An elasto-plastic model to predict permanent indentation due to impact and quasi-static indentation on composite laminates

In this work, a finite element model based on an anisotropic elasto-plastic theory was established to capture permanent indentations on composite laminates under low velocity impact and quasi-static indentation. The parameters in the anisotropic elasto-plastic theory were determined from the analysis results of a micromechanical model. As the reason for the knee-point on the curve of dent depth-impact energy, fiber break was considered in this model. Cohesive elements were used in intrelaminar to simulate the damage of delamination. The numerical analysis was implemented by ABAQUS and the user-defined material subroutine VUMAT. Experimental and numerical studies on two kinds of laminates (T300/6421 and T700/6421) were carried out. The calculated results are coordinate with the tested results well. Results show that fiber breakage happens in the laminates of T300 instead of T700 when impact energy or contact force increases because there is a big difference between the T300 and T700 fibers observed by SEM. A comparison shows it is correlative between the QSI applied energy and the impact energy on T300 laminates. In conclusion, fiber breakage and the match between the fiber and matrix have a significant influence on the permanent indentation and damage behaviours.