Research On Drilling Aircraft Laminated Materials With Variable Parameters

In recent years,the use of carbon fiber reinforced plastic/polymer(CFRP)is rapidly increasing in aircraft structural part with the improvement of aircraft performance requirements.CFRP is usually laminated with metal materials such as aluminium alloy and titanium alloy.They are connected by riveting or screwing,so holes need to be drilled on the connected parts.The quality of connecting holes has direct influence with the strength,rigidity and fatigue life of the connected parts.In this paper,the CFRP/aluminium alloy stacks was took as a study subject,some technology problems on constant parameter drilling process were analyzed.A new drilling technology with variable parameters was proposed and some key problems were studied.The main research content is as follows:(1)The material characteristics of CFRP and aluminium alloy and the problems or defects in drilling CFRP and aluminium alloy were expounded.The qualitative or quantitative analysis was carried out by constant parameter drilling experiments for aperture,roughness,chip,burr and delamination and tearing of composite,etc.The main technology problems in drilling laminated composite components with constant parameters were summarized.(2)The mechanism of chip formation in metal cutting was analyzed.The formation of chips in drilling aluminium alloy and the effects of process parameters on chips were researched.The formation mechanism of exit burr in drilling aluminium was expounded.The burr height was analyzed by regression analysis and the empirical formula of burr height with process parameters was got.A new method of peck drilling with variable feed rate was put forward to resolve contradictions between different requirements of feed speed for chip breaking and burr.The effects of the position of feed rate change and the feed rate after change on chip and exit burr were analyzed.(3)The aperture difference between drilling single-layer materials and drilling multi-layer materials was compared.The drilling parameters of CFRP layer and aluminium alloy layer were changed respectively by variable parameter drilling process.The influence of drilling parameters of each layer on the aperture of CFRP/aluminium alloy stacks was analyzed.A conjecture on the formation of hole wall in drilling laminated composite components was put forward.Then the effects of drilling parameters of aluminium alloy layer on hole wall roughness,export morphology of CFRP and tool wear were further researched.Suggestions on selection of drilling parameters for each layer of materials were given.In this paper,some problems in drilling of CFRP/aluminium alloy stacks with variable parameter were researched and the results have some value in engineering application.These would provide a reference for automatic drilling in aviation manufacturing.