Investigation of Crack Growth Along Curved Interfaces in L-shaped Composite and Polymers

Abstract

Delamination in unidirectional L-shaped composite laminates is modeled with two L-shaped polycarbonate plates bonded to each other where the effect of pre-crack length on the stability of the crack growth is investigated experimentally and computationally. In the experimental study, a unique testing fixture with a sliding platform is designed to create a pure vertical displacement to one of the arms. The full-field technique of photoelasticity is used in order to visualize isochromatic fringe pattern around the crack tip located at the bonded interface of the L-shaped polycarbonate plates. In the computational study, debonding at the interface of L-shaped plates is modeled using dynamic (explicit) finite element analysis in conjunction with cohesive zone methods. In numerical analysis, pure vertical displacement is applied to one of the arms to reflect the same loading condition as the experiment. Experimental and finite element analysis results are in agreement in terms of load–displacement behavior and stress distribution, which indicate a successful use of cohesive zone method in modeling of crack growth. Stable and unstable crack growth regimes, depending on the precrack length, are identified in agreement with energy release rate calculations. The crack growth regimes are also consistent with unstable crack growth observed in L-shaped unidirectional composite laminates.