Single-leg bending (SLB) analysis of a structural adhesive as a function of the adhesive thickness

The mixed-mode static fracture analysis of bonded joints using cohesive zone models (CZM) requires accurate predictions of adhesive strength and fracture toughness. Tensile and shear fracture toughness (G_IC and G_IIC), along with their mixed-mode behaviors, significantly vary with the adhesive thickness (t_A). This work focuses on the numerical analysis of how t_A influences the mixed-mode fracture process in adhesive joints. Experimental data from single-leg bending (SLB) tests is used, involving composite adherends and a ductile adhesive, with t_A ranging from 0.1 to 2.0 mm. The study includes a comparison between experimental and numerical load-displacement (P-δ) curves for validation purposes, followed by the estimation of CZM laws and validation of the fracture envelope across all t_A. The findings enabled a comprehensive numerical evaluation of the t_A effect on fracture behavior in adhesive joints, leading to the proposal of a numerical methodology to analyze mixed-mode bonded joints.