The present article deals with monitoring the changes in the mechanical properties of composites with polymer matrix. The composite was formed from the PA matrix and glass fibers. The composite contains 10 – 30 % glass fibers. The mechanical properties, tensile strength and flexural strength were evaluated on samples of the composite before and after UV radiation on the sample. The largest decline endpoints was recorded in 500 hours of UV exposure. Light microscopy was evaluated distribution of glass fibers in the polymer matrix and the presence of cracks caused by UV radiation.