Composites were fabricated by using glass fabric as the reinforcement and polyester as the matrix with the vacuum assisted resin infusion technique. Specimens were radiated by a Model SJD-1 ultraviolet lamp with various durations. The bending behavior, tensile strength, and the elongation at break of the UV radiated and unradiated composite panels were tested. The deteriorated mechanical properties of treated specimens were noticed. Usually, the bending strength would gradually decrease with prolonged UV radiation. The same trend was also seen for the tensile intensity of the samples. The corrosion process of the polymer caused by the oxygen in the atom state would be accelerated by the presentation of the UV ray, resulting in a serious damage on the material.