Coupling effect of high and low temperature cycle-humidity-load on tensile properties of carbon fiber/epoxy composites

This paper studies the durability of epoxy resin-based-carbon fiber reinforced polymer (EP-CFRP) under the combined action of aggressive environmental conditions and load. Environmental conditions such as high and low temperature cycles of −40-40 ℃ / −40-25 ℃ and humidity (water immersion and no water) are investigated in an unstressed state or loaded in about 30% or 60% of the initial ultimate load. The results indicate that both of the dual-factor coupling of “high and low temperature cycle-humidity” and the three-factor coupling of “high and low temperature cycle-humidity-load” have a greater impact on the durability of EP-CFRP. The tensile strength varies with the cycle of high and low temperature. The overall increase shows a simulated trend of first decreasing, then increasing, and then decreasing; however, the appearance of the peak and valley values are quite different. Humidity and load level have little effect on the tensile modulus of EP-CFRP The microcracks generated at the interface between the resin matrix and the fiber have been proved to be the main reason for the strength reduction at later stage. The coupling effect of humidity and load promotes the expansion of cracks and exacerbates the damage to EP-CFRP. According to the damage analysis, a non-linear fitting method is used to give the residual strength damage model of EP-CFRP after the coupling action of the three factors “high and low temperature cycle-humidity-load”.