A Mode I cohesive law characterization procedure for through-the-thickness crack propagation in composite laminates

A method is proposed for the experimental characterization of through-the-thickness damage propagation in multidirectional carbon fiber reinforced polymer laminates. The compact tension specimen configuration is used to propagate damage stably while load and full-field displacements are recorded. These measurements are used to compute the fracture toughness and crack opening displacement from which a trilinear cohesive law is characterized. The proposed method provides a means to extrapolate to steady-state such that the cohesive law is characterized completely and accurately, even when the test specimens used for the characterization are too small to reach steady-state crack propagation. The characterized cohesive law is demonstrated through a prediction of the structural response and fracture of a geometrically-scaled test specimen.