Initial crack length on the interlaminar fracture of woven carbon/epoxy laminates

Abstract

This paper describes an experimental and numerical study developed to characterize the mode I fracture toughness of woven carbon/epoxy composites, using Double Cantilever Beam (DCB) tests. The laminates were manufactured using an epoxy resin and twelve woven balanced bi-directional layers of carbon fibres, all of them with the same orientation (0/90 °). The interlaminar fracture toughness shows to be practically independent of the initial crack length and the value of GIC, obtained according with the modified beam theory, was about 282 J/m2. Numerical analysis based on the finite element method was also developed to understand the effect of initial crack length. After a mesh refinement study, the numerical predictions were compared with experimental results which validated the model. The total energy dissipated by the specimen is nearly constant. The size of cohesive zone ahead of crack tip is also independent of the initial crack length (a0).