Study On Melt Impregnation Of Continuous Carbon Fiber Reinforced Polypropylene Resin

Continuous fiber reinforced thermoplastic composites are compounded by thermoplastic resins,continuous fibers,and other additives.Compared to thermoset composites,thermoplastic composites have no harmful additives,can be recycled,recycled,and have excellent overall properties.Therefore,thermoplastic composites have been developed and applied in more and more fields such as military weapons,aerospace equipment,automotive parts,and sports equipment.However,thermoplastic composites also have their drawbacks.Compared with the low viscosity of thermosetting resins,the viscosity of thermoplastic resins is usually as high as thousands of pascal seconds.Under normal processing conditions,it is difficult to bond with continuous fibers and many voids are produced,making composites The degree of impregnation is not ideal,affecting its performance,so since the development of thermoplastic composites,its main research direction has been to improve the degree of impregnation,reduce the difficulty of processing,and improve production efficiency.In this dissertation,long fiber reinforced thermoplastic composites was prepared through melt impregnation process.Research focus on impregnation process,impregnation die structure and fiber surface modification to optimize composites properties.Comparing the melt impregnation process of carbon fiber/polypropylene and glass fiber/polypropylene,the results showed that higher breakage occurred for carbon fiber than for glass fiber.Therefore,how to decrease the breakage of carbon fiber need to be paid more attention in thermoplastic composites production.The relationship between processing parameters such as temperature,traction speed,mold gap,and number of pre-dispersed rolls and composites properties was investigated by using DOE experimental program.By analyzing the convergence of the fiber bundle at the die,the Reynolds equation analysis is used to express the distribution of the melt pressure in the wedge zone.Combined with the Darcy's law,the degree of impregnation of the fiber bundle is deduced,and the structural parameters of the die are impregnated with the fiber bundle.Connect and analyze and discuss it to guide the design of the actual die structure.At the same time,the fiber bundles in the die area were analyzed and the Weibull probability distribution was used as the basis to establish a fiber fracture model in the die area.The influence of the die structure on the fracture rate was studied and the die structure was optimized.Studies have shown that a smaller die angle can improve the degree of impregnation,but will increase the fiber fracture rate,die transition fillet is the main cause of fiber fracture.In view of the disadvantages of surface inertness of carbon fiber and weak interfacial bond with resin,carbon fiber surface modification of carbon fiber was performed in this paper.The effective degree of processing means was characterized by testing the interlaminar shear strength and mechanical properties of the composite material.The results show that the carbon fiber surface oxidation and carbon nanotubes modification can significantly improve the interlaminar shear strength and tensile strength of the composites,which are increased by 41.4%and 75.9%,respectively.