Experimental investigation on fly ash particulate reinforcement for property enhancement of PU foam core FRP sandwich composites

Abstract Low-cost industrial byproduct fly ash (FA) particulates were used as reinforcement to improve the mechanical performance of Polyurethane (PU) foam core and PU based laminated sandwich composites. PU foam core specimens were prepared with 5–20 wt % variation of FA fillers with surface treatment using silane solution. Surface treated core specimens were found to exhibit higher shear strength than untreated specimens due to superior interface adhesion properties and uniform distribution of particles. Two different face sheet-core combination sandwiched composite specimens were designed using woven fabric glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) face sheet with surface treated PU foam core. Since shear and bending being the predominant modes of failures in sandwiched composite structures, accordingly shear and three-point bending tests were conducted as per ASTM standard. Enhanced stiffness and up to 39% increase in shear modulus was observed for FA reinforced PU foam (FA-PUF) core than the neat PU core due to a synergistic effect of interfacial bonding between FA and polymer. SEM images explained the enhanced particle dispersion and strut characteristics. With an optimized FA reinforcement, the mechanical performance of the sandwiched composites was found to improve significantly as evidenced from the flexural and shear test diagrams.