Investigation of drilling cf/peek thermoplastic composites with varying helix angle drills and optimization of cutting parameters

Abstract

Drilling of carbon fiber-reinforced polyetheretherketone (CF/PEEK) composites poses challenges such as matrix smearing, burr formation, surface roughness, and delamination due to their thermoplastic properties. This study investigates damage mechanisms during CF/PEEK drilling using carbide drills with helix angles of 20 degrees, 30 degrees, and 40 degrees, and evaluates the influence of machining parameters. The effects of helix angle, cutting speed, and feed rate on thrust force, surface roughness, and delamination factor were analyzed through a full factorial experimental design. Process parameters were optimized using a Taguchi L27 orthogonal array. Findings revealed the lowest thrust force with a 30 degrees helix angle drill at 15 m/min cutting speed and 0.05 mm/rev feed rate. The minimum delamination factor was achieved with a 40 degrees helix angle drill at 15 m/min and 0.075 mm/rev. The lowest surface roughness was observed with a 20 degrees helix angle drill at 15 m/min and 0.05 mm/rev. Optimization, supported by signal-to-noise ratios, confirmed superior hole quality at lower speeds. ANOVA identified the most influential parameters for each response. This pioneering study highlights the critical role of varying helix angle drills in surface roughness, delamination, and cutting forces, offering novel insights into machining thermoplastic composites.