Residual properties of square FRP composite tubes subjected to repeated axial impact

In this paper, the residual properties of square composite tubes under axial impact were experimentally investigated. The effects of damage factors such as the mass of the impactor, incident energy, and number of impacts on their post-impact behaviour were emphasised. Low-velocity impact tests were performed by repeatedly impacting a 100 mm square FRP pultruded tube with energy levels up to 742 J using a drop-weight apparatus. Coupons were then taken from the impacted tubes and tested statically to determine the residual compressive, tensile, and flexural properties. Results show that the levels of impact energy, number of impacts, and the mass of the impactor significantly influenced the residual strength degradation of the impacted tubes. Their effects, however, are almost negligible in the residual modulus property. It was found that the maximum reductions of residual compressive, tensile, and flexural strengths of the impacted tubes are 6.8%, 0.3%, and 10%; respectively. It was also found that effect of impact damage on the reduction of residual compressive strength of the tube is concentrated only in region closer to the impact point.