Material characteristics and residual bond properties of organic and inorganic resins for CFRP composites in thermal exposure

• Characteristics of various resins for CFRP application at high temperature are studied.
• Curing time and exposure temperature are important parameters.
• Inorganic resin shows thermal stability, while organic resin provides strength.

This paper presents the residual characteristics of organic and inorganic resins for structural retrofit using carbon fiber reinforced polymer (CFRP) composites exposed to thermal stress states. A three-phase experimental program is carried out to study the behavior of the inorganic resin, CFRP composites, and resin-concrete interface at elevated temperatures ranging from 25 °C to 200 °C. The properties of the inorganic resin demonstrate strong dependency on curing time and are influenced by the degree of temperature exposure. CFRP composites show a decrease in strength and modulus with an increasing temperature due to the degradation of bond between the fibers and resin. The inorganic resin exhibits better thermal stability than the organic resin, whereas the former illustrates a lower strength than the latter because of insufficient stress-transfer. The composites have failed abruptly, regardless of resin types. The interfacial fracture energy of the resins is reduced with temperature, including the deteriorated morphology of the interface between the concrete substrate and the resin.