Temperature Field Analysis And Control Of Electromagnetic Induction Heating Of Carbon Fiber Composite Materials

Carbon fiber reinforced resin matrix composite shell has the advantages of high specific modulus,high specific strength,strong designability and good corrosion resistance.Therefore,it has been widely used in the fields of aerospace,military,energy,automobiles and pressure vessels.It has become a key component and standardized product of power structure,fuel system,energy storage and transportation.The composite curing process is a key factor affecting the performance and manufacturing costs of composite shells.At present,carbon fiber composite shells are heated and solidified primarily by thermal radiation,thermal convection,and thermal contact.Since heat is gradually trans ferred from the surface of the material to the inside,resulting in low heating efficiency and poor uniformity of the internal temperature field of the material.Traditional heating methods have led to a large loss of energy during the curing and molding process of carbon fiber composite materials.The key to solving this problem is to explore a novel shell heating process.Therefore,based on the conductivity of carbon fiber materials and the non-contact and high-efficiency heating characteristics of electromagnetic induction,a new process for heating and curing carbon fiber composite shells is proposed using electromagnetic induction technology.However,many factors such as coil structure,power output parameters,material heterogeneity and multiphase,and property anisotropy affect the distribution and evolution of the magnetic-thermal-chemical field in the induction heating/curing molding process.Therefore,it is necessary to study the heating mechanism of the induction heating carbon fiber shell,the distribution law of the shell temperature field and the temperature control method to ensure the curing quality of the shell.Carbon fiber composite material is an anisotropic heterogeneous multi-phase material system.The cross-laminated carbon fiber shell has the characteristics of both weaving and laminated structure.The anisotropy of material properties,fiber overlap/woven structure and other factors affect electromagnetic induction heating characteristics of the carbon fiber composite material.In order to study the law of the temperature field of carbon fiber shells,the heating mechanism of carbon fiber shells is explored during induction heating.Therefore,this paper uses carbon fiber composite material equivalent electrical-magnetic-thermal characteristics,control mechanism,composite material induction heating mechanism and multi-physics coupling analysis in the heating process.Electro-magnetic-thermal multi-field coupling finite element analysis model of the shell induction heating process,is established to simulate and calculate the generation and distribution of the vortex electric field,current and heat generation in the fiber texture under the action of the alternating magnetic field.At last,heating mechanism and change law of the carbon fiber shell is clarified during the induction heating process.Since the uniformity of the temperature field distribution during the heating process of carbon fiber composite materials is difficult to effectively evaluate,the image entropy theory is used to establish the relationship between the temperature field of the carbon fiber shell.The uniformity of the temperature field is expressed by the entropy value to realize the quantitative analysis of the uniformity of the temperature field.The temperature field distribution generated by the induction heating carbon fiber shell has a strong nonlinearity,so this paper studies the influence of the coil size/structure/position relationship,induction frequency/current,carbon fiber thermal conductivity/conductivity and other factors on the temperature field distribution.And proposed a design optimization method based on the temperature field uniformity,temperature value and coil length in the center of the coil.The coil diameter,position relationship,a nd the value range of the number of turns are optimized to improve the uniformity of the temperature field while achieving temperature Effective lifting and coil length control.Induction heating carbon fiber shell temperature field control techniques in combination with multi-coils have been studied to improve the accuracy and uniformity of temperature field control during the induction heating curing process for composites.In this paper,the heating area of the shell is increased by the multi-coil combination structure,the influence of coil spacing,magnetic pole direction and combination method on the distribution of magnetic flux,vortex electric field,current and temperature field is studied.In order to solve the problem of temperature field uniformity caused by heating a plurality of coils at the same frequency,a multi-coil coupling heating method with different frequencies is proposed.By changing the mutual coupling between the magnetic fields of the multiple coils at different frequencies,the eddy current and heat generation distribution in the shell is realized to improve the uniformity of temperature field distribution.According to the characteristics of strong coupling and non-linear changes of induction heating and the body heating characte ristics of CFRP,the improved particle swarm fuzzy PID control algorithm with adaptive inertia weights is used.The response rate of induction heating of the carbon fiber shell improves as the temperature rises,reducing temperature overshoot during the heating process and improving the accuracy of temperature field control.In this paper,the control of the shell temperature field during the induction heating process of anisotropic heterogeneous carbon fiber composite materials is studied,and the mechanism analysis of the induction heating of the carbon fiber shell is completed.Moreover,the uniformity of the temperature field is evaluated based on the image entropy theory,and the influence of the changes of induction heating related factors on the distribution of the temperature field is analyzed.The temperature field control technology of the multi-coil combination induction heating carbon fiber shell is studied to improve the control accuracy and uniformity of the temperature field during the curing and molding process of the composite material.Through the research of the above problems,the results of this paper can also be applied to the induction heating curing molding of large curved carbon fiber sheets,anisotropic rotary parts and complex curved parts,reducing production costs,improving production efficiency and molding quality.And this result also applied to analyze and research the temperature field of the carbon fiber shell with the structure of the heterogeneous parts heated by the multi-coil combination.This research provides diversified solutions for expanding the application of high-efficiency non-contact heating technology in the composite material forming process,and provides a corresponding theoretical basis for the development of composite material heating process analysis and control.