Influence of tool parameters on ultrasonic assisted drilling of GFRP composites

Glass fiber reinforced polymer (GFRP) composites are widely used in aviation, aerospace, sports and special vehicles because of their light weight, high wear resistance, good fatigue resistance and low thermal expansion coefficient. However, the anisotropy and low interlaminar strength easily lead to defects such as wire drawing, delamination and tearing during drilling process, which seriously restricts the development of GFRP composites. In this study, the effects of drilling tool material and geometrical parameters on the machining quality of GFRP composites in ultrasonic-assisted drilling are revealed through single-factor experiment. Unidirectional laminated GFRP epoxy plates of 80 x 50 x 5 mm are used in the experiment, and the thrust in the machining process is collected by a dynamometer. An industrial camera is used to record the exit morphology of the hole, and then MATLAB is used for image processing to convert it into a greyscale map. Finally, the size of the delamination factor F-d is obtained according to the equation. The experiment results indicate that using the carbide drilling bit with a diameter of 4 mm and a point angle of 120 degrees is beneficial to reduce the thrust and suppress the machining defects.