Research On Mechanical Properties Of Carbon Fiber Hybrid Material Joint

Carbon fiber reinforced composite material(CFRP)is considered to be a reasonable material for automobiles because of its excellent mechanical properties and ultra-light weight.It is expected that the use of carbon fiber materials will reach 5% of the total number of cars in 2030.In order to study its application in the car body load-bearing structure,realize the reasonable design of the material and structure.Therefore,in this paper,the B-pillar lower joint is selected as the experimental and simulation object.Through the experimental design of mixing and matching three different materials,the three materials are mixed.They are pure thermosetting carbon fiber joints(upper carbon fiber shell,lower plate carbon fiber bottom plate);carbon aluminum joints(upper carbon fiber shell,lower plate aluminum plate);foamfilled carbon-aluminum joints(hollow portion of polyurethane foam filled in the middle of the carbon-aluminum joint).Three kinds of joints were subjected to quasi-static bending test and low-speed dynamic impact test to study the mechanical properties and failure mechanism of their structures.The main content of the thesis includes:For the production and process of carbon fiber standard parts,referring to the standard test method developed by the American Society of Testing Materials,three different standard parts for tensile,compression,and shear parts are made and tested separately to obtain the mechanical properties of the carbon fiber material.Design the simplified structure of the joint under the B-pillar and prepare them.Perform static structural mechanical bending test,test the force-displacement curve of the joint at the compression point under static conditions and obtain mechanical properties such as joint stiffness,strength and peak force to evaluate the bearing performance of the three joints;design and simulate the quasi-static bending test of the joints,compare the simulation results with the test results to verify that the test failure form is accurate and evaluate the performance of the three joints.The stiffness and strength of the three joints is in order that the filled carbonaluminum joint is better than the carbon-aluminum joint than the thermosetting pure carbon fiber joint.The bending performance of the carbon fiber joint is mainly affected by the flexural strength of the bottom plate,and the bending performance of the other two joints is mainly affected by the factor of shear strength of the carbon fiber shell.Design of low-speed impact test for B-pillar joints,the dynamic experiments were conducted at an intermedium strain process.Outputting force and time curve through sensor;high-speed camera which is easy to review and analyze after the experiments shooting the whole process of the experiments.Retrospective analysis of the experimental process,and the new high-speed strain gauge make more stable and accurate testing of the strain of this experiment.The test results obtained the force-displacement curve and stress-strain curve of the three joints,described the entire test process of the three joints,and compared the dynamic bearing performance of the three joints;the dynamic simulation of test process is designed,and the simulation results are compared with the test results to verify the test accuracy.At the same time,the peak force,intrusion amount and specific energy absorption obtained by the three simulation results are compared and evaluated for the three joints.According to the dynamic low-speed impact test of the joint,the severity of the surface damage of the three joints is that the filled carbon aluminum is better than pure thermosetting carbon fiber and better than carbon aluminum;the damage of the joint bottom plate is slightly deformed by the filled aluminum alloy,and the pure thermoset carbon fiber joint bottom plate is slightly deformed,Carbon aluminum chassis aluminum alloy deformation is large.There was no obvious damage to the connection parts of three joints.Finally,the paper summarizes the full-text research results,compares and summarizes the performance advantages and disadvantages of the three material joint structures,and obtains the conclusion that the carbon fiber hybrid material joint structure can take into account the structural stiffness,energy absorption,and cost application feasibility.And analyze the shortcomings of this article to get prospects.The research content will be beneficial to the further engineering application of carbon fiber materials in key body structures.