Mode I Delamination of a Three-Dimensional Fabric Composite

Abstract

Finite element analysis was conducted on the double cantilever beam speci men (DCB) of carbon-epoxy (T300/3501-6) orthogonal interlocked fabric composites. The Mode I strain energy release rate, GI, was evaluated to investigate the influence of through-the-thickness (z-axis) fibers on crack driving force as a function of crack length. The finite element analysis of the DCB specimens showed good agreement with ex perimental results for both compliance and strain energy release rate. The presence of z- axis fibers sharply reduced the strain energy release rate in comparison to the traditional two dimensional (2-D) laminated material. A parametric study revealed that increasing the z-axis fiber stiffness reduces GI. Progressive debonding of the z-axis reinforcement was also modelled. The Mode I strain energy release rate increased as the fiber debonded but was significantly less than the 2-D laminated material in all cases investigated. A model for the prediction of critical load is proposed for Mode I interlaminar fracture of 3-D orthogonal interlocked fabric composites. Fundamental inputs to the model are the z-axis fiber properties, fiber architecture, fiber volume fraction and the Mode I critical strain energy release rate for the 2-D laminate.