Preparation Of Continuous Fiber/Resin Composite Filament And Investigation Of Its Composite FDM-3D Printing Forming Performance

3D printing,also known as additive manufacturing,is a method of solid manufacturing based on 3D digital models of parts through layer-by-layer stacking and forming,which is characterized by high material utilization and the ability to form complex structural parts.Fused Deposition Modeling(FDM)is one of the most commonly used 3D printing techniques and is widely used in the fabrication of polymers.The low mechanical properties of printed parts due to the limitations of their process characteristics have severely limited the scope of application of FDM-3D printed parts.The use of continuous fibers as reinforcement in the preparation process to produce higher performance continuous fiber reinforced thermoplastic composites has become a cutting-edge and interdisciplinary research topic in recent years.For FDM-3D printing continuous fiber reinforced composites,the degree of strength enhancement depends not only on the fiber content and arrangement,but also on the properties of the continuous fiber filaments.However,the existing types of pre-impregnated continuous fiber filaments for FDM3D printing are relatively few.The preparation process is immature,there is a lack of systematic research on the performance of pre-impregnated filaments,and the printing effect of different types of filaments needs further study.To address these problems,first of all,based on the characteristics of continuous fiber FDM-3D printing technology,this paper analyzed the requirements for filament materials and designs and built a pre-impregnated continuous fiber filament preparation equipment;in the second,this paper carried out a study on the preparation process and properties of pre-impregnated filament materials,revealed the mechanism of the influence of fiber and resin content on the mechanical properties of filament materials;last but not least,a study of the pre-impregnated filament printing process was carried out,and optimized printing parameters and fiber arrangement were proposed to prepare continuous fiber composite components with good mechanical properties.The main studies carried out in the project are as follows:Research on the preparation process and mechanical properties of pre-impregnated continuous fiber composite resin filaments.Using the pre-impregnated continuous fiber filament preparation equipment designed by ourselves,this paper analyzed the factors influencing the filament performance and prepared different types of carbon fiber and Kevlar fiber reinforced nylon based filaments,elucidated the correspondence between the traction speed and extrusion head diameter and the diameter of the filaments,and optimized the extrusion head diameter of 0.5 mm and the traction speed of 1.4 mm/s according to the degree of fiber and resin infiltration,surface quality,fiber drama,et al.Further analysis of the effect of different components of fiber and resin content on the tensile strength of continuous fiber composite resin filaments,the best performance of continuous fiber composite resin filaments was obtained:the maximum tensile force of carbon fiber filaments can reach 0.21 KN,and the maximum tensile force of Kevlar filaments can reach 0.19 KN.Study on the effect of different printing parameters and filament resin content on the mechanical properties of continuous fiber reinforced resin composites.The effects of different printing temperatures and filament resin contents on the mechanical properties of the composites were compared with those of various types of CF/PA6 composite filaments:the tensile strength decreased with increasing resin content of the added filament and the shear strength increased with increasing resin content of the added filament,under the condition that the total fiber content of the specimen remained unchanged;comprehensive mechanical properties and printing effect,CF-2k-0.46mm filament was preferably selected to investigate the effect of temperature on the tensile and shear strength of continuous fiber composites.The printing temperature was 280℃,and the fiber infiltration effect was relatively better,and the tensile and shear strengths showed a small peak.The effects of fiber arrangement,fiber reinforcement composition and fiber volume fraction on the mechanical properties of the composites were investigated.The shear strength of the composites was tested by the short beam shear method,and notches were machined in the middle of the specimens to test the notch sensitivity coefficient of the composites.The enhancement effect of the fiber reinforcement composition and arrangement on the tensile and shear strength of the composite was elucidated.The addition of continuous fibers significantly improves the shear strength and tensile strength of FDM-3D printed parts,but the degree of improvement is related to the fiber type and addition method,and does not increase all the time with the increase of fiber content.The addition of 0° arrangement fibers can increase the maximum tensile stress of the material by 10-18 times,and the addition of 90° arrangement fibers can increase the maximum tensile stress of the material by 30%-40%,but can effectively reduce the notch sensitivity factor by 12%-46%,which has a promising future in engineering applications.