| Carbon Fiber Reinforced Polymer(CFRP)has the advantages of high specific strength and high specific modulus,and has received wide attention in recent years with the development of lightweighting in aerospace and automotive industries.According to the nature of matrix,carbon fiber reinforced polymer composites can be divided into thermoset composites and thermoplastic composites.Compared with the two,carbon fiber reinforced thermoplastic composites have the advantages of recyclability,weldability,and large damage tolerance,and are gradually becoming a research hotspot both at home and abroad.In the assembly of composite materials,mechanical connections such as bolting and riveting are the main connection methods in the aerospace industry.The quality of the machining of the connection holes is an important prerequisite for the reliability of the connection structure.At present,the research on CFRP hole manufacturing is mainly focused on carbon fiber reinforced thermoset composites,and the research on the formation mechanism of hole manufacturing damage and optimization of hole manufacturing quality strategy for carbon fiber reinforced thermoplastic composites has not been fully developed.In this paper,Carbon Fiber Reinforced Polyetheretherketone(CF/PEEK)is nvestigated as the research object.Combining with experiments and finite element simulation,the material removal mechanism,drilling force and temperature field distribution law during the drilling process as well as the hole manufacturing quality of CF/PEEK are analyzed.The main research contents are as follows:Based on the anisotropic linear elastic behavior of the fiber and the elastic-plastic behavior of the matrix as well as the damage theory of the fiber and the matrix,the three-dimensional micro finite element simulation model of CF/PEEK orthogonal cutting was established by combining the Cohesive contact theory to simulate the damage generation and extension of the fiber/matrix interface.Through the combination of finite element analysis and experimental verification,the effect of different fiber orientation angle and depth of cut on machining quality was analyzed,and the material removal mechanism and surface damage formation mechanism during CF/PEEK orthogonal cutting process were elucidated.Based on the composite bridging theory,a prediction model of the cutting temperature field during CF/PEEK drilling was developed,by combining the secondary development user subroutines DFLUX and USDFLD.CF/PEEK drilling experiments were conducted.Based on the results of the experiments and finite element analysis,the relationship between cutting parameters and thrust force,torque and hole wall temperature were analyzed and a drilling force model was fitted.The effect of cutting parameters on the temperature change,temperature field distribution and thermal stress inside the CF/PEEK laminate during the drilling process was investigated.The damage characteristics and formation mechanism of CF/PEEK hole drilling were investigated in terms of hole drilling accuracy,hole entrance/exit morphology,and hole wall micro morphology.Combined with the mechanical state of the matrix material PEEK at different temperatures,CF/PEEK drilling experiments were conducted through controlling the cutting environment temperature,and based on the experimental results,the effect of environmental temperature on the quality of CF/PEEK hole drilling was investigated.In this paper,a three-dimensional micro finite element simulation model of CF/PEEK orthogonal cutting and a heat transfer model of the CF/PEEK drilling process are established to reveal the influence of environment temperature on the quality of CF/PEEK hole drilling,which provides a theoretical reference for the formation of high-quality and efficient machining technology for thermoplastic composites. |
