Notched strength and effective crack growth in woven fabric composite laminates with circular holes

The effective crack growth model (ECGM) is extended to evaluate the residual strength of woven fabric composite laminates with circular holes. It is assumed that when the local normal stress caches the tensile strength of the unnotched laminate, damage initiates and propagates with increase of the applied load. The damage is then modelled by a fictitious crack with cohesive stress acting on the crack surfaces. The damage growth is simulated by extension of the fictitious crack step by step and reduction of the cohesive stress with crack opening. The apparent fracture energy (G(c)*) is used to define the relationship between the unnotched strength and the critical crack opening. Based on the equilibrium condition, an iterative technique is applied 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. The residual strength of notched woven fabric carbon/epoxy, glass/epoxy and glass/ polyester composite laminates were evaluated with various hole diameters and specimen widths. Effect of specimen geometry on the critical damage zone size was discussed. The simulations from the effective crack growth model correlate well with the experimental data in open literature.