Longitudinal-Torsional Ultrasonic Vibration Milling of Carbon Fiber Reinforced Epoxy Resin Compound Material: Experimental Investigation and Damage Suppression Mechanisms

Abstract

Carbon fiber reinforced epoxy resin (CF/EP) composite material is widely used in aerospace for their high strength and light weight, but low interfacial bond strength poses secondary processing challenges. Although ultrasonic vibration machining is feasible, the influence of ultrasonic process parameters on the machining effectiveness of CF/EP composite material remains poorly understood. This study employs ultrasonic vibration-assisted milling to compare conventional milling (CM), longitudinal ultrasonic vibration milling (LUVM), and longitudinal-torsional ultrasonic vibration milling (LTUVM). Variations in milling force, processing temperature, top and bottom surface edge damage, and surface morphology are analyzed. The damage suppression mechanisms under LTUVM are investigated, including fiber–resin interface stress, fiber fracture modes, and thermo-mechanical coupling with multidirectional vibration effects on edge damage. Results show all ultrasonic-assisted conditions outperform CM. LTUVM reduces milling force and temperature by up to 23% and 18% compared to LUVM, effectively minimizing warpage, burr, and tear. Surface defects are significantly suppressed, with much lower roughness than the other two conditions. This research explores the mechanisms of damage suppression under LTUVM, providing a basis for high-quality machining of carbon fiber-reinforced polymer composites.