UBC Theses and Dissertations
Adaptive insertion of cohesive elements for simulation of delamination in laminated composite materials Shor, Ofir
Composite materials are increasingly being used in advanced structural ap- plications. Debonding of adjacent laminate layers, also known as delamination, is considered to be one of the most dominant damage mechanisms affecting the behavior of composite laminates. Various numerical methods for simulating delamination in composite materials do exist, but they are generally limited to small-scale structures due to their complexity and high numerical cost. In this thesis, a novel technique aimed to allow efficient simulation of delamination in large-scale laminated composite structures is presented. During the transient analysis, continuum elements within regions where delamination has the potential to initiate are adaptively split through their thickness into two shell elements sandwiching a cohesive element. By elimi- nating the a priori requirement to implant cohesive elements at all possible spatial locations, the computational efforts are reduced, thus lending the method suitable for treatment of practical size structures. The methodol- ogy, called the local cohesive zone method (LCZ), is verified here through its application to Mode-I, Mode-II and Mixed-Mode loading conditions, and is validated using a dynamic tube-crushing loading case and plate impact events. Good agreement between the numerical results and the available experimental data is obtained. The results obtained using the LCZ method are compared favourably with the numerical results obtained using the con- ventional cohesive zone method (CZM). The numerical performance of the method and its efficiency is investi- gated. The efficiency of the method was found to be superior compared to that of the conventional CZM, and was found to increase with increasing model size. The LCZ method is shown to have a lower effect on reducing the structural stiffness of the structure, compared to the conventional CZM. The results obtained from the application of the LCZ method to the various cases tested are encouraging, and prove that the local and adaptive insertion of cohesive zones into a finite element mesh can effectively capture the delamination crack propagation in laminated composite structures. It is expected that further improvements in speed and accuracy will be attained once the algorithm is embedded within commercial finite element solvers as a built-in feature.
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