| Carbon fiber composites are widely used in rail transit,aerospace,medical and other fields due to excellent specific modulus,strength,durability and designability.Many components with complex shapes,such as sheet metal bending parts,deep drawing and calendaring parts,which have been formed with metal materials have also changed their processing methods after switching to composites.In the actual manufacturing process,many composites are preformed to obtain preforms that meets the structural size requirements and then cured.Infrared heating has the characteristics of fast thermal response and easy temperature control.It is mostly used in the preforming process to ensure the smooth formation of the preform.However,due to the anisotropy of composites,the thermal properties of the fiber and the resin are significantly different.The morphology and viscous flow characteristics of the resin change greatly at low and high temperatures.The temperature has a significant effect on the deformability of the preforms,thus affecting the quality of the components and even shortening their service life.In view of the above problems,this paper explored the temperature distribution and heat transfer mechanism of carbon fiber composites during infrared heating preforming process at meso-scale and macro-scale from two aspects of simulation and experimental analysis.It analyzed the influence of heat source parameters on the temperature field distribution.The main research work carried out in this paper was as follows:(1)A numerical simulation study of the temperature field of meso-structure of woven carbon fiber composite was carried out.The analysis showed that the heat was rapidly transferred along the fiber direction,the temperature of the carbon fiber located in the middle plane was greater than that of resin.The temperature in less resin area between the warp and weft yarns was also higher than that in more resin area.The mesoscopic temperature field of the composite was unevenly distributed and the conduction law was not only related to the thermal properties of the material but also related to the structure.The error of the simulation results of the simplified representative volume unit model was less than 7% and the calculation efficiency was doubled.(2)The macroscopic temperature fields of the carbon fiber composite preforms were simulated.The results showed that when the heating distance was 30 cm and the single lamp tube heated the single-layer preform,the temperature field of the carbon fiber composite preform was elliptically distributed,the long axis was parallel to the axis of the infrared lamp tube,and the temperature rise curve showed three-section curve.When the heating distance was 45 cm and the single lamp tube heated the double-layer preform,the temperature field distribution of the heated surface was elliptical,but the ratio of the long axis to the short axis was reduced.Carrying out verification experiments and comparing simulation and experimental results,the error was less than 9%,which proved the reliability of the model.(3)The characteristics of the temperature field distribution of the preform under different heat source parameters were studied and the influence rules were explored using numerical simulations and experiments.Increasing the heating distance had a certain positive effect on improving the uniformity of the temperature field distribution,but the temperature value decreased significantly with the increase of the distance,while reducing the heating distance had a significant effect on increasing the heating rate.When the heating distance was large,the effect of increasing the number of lamps on improving the uniformity of the temperature distribution was not significant.When the heating distance was small,increasing the number of infrared lamps with a certain distance can effectively improve the uniformity of the temperature field distribution in the preform plane. |
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