Research On Recycling Method Of Carbon Fiber Reinforced Resin Composites Using CO₂under Super Critical Conditions

As Carbon Fiber Reinforced Plastics (CFRP) has been widely applied in variousfields, CFRP wastes increase rapidly. Composites contain valuable fibers and resinmatrix which is hard to degrade, if abandoned, it will lead to great waste of resourcesand cause serious environmental problems.CFRP laminated plates as the research object, the pretreatment method was studied.Cutting methods of the CFRP laminated plates were discussed. SEM was used toanalysis the micro incision. Result showed that high speed grinding wheel cutting canobtain smooth cutting surface without napping, the shape was regular, and cuttingdimensions can be guaranteed.Nitric acid treatment method was used for laminated plates layering anddecomposition experimental study. The macroscopic stratification state wascharacterized, and the recycled carbon fibers were characterized. The feasibility of theresearch as a pretreatment method was investigated; SEM showed there was certainresin residue on that fiber surface; Monofilament tensile test results showed that thetensile strength of recycled carbon fiber is75%of the fibrils.Recycling experiment of CFRP using supercritical CO2was carried out. The principleof the recycling experiment is analyzed, experimental system is established, and recycleexperiment was carried out. The results showed that the pure supercritical CO2forlaminated plates treatment effect is not obvious; Entrainer, catalyst can improve theresin decomposition rate; The process parameters, such as temperature, pressure,reaction time all can promote the reaction, the influence of temperature is more obvious.Finite element analysis method are used to simulate the quality diffusion process oftemperature of80℃water in Epoxy Resin CFRP. Composites stress simulationcalculation under hot and humid conditions and supercritical conditions was carried out;Potential damage area of composites under supercritical conditions was analyzed,structure failure process was discussed. Results showed that the hot and humidtreatment accelerated the structure damage under supercritical conditions. Undersupercritical conditions, the interface between carbon fiber and epoxy resin appearlarger shear stress, and the temperature is the decisive factor. Potential damage arealocated at the free end, layering and interface debonding started from the free surface,the main damage form is interface debonding failure and delamination damage.