Light intensity effect on UV cured FRP coupled composite pipe joints

Abstract

In this study, 36 composite pipes were joined with an eight-layer chopped mat and woven fabric that was adhered with UV curing vinylester resin. The joined composite pipes were cured vertically with UV lamps at three different light intensities: 80, 35, and 15 m W/cm 2. The mechanical properties of the cured pipes were evaluated by conducting internal pressure testing and simply supported 4-point bending testing. The effect of UV light intensity on the internal pressure rating, the ultimate bending load, and stiffness was evaluated based on the test results. A finite element analysis, which considered the under-curing along the axial direction and radial direction, was conducted to validate the test results. There was a direct correlation observed between increased light intensity and increased residual mechanical properties such as internal pressure rating, stiffness and peak failure load. The mechanisms for variation in the system properties were found to be under-curing and non-uniform curing in the FRP joint resulting in a loss of ability to effectively transfer load from the pipe to the joint. Additional observed phenomenon was gravity leaching due to vertical curing. All mechanisms were simulated by the introduction of a sliding modulus technique in the conducted finite element analysis. FEA results agreed well with the observed failure modes.