Interfacial fracture energy of a single cantilevered beam specimen using the J-integral method

Sandwich composites are widely used in the aerospace industry due to their high stiffness and strength-to-weight ratios. However, debonding between the core and facesheets in sandwich panels can occur at relatively low out-of-plane loads due to low interlaminar properties. Increasing interlaminar properties is achievable by using through-the-thickness stitching. Current test standards to estimate the fracture energy of composite materials assume small-scale yielding near the crack front and do not consider large plastic zone sizes due to large-scale bridging. Therefore, this study explores the use of the J-integral approach to better approximate the mode I dominant interfacial fracture energy in a stitched sandwich composite specimen that develops large-scale bridging. A single cantilevered beam test is performed to estimate the nonlinear and linear elastic fracture energies experimentally. Additionally, finite element analysis is used to verify the analytical predictions at crack initiation. Results indicate that a J-integral approach is a promising method to estimate the fracture energy of stitched sandwich composites.