| Carbon fiber reinforced plastic (CFRP) has the advantages of high specific performance, outstanding design ability characteristic, high resource utilization ratio, all of which make them suitable for automobile industry. However, during the manufacturing of CFRP products defects have many chances to be introduced into structure, among which voids are the most common one. Voids can reduce the mechanical performance of CFRP and studies have been widely carried out both at home and abroad but there is still a lack of in-depth research on the influences of voids on the mechanical performance of CFRP, which are mainly caused by two reasons:1. characterization of voids needs to be further discussed; 2. numerical method for voids still needs to be advanced. According to the above problems, the scopes of this thesis are as follows:By using the industrial CT and object oriented programming method, voids in CFRP are detected and the sizes, distribution and shapes of voids are obtained after three-dimensional reconstruction from digital images.On the basis of mesoscopic mechanics, modeling of CFRP containing matrix layer is proposed. Comparing to experimental results, the optimal thickness of matrix layer is obtained, which is the foundation of this study.Using finite element analysis software ABAQUS and the proposed modeling idea of CFRP, three-point bending model with voids is presented, and the effects of porosity, shapes, distribution of voids as well as layup sequences on bending stiffness of CFRP are discussed respectively.This thesis proposes a user defined UMAT, which is based on Hashin-type criteria and Linde stiffness degradation scheme, to analyze progressive damage of CFRP. Meanwhile, the interfacial element of cohesive zone model is adopted to study the delamination formation and evolution. Good agreement between experiment and simulation results has been achieved, which proves the correctness of the proposed method. The effects of voids on delamination of CFRP are discussed. |
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