Evaluation of the Hole Quality in High-Speed Machining of Glass Fiber Reinforced Polyester (GFRP) Using End Mill and Brad & Spur Drill Bits

Machining of Glass Fiber Reinforced Polymers (GFRPs) has been challenging, owing to their anisotropic properties, low toughness and laminated structure. Drilling as a critical operation, performed prior to assembling process, causes several types of defects including input and output delamination, fiber pull out and surface roughness. Thrust force is one of the main factors that generates these defects which is dependent on the drilling speed and the drill bit. In the current research, two drilling tools, End Mill and Brad & Spur drill bits, have been compared to find the proper drill bit in drilling of GFRP Composites. The thrust force was measured and the delamination factor was calculated. Moreover, the delamination mechanism was inspected by an image processing software. The results revealed that the delamination factor increases by increasing the thrust force. Thrust force was about ۵۰N in drilling by End mill bit, while it was shifted to ۴۳۰N in drilling by Brad & Spur drill bit. Also, the delamination factor was significantly decreased in drilling by End Mill tool, as the output delamination factor decreased from ۵.۴۶ to ۱.۶۴. Furthermore, due to variation of chipping mechanism, the difference in the input delamination using both drill bits was ignorable.

Keywords:

Glass Fiber , Polyester , Drilling , Thrust Force , Delamination , End Mill , Brad &Spur