Effect of Ultraviolet Irradiation on the Material Properties and Acoustic Emission of a Fiber-reinforced Composite

We report the effect of exposure to up to 300 h of ultraviolet (UV) irradiation on the material properties and acoustic emission (AE) of glass fiber-reinforced composite specimens. The tensile strength decreased by up to 30 % due to photodegradation, which caused extensive matrix cracking and interfacial debonding. Although a global parameter of structural health (the b-value) tended to increase with increasing exposure to UV light, it decreased after 300 h of exposure. The AE signals were more highly attenuated in the irradiated specimens, and the contribution of low-amplitude AE signals to attenuation was greater. To demonstrate the effect of attenuation, a numerical study was carried out based on frequency-dependent attenuation rates calculated from the experimental results. Simulations clarified the influence of attenuation rate on the b-value of the degraded composite.