Durability study of quasi-isotropic carbon/epoxy composites under various environmental conditions

Fibre-reinforced polymer (FRP) composites are gaining more attention for civil, automobile, aircraft and marine applications due to their excellent properties. The present work investigated the effect of ageing on mechanical properties of the autoclave-cured quasi-isotropic carbon/epoxy prepreg composites. The specimens were aged at artificial seawater under ambient, sub-zero (- 15 degrees C), and humid conditions (70% RH. and 40 degrees C) for 12 months. The tensile, flexural and impact properties were determined at regular intervals. The gravimetric study revealed that moisture absorption behaviour depended on the medium and duration of ageing condition. The moisture absorption for the quasi-isotropic carbon/epoxy composite specimens followed a non-fickian distribution. The moisture absorption of the carbon/epoxy composite laminate specimens showed an adverse effect on their mechanical properties. The moisture absorption results revealed that composite specimens aged under ambient condition absorbed more moisture compared with sub-zero and humid conditions. It was evident from the results that there was a 36.06% reduction in tensile properties of the composite specimens aged under ambient condition in comparison with pristine specimens. In contrast, the flexural properties were affected largely at sub-zero condition, and the impact properties were largely degraded at humid condition. The failure surface morphology revealed that matrix cracking and inner fibre debonding were the major causes of degradation in mechanical properties. [GRAPHICS] .