Investigation of delamination during drilling of glass fiber reinforced composite materials used in defense industry

This study addresses the critical challenge of drilling-induced delamination in thick Glass Fiber Reinforced Polymer (GFRP) composites, a defect that compromises structural integrity, increases manufacturing waste, and poses significant risks in critical applications. The study holds particular importance for defense systems, where GFRP composites are extensively employed in ballistic protection components such as spall liners for armored vehicles and naval vessels. Delamination in these applications directly weakens crew survivability by reducing impact resistance and fragment containment capabilities. While existing studies focus on thin laminates and conventional cutting speeds, industrial and defense demands increasingly require high-speed machining of thicker composites to meet stringent performance and reliability standards. This work investigates the effects of cutting speed (500–7500 Rpm), feed rate (200–460 µm/rev), and drill diameter (6, 8, 10 mm) on peel-up and push-out delamination in 10 mm-thick GFRP laminates. Using the Taguchi method, optimal parameters to minimize delamination were identified. Results demonstrate that cutting speed dominates delamination effect, with higher speeds reducing thermal degradation and thrust forces. Lower feed rates mitigate interlaminar separation, while larger drill diameters reduce push-out damage compared to 6 mm tools. Optimal parameters reduce delamination and production reject rates. The study bridges theoretical and industrial gaps, advancing sustainable manufacturing through reduced material waste and enabling precision machining for aerospace, marine, and defense industry.