Equipment And Process Research For 3D Printing Of Continuous Fiber Reinforced Nylon

The 3D printing process of continuous fiber reinforced thermoplastic composites is an advanced manufacturing technology that combines the high freedom of 3D printing with the high performance of continuous fiber reinforced thermoplastic composites(CFRTPC)to achieve rapid prototyping of high-strength,complex parts.However,the 3D printing process of CFRTPC composites still suffers from the outstanding problems of poor surface quality of printed products and weak interface bonding,which makes it difficult to meet the requirements of industrial production for high-performance composite materials and greatly limits the application and development of 3D printed composites.This project uses staple fiber reinforced nylon 6 composite and continuous fiber reinforced nylon 6 composite(CGF/PA6)as printing materials,and uses fused deposition molding(FDM)dual-nozzle 3D printing technology to mold a"sandwich"sandwich composite with short fiber layers on the top and bottom and continuous fiber layers in the middle.The effects of material components and printing process parameters of CGF/PA6 prepreg on the microstructure,porosity and mechanical properties of sandwich structure composites were investigated in this study,which effectively solved the problem of poor surface quality of 3D printed CFRTPC composites.The ultrasonic vibration device was also introduced into the 3D printing process,and the vibration effect and thermal effect of ultrasonic waves were used to promote the full diffusion and fusion of polymer molecular chains at the molten deposition interface,which effectively improved the surface quality and interlayer bond strength of the composites.The main research results are as follows.1.In this project,the CGF/PA6 prepreg wire was prepared by melt impregnation process,and the compatibility of the prepreg with 3D printing technology was explored.The effects of glass fiber type,glass fiber content and compatibilizer content on the comprehensive functions and microscopic morphology of the CGF/PA6 were researched,and the optimal prepreg wire components were determined.2.The sandwich structure composites were prepared by FDM dual-nozzle3D printing process.The effects of temperature,speed and layer thickness of3D printing on the surface quality,mechanical properties,porosity and microstructure of the sandwich structure composites were investigated to determine the optimal printing process parameters.When the thickness of CGF/PA6 sandwich layer was 2.8 mm,the tensile strength,bending strength,bending modulus,impact strength and interlayer shear strength reached 290.7MPa,275.44 MPa,10.761 GPa,168.19 k J/m~2,and 26.52 MPa,respectively.3.An ultrasound-assisted 3D printing device was designed to investigate the effects of ultrasonic frequency on the surface quality,interfacial properties and mechanical properties of the composites.When the ultrasonic frequency was 50 KHz,the tensile strength,flexural strength,flexural modulus,impact strength and interlaminar shear strength of the composites were 521.5 MPa,397.11 MPa,34.42 GPa,272.29 k J/m~2and 62.301 MPa,respectively,comparing with the mechanical properties of the composites without ultrasonic treatment under the same printing process,which were improved by54.57%,28.63%,41.32%,22.74%and 138.43%,respectively.The research results of this study have important theoretical guidance to promote the development of 3D printing technology of CFRTPC composites,which can expand the application of 3D printed CFRTPC composites in the field of structural composite materials.