Research On Remanufacturing Process Of Carbon Fiber Reinforced Resin Matrix Composites

Carbon Fiber Reinforced resin matrix Plastic(CFRP)are widely used in aerospace,wind power generation and other fields due to their excellent characteristics of light texture and high specific strength.However,with the continuous influx of CFRP into the market,the amount of its waste also continues.Since its waste still has high economic value and good mechanical properties,for the purpose of environmental protection and energy saving,the recycling of its waste has become an urgent problem to be solved.The main contents of this thesis are as follows:(1)Conduct strategic research on CFRP waste,classify them according to their size and shape;analyze the advantages and disadvantages of mechanical,chemical and other process methods,according to the types of CFRP waste,select high-temperature pyrolysis method and mechanical repair method as the remanufacturing methods in this thesis.(2)High-temperature pyrolysis tests were carried out on the resin matrix in CFRP under air and nitrogen atmospheres.The results showed that: when the temperature reached above350°C,the quality of the resin matrix began to decline.Tests were carried out under the conditions of different layup angles and different heating rates.The results showed that: the layup angle has little effect on the CFRP pyrolysis test,but with the increase of the heating rate,the high temperature pyrolysis reaction time gradually decreases.Among them,the reaction time required 73 minutes when the heating rate was 10°C/min,and the reaction time required24 minutes when the heating rate was 25°C/min.(3)High-temperature pyrolysis tests were carried out in air atmosphere and nitrogen atmosphere respectively,and the SEM images,EDS energy spectrum and thermogravimetric diagram were compared.The test results show that CFRP can be completely pyrolyzed in an air atmosphere of 500°C,and the residual pyrolytic carbon on the surface of carbon fiber can be completely removed.When the temperature reaches above 500°C,the carbon fiber undergoes an oxidation reaction;when heated to 650°C in a nitrogen atmosphere,the resin matrix can be completely removed,but pyrolytic carbon will remain on the surface of the carbon fiber.Both air and nitrogen atmospheres have defects in the remanufacturing of carbon fibers.(4)CFRP was tested by two-step method.Firstly,it was heated to 650°C in a nitrogen atmosphere,and then heated to 500°C in an air atmosphere,which not only removed the resin matrix and pyrolysis carbo but also ensured that the carbon fiber was not damaged.The tensile strength test of carbon fiber monofilament showed that its mechanical properties can reached88.3% of the original fiber.(5)Based on ANSYS finite element analysis software,the simulation analysis of CFRP laminates with different mechanical repair methods is carried out,and four mechanical repair methods are established: linear,triangular,ladder,and sawtooth.The material of the adhesive layer is epoxy resin.The 3D model of the laminate was simulated under tensile load and it can draw the conclusion that among the layers at various angles,the 90° layer fails first;with the increase of the contact area of the adhesive layer,the natural frequency of CFRP laminates increases,the interlayer stress decreases,the tensile strength increases and CFRP laminates were subjected to mechanical cutting tests at different speeds.The results showed that the cutting surface had a good morphology and regular edges at 10000 r/min,which was beneficial to improve the mechanical properties of CFRP laminates.