Effect of water absorption of the mechanical behavior of fiberglass pipes used for offshore service waters

The use of polymer matrix composite materials at offshore facilities has many advantages, such as weight savings. However, the properties of these composites can be affected when exposed to their service environment, in particular due to water absorption. In this context, fiberglass pipes used for the transport of the so-called service waters must maintain their integrity for long periods of time, without losing their mechanical performance, although directly exposed to water. In this work the water absorption behavior of fiberglass pipes was measured and the effects of the absorbed water on the mechanical performance of the pipes was accessed. The results show that water absorption caused plasticization of the resin, reducing the stiffness of the pipes. However, the tensile strength, and the associated pressure class of the pipes, was not affected. The results show that failure of these pipes after being exposed to water is more probable by mechanical constraints due to large dimensional changes caused by water plasticization and swelling than by the lost of mechanical strength.