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a b s t r a c t In this study, an experimental investigation on the drilling of unidirectional carbon fiber reinforced plastic (UD-CFRP) composite was conducted using polycrystalline diamond (PCD) tipped eight facet drill. The quality of the drilled hole surface was examined through surface roughness measurements and surface damage by scanning electron microscopy (SEM). It was found that fiber pullout occurred in two specific sectors relative to the angle between the cutting direction and the fiber orientation. The thrust force was highly influenced by the feed rate than the cutting speed and it shows a significant variation throughout the rotation of the drill.

The condition of the cutting tool when drilling composite materials is the controlling factor for the surface integrity of hole produced. The high rate of tool wear when drilling composite materials makes finding a way to monitor the condition of the cutting tool without interrupting the drilling process a great necessity. Inspecting the condition of the drill between or during the drilling process is not practical or economical. In an attempt to tackle this problem, a new approach of on-line tool wear monitoring method using an air-coupled audio microphone is proposed. An experimental investigation was conducted on multi-directional carbon fiber reinforced plastic (CFRP) composite material using a high speed steel (HSS) drill. The result shows that, the amplitude of the acoustic signal from the microphone decreases when the amount of flank wear increases and the amplitude of thrust force and torque increases with the increase of the flank wear. This result demonstrates that the proposed approach can be used as an effective and economical tool for on-line monitoring of cutting tool condition.

To avoid the uncertainty of the presence of gaps between CFRP stacks and to eliminate the inspection for gaps after every drilled hole, a novel approach for on-line gap detection and estimation when drilling CFRP composite stacks through various signal profiles was proposed. Experimental investigation of the proposed method was conducted using thrust force, vibration, acoustic emission, and audio signals, which were collected using dynamometer, accelerometer, acoustic emission sensors, and an air-coupled audio microphone respectively. A predetermined gap was introduced between the stacks of CFRP plates in the investigation. The results from this experimental study reveal the potentials of the proposed approach for on-line detection and estimation of gap when drilling CFRP composite stacks.Copyright © 2014 by ASME

In this study, an experimental investigation on the drilling of unidirectional carbon fiber reinforced plastic (UD-CFRP) composite was conducted using polycrystalline diamond (PCD) tipped eight facet drill. The quality of the drilled hole surface was examined through surface roughness measurements and surface damage by scanning electron microscopy (SEM). It was found that, fiber pullout occurred in two specific sectors relative to the angle between the cutting direction and the fiber orientation. The thrust force was highly influenced by the feed rate than the cutting speed and it shows a significant variation throughout the rotation of the drill.Copyright © 2012 by ASME