LAUSR

Abstract Delamination within composite laminates has been typically characterized by the critical strain energy release rate, or fracture toughness, by performing double cantilever beam (DCB) tests. However, significant variations of the fracture toughness can occur across the width of a DCB test article due to the anticlastic curvature of composite laminates in bending. To obtain more accurate fracture toughness values, this study demonstrates a Lagrangian cross-correlation method that uses strain measurements directly from the delamination front in a DCB test to estimate the internal fracture toughness. Unmodified optical fibers were embedded in DCB test articles fabricated from non-crimped carbon fabric using a VARTM process. The variation in the strain energy release rate along the delamination front is obtained using multiple optical fiber passes. Predicted crack lengths, fracture toughness, and flexural moduli are in excellent agreement with those from surface measurements.