Compression characteristics and failure mechanism of thin-walled stiffened composite structures with node interface delamination defect

Stiffened composite panels are widely used in aerospace applications as primary load-bearing components. However, internal laminar defects in these panels can severely impact their mechanical properties. This study investigated the compressive failure mechanism of orthotropic grid-stiffened composite plates. To explore the impact of node interface delamination defects on macroscopic deformation behavior and failure modes, in-plane compression tests were conducted on four typical components. This was followed by an analysis of the macro-microscopic failure morphology of the composites. The results indicated that the failure mode of the stiffened panel plays a crucial role in its ultimate load-carrying capacity. Interface delamination defects at cross nodes had a minimal effect on the load-carrying capacity of small-sized local specimens, leaving their deformation and failure modes unchanged. Yet, these defects significantly compromised the local stiffness and failure modes of large-sized stiffened panels, causing a transition from compression failure to global buckling and local shear failure. Compared to defect-free components, the strength and stiffness decreased by 59.2% and 38.6%, respectively. These results offer valuable insights for the initial design, strength assessment, and damage tolerance design of such stiffened plates.