Accelerated environmental ageing study of polyester/glass fiber reinforced composites (GFRPCs)

The failure of polymer matrix composites upon exposure to the environment has been assessed in the present study. In order to investigate the combined action of temperature, humidity and UV radiation on polymers and composites, an environmental ageing chamber has been constructed and tested. The accelerated environmental ageing was based on two kinds of alternating cycles, which provided humidity, temperature and ultraviolet radiation. The materials examined were isophthalic polyester and isophthalic polyester reinforced with a glass fiber random mat onto which glass fibers were knitted at 0°/90° (GFRPC) at a total volume fraction of approximately 20%. Dynamic mechanical analysis, for a range of temperatures and frequencies under tensile and three-point bending loadings, revealed that the aged materials gained in stiffness, whereas a small deterioration in strength was found. Scanning electron microscopy studies performed before and after environmental chamber conditioning revealed that some microcracks had occurred on the surface of the specimens. Nevertheless, the length of these microcracks was less than the critical value of 0.1 mm, required for crack propagation.