Study on burr occurrence and surface integrity during slot milling of multidirectional and plain woven CFRPs

Abstract

Machining carbon fiber reinforced composite (CFRP) is often accompanied with cutting edge defects and surface damage including interlayer delamination, cavities and debonding of fiber-matrix. A detailed understanding of the effect of fiber configuration and cutting parameters on cutting force, burr occurrence/formation and surface integrity is necessary. In this paper, experimental data is presented relating to fiber burrs on entry surface, cutting force, surface roughness and workpiece integrity when slot milling CFRP laminates with varying fiber configurations (0°/90°, 45°/135° and plain woven) at different cutting speed (60 and 120 m/min) and feed rate (0.05 and 0.1 mm/rev). Lateral cutting force is recorded down to 56 N and highly dependent on fiber orientation. The length (up to ~ 5.6 mm) and amount of fiber burrs are highly related to fiber orientation and fiber cutting angle. Surface roughness Ra down to ~ 1.4 μm was recorded when milling type 2 (45°/135°) and type 3 (plain woven) laminates. Various surface defects predominantly occurred due to different cutting conditions and fiber configurations, which are mainly located in the layers with fibers orientated at 45°/135°. The occurrence and propagation of fiber burrs and surface cavities were also investigated based on different fiber fracture mechanisms.