Mode I strain energy release rate in composite laminates in the presence of voids

The paper presents a new methodology to investigate the effects of voids on the fracture behaviour of woven fabric composites The influence of a single voids was studied considering its presence ahead of the crack tip in a double cantilever beam (DCB) and calculating the effects on the Mode I Strain Energy Release Rate (SERR). As a first step, the beam-on-elastic-foundation theory was improved to account for shear compliance and material orthotropy, then the new formulation had been used for the evaluation of deformed shape, elastic deformation energy and SERR. The presence of the void was simulated as an un-supported zone in the elastic foundation. The validation of the new analytical model, in term of deformed shapes and SERR values, was successfully carried out by suitable 2D Finite Element analyses. The effects of size, location and shape of the void were investigated with larger, elongated voids in the vicinity of the crack tip being more critical.