Experimental Investigation of Contact Stress and Wear Behaviour of Nylon 66/Al₂O₃/WS₂/TiO₂ Hybrid Composite Spur Gears

It is widely known that polymer-based gears are applied in numerous light and low-noise mechanical systems, and their load capacity and wear resistance are limiting for performance critical applications. The current work aims to fabricate and analyze hybrid Nylon 66 (PA66) composites fortified with aluminium oxide (Al₂O₃), tungsten disulfide (WS₂), and titanium dioxide (TiO₂) as candidate gear materials. There were five composite formulations (NTAS 1–5) which were prepared via injection moulding with systematically varying filler ratios. The hardness, tensile strength, flexural strength, impact resistance and dry sliding tribological behavior characteristics of each formulation were also reported. Failure mechanisms were studied using scanning electron microscopy (SEM) to examine fracture and worn-surface morphologies. NTAS 3 showed the best overall performance by all the formulations, where it obtained a Vickers hardness of 78 HV, tensile strength of 66 MPa, flexural strength of 56 MPa, the lowest friction coefficient and the lowest wear rate. From the aforementioned results, the spur gears were developed by NTAS 3 using vertical injection moulding with a custom EN8 steel die. Finite element analysis conducted in ANSYS Workbench confirmed that, under identical loading conditions, the hybrid composite gear exhibited notably lower contact stress than unreinforced Nylon 66 gears. The simulations were experimentally verified on a universal gear test rig with strain-gauge instrumentation, confirming that the strain was reduced by 44% compared to the base-material gear. Accordingly, the NTAS 3 composite has demonstrated good overall performance for moderate-load engineering applications for lightweight and wear-resistance oriented gear application.