Machinability of natural-fibre-reinforced polymer composites: conventional vs ultrasonically-assisted machining

Natural-fibre-reinforced polymer (NFRP) composites are becoming a viable alternative to synthetic fibre based composites in many industrial applications. Machining is often necessary to facilitate assembly of parts in a final product. This study focuses on a comparative experimental analysis of the effects of conventional drilling (CD) and a hybrid ultrasonically-assisted drilling (UAD) of a hemp fibre-reinforced vinyl ester composite laminate. The results obtained indicate that UAD is more efficient when compared to CD for a range of drilling conditions. It yields lower cutting forces and energy resulting in reduced machining-induced damage in the composite, including diminished burr formation and fibre pull-outs. The holes drilled with UAD exhibit improved surface finish and hole quality when compared to those produced with CD. The study demonstrates the applicability of UAD as a viable machining process for improved machinability of heterogeneous NFRP composite materials.