Analysis Of Cutting Fracture Process Of High Viscosity Carbon Fiber Tow Under Different Support Conditions

Forging composite is an important form of Carbon Fiber(CF)application,and short cut carbon fiber is an essential raw material for its production.The existing CF short cut processing technology often uses dry tow for cutting,while the short cut material for forging composite materials uses carbon fiber prepreg tow.Different from the dry tow cutting,the resin is in a high viscosity state during the tow processing of carbon fiber prepreg,which not only has the problems of large cutting force and serious equipment wear,but also easily causes the adhesion between prepreg,cutter and fixture,which seriously affects the processing efficiency and product quality.Therefore,in view of the rigid support,flexible support and unsupported three different support States,the fracture process of carbon fiber prepreg tow during cutting in high viscosity state is analyzed and compared,which has guiding significance for the improvement of short cutting technology of high viscosity carbon fiber tow.First of all,the process of cutting and breaking of carbon fiber tow is explored.The cutting experiments are carried out for carbon fiber monofilament and carbon fiber tow with different number of monofilament.The experimental results are analyzed according the cutting and breaking stress curve,and the process of single filament breaking and different size of CF tow breaking is compared.The phenomenon of fiber slippage in cutting process of carbon fiber tow is found.In order to further confirm this theory,a width constrained cutting experiment was carried out.Secondly,the cutting fracture process of carbon fiber bundles under high viscosity is studied.From the analysis of the experimental results,it can be seen that under high viscosity(viscosity > 2000Pa·s),the increase of the viscosity of epoxy resin will significantly reduce the cutting fracture force of carbon fiber bundles,but the cutting depth will also significantly increase with the increase of the viscosity of epoxy resin.According to the cutting fracture force,cutting depth and cutting process stress curve of carbon fiber tow,and based on the theory of cutting fracture process of carbon fiber tow put forward before,the cutting fracture process model of carbon fiber tow with rigid support and different viscosity is finally established.Thirdly,the cutting fracture experiment of carbon fiber bundle under flexible support was carried out under the condition of high viscosity.Because the cutter will act on the flexible support rubber block under the condition of flexible support,the cutting stress no longer depends on the number of carbon fiber monofilaments at the bottom as the rigid support,and the fracture form of carbon fiber under the flexible support strip is bending fracture,and the deformation of rubber block will affect the strand fracture of carbon fiber It plays an important role.From the experimental results,it can be concluded that under the condition of high viscosity,52 A is an ideal hardness for carbon fiber tow cutting flexible support block.Finally,the process of cutting and fracture of carbon fiber tows in high viscosity state is analyzed.According to the curve of cutting and fracture process and the theory of cutting and fracture process of carbon fiber bundles,the geometric model of cutting and fracture process of carbon fiber bundles in high viscosity state is established.In order to comprehensively analyze the short cutting performance of carbon fiber tow under three kinds of support conditions,the cutting fracture force,cutting depth and the amount of epoxy resin adhesion of the support under three kinds of support conditions were compared.