Characterization of the Hole Quality on ZnO Nanostructured CFRP Composites by High Speed Micro‐Drilling

ABSTRACT

This study investigates the influence of ZnO nanostructure concentration and high‐speed micro‐drilling parameters on the hole quality of carbon fiber‐reinforced polymer (CFRP) composites. ZnO nanostructures were synthesized on woven carbon fibers using a hydrothermal technique with precursor molar concentrations of 15, 25, 35, and 45 mM, and compared against unstructured (neat) CFRP composites. Micro‐drilling experiments were performed using a 0.5 mm diameter micro‐drill bit at three spindle rotational speeds (25,000, 37,500, and 50,000 rpm) and three feed rates (1, 3, and 6 μm/rev) under dry machining conditions. Hole quality was evaluated in terms of surface roughness, delamination factor, circularity, and burr height. The results revealed that ZnO nano‐structuring significantly enhanced machinability by improving interlaminar strength and surface integrity. The 15 mM ZnO nanostructured CFRP exhibited the best performance with surface roughness ranging from 1.8 to 3.8 μm and delamination factor ranging from 1.01 to 1.14. These results showed a 55% reduction in surface roughness and an 18% reduction in delamination factor compared to neat CFRP. Additionally, the entry burr height was in the order of 11 μm for 15 mM CFRP composite, showing a significant improvement compared to others. Further increase in ZnO concentration degraded hole quality; however, the performance remained superior to that of neat CFRP. Furthermore, statistical analysis substantiates the experimental findings. The findings demonstrate that an optimal concentration of ZnO nanostructures, combined with appropriate high‐speed micro‐drilling conditions, can substantially improve hole quality in CFRP composites, offering valuable insights for precision micromachining of multifunctional nanostructured polymer composites.