Effects of hydrothermal aging on carbon fibre/epoxy composites with different interfacial bonding strength

This paper presents an investigation on the effects of hydrothermal aging on carbon fibre reinforced polymer (CFRP) composites with different interfacial bonding strength. The combination of electrochemical oxidation and sizing treatments effectively enhanced the long-term interlaminar shear strength (ILSS) retention from 0.24-0.38 to 0.74-0.86 for CFRP in hydrothermal environment, which basically met the specified environmental reduction factor CE (0.85) given in ACI 440.2R-08. The improved durability of fibre/epoxy interface was also evidenced by the moisture absorption and desorption tests and scanning electron microscopy (SEM). In addition, the dynamic mechanical thermal analysis (DMTA) was directly used to characterize the degradation of interface adhesion for CFRP, and the damping at fibre/epoxy interface (tan δin) was evaluated and finally linked with the ILSS results.