Study on Mixed-Mode Interlaminar Fracture of Laminated Composites
The superposition-finite element method is developed to analyze the mixed-mode delamination in laminated composites. Both a coarse global mesh and an overlaying fine local mesh are integrated into the finite element analysis model. The whole design domain is discretized by a uniform global mesh, while the high stress regions are discretized by fine local meshes. Local mesh is built independently from the global mesh, which greatly simplifies the model generation procedures. Strain energy release rate is calculated based on the modified virtual crack closure-integral method, which is used to describe the propagation of delamination in laminated composites. Mixed-mode bending tests are performed for unidirectional and cross-ply carbon fiber reinforced laminated composites to characterize the interlaminar fracture behavior under mixed-mode I/II loading conditions. The interlaminar fracture toughness is also given for different mixed-mode ratio. It is seen that fracture resistance for laminated composites exhibit R-curve behavior (increase as delamination propagation). However, once the delamination is sufficiently long, the interfacial fracture toughness changes slightly as the delamination extended and become almost independent of the delamination length. The results of finite element method are in good agreement with the experimental results and provides a basis for establishing failure criterion used in damage tolerance analysis of composite structures.
X. L. Fan and Q. Sun, "Study on Mixed-Mode Interlaminar Fracture of Laminated Composites", Applied Mechanics and Materials, Vols. 110-116, pp. 1345-1352, 2012