Numerical investigation of transverse bridging development in mode I delamination of fiber-reinforced composite laminates

Transverse fiber bridging is an extrinsic toughening mechanism in cross-ply composite laminates, but its numerical representation remains challenging because it involves coupled transverse cracking and interlaminar delamination. This study develops a cohesive-zone-based finite element model to investigate the apparent bridging response during Mode I delamination in cross-ply double cantilever beam (DCB) specimens with prescribed transverse cracks. Delamination growth is simulated using cohesive elements, while transverse cracks are explicitly introduced in the 90 ∘ sublaminate. Experimental data reported in the literature are used to relate in-plane strain, transverse crack density, and propagation fracture toughness, from which representative transverse crack spacings are derived. The model is validated against reported DCB responses for cross-ply laminates with and without pre-induced transverse cracking. Parametric studies are then performed to evaluate the effects of interfacial heterogeneity configuration, interface strength contrast, transverse crack spacing, specimen width, and 90 ∘ ply thickness. Within the proposed equivalent cohesive-interface representation, the results show that the apparent bridging response is governed mainly by the local interfacial heterogeneity configuration and transverse crack spacing, while global specimen dimensions have a secondary influence. The proposed model provides a mechanistic framework for interpreting bridging-enhanced Mode I delamination resistance and may help guide the design of interface architectures in damage-tolerant composite laminates.