Quantification of Swelling Stress Induced Mechanical Property Reduction of Glass Fiber/Epoxy Composites Immersed in Aqueous 10 % Sulphuric Acid by Instrumenting with Distributed Optical Fiber Sensors

Glass fiber/epoxy (GF/E) composites are being extensively scaled-up as anti-corrosion materials in chemical industries because of the relatively low-cost, and are easy to manufacture. Nonetheless, Glass fiber/epoxy composites are not entirely immune to corrosion when exposed to dilute acidic solutions due to the reduction in mechanical strength caused by swelling, which adversely affects the structural integrity. Mathematical correlations quantifying the stress and mechanical property reduction with the time of exposure are a tool to design the service life. The composite structure has been monitored throughout its service life in the present study, by instrumenting the GF/E composite with distributed optical fiber sensors (DOFS). The instrumented composites along with test specimens are aged in aqueous 10 % sulphuric acid environment at room temperature to measure the mechanical properties and weight gain due to the transport of the acidic medium. The strain evolution with the time of exposure is recorded by processing the signals received from the DOFS. The experimental gravimetric data are fitted into the Langmuir model, and the model parameters such as diffusivity (D), β and γ are evaluated. Finally, mathematical correlations developed by quantifying the stress and reduction in mechanical properties with exposure time can be used to determine the mechanical health of GF/E composite structure exposed to sulphuric acid solutions. The changes in the microstructure of GF/E composites is also investigated using field emission-scanning electron microscope (FE-SEM). The technique of instrumenting the GF/E composites by embedding it in the composite structure during the fabrication process is also developed.