Impact of fiber orientation on cutting forces and surface quality in flax/epoxy composite machining

Flax/epoxy composites are recognized as an eco-friendly alternative to synthetic fibers in engineering. Understanding how fiber orientation affects cutting forces and surface characteristics is essential for machining these materials. This study investigates the relationship between fiber orientation and cutting forces (feed, normal, passive) as well as surface roughness in flax/epoxy composites. Results show that fiber orientation significantly impacts cutting forces. Cutting parallel to fibers (0° and 90° orientations) generally requires less force, with 0° needing higher normal force. At 0° orientation, feed force is 46.47 N, normal force is 58.86 N, and passive force is 54.44 N. At 90° orientation, feed force is 56.66 N, normal force is 44.68 N, and passive force is 50.95 N. Oblique orientations (45° and −45°) require higher forces, especially 45°, with the highest normal force of 77.95 N. Surface roughness analysis shows 90° orientation results in the lowest average roughness (Ra) of 10.97 µm but the highest surface roughness (Sa) of 34.25 µm. Conversely, 45° orientation has the highest Ra of 14.2 µm but lower Sa of 22.6 µm. Ra and Sa values for 0° orientation are 13.72 µm and 24.6 µm, and for −45° orientation, they are 12.3 µm and 21.8 µm. Correlation analysis reveals significant relationships between cutting parameters and surface quality, with higher feed rates correlating with smoother surfaces (lower Sa and Ra values). Fiber orientation also significantly influences fluffing defects, with 0° orientation minimizing these defects, while 45° and −45° orientations result in varied patterns.