BUILDING-BLOCK VALIDATION OF COHESIVE ZONE MODELS IN FRACTURE SIMULATION OF AIRCRAFT THIN-WALLED METALLIC STRUCTURES

The Cohesive Zone Model (CZM) exhibits tremendous application potential in the fracture assessment of aircraft metallic thin-walled structures due to its advantages of requiring few parameters, easy calibration, and strong robustness. However, actual aircraft structures feature complex configurations, and crack propagation is often accompanied by out-of-plane buckling. Whether the cohesive parameters calibrated from anti-buckling small specimens can be applied to such structures across different scales and configurations remains to be systematically investigated. To address this issue, this paper focuses on the quasi-static Mode I crack propagation in aircraft metallic thin-walled structures. Strictly following the NASA building block validation approach, the applicability of cohesive parameters calibrated from anti-buckling small specimens is systematically verified in predicting the fracture behavior of large flat panels, collinear multi-crack panels, and flat stiffened panels. Results indicate that, under a given material and thickness, the calibrated cohesive parameters are independent of in-plane geometric dimensions and the loading type when both the crack length and the uncracked ligament size are no smaller than four times the thickness. The cohesive parameters calibrated from anti-buckling small specimens can not only accurately predict the crack propagation process of large anti-buckling structures—obtaining characteristic parameters such as residual strength, multi-crack link-up load, and stiffener strain distribution—but also enable effective simulation of the out-of-plane buckling displacement distribution and accurate prediction of the residual strength for both large flat panels and flat stiffened panels. This study effectively verifies that as an elastoplastic fracture analysis model, the cohesive parameters of CZM calibrated via buckling-resistant small specimens possess cross-scale transferability, which is of significant engineering value for residual strength assessment, damage tolerance design and service life prediction of aircraft metal thin-walled structures.