HPHT hot-wet resistance of reinforcement fibers and fiber-resin interface of advanced composite materials

Abstract

Advanced fiber-reinforced polymer-matrix composites are used extensively in oilfield downhole operations because of their performance, lightweight and easy-removal advantages. However, high-pressure/high-temperature (HPHT) corrosive borehole environments pose significant challenges to these materials. It is well known that a hightemperature hot-wet environment degrades most matrix resins. Effects of this environment on various advanced reinforcement fibers and the fiber/resin interfaces in composites, however, have not received enough attention. In this study, E-glass, S2-glass, aramid and carbon fibers were studied in weaved tape and braided sleeve forms. Tape pull tests were conducted before and after hot-wet exposure in 3% NaCl brine at room temperature, 66 °C, 121 °C, 204 °C under 34.5 MPa for 168 h. SEM, EDS, FTIR, TGA and DSC techniques were used to identify the degradation mechanisms of various fibers from the environmental exposure. Glass and aramid fibers were determined to be susceptible to severe hydrolytic degradations when immersed in a HPHT wet environment. The fiber-resin interfaces of the continuous and chopped glass and carbon fiber-reinforced thermoset and thermoplastic matrix composites were examined under microscopy after the hot-wet exposure and revealed major differentiations. The effects of the fiber-resin bonding strength and interface debonding after the environmental exposure on the mechanical properties of the composites were also evaluated.