Combined hygrothermal aging and mechanical loading effect on unidirectional glass/epoxy composites

Composites are subjected to different use conditions. Hence, the mechanical properties under different aging conditions are crucial in the composite field. This study aims to investigate the aging effect of a glass/epoxy unidirectional composite in three distinct conditions: mechanical, hygrothermal (hot water), and combined (mechanical and hygrothermal) aging. The composites in the longitudinal [0°] and transversal [90°] directions were molded by RTM with a 37% volume fraction. The aging effects on tensile, compressive, shear, short-beam properties, and dynamic-mechanical characteristics, in 0° and 90° fiber direction, were studied. The aging conditions are affected differently, depending on the property analyzed. Comparing aged and non-aged composites, the tensile (from 380 GPa to 140 GPa and from 80 GPa to 40 GPa for non-aged and combined aging in 0° and 90° directions, respectively) and compressive strength (from 250 MPa to 50 MPa and from 100 MPa to 25 MPa for non-aged and combined aging in 0° and 90° directions, respectively) showed greater relative drop than the elastic modulus (a decrease of 3–4 GPa for all aging analyzed compared to the no-aged composites) due to a deleterious effect on the interface and the chemical aging present in the polymeric matrix attenuates the deleterious effect on it. Besides, the properties measured in the 0° direction were more affected than in the 90° direction with the combined aging the most affected property.