Research On Drilling Of Carbon Fiber Reinforced Plastics (CFRP) And Titanium Alloy Stacks

In a wide range of applications dissimilar material stack-ups of carbon fiber reinforced plastics (CFRP) and mental are used for wing or tail plane structures. Assembly of these materials by riveting or bolting requires realization of a very number of holes. To improve the joint strength, stiffness, and security of multilayer materials, fasten holes are drilled through multi-material stacks instead of drilling each composite and metallic material separately in the assembly processes. However, due to laminated constructions of CFRP and different machining properties, drilled holes quality is difficult to be guaranteed and tool wear is intense. Especially, as the development of aeroplane flexible assembly technology and digital manufacturing technology, one of the key technologies is drilling of dissimilar material stack-ups of CFRP and titanium (aluminum) alloy in the same working procedure.This paper were supported by National Natural Science Foundation of China (NSFC), the National High Technology Research and Development Program ("863" Program) of China, and Science and Technology Research Project for College Supported by Education Bureau of Liaoning Province. Experimental investigation and theoretical analysis of drilled holes defect were carried out in drilling CFRP and titanium alloy stacks. The main contents and the academic achievements in this study are shown in the following:(1) Based on the superior characteristics of polycrystalline diamond (PCD) such as hardness, toughness, and wear resistance, we initially designed the PCD drill for drilling of CFRP and titanium alloy stacks including structure of drill, incising of polycrystalline diamond compact, and brazing technology of polycrystalline diamond compact. The geometrical parameters and blade's particle size of PCD drill were optimized in the next research.(2) CFRP laminates and titanium alloy were drilled separately with different kinds of drills. In drilling of CFRP laminates, the choice of drilling parameters, the drilled holes quality, and the tool wear were investigated. In drilling of titanium alloy, the burr formation mechanism, burr category and chip entanglement phenomenon while continuous drilling with constant feed rate are experimentally investigated, respectively. Furthermore, we put out a new method of fitful drilling with variable feed rate and analyze the cutting force performance of PCD drill and drilled holes quality of titanium alloy. (3) In drilling of CFRP and titanium alloy stacks, damage features model was established. Selecting appropriate machining parameters position for each material, analyzing effect of parameters on drilled holes quality and circularity, and observing tool wear varying number of holes drilled in drilling of CFRP-titanium alloy stacks with alternating machining parameters. To explore and realize an economical drilling processes of CFRP-titanium alloy stacks.