Effect of Ply Thickness and Fibre Orientation on Delamination Initiation in Broken Ply Composite Laminates

Abstract

The present study examines the delamination initiation at the interface of broken and continuous plies in case of GR/E and GL/E laminates with broken central plies. A full 3D FE analysis has been performed with each layer of the laminate modelled as homogenous and orthotropic. The interface between the broken and continuous plies has been modelled with a thin resin rich layer. Eight-noded isoparametric layered elements have been used to model the laminate specimen. Also, 3D contact elements are used to prevent the interpenetration of delaminated faces at the interface. Based on the results of 3D FE analysis, GI, GI, and GI,, have been calculated at the delamination front using Irwin's Crack Closer Integral. It has been observed that the delamination initiation is a mixed mode phenomenon even in the case of uniaxial loading. Brewer and Lagace's Quadratic Stress Criterion has been used in conjunction with Linear Elastic Fracture Mechanics (LEFM) to calculate the delamination initiation strain and the critical strain energy release rate (Gc). The effects of various factors such as ply thickness, fiber orientation, resin stiffness on Gc have been studied for GR/E and GL/E laminates having broken central plies.