Effect of fibre distribution on structural behaviour of pultruded composite profiles

Effect of fibre distribution on structural behaviour of pultruded composite profiles

Fibre-reinforced polymer (FRP) composites are widely used in various industries due to their high strength-to-weight ratio, corrosion resistance, and tailored mechanical properties. However, manufacturing-induced imperfections, such as non-uniform fibre distribution (NUFD), voids, and fibre waviness, can compromise their performance and structural integrity. This thesis comprehensively investigates fibre distribution imperfections in hollow box FRP structures, focusing on manufacturing, characterization, and performance analysis to enhance the understanding of their impact on mechanical properties and structural behaviour. A novel approach, Filtered Canny Misalignment Analysis (FCMA), is introduced for characterizing fibre waviness in continuous fibre-reinforced composites, demonstrating improved accuracy, efficiency, and robustness compared to existing methods. The FCMA method is applied to quantify in-plane and out-of-plane fibre waviness in hollow composite columns, which is then used as input for a finite element model to evaluate the impact of fibre waviness on stress distribution under axial compression. The formation and impact of Non-Uniform Fibre Distribution (NUFD) in pultruded fibre-reinforced polymer (PFRP) composite profiles are investigated using image analysis and experimental testing. It is demonstrated that compressive strength at the material level decreases proportionally with the fibre volume fraction caused by NUFD, while finite element modelling highlights corner defects generated by NUFD at the full-scale structural level are more sensitive to local buckling failure compared to wall defects. The effect of NUFD on the flexural performance of pultruded glass FRP box beams is investigated, revealing that corner NUFD has a greater negative impact on local buckling capacity than flange NUFD. A linear relationship between the rotational restraint coefficient and corner fibre volume fraction is established, providing insight into the influence of material imperfections on load capacity. Finally, a numerical simulation and experimental investigation of the pull-braiding process for manufacturing braided composite profiles are conducted. A bi-axial braiding technique combined with pultrusion is employed, and the developed numerical model accurately simulates the braiding process, predicting the geometrical features of the braided structures. The study identifies defects in the composite profiles, providing a foundation for future research in the development of advanced composite materials with tailored mechanical properties.

File reproduced in accordance with the copyright policy of the publisher/author.