Experimental Investigation and Multi-Objective Optimization of Mechanical, Thermal, and Tribological Properties of Fly Ash and Carbon Fiber Reinforced Epoxy Hybrid Composites

Abstract

Hybrid polymer composites reinforced with industrial waste materials and high-performance fibers have emerged as promising candidates for lightweight structural applications due to their enhanced mechanical performance, improved wear resistance, and sustainable material utilization. This study investigates the influence of fly ash (FA) and short carbon fiber (CF) reinforcement on the mechanical, thermal, and tribological behavior of epoxy composites. Composite laminates containing varying fly ash contents (0–12 wt.%) and carbon fiber contents (0–10 wt.%) were fabricated using the hand lay-up technique followed by compression molding to minimize void formation and improve interfacial bonding. Tensile, flexural, compressive, hardness, impact, and wear tests were conducted according to ASTM standards. Thermal stability was evaluated using thermogravimetric analysis (TGA), while fracture morphology was analyzed using scanning electron microscopy (SEM). Multi-objective optimization based on the Taguchi method and Grey Relational Analysis (GRA) was employed to determine the optimal reinforcement combination. The illustrative results indicate that the hybrid composite containing intermediate fly ash and carbon fiber contents provides the most balanced mechanical and tribological performance. The tensile strength, flexural strength, and wear resistance show considerable improvement compared with the neat epoxy system, whereas excessive fly ash loading results in particle agglomeration and localized stress concentration. SEM observations reveal improved matrix–reinforcement adhesion and reduced fiber pull-out in the optimized composite. These findings demonstrate the potential of fly ash/carbon fiber reinforced epoxy composites for lightweight automotive, aerospace, and engineering applications while promoting sustainable utilization of industrial waste.