Examining the impact of moisture on the mechanical and vibrational characteristics of quasi isotropic kevlar-basalt/epoxy hybrid composites

This research explores the effects of moisture absorption on the mechanical and vibrational performance of Kevlar-basalt/epoxy laminates, which are significant for their strength-to-weight ratio yet susceptible to hygrothermal aging. The quasi-isotropic orientation of [0°/45°/90°/45°/0°] was selected with three Kevlar (0° and 90° orientation) and two basalt (45° orientation) layers. The fabricated laminates were subjected to ageing environments viz., ambient temperature ageing (ATA) and cold temperature ageing (CTA) by immersing in water for a period of six months. The specimens saturated with moisture were analyzed for mechanical and vibrational tests such as tensile, 3-point bending, Charpy impact and impact hammer tests to understand the post ageing behavior of the laminates. ATA and CTA specimens absorbed 4.52% and 3.21% moisture, respectively at saturation. ATA specimens experienced the largest tensile strength reduction of 28.64%, while CTA specimens declined by 14.84%. Flexural strengths decreased by 17.52% for ATA and 7.66% for CTA. CTA specimens retained the highest impact strength at 80.39%, followed by ATA at 75.44%. Increased moisture content led to a higher damping ratio and lower natural frequency, with ATA specimens showing more matrix deterioration, fiber-matrix interface weakening, and delamination than CTA specimens.