Study On Multi-axial Warp Knitting Fabric Pultrusion Technology And Its Application In Rail Transit Vehicle Parts

This study explores the application of multi-axial woven fabric pultrusion technology in typical components of rail transportation structures.By focusing on the structural characteristics and operational requirements of key load-bearing and secondary load-bearing components in rail vehicles,the researchers conducted an in-depth investigation starting with hat-shaped beams.They emphasized the design of fabric layup,preforming,and closed-mold injection molding techniques for pultrusion preparation of hat-shaped beams.Through characterization analysis and mechanical performance testing,the researchers confirmed the good processability and mechanical properties of pultruded components made from multi-axial woven fabric.Additionally,they extended their research to the design and preparation techniques of complex multi-cavity support grooves based on hat-shaped beam pultrusion technology.They also developed preforming techniques suitable for fabric pultrusion of multi-cavity structures.The study gradually expanded to cover research on complex multi-cavity irregular structures and large-width components,along with the design of novel connectors for pultruded sections.These breakthroughs contribute to the application of composite pultrusion technology in major components and load-bearing structures of rail vehicles.The mechanical performance of the designed fabric pultruded components was analyzed using simulation methods,and non-standard component-level tests were conducted.By comparing the simulation results with the mechanical performance test results,the feasibility and advancement of multi-axial woven fabric pultrusion technology for large-scale,cost-effective applications in rail vehicles were demonstrated.This study provides a reliable technical solution for the lightweight and cost-effective application of composite materials in the next generation of rail vehicles.It aligns with the national goals of carbon neutrality and the development needs of energy efficiency,emission reduction,and lightweight in the rail transportation industry.It will drive the widespread use of domestically produced carbon fiber composite materials in the field of rail transportation,enhance regional economic strength,improve industrial structures,and strengthen the core competitiveness of China’s rail transportation equipment.The main research work and achievements are as follows:1)Analysis of carbon fiber multi-axial woven fabric materials and research methods for rail transportationStarting from the application requirements of rail vehicles,the performance suitability of multi-axial woven fabric in rail transportation vehicles was studied.Based on the structural differences between multi-axial woven fabric composites and traditional composites,modeling and analysis methods for multi-axial woven fabric were established.2)Preparation and performance testing of carbon fiber multi-axial woven fabric pultruded laminatesPultrusion process was used to produce laminates of carbon fiber multi-axial woven fabric.Laminates were prepared using 25 K tow woven LPTN800 four-axial woven fabric and carbon fiber yarn.To analyze the performance difference between the pultruded laminates and the yarn flat panels,mechanical performance tests were conducted on both types of samples.Comparing the results of the yarn panels with the four-axial woven fabric pultruded laminates,it was observed that the axial performance(0° direction)of the four-axial woven fabric was lower than the yarn pultruded panels,but the non-axial performance(90° direction)improved significantly.This provides a basis for designing beam structures under complex conditions and serves as reference data for evaluating the mechanical performance of fabric pultrusion in rail transportation.3)The design and verification of composite materials for closed hat-shaped beam using yarn pultrusion and fabric pultrusion.Different schemes for fabric layup and yarn pultrusion were designed.The simulation analysis results of different schemes under typical conditions in rail transportation were studied.The feasibility of using the best four-axial woven fabric for pultrusion of a single-cavity hatshaped beam was investigated.The study included cavity layup design,encapsulation scheme,preforming design,mold design,and molding technology.A preforming fabric cavity encapsulate,preforming tooling,and molding molds for hat-shaped beams were designed and developed.The samples were produced using closed mold injection molding,and the curing degree,porosity,fiber distribution,internal defects,and mechanical properties of the components were characterized and tested.The study explored the feasibility and mechanical performance of pultruded structures using carbon fiber multi-axial woven fabric.The results showed good mechanical performance,processability,and quality of the pultruded hat-shaped beams,suggesting great potential for their large-scale application.4)Design and preparation technology of multi-cavity irregular support grooves and their application research.To further investigate the feasibility of complex multi-cavity load-bearing beam structures in rail transportation,the design,encapsulation,preforming,and overall component simulation analysis of carbon fiber axial fabric pultrusion were carried out focusing on support grooves in equipment compartments.The mechanical performance analysis and testing under overall equipment compartment conditions were conducted to study the feasibility of their application in equipment compartments.Through the development of fabric layup design and complex multicavity preforming technologies using carbon fiber multi-axial woven fabric,complex multicavity support grooves were successfully produced and applied in equipment compartments made of carbon fiber composite materials for mechanical performance testing.The results showed that the support grooves did not deform or suffer damage during the overall equipment compartment testing,meeting the application requirements of rail transportation equipment compartments.5)Design,preparation technology,and application research of large-width skirt panels made of composite materials.Functional and load condition analysis of large-width skirt panel structures led to the design of composite material structures for traditional carbon steel skirt panels.A novel pultrusion structure scheme for composite skirt panels was designed to reduce the number of connections compared to the original metal skirt panels and achieve efficient connections suitable for the pultruded skirt panel cross-section.Building upon the fabric layup design and preforming scheme of hat-shaped beams and complex multi-cavity support grooves,the skirt panel was designed with fabric layup and preforming schemes.Samples of large-width skirt panels were produced and subjected to mechanical performance testing.The results showed improved mechanical performance compared to carbon steel skirt panels,achieving a weight reduction of 50%compared to carbon steel skirt panels.The goal of this research is to achieve low-cost mass production of composite materials for rail transportation vehicles,with a focus on high-speed train sets.The study involves the design,preforming,and molding technology research for typical load-bearing and secondary loadbearing components using fabric as the reinforcing material.Key technical challenges such as complex support groove layup design,precise preforming of carbon fiber,and closed mold multipoint injection molding have been overcome.The project has the capability to design carbon fiber composite components for high-speed train sets and has generated complete sets of design data for production.A process system for multi-cavity pultrusion of carbon fiber fabric and rapid pultrusion of large cross-sections has been established.The project aligns with the needs of energy-saving,emissions reduction,and lightweight development in rail transportation and will strongly promote the mass application of domestically produced carbon fiber composite materials in the field of rail transportation.It is of great significance in enhancing regional economic strength,promoting industrial structure upgrading,and consolidating the core competitiveness of China’s rail transportation equipment.