Crashworthiness Of Carbon Fibre Thin-walled Beam Filled With Aluminum Honeycomb Used In Vehicle

With the ever-increasing production and sales of automobiles and the frequent occurrence of various traffic accidents,it is decisive to study the crashworthiness of automobiles in depth.The crashworthiness of automobiles is related to the safety of occupants,and is the core content of automobile safety design.The function of the energy absorbing component is very important.Carbon fibre reinforced plastic(CFRP)is an emerging lightweight material that is not only lighter in weight than metal materials such as aluminum alloy,but also has better energy absorption efficiency and high design freedom.It can be used as an energy absorbing component,supplemented by aluminum honeycomb and reasonable design,which can meet the increasingly demanding energy-absorbing requirements,while at the same time greatly reducing the weight.Therefore,research on collision safety of this emerging material and new structure is of important engineering application value.In this paper,the energy-absorbing analytical model,the numerical simulation technology,failure modes and energy absorption mechanisms of structures,influencing factors of energy absorption characteristics,and the related optimal structure theory and methods were analyzed in depth with the research results as follows:(1)The energy-absorbing theoretical model under two typical working conditions was established.Against specific lamination method,the energy-absorbing theoretical model of metal thin-walled beam was referenced for correction,and the filling effect of aluminum honeycomb was considered.The average crushing load prediction mathematical model of CFRP thin-walled beam filled with aluminum honeycomb under two typical working conditions was further established and its accuracy was verified by experiment.(2)Three key factors affecting the accuracy control of composite materials under dynamic impact loading were determined.They include,the three-dimensional dynamic constitutive relation of CFRP energy-absorbing materials considering the strain rate effect was established;the corrected Chang-Chang failure criterion and the stiffness degradation model based on fracture toughness were proposed so as to build the three-dimensional dynamic constitutive model.The comparison between numerical simulation and experiment shows that the material constitutive model obtained meets the requirements of collision simulation accuracy.(3)By means of numerical simulation and dynamic impact test,the failure modes of CFRP thin-walled beam filled with aluminum honeycomb under two typical working conditions were analyzed.Studies show that the failure modes under axial compression mainly include three types such as layer bending failure,lateral shear failure and local buckling failure.The transverse bending process is different from the axial compression,and its failure mode mainly incorporates lateral shear failure and layer bending failure.Besides,the energy-absorbing mechanisms of the corresponding failure modes under two working conditions were analyzed and the results show that the lateral shear failure has the highest utilization rate of materials and the most absorbed energy.(4)Based on numerical simulation and dynamic impact test,the effect of different factors on the energy-absorbing characteristics under axial impact conditions was studied.The influence factors include: wall thickness,tube length,lamination angle,lamination ratio,impact velocity,aluminum honeycomb filling effect and side length of the aluminum honeycomb core.It is found that proper wall thickness and tube length are beneficial to the energy absorption of the structure;the selection of lamination angle and ratio cuts both ways,and should be considered as a whole in the design.Excessive impact velocity is not conducive to occupant protection,and the design of energy-absorbing structure should also ensure that the impact energy is fully absorbed.The aluminum honeycomb filled thin-walled beam can obviously improve the crashworthiness of CFRP thin-walled beam,and the smaller the side length of the aluminum honeycomb core under axial impact,the more favorable it is to the improvement of the energy-absorbing characteristics of the crash-resistant structure.The double chamfering initiation method is more beneficial to controlling the structural damage and the energy absorption of energy-absorbing units.Under the impact condition,the load-displacement curve oscillates more violently than that under the quasi-static condition,and absorbs more energy.(5)Based on numerical simulation and dynamic impact test,the influence factors of the energy-absorbing characteristics under lateral impact were also analyzed.The influence factors include: wall thickness,lamination angle,lamination sequence,lamination ratio,impact velocity and aluminum honeycomb filling effect.Studies have shown that proper increase of wall thickness can effectively improve the energy absorption(EA)and specific energy absorption(SEA);the effects of the lamination angle and the lamination ratio are just the opposite of those under the axial impact condition.The selection of different angles and ratios cuts both ways and a comprehensive consideration is needed in design.Cross-laminations of large and small angles can absorb more energy during the impact process.The impact velocity has the effect similar to that under axial impact,so formation of excessive initial load peak value Fmax should be avoided so as not to cause damage to occupant.The design of energy-absorbing structures should also ensure the full absorption of impact energy.The aluminum honeycomb filled CFRP thin-walled beam can significantly improve the buffer energy-absorbing characteristics,and the smaller the side length of the aluminum honeycomb core under the lateral impact,the more favorable it is to the improvement of the energy-absorbing characteristics of the crash-resistant structure.(6)Specific to the two typical working conditions,crashworthiness optimization of the filled structure was performed.The optimization design method incorporating the use of orthogonal test to select sample points,the agent model based on radial-basis method to build evaluation index,and the NSGA-II multi-target genetic optimization algorithm for solving the optimal Pareto solution set was proposed.The optimized design results have improved the safety features of the energy-absorbing structures.The design method is of high computational efficiency and suitable for composite engineering problems.