Factors affecting hole quality during drilling of natural fiber-reinforced composites: A comprehensive review

In recent years, with greater emphasis on environmental and sustainability aspects of engineering materials, natural fiber-reinforced polymer composites (NFRPCs) have gained significance in practical applications because of their numerous advantages. Although many researchers have developed NFRPCs using various types of natural fibers and matrix materials, in real-world applications of NFRPCs, secondary operations, such as milling and drilling, are necessary to complete the components or parts assembly. Because the drilling of NFRPCs is different from drilling of metals, there are concentration of studies interested in the aspects of drillability of NFRPCs in order to assess and understand issues related to drilled hole quality in NFRPCs. In this paper, a comprehensive review of factors that affect the drilled hole quality in NFRPCs is presented. Past researches where correlation between the manufacturing methods of NFRPCs and drillability of the composites are reported are reviewed in-depth. The novelty of this review is that it identifies the major factors that affect the quality of the drilled features from a composite manufacturing perspective and provides recommendations for the best NFRPCs manufacturing process to produce drill-friendly composites. The major factors were classified into composite manufacturing factors and drilling parameters factors.