Understanding mode II delamination in thermoset composites remains incomplete, particularly when fabrication-induced variability affects interfacial characteristics and fracture performance. This research fabricates unidirectional carbon/epoxy prepregs via hot-press (HP) and vacuum-bagging (VB) techniques and evaluates their interlaminar fracture behaviour through End-Notched Flexure (ENF) testing. Results indicate that the mode II fracture toughness (GIIC) of VB specimens (1387 N/m) is approximately 33% lower than that of HP specimens (2058 N/m). Scanning electron microscopy (SEM) reveals reduced shear cusp density and matrix cracking in VB specimens. Delamination behaviour is simulated using a symmetric Trapezoidal Traction-Separation Law (TTSL) with pseudo-plasticity parameter Γ = 0.99, which, aside from differing GIIC values, employs a consistent set of cohesive parameters (interface stiffness kIIC = 4.5×105 MPa/mm and interface strength tu,II = 100 MPa) to accurately reproduce the force-displacement response in both fabrication methods. A higher GIIC value corresponds to greater crack extension (da) in simulated damage profiles, with da = 2.9 mm and 2.5 mm in HP and VB specimens, respectively. The numerical model is further validated using VB specimens with varied initial crack lengths, consistently producing reliable results. These outcomes validate the proposed unified framework, with all cohesive parameters, except for the experimentally determined GIIC, which are kept constant (Γ, kIIC and tu,II). This approach significantly reduces the need for extensive parametric studies in numerical simulations, thereby improving efficiency and consistency.      «

Understanding mode II delamination in thermoset composites remains incomplete, particularly when fabrication-induced variability affects interfacial characteristics and fracture performance. This research fabricates unidirectional carbon/epoxy prepregs via hot-press (HP) and vacuum-bagging (VB) techniques and evaluates their interlaminar fracture behaviour through End-Notched Flexure (ENF) testing. Results indicate that the mode II fracture toughness (GIIC) of VB specimens (1387 N/m) is approxim...     »