Mechanical properties and failure behaviors of T1100/5405 composite T-joint under in-plane shear load coupled with initial defect and high-temperature

The T1100/5405, a novel carbon fiber resin matrix composite, boasts superior specific strength, stiffness, and broad applicability. This study rigorously investigated the in-plane shear performance and thermally coupled damage failure mechanisms of this composite in a T-joint context under initial defects, being highly relevant for hypersonic vehicles in high-temperature environments. Experimental tests yielded mechanical property pa-rameters and in-plane shear data for varying test temperatures (25 degrees C, 150 degrees C) and defect radius (0 mm, 15 mm). Compared to flawless samples at room temperature, the synergistic impact of high temperature and defects expedited the structural damage failure process, reducing load-bearing capabilities significantly. A numerical model was established based, on the inherent structural relationship of the cohesive zone model and the con-tinuum damage mechanics of the composite, whose accuracy was confirmed by experimental data. Further analysis revealed that a high-temperature environment would exacerbate the damage failure process of initial defects. Specifically, as the temperature rose, the defect radius increased, thus diminishing the shear capacity of T-joint. The maximum structural ultimate load has been reduced by 67.54 %, which was perfectly aligned with experimental results. Consequently, the study provides practical insights for the structural design of hypersonic vehicle composite.