Effect of temperature on the tensile strength and failure modes of angle ply CFRP tubes under hoop loading

A comprehensive study was undertaken to characterise carbon fibre reinforced plastic (CFRP) tubes at different temperatures. Quasi-static burst tests were performed on tubes of 25 degrees, 55 degrees and 75 degrees winding angle. The tubes were burst under internal radial pressure with minimum end constraints. An experimental rig and two conditioning tanks were designed and built to test the specimens at three temperatures; -46 degrees C (low temperature), +20 degrees C (room temperature) and +70 degrees C (high temperature). For each test the internal pressure and the strains in both circumferential and longitudinal directions were recorded using a digital processing equipment. For a particular batch of tubes, tested at three different temperatures, a decrease in hoop strength and modulus of the 55 degrees tubes with increasing temperature was recorded; the effect was less pronounced on the properties of 25 degrees and 75 degrees tubes. The use of a non-structural liner during the tests led to higher ultimate strength and strain of 55 degrees tubes but had negligible effects on the behaviour of 75 degrees tubes. The use of a liner in 25 degrees tubes altered the mode of failure, resulting in a very large tube deformation with no noticeable increase in burst pressure. Micrographic analysis was also undertaken to study the failure mechanisms during pressurisation of lined and unlined tubes.