A fatigue degradation law for cohesive interface elements – Development and application to composite materials

A cohesive zone interface element degradation law is presented for analyzing delamination crack propagation under cyclic loading. Development of the law is based on a detailed study of the numerical cohesive zone and the extraction of strain energy release rate from this zone, enabling a direct link with experimental Paris Law data. The law is implemented using three-dimensional interface elements within the explicit finite element code LS-Dyna. Validation is presented by way of application to composite material fatigue fracture toughness tests; Double Cantilever Beam for Mode I, End Notch Flexure for mode II and Mixed Mode Bending for the mixed mode case. In all cases good agreement with experimental data available in the open literature and/or theoretical solutions was obtained.