The Effect of Ultraviolet Light on Mechanical Properties of Kevlar 49 Composites

The relationship betwen specimen thickness and tensile strength in Kevlar 49 composites following exposure to ultraviolet light is investigated. Specimens of 0.13, 0.25, and 0.50 mm thickness molded from one, two, and four layers of Fiberdux 914k-49-5 prepreg are exposed to ultraviolet light in a Spectrotest apparatus, which has a low pressure xenon burner with a spectral range of 0.29-0.60 microns, for 500 and 1000 hours. The tensile stiffness and tensile strength data reveal that the ultraviolet light caused a decrease in the tensile strength and tensile retention of the 0.13 mm (1 ply) specimen; however, the 0.25 mm (2 plies) and 0.50 mm (4 plies) specimens, and the initial tensile elastic modulus for each specimen are unaffected by the exposure.