Research On CFRP Ultrasonic Vibration Small Hole Drilling Delamination And Process Optimizatio

Carbon fiber reinforced composite(CFRP)is a lightweight composite material with high mechanical properties,which has been widely used in advanced equipment of national defense.In the field of aerospace,T700 series of CFRP has been used as the main load-bearing component of aircraft.When CFRP is used as a structural component,it needs to be riveted or bolted to other parts,so it needs to be drilled to make holes.However,due to the anisotropy of CFRP laminates,the defects such as delamination,burr,tearing are easy to appear in the drilling process.Delamination is the most important defect restricting the application of CFRP.This defect will greatly shorten the service life of structural parts and even make them scrap directly.In order to reduce the occurrence of delamination defects in hole making,this paper takes the processing of small aperture of CFRP material less than 5mm as the research object,analyzes the generation mechanism of delamination in the process of ultrasonic vibration assisted drilling,carries out the ultrasonic vibration small hole drilling test,and uses the NSGA-Ⅲ algorithm to optimize the processing parameters.The main research contents are as follows:(1)Analysis of the delamination mechanism of CFRP ultrasonic vibration assisted drilling.The macro and micro delamination mechanism of CFRP conventional drilling was analyzed,the influence of ultrasonic vibration kinematics and size effect on the delamination of drilled holes were explored,and the delamination mechanism of CFRP ultrasonic vibration small hole drilling was further analyzed.Combining the finite element method with the theoretical research,the mechanism and influencing factors of delamination in the process of processing are explored from the macro and micro perspectives respectively.(2)Experimental study on thrust force and torque of CFRP ultrasonic vibration assisted drilling.The influence of process parameters on thrust force and torque was studied,and the changes of thrust force and torque with process parameters under different processing methods were compared.The regression models of thrust force and torque were established respectively and the range of process parameters that can reduce thrust force and torque were obtained by using response surface method.(3)Experimental study on delamination of CFRP ultrasonic vibration assisted drilling.The influence of process parameters on the delamination of the entrance and exit of drilling holes was analyzed.Studied and compared the delamination of drilling holes with process parameters under different processing methods.The influence of size effect on hole delamination was explored,and the influence of thrust force and torque on hole delamination was explored.The regression models of entrance peel-up delamination and exit push-out delamination were established respectively,and the range of process parameters that can reduce delamination of drilling holes were obtained by using response surface method.(4)Research on optimization of process parameters of ultrasonic vibration drilling for small diameter Holes.Taking the thrust force,torque,entrance peel-up delamination and exit push-out delamination as the optimization objectives,an optimization model was established.NSGA-Ⅲ algorithm was used to solve the optimization model.By optimizing the process parameters,the specific process parameters which can comprehensively reduce the four optimization objectives are obtained.This research can provide ideas for optimizing processing parameters,and lay a foundation for high-quality CFRP processing.It is beneficial to improve the utilization rate of CFRP and produce certain social benefits.