Post-buckling induced delamination propagation of composite laminates with bi-nonlinear properties and anti-penetrating interaction effects

Abstract

This paper presents a unique theoretical analysis for the multiple failures of in-plane loaded composite laminates containing a through-width delamination. Under the action of the in-plane load, the delaminated laminates undergo first post buckling failure, then delamination propagation. The anti-penetrating contact effect occurred at the interfaces of the delamination is identified by analyzing the local transverse deformation and is incorporated into the multiple failure stages. Based on von Karman nonlinear geometric relationships, the post-buckling equilibrium path of the delaminated laminates characterized by the in-plane load vs deflection amplitude curves is solved. Expression of energy release rate is derived from variational principles as the summation of the products of shear forces and deflection slopes at the delamination fronts. With the available solutions from post-buckling analysis, threshold to initiate the delamination to propagate is computed according to Griffith fracture criterion and is calculated for different delamination conditions by developing Matlab program. It is found that the delaminated laminate undergoes a consistently macroscopic deflection with microscopic local buckles on the interfaces of the delamination. For all cases, Mode I delamination propagation can never occur due to the contact behavior. Instead, Mode II delamination propagation prevails regardless of the delamination size and position. The analysis presented in this paper accounts for nonlinear geometric deformation, nonlinear constitutive behavior and anti-penetrating interaction effects and identifies multiscale deformation modes involved in different failure mechanisms, thereby demonstrates the latest research idea for the current frontier problems.