A holistic comparison of a trailing edge rib demonstrator made with three different PEEK thermoplastic composite form factors: unidirectional, fabric and braid

Abstract

This study investigates the forming quality and mechanical performance of a trailing edge rib made with three different carbon fiber PEEK form factors, tape, fabric, and braid. It was found tape ribs developed the most severe level of wrinkling and waviness leading to premature ILT failure in the flange. This contrasted with braid and fabric ribs, which failed in compression buckling and had almost three times the deformation before ultimate failure. Moreover, the reinforcement form factor, combined with a high elongation to break matrix like PEEK, was found to have a significant effect on crack propagation and toughness leading to the different failure modes. The trade-offs between tape, fabric and braid form factors are similar to those with thermosets, but seemingly exaggerated, considering fabrics and braids displayed a large amount of plastic deformation while PEEK tape laminates displayed failure progression similar to thermoset composites. These findings have important implications for the design and optimization of thermoplastic composites in new aerial mobility vehicles expected to operate at higher frequency in environments with more varied damage hazard potential.