Hole integrity of carbon fibre reinforced epoxy composites using combined punching and drilling techniques

Drilling is the most common technique in the hole making of composite panels. Based on the previous study, punching was proposed to replace drilling. This study aims to investigate the effect of hole-making techniques, i.e. new combined technique and conventional drilling technique to the hole quality and performance by conducting experiment based on surface roughness and bearing strength, respectively. The surface roughness measurement was performed oversampling with 3.6-mm thickness at four quadrant points along the hole wall. A bearing test was conducted according to ASTM D5961 procedure-A double shear with a single-pin fastener. The failure modes resulting from an experiment are quantified and compared. It was found that there is a slight difference in the initial ply failure load (IPFL) between the conventional drilling and both combined technique for 0.65% and 7.90%, respectively. However, the difference is still low, i.e. less than 10%. The results confirmed that the use of the combined technique is almost similar to the conventional drilling alone in terms of bearing strength, failure mode, and surface roughness.