Research On Drilling Process Parameters Optimization And Damage Mechanism Of CFRP

CFRP,because of its superior material properties,widely used in aviation aircraft,defense industry and other industries.In order to facilitate the structure of the connection,composite plate containing many holes and blind holes need to be processed.However,the high hardness of the carbon fiber and high viscosity of the epoxy resin mixed in the processing of drilling these holes,because of the anisotropy of the material properties and low bond strength,it will produce a lot of drilling defections.However,most of the researches on the mechanism of CFRP are only on the processing technology,seldom of then are further discussion on how to evaluate pore quality.The air hole carbon fiber composite material was used as the raw material to carry on the hole-making experiment,and then the common pore-forming damage was studied.The main contents and results are as follows:Firstly,the author analyzes the common form of hole-making damage,analyzes the one-dimensional theoretical system of pore quality,and establishes three-dimensional layered volume evaluation method,and gives the three-dimensional layered volume mathematical formula.The drilling quality was evaluated by scanning electron microscopy(SEM).The data was used to evaluate the effectiveness and rationality of the three-dimensional layered volume evaluation method.Then,the formation mechanism of defects such as burr,tearing,and export hierarchy was analyzed for the evaluation of pore-forming damage.According to evaluate the degree of different defect forms on export quality,a three-dimensional comprehensive damage evaluation standard was established.The drilling experiment is designed to validate that a single evaluation criterion can not accurately reflect the quality of hole-making export.The evaluation model proposed in this paper can more effectively consider the effect of hole defects on the quality of hole-making export.By using the Memetic algorithm and combining with the rules of placement,especially the anti-layering rules,the optimization model of laminated plates is put forward.The objective function and constraint condition are introduced,and the optimization algorithm is used to get the layered order of carbon fiber sheet.The CFRP drilling experiment was carried out to study the effect of the angle of the ply on the axial force of the carbon fiber composite drilling under different drilling speed conditions.Finally according to the characteristics of the brittle and elastic materials,the elastic fracture mechanics was used to deduce the axial force of the critical drilling of carbon fiber composites.According to the basic principle of fracture mechanics,the energy balance formula in drilling process is listed.Combined with the classical bending theory,the theoretical formula of the critical axial force with pilot hole is solved.The influence of prefabricated hole on the axial force during drilling of CFRP is studied.Finally,the role of pilot hole in CFRP drilling is analyzed.