An insight into the mechanical behavior and failure mechanisms of T-stiffened composite structures with through-interface debonding defects

A robust 3D finite element model framework was established to capture the mechanical behavior and failure mechanisms of intact and through-interface debonding T-stiffened composite structures based on the progressive damage model and the cohesive zone model. Meanwhile, specimens with and without interface debonding defects were fabricated to validate the reliability and robustness of the proposed modeling framework. Finally, a parametric study was conducted on the types of interfacial debonding to further explore the effect on the buckling load, delamination initiation load, and ultimate load-carrying capacity of the composite stiffened structure. The results indicate that the load-carrying capacity of both single interface defects and double interface defects decreases gradually with increasing defect length and converges to a constant value. The reductions were 28.31% and 47.68%, respectively, compared to the intact structure. Interestingly, interfacial debonding has the most significant effect on the ultimate load at the 1/4 position. Moreover, interface debonding defects not only severely weaken the ultimate load-carrying capacity of the structure but also significantly alter the post-buckling path and failure mechanism, resulting in distinct degrees of deformation and damage morphology.