Analysis of Machining Parameters Influencing Thrust Force in Drilling of Carbon Dot Nanoparticle-Reinforced Epoxy Matrix Composites

Epoxy matrix composites reinforced with carbon dot nanoparticles are increasingly utilized in industries due to their enhanced mechanical, thermal, and electrical properties. Drilling, a critical machining process for assembling these composites, often induces defects such as delamination and stress concentration, impacting structural integrity. This study systematically investigates the influence of machining parameters—spindle speed, feed rate, and drill bit diameter—on the thrust force during drilling of carbon dot-reinforced epoxy composites. A full factorial design of experiments was employed, with thrust forces measured using a high-precision load cell. Statistical analysis, conducted via Minitab software, revealed that drill bit diameter is the dominant factor, contributing 66.18% to thrust force variation, followed by spindle speed (19.90%) and feed rate (7.16%). The regression model, with an R-squared value of 98.90%, highlights significant linear and nonlinear interactions among parameters. Increasing feed rate and tool diameter markedly elevate drilling forces, while higher spindle speeds slightly reduce them. The incorporation of carbon dots up to 1 wt.% reduces thrust force by enhancing interfacial bonding, though excessive concentrations may induce embrittlement. Optimization results identify the ideal settings as spindle speed at 2500 rpm, feed rate at 10 mm/min, drill bit diameter at 0.3 mm, and carbon dot concentration at 1 wt.%, achieving a minimal thrust force.