Failure analysis of GFRP columns subjected to axial compression manufactured under various curing-process conditions

Abstract

Fibre reinforced polymers are one of the most used materials in the manufacturing of thin-walled structures due to their favourable mechanical properties in terms of strength-to-weight ratios. The curing-process conditions of polymer-based composites can be a source of the residual stresses which can play the main role in failure mechanisms of a composite. The work presents a comparative failure analysis following the post-buckling state of thin-walled composite columns made by autoclave methods with various curing parameters and geometrical concepts. The study inspected the compression of thin-walled composite profiles with C-shaped sections and square cross-sections made of unidirectional preimpregnated tapes of glass/epoxy. It was presented that the boundaries of the halfwaves of the composite flanges are the initiation point of local but catastrophic damage (out-of-plane buckling and plies split) of the composite. These regions are stress concentration points in columns. However, the dominant form of damage is delamination. Delamination is the propagation stage of failure of composite, which propagates from initiation points. The progress of delamination occurs because of increasing load, halfwave deformation and column stiffness reduction. Depending on the curing parameters and geometrical concepts some additional, important failure initiation mechanisms, such as stepped cracks and fibre rupture, were noticed.