents an integrated approach to modeling the dynamic and thermo-mechanical behavior of bridges under fire conditions. The framework combines fire dynamics with structural analysis to simulate how elevated temperatures affect the mechanical properties and performance of bridge components. The model captures the progression of fire-induced damage, stress distribution, and deformation across the structure. Results provide insights into the resilience and failure mechanisms of bridges exposed to extreme thermal environments. This work advances the understanding of structural behavior under fire, offering valuable tools for improving bridge design and fire safety strategies.
Haj-Ali, R., and Aboudi, J.,” Discussion Paper: Has Renaming the High Fidelity Generalized Method of Cells been Justified?” Int. J. Solids and Structures, Vol. 49, Issues 15–16, pp. 2051-2058, 2012.
This discussion paper examines the justification for renaming the High-Fidelity Generalized Method of Cells (HFGMC), a micromechanical framework widely used in composite material analysis. The authors critically evaluate the implications of the renaming, considering its impact on clarity, consistency, and the recognition of the method's foundational principles. The paper highlights the strengths of the HFGMC framework, including its robust predictive capabilities, while addressing the rationale behind the proposed name change. By exploring both the technical and practical aspects, the discussion provides valuable insights into the broader implications of terminology within the scientific community. This work contributes to the ongoing dialogue on the standardization and evolution of technical methodologies.
Sasson A., Patchornik, S., Eliasy, R., Robinson, D., and Haj-Ali, R., “Hyperelastic Mechanical Behavior of Chitosan Hydrogels for Nucleus Pulposus Replacement - Experimental Testing and Constitutive Modeling,” Journal of the Mechanical Behavior of Biomedical Materials, Vol. 8, pp. 143-153, 2012.
The paper investigates the hyperelastic mechanical behavior of chitosan hydrogels for potential use in nucleus pulposus replacement. Through experimental testing and constitutive modeling, the research characterizes the hydrogels' ability to replicate the mechanical properties of native nucleus pulposus tissue. The findings demonstrate the material's high elasticity, strength, and suitability for withstanding physiological loading conditions. The constitutive model developed provides a detailed representation of the hydrogels' nonlinear mechanical behavior, enabling accurate predictions of their performance. This work advances the understanding of chitosan hydrogels as biomaterials, offering promising insights for their application in spinal disc regeneration and repair.
Marom, G., Haj-Ali, R., Raanani, E., Schafers, H-J, and Rosenfeld, M.,” A fluid-structure interaction model of the aortic valve with coaptation and compliant aortic root," Medical & Biological Engineering & Computing, 50:173-182, 201
This study presents a fluid-structure interaction (FSI) model of the aortic valve, integrating valve coaptation and a compliant aortic root to replicate physiological conditions. The model simulates the interactions between blood flow, valve leaflets, and the aortic root, offering detailed insights into stress patterns, deformation, and coaptation dynamics. The analysis highlights the importance of root compliance in ensuring valve functionality and minimizing mechanical stress. These findings enhance the understanding of aortic valve biomechanics and provide valuable input for improving prosthetic valve designs and surgical techniques. This work contributes to the advancement of FSI modeling in addressing aortic valve pathologies.
Johnson, S., Wei, B., and Haj-Ali, R., " A stochastic fatigue damage model for composite single lap shear joints based on Markov chains and thermoelastic stress analysis," Journal of Fatigue and Fracture of Engineering Materials & Structures, Vol. 33, 897-910, 2010.
This study introduces a stochastic fatigue damage model for composite single lap shear joints, utilizing Markov chains and thermoelastic stress analysis (TSA). The model predicts the progression of fatigue damage by combining probabilistic methods with TSA to capture stress distributions and damage accumulation under cyclic loading. The framework provides a detailed understanding of the joint’s mechanical behavior and its response to fatigue stresses. Results demonstrate the effectiveness of the model in predicting fatigue life and identifying critical damage zones. This work contributes to enhancing the reliability and design of composite joints, offering valuable tools for engineering applications where fatigue performance is critical.
Haj-Ali, R., and Aboudi, J., “Formulation of the high-fidelity generalized method of cells with arbitrary cell geometry for refined micromechanics and damage in composites," Int. J. Solids and Structures, Volume 47, Issues 25-26, pp. 3447-3461, 2010.
This study presents an advanced formulation of the high-fidelity generalized method of cells (HFGMC), accommodating arbitrary cell geometries for enhanced micromechanical modeling and damage analysis in composites. The framework extends the capabilities of traditional micromechanical approaches by enabling more precise representation of complex microstructures and material behavior. It captures the interactions between phases and predicts progressive damage with greater accuracy. The results validate the method's ability to handle a wide range of composite configurations and loading conditions. This work provides a powerful tool for improving the understanding and design of composite materials in engineering applications.
Joonho Choi, Heesun Kim and Rami Haj-Ali, "Integrated fire dynamics and thermomechanical modeling framework for steel-concrete composite structures," Steel and Composite Structures, Vol. 10, No. 2, 2010.
This study develops an integrated modeling framework to analyze the fire dynamics and thermomechanical behavior of steel-concrete composite structures. The framework combines fire simulation with structural analysis to evaluate the effects of elevated temperatures on the mechanical performance of composite elements. It captures the thermal and mechanical interactions between steel and concrete, providing detailed insights into stress distribution, deformation, and potential failure mechanisms under fire conditions. The results highlight the structural resilience and vulnerabilities of composite systems, offering guidance for enhancing fire safety in design and construction. This work advances the understanding of fire-induced behavior in composite structures, contributing to improved safety standards.
Choon Hwai Yap, Hee-Sun Kim, Kartik Balachandran, Michael Weiler, Rami Haj-Ali and Ajit P. Yoganathan, " Dynamic deformation characteristics of porcine aortic valve leaflet under normal and hypertensive conditions," Am J Physiol Heart Circ Physiol 298:395-405, 2010.
This study investigates the dynamic deformation characteristics of porcine aortic valve leaflets under normal and hypertensive conditions. The research focuses on how hypertension alters the mechanical behavior of the valve, particularly in terms of leaflet deformation and valve performance during the cardiac cycle. Through experimental testing, the study highlights significant changes in valve dynamics under elevated pressure conditions, providing insights into potential mechanisms of valve dysfunction. The findings contribute to the understanding of how altered hemodynamics affect valve mechanics, offering valuable information for improving the diagnosis and treatment of valvular heart diseases. This work advances the field of cardiovascular biomechanics by exploring the impact of hypertension on aortic valve function.
Wei, B-S, Johnson, S., and Haj-Ali, R.,” A Stochastic Fatigue Damage Model for Composite Materials Based on Markov Chains and Thermography,” Int. J. Fatigue, Volume 32, Issue 2, Pages 350-360, 2010.
The research presents a stochastic fatigue damage model for composite materials, combining Markov chains and thermography to predict damage progression under cyclic loading. The model integrates probabilistic methods with thermal imaging techniques to capture the evolution of fatigue damage in composite materials. It provides a detailed understanding of stress distributions, damage initiation, and accumulation, enhancing the ability to predict the fatigue life of composites. Experimental results demonstrate the model's effectiveness in identifying critical damage areas and improving the accuracy of fatigue life predictions. This work contributes to the development of more reliable models for assessing the durability and performance of composite materials in engineering applications.materials in reducing environmental impact.
Haj-Ali, R.M., Cohesive micromechanics: A new approach for progressive damage modeling in laminated composites, Int. J. Damage Mechanics, Vol. 18, No. 8, 691-719, 2009.
This study introduces a new approach for progressive damage modeling in laminated composites through cohesive micromechanics. The framework incorporates cohesive zone modeling to simulate the initiation and progression of damage at the interfaces between layers in composite materials. It provides a detailed understanding of how damage evolves under various loading conditions, allowing for more accurate predictions of material failure. The study highlights the effectiveness of this approach in capturing both the mechanical behavior and damage mechanisms in laminated composites. This work advances the field of damage mechanics, offering valuable insights for optimizing the design and performance of composite structures in engineering applications.
Haj-Ali, R., and Aboudi, J., “Nonlinear Micromechanical Formulation of the High Fidelity Generalized Method of Cells,” Int. J. Solids and Structures, Volume: 46 (13), pp. 2577-2592, 2009.
This study presents a nonlinear micromechanical formulation of the High-Fidelity Generalized Method of Cells (HFGMC) to enhance the analysis of composite materials. The framework extends traditional micromechanical approaches by incorporating nonlinear material behavior, enabling more accurate predictions of stress, strain, and damage progression under complex loading conditions. The model accounts for the interactions between different material phases and captures the nonlinear response of composites more effectively. The study demonstrates the method’s ability to handle various composite configurations, offering improved accuracy in predicting material behavior. This work advances the capabilities of micromechanics, providing a powerful tool for the design and optimization of composite materials in engineering applications.
Haj-Ali, R.M., Choi, J., Wei, B-S, Popil, R., and Schaepe, M., Refined Nonlinear Finite Element Models for Corrugated Fiberboards, Composite Structures, Composite Structures, Vol. 87, No. 4, pp. 321-333, 2009.
This study develops refined nonlinear finite element models to analyze the mechanical behavior of corrugated fiberboards under various loading conditions. The models account for the unique structural properties of fiberboard materials, including their anisotropic nature and the interaction between the corrugated layers. The research emphasizes the importance of capturing nonlinear material responses to predict deformation, stress distribution, and potential failure more accurately. Validation against experimental data confirms the effectiveness of the models in simulating real-world conditions. This work enhances the understanding of corrugated fiberboard mechanics, offering valuable insights for improving their design in applications such as packaging and construction.
Haj-Ali, R. M., and Muliana, A. H., A micro-to-meso Sublaminate Model for the Viscoelastic Analysis of Multi-layered FRP Composite Structures, Mechanics of Time Dependent Materials, 12, pp. 69-93, 2008.
This study introduces a micro-to-meso sublaminate model for the viscoelastic analysis of multi-layered fiber-reinforced polymer (FRP) composite structures. The model bridges the microscale material behavior with the mesoscales of the layered composite, allowing for accurate predictions of viscoelastic response under time-dependent loading conditions. It accounts for the complex interactions between layers and the viscoelastic properties of the materials, providing a comprehensive approach to analyzing composite structures. The model is validated through numerical examples, showing its effectiveness in predicting the time-dependent behavior of FRP composites in engineering applications.
Haj-Ali, R.M., Dasi, L. P., Kim, H-S, Choi, J., Leo, H.W., and Yoganathan, A.P., Structural Simulations of Prosthetic Tri-leaflet Aortic Heart Valves, Journal of Biomechanics, Vol. 41, No. 7, pp. 1510-1519, 2008.
This study presents structural simulations of prosthetic tri-leaflet aortic heart valves to evaluate their mechanical performance under physiological conditions. The authors use computational models to simulate the valve's behavior, including leaflet deformation, stress distribution, and fluid-structure interaction. The research aims to optimize the design of prosthetic valves by analyzing how different structural features influence their functionality and durability. The simulations provide valuable insights into the biomechanics of aortic valves, contributing to the improvement of valve design and performance in clinical applications.
Muliana, A. H., and Haj-Ali, R. M., A Multi-scale Framework for Layered Composites with Thermo-rheologically Complex Behaviors, International Journal of Solids and Structures, Vol. 45, No. 10, pp. 2937-2963, 2008.
This study presents a multi-scale framework for analyzing layered composites with thermo-rheologically complex behaviors. The framework integrates both microscopic and macroscopic scales to model the thermomechanical response of composite materials, accounting for the time and temperature-dependent properties of the constituent materials. The approach aims to improve the understanding of how these materials behave under varying thermal and mechanical loading conditions, providing insights into their performance in practical applications. The model is validated through various examples, demonstrating its effectiveness in predicting the behavior of layered composites with complex rheological properties.
Haj-Ali, R. M., Kim, H-K, Koh, S-W, Saxena A., and Tummala, R., Nonlinear constitutive models from nanoindentation tests using artificial neural networks. International Journal of Plasticity (IJP), Vol. 24, No. 3, pp. 371-396, 2008.
This study develops nonlinear constitutive models derived from nanoindentation tests using artificial neural networks (ANNs). The authors use ANNs to extract material properties from experimental nanoindentation data, enabling the construction of accurate models for predicting material behavior under complex loading conditions. The approach offers a robust method for determining constitutive parameters without relying on traditional experimental testing methods. The model is validated through comparisons with experimental results, demonstrating its ability to effectively predict the nonlinear response of materials. This work provides a powerful tool for materials characterization, particularly in cases where conventional methods are difficult to apply.
Haj-Ali, R. M., Wei, B-S, Johnson, S., and El-Hajjar, R.F., Thermoelastic and Infrared-Thermography Methods for Surface Strains in Cracked Orthotropic Composite Materials, Engineering Fracture Mechanics, Vol. 75, No. 1, pp. 58-75, 2008.
his study explores the use of thermoelastic and infrared-thermography methods to measure surface strains in cracked orthotropic composite materials. The authors apply these techniques to capture the distribution of surface strains, particularly around the crack tips, providing insights into the fracture behavior of orthotropic composites under loading conditions. The study demonstrates the advantages of combining thermoelastic stress analysis with infrared thermography for non-destructive evaluation of damage in composite materials. The results show that these methods are effective for monitoring crack progression and characterizing the mechanical performance of cracked composite materials.
Haj-Ali, R. M., Kim, H-K, Nonlinear constitutive models for FRP composites using artificial neural networks, Mechanics of Materials (MOM), Vol. 39, No 12, pp. 1035-1042, 2007.
The research introduces nonlinear constitutive models for fiber-reinforced polymer (FRP) composites using artificial neural networks (ANNs). The authors utilize ANNs to derive accurate constitutive relationships from experimental data, capturing the complex nonlinear behavior of FRP composites under different loading conditions. The models are validated through comparisons with experimental results, demonstrating their ability to predict the material's mechanical response more effectively than traditional methods. This approach offers a powerful tool for improving the design and performance prediction of FRP composites in engineering applications.
Haj-Ali, R., Kilic, M, and Muliana, A. H., Nested Nonlinear Micromechanical and Structural Models for the Analysis of Thick-Section Composite Materials and Structures, Composites Science and Technology, Vol. 67, Issue 10, pp. 1993-2004, 2007
The paper presents nested nonlinear micromechanical and structural models for analyzing thick-section composite materials and structures. The authors combine micromechanics with structural analysis to accurately predict the behavior of composite materials under complex loading conditions. This approach accounts for material nonlinearity, including damage and failure mechanisms, providing a more detailed understanding of composite behavior. The models are validated through numerical examples, showing their effectiveness in predicting the performance of thick-section composites. This methodology offers a valuable tool for the design and optimization of composite materials in engineering applications.
Haj-Ali, R. and Muliana, A. H., A Multi-Scale Nonlinear Framework for the Long-Term Behavior of Layered Composite Structures, ASCE, Journal Engineering Mechanics, Vol. 132, Issue 12, pp. 1354-1362, 2006.
The paper introduces a multi-scale nonlinear framework for analyzing the long-term behavior of layered composite structures. The authors combine micromechanical and macroscopic approaches to model the time-dependent response of composite materials under various loading conditions. This framework accounts for the nonlinearities and damage mechanisms that occur over extended periods, providing a more accurate prediction of composite material performance. The model is validated through numerical examples, demonstrating its effectiveness in assessing the long-term behavior of layered composite structures. This approach offers significant improvements in the design and analysis of composite materials used in structural applications.
Haj-Ali, R., El-Hajjar, R. F., and Muliana, A. H., Cohesive fracture modeling of crack growth in thick-section composites, Engineering Fracture Mechanics. Vol. 73, No. 15, pp. 2192-2209, 2006.
The paper develops a cohesive fracture modeling approach to analyze crack growth in thick-section fiber-reinforced polymer (FRP) composites. The methodology integrates cohesive zone models (CZMs) with finite element analysis to simulate the initiation and propagation of cracks under various loading conditions. The study emphasizes the influence of material heterogeneity, fracture energy, and interfacial behavior on the crack growth process. Extensive validation is conducted against experimental results, demonstrating the model's ability to capture complex fracture mechanisms, including progressive damage evolution and failure. The research provides detailed insights into the fracture behavior of thick-section composites, offering a robust predictive tool for evaluating structural integrity and optimizing the design of composite materials used in high-performance applications.
Muliana, A.H. and Haj-Ali, R. M., Analysis for Creep Behavior and Collapse of Thick-Section Composite Structures, Composite Structures, Vol. 73, No. 3, pp. 331-341, 2006.
The paper explores the creep behavior and potential collapse mechanisms of thick-section composite structures under long-term loading conditions. A detailed analytical framework is developed to study time-dependent deformation, incorporating material viscoelasticity and structural stability. The analysis investigates the influence of key factors such as loading magnitude, temperature, and geometric dimensions on creep progression and failure modes. Validation of the model is achieved through comparisons with experimental observations, highlighting its accuracy and practical relevance. The results offer critical insights into the long-term performance and safety of thick-section composite structures, providing valuable guidelines for their design and assessment in engineering applications requiring high reliability.
Muliana, A.H. and Haj-Ali, R. M., Multi-scale Modeling for the Long-term Behavior of FRP Composite Structures, AIAA Journal, vol. 43, No. 8, pp. 1815-1822, 2005.
The paper presents a multi-scale modeling approach to predict the long-term behavior of fiber-reinforced polymer (FRP) composite structures. The methodology integrates microscale material properties with macroscale structural analysis to capture time-dependent phenomena such as viscoelasticity and stress relaxation. The study emphasizes the importance of coupling material-level behavior with structural response to achieve accurate predictions of long-term performance. Validation is conducted through comparisons with experimental data, demonstrating the model's capability to account for various loading and environmental conditions. The findings provide a comprehensive framework for analyzing the durability and reliability of FRP composite structures, offering practical tools for engineers in aerospace and other advanced industries where long-term performance is critical.
El-Hajjar, R. F. and Haj-Ali, R. M., Mode-I Fracture Toughness Testing of Thick Section FRP Composites using the ESE(T) Specimen, Engineering Fracture Mechanics. Vol. 72, No. 4, pp. 631-643, 2005.
The paper investigates the Mode-I fracture toughness of thick-section fiber-reinforced polymer (FRP) composites using the End-Notched Split Tensile (ESE(T)) specimen. An experimental methodology is developed to evaluate the fracture behavior and mechanical performance of FRP composites under Mode-I loading conditions, focusing on critical parameters such as crack initiation and propagation. The study highlights the reliability and applicability of the ESE(T) specimen for fracture toughness testing in thick-section composites. Results provide insights into the material's resistance to crack growth, offering valuable data for the design, analysis, and optimization of FRP composite structures in advanced engineering applications.
Haj-Ali, R. M., Muliana, A. H., A multi-scale constitutive formulation for the nonlinear viscoelastic analysis of laminated composite materials and structures, International Journal of Solids and Structures, Vol. 41, No. 13, pp. 3461-3490, 2004.
The article presents a multi-scale constitutive formulation for the nonlinear viscoelastic analysis of laminated composite materials and structures, addressing the complex behavior of these materials under various loading conditions. It introduces a hierarchical approach that combines both micromechanical and macromechanical models to capture the time-dependent, nonlinear responses of laminated composites. The paper details the development and implementation of the formulation, which accounts for the interactions between different scales of the composite structure. Several numerical examples are provided to demonstrate the accuracy and effectiveness of the approach in predicting the viscoelastic behavior of composite materials. Overall, the publication emphasizes the advantages of this multi-scale method for the analysis of laminated composites in engineering applications.
El-Hajjar, R. F., and Haj-Ali, R. M., In-plane Shear Testing of Thick-Section Pultruded FRP Composites using a Modified Arcan Fixture, Composites Part B: Engineering, Vol. 35, No. 5, pp. 421-428, 2004.
The paper investigates in-plane shear testing of thick-section pultruded fiber-reinforced polymer (FRP) composites using a modified Arcan fixture. The authors introduce an enhanced version of the Arcan fixture to address challenges associated with testing thick-section composites, aiming to provide accurate shear stress measurements. The study examines the performance of the modified fixture in evaluating the shear properties of pultruded FRPs, which are crucial for assessing the material's strength and durability under shear loading. The paper presents experimental results and discusses the effectiveness of the modified fixture in minimizing errors and improving the precision of shear testing for thick-section composites. The proposed method is presented as a valuable tool for better understanding the shear behavior of pultruded FRP composites in engineering applications.
Haj-Ali, R. M., Muliana, A. H., Numerical Finite Element Formulation of the Schapery Nonlinear Viscoelastic Material Model, International Journal for Numerical Methods in Engineering (IJNME), Vol. 59, No. 1, pp. 25-45, 2004.
The paper presents a numerical finite element formulation for the Schapery nonlinear viscoelastic material model, which is widely used to describe the time-dependent behavior of materials. It develops a finite element approach that integrates the Schapery model, enabling the simulation of complex viscoelastic responses under various loading conditions. The article details the mathematical formulation and implementation of this model, highlighting its ability to capture both the nonlinear and time-dependent characteristics of materials. The publication demonstrates the application of the model in several numerical examples, showing its effectiveness in accurately predicting material behavior. Overall, the paper emphasizes the advantages of using this finite element formulation for simulating nonlinear viscoelastic materials in engineering applications.
El-Hajjar, R. F., and Haj-Ali, R. M., Infrared (IR) Thermography for Strain Analysis in Fiber Reinforced Plastics, Experimental Techniques, Society for Experimental Mechanics (SEM), Vol. 28, No. 2, pp. 19-22, 2004.
The paper explores the use of infrared (IR) thermography for strain analysis in fiber-reinforced plastics (FRPs). The authors introduce IR thermography as a non-destructive testing technique to monitor the strain distribution and detect potential damage in FRP materials. The study demonstrates how temperature changes, resulting from strain-induced deformation, can be captured using infrared imaging, providing insights into the material's behavior under mechanical loading. The paper highlights the advantages of IR thermography, such as its ability to assess large areas quickly and its effectiveness in identifying hidden defects, cracks, and delaminations within FRPs. This technique is presented as a valuable tool for evaluating the performance and integrity of fiber-reinforced composites in both experimental and field applications.
Muliana, A.H. and Haj-Ali, R. M., Nested nonlinear viscoelastic and micromechanical models for the analysis of pultruded composite materials and structures, Mechanics of Materials (MoM) Journal, Vol. 36, No. 11, pp. 1087-1110, 2004. (Impact Factor: 1.9, ISI-Citations=16)
The paper presents nested nonlinear viscoelastic and micromechanical models for the analysis of pultruded composite materials and structures. The authors combine nonlinear viscoelastic behavior with micromechanical models to better capture the complex response of pultruded composites under various loading and environmental conditions. The study addresses the interactions between the fibers and matrix, considering both time-dependent and nonlinear material behavior. The nested modeling approach allows for a more detailed analysis of how these composites respond to stress, strain, and temperature variations over time. The paper emphasizes the importance of accurately modeling the viscoelastic and micromechanical properties of pultruded composites to predict their long-term performance and durability in engineering applications. The approach provides valuable insights into the design and analysis of composite structures subjected to complex loading scenarios.
Haj-Ali, R. M., Muliana, A. H., Micromechanical Models for the Nonlinear Viscoelastic Behavior of Pultruded Composite Materials, International Journal of Solids and Structures, Vol. 40, No. 5, pp. 1037-1057, 2003. (Impact Factor: 1.68, ISI-Citations=21)
The paper develops micromechanical models to analyze the nonlinear viscoelastic behavior of pultruded composite materials. The authors focus on the time-dependent mechanical response of these composites under various loading conditions, incorporating both nonlinear and viscoelastic effects. The study presents a micromechanical approach that models the interactions between fibers and matrix, accounting for the influence of temperature and loading rate on the material’s overall behavior. The paper provides a framework for predicting the viscoelastic response of pultruded composites, highlighting the importance of considering both the nonlinear and time-dependent characteristics for accurate material modeling. This approach offers valuable insights for the design and performance assessment of composite materials used in engineering applications where long-term durability and time-dependent behavior are critical.
El-Hajjar, R.F, Haj-Ali, R. M., A Quantitative Thermoelastic Stress Analysis Method for Pultruded Composites, Composite Science and Technology Journal, Vol. 63, No. 7, pp. 967-978, 2003
The paper presents a quantitative thermoelastic stress analysis method for pultruded composites, focusing on the effects of thermal loading on the mechanical performance of these materials. The authors develop a framework that integrates thermoelastic principles with the unique characteristics of pultruded composite structures. The study examines how thermal stresses interact with the material's elastic properties, considering factors such as temperature gradients and the anisotropic nature of the composite. The paper introduces a method for calculating stress distributions and predicting the structural response of pultruded composites under varying thermal conditions. This approach provides a more accurate understanding of the material's behavior, helping to improve the design and performance prediction of composite structures subjected to thermal loads in engineering applications.
Kilic, M., Haj-Ali, R. M., Elastic-Degrading Analysis for Pultruded Composite Structures, Composite Structures, Vol. 60, No. 1, pp. 43-55, 2003.
The paper presents an elastic-degrading analysis for pultruded composite structures, focusing on the degradation of material properties under mechanical loading. The authors develop a model that combines elastic behavior with damage progression to predict the performance of pultruded composites as they experience degradation. The study addresses how factors such as matrix cracking, fiber-matrix interaction, and overall stiffness reduction affect the structural integrity of composite materials. The elastic-degrading model allows for the simulation of both the initial elastic response and the subsequent degradation, providing a more accurate representation of the material behavior over time. Through this approach, the paper offers insights into the design and durability of pultruded composite structures, highlighting the importance of considering material degradation in the analysis for better performance prediction in engineering applications.
Haj-Ali, R. M.,El-Hajjar, R. F., Crack Propagation Analysis of Mode-I Fracture in Pultruded Composites using Micromechanical Constitutive Models, Journal Mechanics of Materials (MOM), Vol. 35, No. 9, pp. 885-902, 2003.
The paper investigates crack propagation in pultruded composites under Mode-I fracture using micromechanical constitutive models. The authors focus on the analysis of crack initiation and growth in these composites, incorporating micromechanical models that account for the behavior of individual fibers and the matrix material. The study explores the fracture toughness and the critical conditions for crack propagation, emphasizing how the interaction between the fiber and matrix influences the overall crack growth process. The paper also presents a numerical approach to simulate the fracture behavior, providing a more accurate prediction of failure in pultruded composite materials. By integrating micromechanical modeling into the analysis, the authors offer valuable insights into the fracture mechanics of pultruded composites, which can aid in the design of more durable and reliable composite structures.
Kilic, M., Haj-Ali, R. M., Progressive Damage and Nonlinear Analysis of Composite Structures, Composites Part B: Engineering, Vol. 34, No. 3, pp. 235-250, 2003.
The paper addresses the progressive damage and nonlinear analysis of composite structures, focusing on the evolution of damage under various loading conditions. The authors develop a comprehensive framework that integrates progressive damage models with nonlinear analysis to predict the behavior of composite materials as they undergo degradation. The study highlights key failure mechanisms, including matrix cracking, fiber breakage, and delamination, and examines how these affect the structural integrity and performance of composite materials over time. The paper also discusses numerical methods and computational techniques for simulating the nonlinear response and damage progression in composite structures. Through this approach, the authors provide valuable insights into the design and optimization of composite materials for engineering applications, emphasizing the importance of accurately modeling damage for reliable performance prediction.
Haj-Ali, R. M., Kilic, M., Nonlinear Constitutive Models for Pultruded FRP Composites, Journal Mechanics of Materials (MOM), Vol. 35, No. 8, pp. 791-801, 2003.
The paper focuses on the development of nonlinear constitutive models for pultruded fiber-reinforced polymer (FRP) composites. The authors present mathematical models that capture the complex mechanical behavior of pultruded FRP composites under various loading conditions. These models account for both the nonlinear stress-strain relationship and the progressive damage mechanisms such as matrix cracking, fiber failure, and fiber-matrix delamination. The publication emphasizes the importance of incorporating material degradation and nonlinearities into the analysis to provide more accurate predictions of the composite's performance. Additionally, the study discusses the use of these models in engineering applications, particularly in structural design, where the accurate representation of FRP composite behavior is crucial for ensuring reliability and safety.
Muliana, A. H., Steward, R., Haj-Ali, R. H., and Saxena, A., Artificial Neural Network and Finite Element Modeling of Nano-Indentation Tests, Metallurgical and Materials Transactions - A, Vol. 33A, No. 7, pp. 1939-1947, 2002.
The paper examines the use of artificial neural networks (ANN) and finite element modeling (FEM) to analyze nanoindentation tests. The study combines these computational techniques to better understand the mechanical properties of materials at the nanoscale. The authors develop an ANN model to predict material behavior during nanoindentation based on input parameters such as load, indentation depth, and material characteristics. The FEM simulations are used to replicate the indentation process, providing insights into stress distribution and deformation mechanisms. The paper highlights the effectiveness of using ANN to enhance the accuracy of FEM predictions and improve the understanding of material responses during nanoindentation, offering potential applications for material design and characterization in various industries.
La Saponara, V., Muliana, H., Haj-Ali, R. M., and Kardomateas, G., A., Experimental and Numerical Analysis of Delamination Growth in Double Cantilever laminated Beams, Engineering Fracture Mechanics, Vol. 69, No. 6, pp. 687-699, 2002.
The paper investigates the delamination growth in double cantilever laminated beams through both experimental and numerical analyses. It examines the fracture behavior of laminated composite materials, specifically focusing on delamination propagation under different loading conditions. The study presents a comprehensive experimental setup to observe and measure delamination initiation and growth, while also developing numerical models to predict the fracture mechanics of the beams. The authors emphasize the significance of material properties, such as the interlaminar fracture toughness, and their effect on delamination progression. Through a combination of experimental data and finite element simulations, the publication provides insights into the factors influencing delamination resistance and offers recommendations for improving the design and durability of laminated composite structures.
Citipitioglu, A. M., Haj-Ali, R. H., and White, D. W., Refined 3D Finite Element Modeling of Partially-Restrained Connections Including Slip,” Journal of Constructional Steel Research (JCSR), Volume 58, Issues 5-8, pp. 995-1013, 2002.
The article introduces a refined 3D finite element modeling approach for analyzing partially-restrained connections, including the effects of slip, which are crucial for accurately predicting the behavior of steel structures. It develops an advanced finite element model that accounts for both the geometric and material nonlinearities present in partially-restrained connections. The paper details the formulation and implementation of the model, incorporating the effects of slip, which is essential for simulating real-world behavior under loading. Several case studies are presented, demonstrating the model's ability to predict connection response more accurately than traditional methods. Overall, the publication highlights the importance of this refined modeling technique for improving the design and analysis of steel connections in structural engineering.
Haj-Ali, R. M., Kilic, M., Nonlinear Behavior of Pultruded FRP Composites, Composites Part B: Engineering, Volume 33, No. 3, pp. 173-191, 2002.
The paper explores the nonlinear behavior of pultruded fiber-reinforced polymer (FRP) composites, focusing on the mechanical response under various loading conditions. It addresses the complexities of FRP composites, which exhibit nonlinearities due to factors such as matrix cracking, fiber-matrix interactions, and microstructural damage. The authors examine the stress-strain relationships and failure mechanisms in these materials, highlighting how factors like temperature, loading rate, and fiber orientation influence the overall performance. The publication also presents analytical and numerical models to predict the nonlinear behavior of pultruded FRP composites, emphasizing the importance of accurate modeling for engineering applications. Additionally, it discusses the impact of damage accumulation and the need for improved design guidelines to optimize the use of FRP composites in structural applications.
Haj-Ali, R. M., Kilic, M., and Zureick, A-H, Three-Dimensional Micromechanics-Based Constitutive Framework for Analysis of Pultruded Composite Structures, ASCE J. Eng. Mechanics, Vol. 127, No. 7, pp. 653-660, 2001.
The paper presents a three-dimensional micromechanics-based constitutive framework for analyzing pultruded composite structures, aiming to improve the prediction of their mechanical behavior. It develops a detailed micromechanical model that incorporates the interactions between the fibers, matrix, and the overall composite material, providing a more accurate representation of the material’s response under various loading conditions. The article describes the formulation of this 3D framework, which captures the nonlinearities and complexities inherent in pultruded composite structures. Several numerical examples are presented to validate the model's ability to predict the performance and failure of these structures. Overall, the publication emphasizes the potential of micromechanics-based models for enhancing the design and analysis of pultruded composite materials in engineering applications.
Haj-Ali, R. M., Pecknold, D. A., Ghaboussi, J., and Voyiadjis, G., Z., Simulated Micromechanical Models using Artificial Neural Networks, ASCE J. Eng. Mechanics, Vol. 127, No. 7, pp. 730-738, 2001.
The paper presents simulated micromechanical models using artificial neural networks (ANNs) to predict the behavior of composite materials under various loading conditions. It develops a neural network-based framework that simulates micromechanical processes, capturing the complex interactions between material constituents such as fibers and matrix. The article details the formulation of the ANN model, emphasizing its ability to learn from experimental data and predict material responses with high accuracy. Several case studies are provided to demonstrate the model's effectiveness in simulating micromechanical behavior and enhancing material design. Overall, the publication highlights the potential of using artificial neural networks to improve the analysis and optimization of composite materials in engineering applications.
Haj-Ali, R.M., Kurtis, K.E., and Sthapit, A. R., Neural Network Modeling of Concrete Expansion During Long-Term Sulfate Exposure, ACI Materials J., V. 98, No. 1, pp. 36-43, 2001.
The paper presents a neural network modeling approach to predict concrete expansion during long-term sulfate exposure, addressing a significant concern in the durability of concrete structures. It develops a neural network model that learns from experimental data to predict the expansion behavior of concrete exposed to sulfate environments over extended periods. The article details the formulation and training process of the neural network, which captures the complex, time-dependent chemical reactions and material responses involved in sulfate-induced expansion. Several case studies are used to validate the model's predictions, demonstrating its accuracy in forecasting concrete degradation under sulfate exposure. Overall, the publication highlights the potential of neural network models for enhancing the prediction and prevention of concrete deterioration in sulfate-rich environments.
Gullerud, A. S., Xiaosheng, G., Dodds, R. H., Jr., and Haj-Ali, R. M., Simulation of Ductile crack growth using Computational Cells: Numerical Aspects, Engineering Fracture Mechanics, Vol. 66, pp. 65-92, 2000.
The paper explores the numerical aspects of simulating ductile crack growth using computational cells, providing a detailed approach to modeling crack initiation and propagation in materials. It develops a computational framework that utilizes a cell-based method to track crack growth, capturing the complex interactions between the material and the propagating crack. The article discusses the implementation of the numerical model, emphasizing its ability to simulate ductile fracture in a way that is both accurate and computationally efficient. Various examples are presented to validate the model's effectiveness in predicting crack growth under different loading conditions. Overall, the publication underscores the potential of using computational cells to enhance the simulation of ductile crack growth in engineering applications.