Failure load analysis of C-shaped composite beams using a cohesive zone model

Delamination-based failure is commonly observed in curved composite structures owing to the significant curvature-induced through-thickness stresses present therein. To gain further insights on this failure mode, we investigated the initiation/propagation of delamination in C-shaped composite beams under an opening load and determined their failure load utilizing a three-dimensional finite element simulation based on a cohesive zone model (CZM). Several cohesive parameters (e.g., initial interface stiffness, cohesive zone length, and interface strength) were examined to construct an optimal CZM for the chosen loading conditions, with all parameters except for mode II fracture toughness (directly obtained from end-notched flexure test results) determined by an extensive literature survey. The predicted beam failure loads were compared with experimental results, with the obtained maximum prediction error of 8.4% indicating good agreement. Finally, the predicted position of delamination initiation was found to be heavily dependent on the ratio of the shear strength to the normal strength of the interlayer.