Relationship between the drilling condition and the damage (delamination) zone of glass-fiber-reinforced plastic composites

Delamination is one of the main defects observed from the drilling of composite materials, and can be an important limiting factor for the use of composite materials. In this study, the delamination area factor for GFRP (Glass Fiber Reinforced Plastic) drilling was proposed to quantify the practical delamination zone via digital imaging of the damage zone around the hole and by calculating the damage zone by pixel. From the tests, it was concluded that a higher drill feed rate reduced the delamination zone and the cutting speeds have no influence on the delamination zone. Also, the proposed delamination area factor was more suitable and useful for delamination zone evaluation than the existing delamination factor.