Hole integrity of carbon fibre reinforced epoxy composites using combined punching and drilling techniques
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ORIGINAL ARTICLE
Hole integrity of carbon fibre reinforced epoxy composites using combined punching and drilling techniques M. S. Abdullah 1 & A. B. Abdullah 1
&
Z. Samad 1
Received: 16 April 2020 / Accepted: 1 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract 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. Keywords Hole integrity . Punching . Drilling . Bearing strength
1 Introduction The use of a mechanical joint in composite structures has been used steadily in recent years due to ease of access in assembly for inspection, maintenance, and repair work compared with the bonded joint [1, 2]. However, due to structural discontinuities in joint geometry, the load transmitted via fastener gives rise to the stress concentration around the hole-fastener boundary and might cause the premature failure of the entire structures [3, 4]. Since most of the existing method which produces holes in a laminated composite is drilling that involved direct contact between the workpiece and cutting tool (except for those related to an unconventional method), the tool being used faced extreme tool wear [5]. The defect in holemaking processes associated with drilling-induced damage due to the tool wear, including the time needed to
* A. B. Abdullah [email protected] 1
Metal Forming Research Laboratory, School of Mechanical Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
regrind the tool, caused the manufacturing cycle time and production cost increase [6]. The input process parameters like tool geometries, tool materials, and cutting parameters affect directly to the hole quality. Hole quality can be characterized based on a few criteria, including delamination factor, out-of-roundness, cut neatness, surface roughness, damaged surface layer, fibre fracture, burr formation, and crack [7, 8]. However, in composite laminates, damage due to delamination is a great concern in drilling. For example, it wa
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