Effect of hybrid architecture on interlaminar fracture and failure mechanism in braided-wound composites

Delamination is a major failure mode of composite materials and significantly affects the structural integrity. However, existing studies have primarily concentrated on traditional composite laminates, and the interlaminar fracture behavior of triaxially braided and braided–filament-wound hybrid composites remain inadequately understood. This study aims to systematically investigate the mode I interlaminar fracture behavior of braided–braided interface and braided–wound interface in two-dimensional triaxially braided–filament-wound hybrid composites. Double cantilever beam (DCB) specimens with symmetric configurations were designed to ensure pure mode I crack propagation. Quasi-static DCB tests were conducted to determine interlaminar fracture toughness, and the effects of interface type and braiding angle were evaluated. Optical microscopy and scanning electron microscopy were employed to elucidate the underlying failure mechanisms. The results demonstrate that the introduction of filament-wound layers significantly improves the stick–slip behavior of crack propagation and markedly increases the initial fracture toughness compared with pure braided interface. The braiding angle and crack propagation orientation strongly influence fracture toughness due to differences in fiber bridging, pull-out, and energy dissipation mechanisms. The hybrid interfaces exhibit rougher fracture surfaces and more pronounced fiber breakage, indicating enhanced resistance to delamination. This study provides novel experimental data and mechanistic insights into the fracture behavior of heterogeneous braided–wound interfaces.