Study on the failure mechanism of suture CFRP T-joints under/after the low-velocity impact loading

Abstract This investigation employs low-velocity impact (LVI) and quasi-static compression testing to evaluate failure modes in hot-pressed CFRP T-joints under corner-based out-of-plane impacts. Post-impact tensile testing quantifies LVI-induced strength reduction mechanisms. In order to improve the strength of CFRP T-joints, the effects of impact resistance and residual strength were studied by changing different suture methods and parameters. Experimental results demonstrate that the improved lock stitching significantly enhances the mechanical properties of T-joints. This improvement is attributed to the tighter interfacial connection between specimens and fibers achieved through the optimized stitching pattern. The ductile deformation of stitches enables effective energy absorption during impact loading, thereby reinforcing the structural integrity of the composite assembly. For instance, after the same LVI loading, the tensile strength of IS-20 J is more than 19.8% higher than that of US-20 J.