Cutting force suppression and surface integrity in longitudinal torsional ultrasonic vibration cutting of aramid paper honeycomb core for sandwich structures

As a key lightweight structural material in the aerospace field, aramid paper honeycomb cores are prone to tearing and crushing damage during conventional machining processes. This study investigates the optimization mechanisms of Longitudinal-Torsional Ultrasonic Vibration (LTUV)-assisted cutting on the machinability of this material. Utilizing a self-developed LTUV system and employing a full factorial experimental design combined with analysis of variance, the influences of vibration amplitude, spindle speed, and feed rate on cut-ting forces and surface morphology were systematically quantified. The results indicate that spindle speed (partial η² = 0.825) and vibration amplitude (partial η² = 0.801) are the most significant factors affecting cut-ting force. Under the optimal parameter combination (amplitude: 3.2 μm, feed rate: 200 mm/min, spindle speed: 2700 rpm), LTUV reduced the cutting force by approximately 40% compared to conventional machining. Sur-face morphology analysis reveals that LTUV promotes brittle fracture of the material through the periodic tool-workpiece separation effect, leading to significantly improved uniformity of burr size, substantial sup-pression of aramid fluff residue, and effective mitigation of node crushing. However, excessively high amplitude was found to degrade surface quality. This study establishes a process optimization window characterized by “moderate amplitude, low feed rate, and high spindle speed,” and elucidates the mechanism by which LTUV synergistically reduces machining-induced damage through friction reversal and strain rate strengthening effects. The findings provide a reliable process basis for manufacturing high-integrity cores, which is a prerequisite for fabricating high-performance aerospace sandwich structures with superior bonding quality.