Effect of Exposure Time to UV Radiation on Mechanical Properties of Glass/Epoxy Composites

Abstract

Glass Fiber Reinforced Polymer (GFRP) is commonly used in outdoor applications that expose it to environmental conditions capable of degrading its properties, notably ultraviolet (UV) radiation. In this study, we subjected GFRP to UV radiation for a duration of up to 180 days in an accelerated aging chamber. The composites underwent mechanical testing through tensile and flexural evaluations, while chemical and physical changes in the composite were assessed using Fourier-Transform Infrared Spectroscopy, Thermogravimetric analysis, and optical microscopy. Tensile tests revealed a noticeable reduction in GFRP strength after just one month of UV exposure, with a decrease of 18.7% observed at 90 days of exposure. In contrast, the behavior of the composite under flexural testing showed an initial improvement in strength after 30 days of UV exposure, with a significant increase of 54.1%. With longer exposure times, flexural strength gradually decreased but remained 18.9% higher than the strength of the unaged composite after 180 days of UV exposure. Other characterizations indicated material degradation, marked by phenomena such as photo-oxidation, composite yellowing, and the appearance of microcracks on the surface. These factors collectively contribute to the reduction in composite strength. Despite the visible degradation, the aged composite may exhibit improvements attributed to post-curing. However, over more extended periods, it may experience a decline in mechanical properties. Consequently, longer degradation times may unveil a behavior pattern distinct from what is observed during shorter periods, contingent upon the specific mechanical load under consideration.