Factors influencing machining quality of carbon and glass fiber epoxy composites: a comprehensive review

Purpose This review provides a comprehensive assessment of the machining challenges associated with carbon fiber reinforced polymers (CFRP) and glass fiber reinforced polymers (GFRP) composites, which are widely used in high-performance structural applications due to their excellent strength-to-weight ratio, corrosion resistance and the ability to be tailored in specific ways. Nevertheless, their multilayered and anisotropic nature adds considerable complexity to the machining process, often leading to defects. This paper aims to give key insight into machining issues, focusing on parameter-response relationships that govern surface quality and defect formation. Design/methodology/approach The literature survey covered a broad range of machining methods, including conventional machining methods such as CNC drilling and milling, as well as nonconventional methods such as abrasive waterjet machining, ultrasonic machining and laser cutting. For the traditional methods, the influences of feed rate, cutting speed, depth of cut, tool geometry, tool material and coolant use were studied. In nonconventional machining, several crucial factors, including jet pressure, abrasive characteristics, laser power and thermal interaction, were taken into account. Specific attention was given to machining-induced defects, i.e. delamination, fiber pull-out and matrix cracking, tool wear, kerf taper, heat-affected zones and surface degradation because they depend on the process parameters and identify potential damage-reduction methods. Findings The machining behavior of CFRP/GFRP composites depends strongly on tool geometry, thermal load and parameter selection. Optimized drilling parameters, such as 70–90 m/min cutting speed, 0.01–0.05 mm/rev feed rate, multifacet carbide/polycrystalline diamond coated drill bit with 45-degree helix angle, can minimize thrust force, delamination, fiber pull-out and other machining flaws. The milling operation with 100–200 m/min cutting speed for carbide tool, 0.02–0.1 mm/rev feed rate and 0.1–1.0 mm depth of cut controls machining damage like fiber fraying, delamination and also increases machining efficiency. Abrasive water jet machining (AWJM) has a high success rate in cutting carbon and glass-epoxy composites. AWJM performs effectively at 200–350 MPa pressure, 1–3 mm stand-off distance, 80–120 mesh garnet abrasive particles and 200 mm/min cutting speed, yielding low kerf taper and minimal fiber breakout. Ultrasonic machine achieves precise material removal with 20–40 kHz frequency, 5–15 µm amplitude, 0.1–0.3 MPa pressure, 0.1–0.5 mm/min feed rate and 5–10 L/min slurry flow provides minimal subsurface damage in composite laminate. Laser machining provides precision, noncontact ablation using 50–300 W power, 20–50 kHz frequency, 10–50 ns pulses and inert assist gases, effectively constraining HAZ formation and preserving fiber–matrix integrity. Better parameter selection, including adaptive solutions and combined machining strategies, can prolong tool life, reduce defects and improve surface integrity. Originality/value This paper presents a critical and consolidated study of machining techniques for CFRP and GFRP composite materials, suggesting parameters that can serve as a bridge between conventional and nonconventional machining methods. These results can be used to establish defect-mitigation techniques, improve machinability and inform future research in manufacturing composites.