UV-cured FRP joint thickness effect on coupled composite pipes

In this study, 36 FRP composite pipes were joined with various layers of fiber-reinforced UV curing vinylester. Twelve of the composite pipes were joined with an eight-layer weld, 12 with five layers and 12 with three layers; each configuration used exactly one layer of E-glass woven fabric with the remaining layers being comprised of chopped strand mat of various widths. The joined pipes were cured with UV lamps at 80 milli-Watts per square centimeter. The mechanical properties of the cured pipe joints were evaluated by conducting internal pressure testing and simply supported four-point bending testing. The effect of joint thickness on the internal pressure rating, ultimate bending load, and stiffness was evaluated to determine the role of joint thickness in under-curing of UV curing vinylesters. There was a direct correlation observed between joint thickness and internal pressure rating. The five-layer and three-layer joints each performed better than the eight-layer joint in bursting. The mechanism for variation in the residual properties was found to be the degree of cure and was validated by finite element analysis that utilized a composite model that simulates variable cure.