CDM 3-D Numerical Model For Predicting The Strength Of Notched Composite Laminates

Inevitably there will be kinds of notch like open hole or cutting in the engineering composite structures. The existence of the notches destroyed the continuity of the fiber, which changed the force transmission route of the structure. Because of the sudden change of local stiffness, the stress concentration exists around the region of notch, which seriously affects the performance of the composite structures. The specific failure characteristics of the composite materials, such as anisotropy, various damage modes and complex damage mechanism, give a great challenge to the analysis of its failure. This thesis mainly studies problem about the residual strength of notched composite laminates.(1) A comprehensive review and survey of the engineering estimation method and numerical simulation method for the residual strength of notched composite laminates were conducted.(2) A large number of tensile tests of different kinds of composite with different types of notch were collected. The characteristic length of different composites was estimated by using the Point Stress Criterion and the Average Stress Criterion method, for engineering use of estimating notched strength.(3) A three-dimensional model was proposed in this text based on Continuum Damage Mechanics(CDM). This model was capable to predict several possible in-plane failure modes(e.g., fiber failure, inter fiber failure) and interlaminar failure modes. 3D Puck failure criterion and Aymerich criterion were used to judge two kinds of damage above. After the failure of material, the linear softening model based on CDM was used for the damage evolution. In the model, the lamina’s in-situ effect and the shear nonlinear behavior were considered.(4) The progressive failure process of quasi-isotropic and angle-ply laminates with central open hole or central slit, cross-ply laminates with sharp notch was simulated, with ABAQUS and UMAT subroutine. It is found that the analysis results are in good agreement with the experimental results, prove that the present model is capable of predicting the tensile strength of notched composite laminates.