Rate Effects on Aramid Fibre/Epoxy (KRP) Tubes Under Hoop Loading

A comprehensive experimental study was undertaken to evaluate strain rate effects on the hoop burst strength, hoop modulus, strain to failure and Poisson's ratio of Kevlar reinforced plastic (KRP) angle ply filament wound tubes. Both static and dynamic tests were performed on tubes of winding angle 25 ° , 45 ° , 55 °, 65° and 75 ° , which were burst under internal radial loading with minimum end constraints. For each test, the inter nal pressure and the strains in both circumferential and longitudinal directions were re corded on suitable digital processing equipment. For a particular batch of tubes tested at different strain rates, the results showed a signifi cant rise in the hoop burst strength with increasing strain rate, for all tubes. The high winding angle tubes (65° and 75°) failed by catastrophic fibre fracture; the strain to failure values increased with increasing strain rate and the hoop modulus remained fairly constant over the tested strain rate range. The lower winding angle tubes were characterised by an "initial failure" associated by resin cracking and leading to a subsequent degradation in tube modulus. The use of a non-structural liner during quasi-static tests leads to a signifi cant increase in ultimate strength and strain of all tubes tested with the exception of the 25°.