Determination of the fracture process zone under Mode I fracture in glass fiber composites

This study provides a simple yet effective procedure for the characterization of the fracture process zone (FPZ) developing in the interface of unidirectional laminates under Mode I delamination fracture. Double cantilever beam (DCB) coupons have been manufactured and tested. Three data reduction schemes available in the literature have been utilized for the calculation of the energy release rate (ERR) magnitude as a function of crack extension and the corresponding R-curves have been constructed. The R-curves were then reconstructed in terms of the experimentally registered pre-crack tip opening displacement (delta*) and analytical functions have been used to describe their concatenate trend. The J-integral approach was then applied over the analytical functions to derive the corresponding bridging laws that describe the FPZ. The derived bridging laws were appropriately modified according to three different traction-separation models and implemented into user-developed interface finite elements (UEL) for the simulation of the fracture tests in ABAQUS (R) commercial software. Comparisons between numerical and experimental results have shown that the proposed straightforward procedure leads to an effective traction-separation law that can be used as a material property of the modeled interface.