Study On Temperature Field And Thermal Stress Field Of Aramid Fiber Composites During Drilling Process

Aramid fiber reinforced composites(AFRP)have many excellent properties,such as strength,toughness,light weight,high strength and impact resistance,and are more and more widely used in aerospace,military,civil and other fields.However,aramid fiber composite is a typical hard-to-process material with low thermal conductivity,strength,toughness and anisotropy.Compared with carbon fiber reinforced polymer(CFRP),aramid fiber composite is more prone to defects,such as burr,tear,delamination,thermal damage and so on.As one of the most common processing methods for aramid fiber composites,hole-making is more likely to produce various processing defects than edge-cutting.Thermal damage is one of the most common defects.These defects have a serious impact on the service performance of aramid fiber composite components,which restricts the further application of composite components.In this paper,the temperature field and thermal stress field of aramid fiber composites in the process of hole-making are studied from the aspects of numerical simulation and experimental analysis,and the removal of aramid fiber composites by ambient temperature is analyzed,based on the relevant contents of the project of National Natural Science Foundation of China "Mechanical-thermal Coupling Mechanism and Damage Reduction Strategy in the Processing of High Strength and High Toughness Composites".The influence law of drilling process,the temperature variation characteristics and thermal stress field of traditional twist drill and thin-walled sleeve drilling,the meso-thermal stress field of materials,and the influence factors of drilling process temperature and its influence law.The main research contents and related achievements of this paper are as follows:(1)Through experiments,the effects of the removal process of aramid fiber composites and the change of environmental temperature on the scratch quality were analyzed.The cutting characteristics of aramid fiber composites were analyzed,and the flying-cutting model of aramid fiber composites removal process was established.A thin-walled sleeve hole-making tool was developed to reduce the hole-making damage.(2)Based on the characteristics of aramid fiber composite material and drilling process,the moving heat source model of drilling process is established,and the temperature field model of traditional twist drill and thin-walled sleeve drilling for aramid fiber composite material is established.By means of sequential thermo-mechanical coupling,the analysis model of thermal stress field in the pore-making process was established,and the meso-thermal stress field model in the temperature change process of aramid fiber composites was established through the material meso-model.(3)The numerical simulation and analysis of temperature field of traditional twist drill and thin-walled sleeve drill for aramid fiber composites are carried out.The results show that under the same cutting parameters,the temperature of thin-walled sleeve drill is higher than that of traditional twist drill,and the characteristics of temperature rise at the bottom of material show a cubic curve.The glass transition temperature of aramid fiber composites is easily higher than that of aramid fiber composites during the pore-making process.There are obvious heat-affected zones on the bottom of aramid fiber composites and the temperature rise rate is different in different zones.(4)Based on the sequential thermo-mechanical coupling method,the thermal stress field numerical simulation analysis of aramid fiber composite during hole-making process and the meso-thermal stress field simulation analysis of material temperature change process were carried out.The results show that the distribution of thermal stress field is inhomogeneous.The maximum thermal stress is at the bottom hole wall of the material.The distribution of meso-thermal stress field varies with the distribution of fibers.(5)The validation test of the hole-making temperature of aramid fiber composites was carried out,and the simulation results were in good agreement with the experimental results,which further verified the validity of the finite element model.Through numerical simulation and experimental analysis,the temperature field of aramid fiber composites under different cutting parameters,different ambient temperatures and different processing technologies was studied,and the influence rules and characteristics of different conditions on temperature during drilling process were further explored,so as to explore its low-damage drilling strategy.