Experimental investigations on the moisture absorption and mechanical behaviour of basalt-aramid/epoxy hybrid interply composites under different ageing environments

The structural components made of polymer composites in aviation, automobile, and marine applications are subjected to various environmental conditions throughout their design service life. Furthermore, the examination of the effect of various ageing environments on moisture absorption and mechanical behaviour is essential to protect the structures from premature and catastrophic failures. This study evaluates the influence of three different ageing conditions, namely, ambient (25°C), sub-zero (−10°C), and humid (40°C and 60% relative humidity) on the mechanical properties of hybrid interply basalt-aramid/epoxy composites. The compression molding process was adopted to fabricate the specimens and the specimens were aged in a distilled water environment for a period of 180 days. The aged specimens were subjected to static and dynamic mechanical tests viz. tensile, flexural (3-point bending), short-beam shear (SBS), and Charpy impact tests to study the behaviour, and then results were compared with the unaged specimens. Fourier Transform Infrared Spectroscopy (FTIR) was also performed to analyze the chemical changes within the composites due to the ageing process. It was witnessed that moisture absorption rate increases with - increase in ageing period and attains a state of saturation between 1.8% and 5.44% depending on the ageing conditions. Investigations revealed that moisture absorption has an unfavourable effect on the mechanical performance of the composites. The retention of mechanical strengths of aged composites is in the order of Unaged > Sub-zero > Humid > Ambient. Fractured tensile specimens were analyzed for microscopic observation using Scanning Electron Microscope (SEM) to study the damage morphology. Matrix decomposition, matrix cracks, and interfacial debonding were the major failure modes observed in aged composites.