Research on the critical buckling load of pultruded ribbed Glass Fiber Reinforced Polymer (GFRP) tubes under axial compression

To enhance the bending critical load capacity of Glass Fiber Reinforced Polymer (GFRP) tubes under axial compression, two ribbed GFRP tube designs (D48 and D60) and a specialized axial loading device were developed for compression testing. This study examines the influence of wall thickness and slenderness ratio on the bending critical load capacity and failure modes of GFRP tubes subjected to axial loads. Tensile and compressive tests on GFRP laminates were conducted to determine key material properties, including ultimate load capacity, elastic modulus, and Poisson's ratio in the fiber direction. Results from the axial compression tests reveal that, with a constant cross-sectional area, thinner walls improve the tubes' resistance to axial bending instability. However, reducing wall thickness alters the failure mode, shifting from global delamination to local buckling. Furthermore, as the slenderness ratio increases, the failure mechanism transitions from strength-controlled to stability-controlled, resulting in a significant reduction in load capacity.