Numerical study on the GFRP T-joint failure under three-point bending

The aim of this paper is to study the damage mechanism of glass fiber-reinforced polymer (GFRP) T-joints under three-point bending loads. To investigate the failure mechanism of composite T-joints under three-point bending, a three-dimensional finite-element model of a T-joint made from glass fiber-reinforced composite material was constructed. The results reveal that cracks initiate in the triangular region and gradually propagate, ultimately leading to complete debonding failure at the skin interface. Optimization of layup angles significantly impacts structural strength, where the incorporation of 45° and −45° layers disperses stress concentration and enhances interface performance. Specifically, the critical failure load of the [0/45/0/−45/0/90]_2s layup configuration increased by approximately 14% compared with the traditional [0/90]_6s layup. Material comparison shows that carbon fiber-reinforced polymer exhibits higher flexural strength and crack resistance than GFRP. Hybrid layup designs (e.g. alternating stacking of carbon/glass fibers) further improve structural load-bearing capacity. The study validates the reliability of the Hashin criterion-based finite-element model in predicting damage evolution and failure modes, providing a theoretical foundation for the optimized design of composite T-joints.