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Title: Progressive Failure Analysis of Double-Notched Composite Laminates
Keywords: Progressive, failure, analysis, double-notched, composite, laminate
Issue Date: 30-Dec-2010
Citation: PHAM DINH CHI (2010-12-30). Progressive Failure Analysis of Double-Notched Composite Laminates. ScholarBank@NUS Repository.
Abstract: Failure analysis in composite laminates is traditionally modeled by the material property degradation method for the in-plane damage prediction which assumes that a damage material can be replaced by an equivalent material with degraded properties. The delamination in composites, on the other hand, is often accounted for by the fracture mechanics approach which relies on the assumption of an initial crack. Therefore, a general method to account for both the in-plane damage and delamination in composites has not been fully developed. In this thesis, the progressive failure analysis of double-notched composite laminates is illustrated by the implementation of the material property degradation method, continuum damage mechanics and cohesive element method. These combined approaches help predict both the in-plane damage and delamination in composites. Furthermore, various failure criteria are employed in this thesis to significantly present a comparative study between different failure models on notched composites since most of the comparative studies in the literature have been performed only on unnotched composites. Various failure models are used to model the damage propagation in notched cross-ply and quasi-isotropic composite laminates subjected to tension. The simulation results of laminates using both carbon/epoxy and glass/epoxy composites agree well with the experimental observations. These results signify the necessity of introducing a fracture process in the fiber failure modeling to better predict the failure in notched composites. In addition, the mesh-dependency and the parametric studies of cohesive elements and MPDM scheme are all presented on the notched quasi-isotropic laminate. The results of the mesh-dependency show that the FE models need to be built with three-dimensional elements and blunt notch to provide mesh-independent results. Besides, the parametric study of cohesive elements shows that the failure prediction is not so sensitive to the values of the cohesive strengths and strain energy release rates chosen while the parametric study of MPDM scheme reveals a need to assign relatively small stiffness values in MPDM to produce reasonable results. Finally, the notch-size and ply-level scaling effects of the notched quasi-isotropic laminate are investigated. It is found that a strength reduction with increasing size of the specimens has been obtained in experiment and this trend has been captured computationally. The ply-level scaled laminate shows clearer fiber failures and delamination than the notch-size scaled laminate. These notch-size and ply-level scaling effects are reasonably mirrored by all failure models.
Appears in Collections:Ph.D Theses (Open)

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