Exploring milling behavior of carbon–Kevlar hybrid composites: Role of cutting direction and matrix

Carbon–Kevlar hybrid composites are widely used in aerospace, automotive, and defense applications because of their balanced stiffness, toughness, and impact resistance. However, their heterogeneous architecture creates significant challenges during machining. Although the influence of matrix type and fiber orientation on machining has been individually studied, the combined effect of cutting direction and matrix system during milling of carbon–Kevlar hybrid composites has not been systematically investigated. Therefore, this study investigates the milling behavior of thermoplastic polypropylene-based (CKFPP) and thermosetting epoxy-based (CKFEPX) carbon–Kevlar hybrid composites under carbon-in-feed (CIF) and Kevlar-in-feed (KIF) cutting directions. Machining performance was evaluated in terms of machining temperature, machining force, delamination factor, and surface roughness. CKFPP exhibited lower average temperature, force, delamination, and surface roughness by 15.68%, 41.92%, 15.14%, and 33.42%, respectively, compared to CKFEPX. CIF direction produced better machining performance than KIF. The study provides insights into the combined role of the matrix system and cutting direction in improving machinability and surface integrity of hybrid composites.