Study On The Fracture Process Of Carbon Fiber Tow In Chopping And Its Application

Carbon fiber is recognized as next generation high-performance material, and chopped carbon fiber is one of its important application forms. At present, the production of chopped carbon fiber mainly adopts chemical fiber chopping technology, leading to poor product quality, serious cutting tool wear, low production efficiency and other problems. In this paper, the fracture process of carbon fiber tow in chopping by radial cutting technology was studied through mathematical modeling and carbon fiber tow cutting experiments, and the research results were applied to the optimization of chopping equipmentCutting process of carbon fiber chopping was analyzed and simplified as elastic support vertical cutting model. Through force analysis of fiber tow in the elastic support vertical cutting model, it was found that in cutting process of carbon fiber tow, monofilament bends, leading to axial compressive deformation inside and tensile deformation outside, besides the friction force of support also makes axial tensile deformation of the monofilament. Through analyzing the structure characteristics, physical properties and fracture characteristics of carbon fiber, it was found that carbon fiber is brittle material, the fracture of which conforms to Griffith theory of micro cracks, and both of the compressive deformation and tensile deformation can be origin of brittle fracture, besides for lining monofilaments, cutting action can also be origin of brittle fracture.Based on the elastic support vertical cutting model, elastic support cutting without stress experiment was designed. To analyze the effect of axial compressive deformation and tensile deformation on the fracture process of carbon fiber tow cutting, elastic support cutting with tension experiment was designed. To study the function of the support in the cutting process, unsupported cutting with tension experiment was designed. By analyzing the effect of cutting depth, hardness of support, pretension, radius of cutting tool edge, feed speed of cutting tool and physical properties of carbon fiber on cutting force and fracture morphology in these three fiber tow cutting experiments, the following results were obtained: the fracture process of carbon fiber is from inside(contact with the cutting tool) to outside; when the radius of cutting tool edge is small, for some monofilaments cutting fracture is the origin of brittle fracture, for the other monofilaments compression fracture is the origin of brittle fracture; with the increase of cutting tool edge radius, the origin of monofilaments brittle fracture gradually transforms into compression fracture. The research results of carbon fiber tow fracture process were applied to the optimization of radial cutting machine.