Small hole drilling behaviour and damage optimization in additively manufactured Kevlar fiber reinforced polymer laminates

This study investigates the small-hole drilling behaviour of additively manufactured hybrid Kevlar fiber reinforced polymer (KFRP) laminates, addressing the critical challenge of drilling-induced damage in advanced composite structures, and introduces an integrated experimental-MCDM framework for robust optimization of drilling parameters. KFRPs are gaining importance in aerospace and automotive sectors due to their exceptional toughness, impact resistance, and low weight. However, drilling these composites remains challenging because of excessive thrust, torque variation, fiber pullout, and delamination, which compromise hole integrity. The experiments were conducted on 3D-printed laminates fabricated using Fused deposition modelling (FDM), considering drill diameter (1.0–1.6 mm), spindle speed (2000–3000 rpm), and feed rate (0.01–0.03 mm/rev). Results revealed that thrust force increased notably with drill diameter (17.02–49.96 N), while torque peaked at 1.3 mm due to complex fiber-tool interactions. Delamination emerged as the predominant damage, intensifying with higher feed rates. To achieve optimal drilling conditions, Multi-Criteria Decision-Making (MCDM) techniques TOPSIS, COCOSO, and MOORA were employed. All methods converged on the 1.3 mm drill, 3000 rpm spindle speed, and 0.01 mm/rev feed rate as the optimal parameters, minimizing thrust (13.303 N), torque (0.09 Nm), and delamination (Fd = 1.154). Sensitivity analysis validated the robustness of these results, highlighting delamination weighted scenarios favouring the 1.6 mm drill. The study uniquely integrates experimental analysis with MCDM optimization, establishing a systematic framework for precision drilling of additively manufactured KFRPs. The proposed framework provides a practical decision-support tool for selecting drilling parameters in hybrid composite machining, with direct relevance to precision manufacturing applications.