Numerical Study On Failure Behavior Of Composite Structure Components Based On LaRC05 And XFEM

Advanced composites(Fiber-reinforced polymer matrix composites)have excellent characteristics,such as high specific strength and specific stiffness,designable performance and ease to building,etc.Compared with traditional metallic materials,composite materials are more sensitive to out-of-plane loads,and have more complex failure behavior and damage modes.These characteristics bring challenges to the strength analysis and structural design of composites.To assess safety margin of composite materials and obtain optiminized structural design,it is critical to have a deep understanding of the failure mechanism of composites and develope the strength analysis model and method that based on its physical mechanism,which is helpful to reduce the cost shorten the research period,and improve the industrial competitiveness.To accurately predict the failure initiation and propogation process of composite laminates,a new numerical analysis method integrating LARC05 failure criterion(a failure mechanism based failure criterion)and XFEM(Extended Finite Element Method)is proposed in this paper.The method can take into account of the complex failure behavior of composites,such as the in-situ effect,shear nonlinearity,kinking failure,splitting failure and their coupling effects.Both the initiation and propogation of failure can be visually produced by XFEM.The validity of the numerical model is disussed with the experimental results of unidirectional open-hole plate under tension,open-hole laminated plate under tension and bolted single-lap composite joint under tension.The main contents are arranged as:Firstly,failure theories of composites and the state-of-art of failure analysis and stiffness degradation method of open-hole plate and fastened composite joints is reviewed in the first chapter.Then,brief introduction of the LARC05 theory,principles of XFEM and their integrating technique are given in the second chapter.Afterwards,the analysis and discussion of failure modes and crack propogation of unidirectional open-hole plate based on the LaRC05 integrated XFEM model is presented in the third chapterIn the forth chapter,LaRC05 integrated XFEM method is applied to analysis the failure behavior of open-hole composite laminates under tension.The comparison between experimental data,the predictions in this work and predictions based on LaRC03 is carried out to verify the effectiveness of the model,where both failure mode and load-displacement curves are discussed.In the fifth chapter,LaRC05 integraed XFEM method is also used to investigate the failure load and crack growth of bolted single-lap composite joint.The predictions are comparied with the experimental data,as well as the predictions based on Hashin criteria where both the failure mode and load-displacement curve were investigated.The main conclusions are as follows1.The comparison study of tension failure of the unidirectional open-hole plate shows that the model created in this paper can effectively capture the various failure modes and crack propagation of the unidirectional open-hole plate,which indicats that the model is capable of describing the complex failure behavior of the unidirectional open-hole plate.2.The comparison study of the open-hole laminated plate shows that the method proposed here can be used to either descript the failure mode observed in experiments or to predict the displacement-load curves.The prediction errors are less than 7% for all the three kinds of laminates involved here.3.The comparison study of the bolted single-lap composite joint shows that the damage initiates near the faster clamped area in the fitting ply between composite laminated plates and metal plates.The predicted value of ultimate load shows an error of 5.29% compared with the test data.