Formation of non-uniform fibre distributions in winding-pultrusion process and its effect on axial compressive properties of hollow GFRP profiles

This study investigated the formation and impact of Non-Uniform Fibre Distribution (NUFD) in pultruded Glass Fibre Reinforced Polymer (GFRP) composite profiles. These profiles, manufactured through a pull-winding process, are low-cost, high-volume structure materials. NUFD, a result of defects such as fibre waviness, wrinkling and voids, lead to differences in fibre volume fraction through the profile cross-section. Image analysis was used to measure the NUFD, and its effect on the axial compressive behaviour was evaluated at both material and structural levels. Results show that material compressive strength has a maximum strength reduction of 11% observed in the tested material coupon. In long-column structural applications governed by local buckling failure mode, the finite element analysis highlights that the corner NUFD can lead up to a 9% reduction in axial compressive peak load due to the rotation stiffness variation when corner fibre content decreases by 30%.