Hydrothermal aging effect on the tensile properties of hybrid aramid/glass/epoxy composites: Comparison of distilled water and seawater

This paper evaluated the effect of water adsorption on the tensile characteristics of hybrid aramid/glass/epoxy composites. The composite samples ([G(6)](S), [A(6)](S), [G(3)A(3)](S), [A(3)G(3)](S) immersed in hydrothermal aging conditions (distilled water at 25 degrees C, distilled water at 70 degrees C, seawater at 25 degrees C, seawater at 70 degrees C) for 1000 h. The kinetic diffusion parameters of hybrid and plain specimens were evaluated experimentally and theoretically. Further, the effects of the stacking sequence of fabrics, seawater/distilled water aging, and temperature on the tensile behavior of dry, wet, and re-dried specimens were systematically discussed. At the end of the test, SEM images were obtained from the surfaces of the broken samples. Water gain plots for various conditions displayed that the samples absorbed more water when the aramid fabrics were on the outer surface of the hybrid composites. The hydrothermal aging significantly decreased the tensile strength of hybrid aramid/glass/epoxy and plain glass/epoxy composites. The tensile strength decrease rate of samples immersed in distilled water was higher than in seawater. Besides, the re-drying process induced more tensile strength degradation for both water types. SEM results showed that delaminations increased with aging and increasing temperature.