High-performance bio-inspired composite T-joints

This paper introduces a novel bio-inspired design strategy based on the optimised topology of bird bone's joint to improve the strength-to-weight ratio and damage tolerance of composite T-joints. Better structuring the constituents' materials near the sharp bends results in re-distribution of stress over a larger area and reduces the stress concentration. This is done by an integrally formed support structure that is spaced apart from the main body of the T-joint in the vicinity of the bend using a Polyvinyl Chloride (PVC) foam. The support structure acts as a buttress across the bend and improves the performance of the T-joint. The T-joints are fabricated using wet layup process, from 2/2 twill TC35-carbon fibre fabric/SR5550 epoxy resin, and are subjected to quasi-static and fatigue bending, and quasi-static tensile pull-out tests. The quasi-static results reveal that the bio-inspired T-joint design has huge improvements compared to a conventional T-joint in the elastic stiffness (over 60%), peak load (over 40%) and absorbed mechanical energy (over 130%). There is only 3% weight increase in the bio-inspired T-joint compared to the conventional one. The fatigue results show a significant improvement for the bio-inspired design proving the efficiency of the novel bio-inspired design for both quasi-static and cyclic loadings.