The prime importance of this work is that to compare the influence of hygrothermal analysis on the physical properties of different variant of interpenetrating polymer network (IPN) blend reinforced with E-Glass/Carbon and combination of both (hybrid) fibers. In this study, combinations of epoxy (EP)/polyurethane (PU), vinyl ester (VER)/polyurethane (PU), and epoxy (EP)/vinyl ester (VER) have been taken as the matrix material (IPN) to reinforce the glass, carbon, and combination of both fibers. Moreover, prepared specimens are subjected with boiling water immersion test by maintaining the temperature of 45°C, 55°C, and 65°C in order to thoroughly understand the influence of moisture absorption and temperature in their physical attribution as per ASTM standards. Besides, to better understand the thermal stability and compatibility, thermal-gravimetric (TGA) analysis and burn-off test were conducted as well. During this study, it was found that, combination of VER/PU possesses the high moisture absorption resistance amongst all variants (0.725% for 45°C, 0.854% for 55°C, 1.234 for 65°C). Similarly, epoxy/vinyl ester reinforced glass fiber IPN laminate (EVG) has shown notable TGA value as 418.6°C, as well burn-off test also shown that hybrid IPN composites have better wettability (less void presence) than all other laminates (EPGC-0.9%, VPGC-0.89%, EVGC-0.92%). Further, losses of physical strengths have been noticed on all specimens upon subjection on hygrothermal environment irrespective of IPN blend and fiber constituents.

Conventional steel springs have gradually been replaced with composite materials due to their inherit properties like high strength-to-weight ratio, relatively inexpensive ratio, and resistance against corrosion. Also, fiberglass reinforced plastic usages and its implementation is subjected in variety of fields such as vehicle and locomotive bogies, heavy commercial vehicles like vans and trucks. The current study looks at a composite material that can be used in the composite leaf spring suspension system. In this particular research, several blends of interpenetrating polymer networks (IPNs) have been used as the matrix material with the reinforcement of E-Glass fiber. The implemented combination blends are epoxy with polyurethane (EP), vinyl ester with polyurethane (VP) and epoxy and vinyl ester (EV). However, this research work also examines the characterisation and physical properties of the composite material leaf spring (CMLS) in narrow manner. Consecutively, tests were carried out for three types of composites by varying the various blend ratios of IPNs with the standard reinforcement of E-Glass fiber. Besides, to evaluate and compare their individual uniqueness, their physical characteristics tests like compression test, hardness test, tension and cyclic load parameters are found and their corresponding results were compared with each other.