Adhesive and cohesive failure analyses of bonded FRP composite tubular T-joints in combined axial compression and out-of-plane bending

Tubular T-joints are the most widely used structural connectors. FRP composites, with their superior intrinsic properties, can be a more suitable choice than steel. Computational fracture mechanics has been employed to develop finite element models for predicting adhesive and cohesive failures in bonded composite T-joints under combined loading, with clamped chord and brace. Three-dimensional stress analysis, in conjunction with appropriate failure criteria (Tsai-Wu for adhesive failure and parabolic yield for cohesive failure), revealed that the saddle point ( β = 0°) along the bottom toe line and middle fillet line of the bonded T-joint is particularly prone to adhesive and cohesive failures, respectively. Fracture growth analysis using VCCT demonstrated a predominant radial propagation of both adhesive and cohesive failures, primarily governed by opening mode. Simultaneous failure growth leads to mutual retardation, with cohesive failure significantly contributing to the suppression of adhesive failure propagation. Despite the interaction effects, fracture propagation within the bonded T-joint has intensified local stress concentrations, adversely impacting the structural integrity of the joint. Structural integrity of bonded T-joints to adhesive failure can be enhanced by using a circumferentially oriented ([0] 16 ) brace along with a cross-ply ([0/90] 4S ) chord for smaller cracks ( a a / f b ≤ 0.3), while circumferential ([0] 16 ) chord for larger cracks ( a a / f b ≤ 0.3). Circumferentially ([0] 16 ) oriented fiber reinforced brace and chord are proposed for improving the overall joint fracture resistance against simultaneous influence of adhesive and cohesive failures.