Experimental Study On Drilling Several Composites

Composites are characterized by superior strength-to-weight and stiffness-to-weigh ratios, low expansion coefficient, good thermal shock, good heat resistance, which have been widely used in military field such as airplanes and spaceships, and civil field such as automobile, electronic communication and high speed machine, etc. As a kind of high-performance component, they have taken the place of aluminum alloy, titanium alloy and steel somewhere. However, their character such as high strength, low conduction and anisotropy makes them difficult to machining. There are some disfigurements such as burr, delamination and avulsion when they are drilled by traditional tools. This paper is about how to eliminate the disfigurements and reduce the abrasion of tools, and some methods are developed to improve the machining quality, and the results are in good angreement with theoretical model.The study is mainly about four parts below.(1) The machinability of four composites such as glass fibre reinforced plastics, high-module carbon fiber composites M40/AG-80, high-intensity carbon fiber composites T300/AG-80 and carbon fibre front panel/aluminum honeycomb core composites was analysized, and many drilling experiments were performed with the high speed drilling system and the drilling force measuring system. The core-drill was compared with the standard sintered-carbide drill. Morever, when the process parameters, tool shape and axial force were optimized, the best tool shape to machining and the range of machinable process parameters were obtained.(2) There are always some disfigurements such as burr and delamination which are hardly to avoid when C/E composites are drilled with standard sintered-carbide drill. Therefore, the core-drill was used, which was compared with standard sintered-carbide drill on many facets such as tool shape, drilling process, axial force, machining quality, efficiency, cutting scraps and abrasion, etc. And the results showed that the core-drill was better than standard sintered-carbide drill while drilling C/E composites.(3) C/E composites were still drilled with sintered-carbide drill when the core-drill method was impracticable. To get better machining quality, the helical drill point tools were used in the test, and the axial force and machining quality of blade model was also analysized. The reasonable blade model parameters were obtained on the basis of the process experiments. Then the same study on the aluminium alloy was also evaluated to make it possible to machine the workpiece that was combined with composites and aluminium alloy.(4) To increase the life of sintered-carbide drill, the high-intensity pulsed ion beam(HIPIB) was proposed. The life of strengthened tool was compared with the original one, it was concluded that HIPIB can enhance the abradability of sintered-carbide tool and can increase its life.