Experimental Investigation of Laser-Assisted Ultrasonic Vibration Milling of CF/PEEK-Based CFRTP Unidirectional Laminates

Carbon fiber-reinforced polyetheretherketone is widely used in aerospace, transportation, and medical devices because of its high interlaminar and intralaminar fracture toughness, excellent mechanical properties, and long-term stability at elevated temperatures. However, its two-phase structure, consisting of brittle fibers embedded in a tough matrix, presents significant machining challenges. In this study, a two-stage laser–ultrasonic vibration-assisted milling process was investigated by combining laser-induced matrix thermal softening and decomposition with high-frequency, intermittent tool–workpiece contact. Unidirectional laminates with 0° and 90° fiber orientations were machined to systematically evaluate the effects of processing parameters on cutting force, measured surface temperature, surface roughness, and machining defects. The proposed process reduced the cutting force by 7.4–26.1%, improved surface roughness, and reduced observable machined surface defects. Appropriate laser and ultrasonic parameters were associated with lower measured surface temperatures and fewer observable fiber fracture and fiber–matrix separation features, thereby improving machined surface quality. These findings clarify the synergistic effects of laser and ultrasonic parameters and provide a basis for process optimization and high-quality machining of carbon fiber-reinforced polyetheretherketone composites.