Mechanical behaviour of an epoxy-glass composite under photo-oxidation

Abstract

In previous papers the photo-degradation of an epoxy resin (DGEBA) cross-linked with the hardener methyltetrahydrophthalic anhydride (MTHPA) in a tubular stratified glass-epoxy composite has been studied. The photo-chemical evolution was analysed by FT-IR spectrophotometry with attenuated total reflection (ATR) and by X-ray analysis. The analyses confirm the presence of a thin photo-oxidation layer at the surface of the material, which was shown by measurement of the organic matrix's ablation. After the establishment period, the layer and the ablation of the organic matrix evolve spatially at a constant rate. Despite an ablation of about 15–30 μm of the organic matrix, stress tests made on the samples artificially photo-aged for 1000 h or naturally for 2 years did not show any weakening in the material. This proves that photochemical degradation is superficial. For that reason, we designed a tension device that can function inside the artificial photo-ageing cell. Nevertheless, we wanted to verify if the combined action of mechanical stress, photo-oxidative constraints and temperature provoke a weakening in the material by synergy. We show that the effect of the mechanical stress can be analysed on a time scale significantly inferior to that of the physico-chemical stress.