Investigation of the effect of different parameters in the drilled hole quality in composite materials

Abstract

Two different delamination mechanisms that need to be controlled by the drill geometry and thrust force will be observed in the drilling of composites. The studies which have been done up to now focus on the thrust force aspect and drill bit geometry at a constant feed rate. It is possible to find a feed rate at the beginning of the penetration that corresponds to the rate at which the laminates are peeled out. Moreover, at the exit, the fiber push-down mechanism is active, which can be controlled by controlling the maximum thrust force. Thrust force itself depends on the feed rate, so there should be a “feed ratedepth” graph minimizing the delamination. This implies that the feed rate may need to be changed from high to low as the drill bit enters and exits. To find the best result several experiments are being run at the constant feed rate. Some of these feed rates will give reduced fiber pull outs at the entrance and some will result in acceptable fiber push downs at the exit. The best graph will be extracted by analyzing the delamination for each feed rate. For measuring, a microscope should be used to determine the areas with the maximum delamination along the cross section of the hole. Also, measuring the surface roughness is another method of determining the delamination, but it should be done at a certain depth at the entrance as well as exit, not all of the thickness at once. [1]