Leakage failure in fibre-reinforced polymer composite tubular vessels at elevated temperature

Pressure-containing structures made from fibre-reinforced polymer composites are increasingly used in harsh environments. This is in part due to their good corrosion resistance. Assessing the performance of such structures often requires consideration of different temperature regimes. Compared to metallic structures, pressurized composite structures exhibit complex damage behaviour which commonly includes fluid leakage that is induced by micro-cracking of the polymer matrix. This is an important damage mode to consider since it not only affects the pressure capacity of unlined components but also causes reduced stiffness and, possibly, fluid ingress into the structure. Leakage behaviour, and thus the occurrence of matrix cracking, may conveniently be assessed through pressure testing. Since fluid properties vary with test temperature, an appropriate testing scheme is required to obtain truly comparable leakage thresholds. The work described in the present paper involves a permeability based testing methodology. Fibre-reinforced tubular specimens were used in this study with either an epoxy or bismaleimide matrix material, which are intended for room and elevated temperature service, respectively.