An Effective Crack Growth Model for Residual Strength Evaluation of Composite Laminates with Circular Holes

Abstract

A new effective crack growth model (ECGM) is developed to evaluate residual strength of composite laminates with circular holes. When the local normal stress reaches the tensile strength of the unnotched laminate, damage is assumed to initiate and it propagates with increase of the applied load. The damage is modelled by a fictitious crack with cohesive stress acting on the crack surfaces and the damage growth is simulated by extension of the fictitious crack and reduction of the cohesive stress with crack opening. The apparent fracture energy (G:) is used to define the relationship between the unnotched strength and the critical crack opening. Based on the equilibrium condition, an iterative technique is developed to evaluate the applied load required to produce the damage growth. The residual strength of notched composite laminates is defined by the unstable point of the applied load with damage growth. AS4-carbon/948A1 epoxy [0/90]_4s, and [0/±45/90]_2s, composite laminates were manufactured and residual strength tests were conducted for composite laminates with various hole diameters and specimen widths. Effect of the damage increment on the convergence of the residual strength was investigated and the stress redistribution with damage growth in the composite laminates was discussed. The residual strength predicted from the new model correlates well with experimental data for the different laminate configurations.