A Comprehensive Review on Non-conventional Mechanical Machining of Carbon Fiber-Reinforced Composites

Carbon fiber-reinforced polymer (CFRP) composites are increasingly employed in aerospace and automotive structures, yet their anisotropy and poor thermal conductivity make conventional machining prone to severe defects such as delamination, matrix cracking, and tool wear. This review provides a comprehensive analysis of non-conventional mechanical (NCM) machining processes, particularly abrasive waterjet machining (AWJM) and rotary ultrasonic machining (RUM), focusing on their mechanisms, parameter effects, modeling approaches, and optimization strategies. Comparative evaluation shows that optimized AWJM parameters (water pressure 300–380 MPa, traverse speed ≤ 1 mm/s, standoff distance 1–2 mm) can reduce kerf taper by 25–35%, surface roughness by 30–45%, and delamination by up to 40% relative to unoptimized settings. RUM, through the integration of ultrasonic vibration, achieves 60–90% lower thrust forces, 20–40% longer tool life, and 50% lower burr formation compared with conventional drilling. Finite element, CFD–FEA coupled, and SPH-based simulations have been instrumental in elucidating the dynamic interactions of abrasives and fiber–matrix interfaces, enabling predictive control of damage evolution. Recent developments in hybrid approaches, such as synchronized abrasive jets, multi-pass cutting, and longitudinal–torsional ultrasonic modes, further enhance process stability and precision. Future research should focus on AI-driven predictive modeling and multi-objective optimization and sustainable coolant and abrasive recycling systems, thereby advancing high-quality, damage-controlled machining of CFRP composites.