The effect of residual stresses and wind configuration on the allowable pressure of thick-walled GFRP pipes with closed ends

An investigation into the benefits of winding thick-walled glass fibre reinforced plastic (GFRP) pipes with two layers of different winding angles is presented. It is shown that layered pipes allow significantly greater internal pressures to be carried than can be achieved by pipes wound only at +/- 55 degrees if process induced residual stresses are ignored. It was found, also, that residual stresses severely reduce the allowable operating pressure of GFRP pipes. The reduction was most significant for the layered pipes, however, and this severely impacts on their utility. The most efficient pipe was nevertheless found to be a layered pipe, wound with a +/- 65 degrees/+/- 47 degrees combination. This pipe gives a 12 % improvement on the allowable pressure of the +/- 55 degrees pipe. This small performance benefit is achieved at the cost of significantly greater manufacturing complexity, and so the +/- 55 degrees pipe is probably still the most practical wind configuration.