The effect of hygrothermal aging and UV radiation on the low-velocity impact behavior of the glass fiber-reinforced epoxy composites

The present work examines the effects of hygrothermal and UV radiation aging on the reinforced epoxy composites. The role of temperature in the hygrothermal aging process on tensile properties, impact behavior of composites and compression-after impact was investigated. Among four different chosen aging conditions, three of them were hygrothermal and last one was composed of both hygrothermal and UV radiation. Unidirectional e-glass fiber fabrics with an areal density 300 g/m2 as reinforcement and epoxy matrix were used. Composites were manufactured using vacuum-assisted resin infusion molding. The goal of this study was to investigate the effect of UV radiation and aging temperature with respect to the glass transition temperature. In this context, aging procedures were carried out in two different ways for 70 °C temperature with and without UV radiation. As a result of the test, the tensile strength, tensile modulus, absorbed energy, interlaminar shear strength (ILSS), and compression-after impact (CAI) strength of the glass reinforced composites decreased for all conditions. Despite being under the same ambient temperature and humidity, the samples which were exposed to UV radiation had lower mechanical properties. The reduction of tensile strength of specimens exposed to 70 °C and 70% humidity with and without UV radiation were 24% and 10%, respectively. The temperature of hygrothermal conditions significantly affected the perforation threshold. In low impact energies, delamination was the primary damage mode, while fiber breakage becomes more important in the composite at high impact energy levels.