Effects of Sulfuric Acid on Durability Characteristics of CFRP Composite Sheets

This paper presents the chemical, physical, and mechanical characteristics of carbon fiber–reinforced polymer (CFRP) composite sheets subjected to sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$ ). Test coupons are submerged in a 5% ${\mathrm{H}}_2{\mathrm{SO}}_4$ solution for up to 6 weeks, and their responses are measured by Fourier transform infrared spectroscopy, thermogravimetric analysis, dynamic mechanical analysis, and destructive mechanical loading. Also examined are the pH variation of the solution and the microscopic surface textures of the specimens with an increase in exposure time. The aliphatic amine and alkane functional groups of the CFRP are activated by sulfuric acid, including chain scission reactions that cause interfacial deterioration between the carbon fibers and resin. The acid exposure decreases the energy storage and dissipation capacities of the CFRP, as well as its glass transition temperature. The chemically induced damage in the fiber-resin interface is responsible for lowering the load-carrying capacity of the CFRP, along with strain softening. An analytical model is developed based on a Weibull distribution, which quantifies the degree of reliability and hazard associated with acid-damaged CFRP. An environmental reduction factor is calibrated and proposed to replace the standard factor for CFRP strengthening in chemical plants and wastewater treatment plants.