Strength of filament wound GRP tubes with axisymmetric steps

Abstract

Internal pressure tests have been conducted on 100 mm diameter, 1.7 mm thick, ±75° winding angle filament wound E-glass fibre reinforced epoxy resin tubes with and without end reinforcements in the form of abrupt, 6 mm thick, axisymmetric steps. Theoretical investigations were carried out using computer programs based on three-dimensional finite element and thin shell analyses. The experimental strain distributions in the region of the steps were found to agree closely with the finite element predictions at low pressures but not at high pressures. Theoretical analysis suggested that the burst pressures of stepped tube should be an order of magnitude lower than that of unreinforced tubes but the actual burst pressures were similar for tubes with and without steps. Photomicrographs of sectioned specimens are presented and reasons for the difference between theoretical and experimental burst pressures are discussed.