Research On Damage Evolution Of Laminates Based On Nonlocal Theory

Carbon-fiber reinforced composite materials are widely used as the load bearing structures in various fields, such as aviation, aerospace, automotive, marine, wind power and other industries, especially in the aviation and aerospace structures is indispensable. Carbon/epoxy composites has advantages of high-strength, highstiffness, and excellent fatigue properties. Due to low fracture toughness composites is susceptible to impact loads. Impact behavior is very complex. Impact damage pattern is difficult to predict because they depend on many parameters, such as the geometry of the composite structure, the impactor, velocity of impactor, boundary conditions and ply sequences. Therefore, it is necessary to investigate the failure behavior of composites subjected to impact load.For strain softening material, the use of element based on classical local continuum is prone to pathological mesh dependence. In this context, we propose Hashin failure criteria based on strain and the evolution of the fiber and matrix. Developed algorithms with nonlocal are implemented as user defined material subroutines for ABAQUS. In the subroutine whether the damage of fiber and matrix are judged according to Hashin failure criterion. By definition of damage evolution, we completed the simulation of composite laminate.In order to verify the accuracy of the subroutine, we carried out a single element analysis simulating two kinds of ply sequence under tensile and shear condition, which verifies the evolution of the damage variable. And then we conduct a mesh density test to verify the results simulated by the subroutine proposed in this paper does not show pathological mesh dependency. We simulate composite laminates with central hole under tensile load, getting the progressive failure behavior via Hashin failure criteria. According to the impact test of the composite beam web, we build a simulating model. We introduce an adhesive layer to simulate delamination. The damage of fiber and matrix is judged by Hashin failure crit eria. We get the displacement-time curve, velocity-time curve, the contact force-time curve of impactor. Finally we make comparisons of finite element simulation results and experimental results, verifying the validity of the simulation model.