Study On Temperature Sensitivity Performance Of AL-CFRP Circular Tubes Under Axial Crushing

Aluminum-carbon fiber composite（AL-CFRP）tubes can be used as front rails for automotive applications.The structure combines light and high strength CFRP with high ductility metal aluminum to improve lightweight performance while maintaining structural crashworthiness.Al-CFRP circular tube is a composite structure of two materials.Under the condition of axial crushing,the failure mechanism and failure mode of the two materials are different,and the failure mode of the composite structure is more complex than that of the single material structure.In addition,CFRP is temperature-sensitive,which results in the change of axial crushing performance of Al-CFRP circular tubes at different temperatures.In this paper,axial crushing test and LS-DYNA finite element analysis software are combined to study the axial crushing performance of CFRP and Al-CFRP circular tubes at different temperatures.The temperature test of CFRP laminates was carried out by selecting appropriate metal and CFRP material models,the contact between carbon fiber layers and the contact between carbon fiber and aluminum alloy.MAT24 elastoplastic material model was used for metal materials.MAT54 material model was used for CFRP materials.Contact type cohesion method was used for the interlamination contact of carbon fiber and the contact between carbon fiber and aluminum alloy.TIEBREAK failure criterion was used to determine the initiation of damage,and damage evolution was carried out based on the release rate of fracture energy.The tensile test,compression test and in-plane shear test of CFRP laminates were carried out to obtain the mechanical properties of CFRP laminates at different temperatures.Quasi-static axial crushing test and simulation of CFRP circular tubes at 25℃,50℃and 80℃were carried out to analyze the failure mode,crushing load-displacement curve and axial crushing performance of CFRP circular tubes.Firstly,the axial crushing tests of two different lay-up forms[（90°）₆/（0°）₆]and[（0°）₆/（90°）₆]at 25℃were carried out.Secondly,the axial crushing tests of the lay-up forms[（0°）₆/（90°）₆]at different temperatures were carried out to establish the quasi-static axial crushing model of the CFRP circular tube with four layers of shell elements.The test results were compared.Finally,the sensitivity of axial crushing performance of CFRP circular tubes to temperature was analyzed.The quasi-static axial crushing test and simulation of Al-CFRP tubes were carried out at 25℃,50℃and 80℃.The failure mode,crushing load-displacement curve and energy absorption of Al-CFRP tubes and carbon fibers were analyzed.The quasi-static axial crushing model of Al-CFRP circular tubes was established,in which the carbon fiber circular tubes were laid in the form of[（0°）₆/（90°）₆].The numerical simulation results were compared with the experimental results to verify the accuracy of the numerical simulation method.Finally,the sensitivity of the axial crushing performance of Al-CFRP circular tubes to temperature was studied.The quasi-static axial crushing of AL-CFRP tubes at 25℃,50℃and 80℃was tested and simulated.The failure modes,crushing load-displacement curves and energy absorption of aluminum tubes and carbon fiber tubes were analyzed.The quasi-static axial crushing model of AL-CFRP circular tubes was established,in which the carbon fiber circular tubes were laid in the form of[（0°）₆/（90°）₆].The numerical simulation results were compared with the experimental results to verify the accuracy of the numerical simulation method.Finally,the sensitivity of the axial crushing performance of AL-CFRP circular tubes to temperature was studied.The temperature sensitivity of Al-CFRP and CFRP tubes with a laying angle of[（0°）₆/（90°）₆]was studied.Fiber tension and compression damage in CFRP tubes are not affected by temperature.The higher the temperature is,the faster the damage expands and the more serious the damage is.The tensile damage of the matrix is most obviously affected by temperature.With the increase of temperature,the total internal energy of carbon fiber tube and aluminum tube decreases gradually,and the percentage of internal energy of aluminum tube increases gradually,and the percentage of internal energy of carbon fiber tube decreases gradually.Al-CFRP circular tubes have better axial crushing performance than CFRP circular tubes.When Al-CFRP circular tubes are used in automobiles as front rails,considering the influence of temperature on the axial crushing performance of Al-CFRP circular tubes,the design safety factor should be improved to avoid the harm caused by temperature sensitivity.