Optimizing high-speed micro drilling parameters for CFRP/Graphene composites: Response surface methodology and sobol sensitivity approach

Abstract

Carbon fiber reinforced polymer (CFRP) laminates, when enhanced with graphene nanoplatelets, exhibit superior stiffness, strength-to-weight ratio, and thermal conductivity, making them attractive for aerospace applications. However, in high-speed micro-drilling, the presence of graphene also alters tribological behavior, increases abrasiveness, and modifies thermal transport, intensifying the risks of delamination, matrix degradation, and tool wear. This work develops an integrated experimental–statistical framework that couples Response Surface Methodology (RSM) with variance-based Sobol global sensitivity analysis and a Desirability Function Approach (DFA) to systematically optimize spindle speed, feed rate, drill diameter, and graphene content. Sobol analysis distinguished feed rate (52.2%) and drill diameter (46.7%) as the principal determinants of thermal loading, while spindle speed governed thrust generation (80.4%), entry delamination (95.7%), and exit delamination (60.7%). Multi-objective optimization yielded an operating window (18000 rpm, 25.35 mm/min feed, 0.40 mm drill diameter, neat CFRP) that simultaneously reduced peak drilling temperature by 18%, cutting force by 22%, and delamination damage at entry and exit by 27% and 21%, respectively. These improvements are mechanistically attributed to the minimization of interlaminar shear stresses, controlled heat flux at the tool–workpiece interface, and improved chip evacuation dynamics at the optimal parameter combination. Beyond statistical modeling, this study establishes a predictive–diagnostic methodology capable of guiding industrial high-speed micro-drilling operations toward balanced thermal–mechanical performance in nano-reinforced composite systems.