Study On Crashworthiness Of CFRP Thin-Walled Tube Filled With Gradient Foam Aluminum Structure For Vehicle Frontal Impact

With the rapid development of automobile industry,the problem of automobile safety has become more and more serious,and at this stage,China is facing serious energy shortage and environmental pollution,so it has put forward higher requirements for automobile crash safety and light weight design.Aluminum foam,as a lightweight foam metal,has good energy-absorbing properties and low price,and is an ideal filler material for energy-absorbing structures.Therefore,it is very important to study the impact resistance of CFRP thin-walled tubes filled with gradient aluminum foam inside the structure to improve the safety and lightweight design of automobiles.Firstly,based on the composite mechanics and composite failure mode,the material failure criterion and stiffness degradation model for CFRP thin-walled square tube and Crushable Foam material model for aluminum foam are determined,and the axial crush progressive damage model of CFRP thin-walled tube internal filled gradient aluminum foam structure is established.The experiments were carried out to investigate the influence of layup angle,layup ratio,layup sequence,wall thickness of square tube,aluminum foam density and gradient on the energy absorption characteristics of the energy-absorbing structure.The results show that(1)the larger the lay-up angle,the increased circumferential lay-up ratio,and the circumferential/axial/peripheral fiber layup sequence can improve the specific energy absorption of the energy-absorbing structure,but the initial load peak will increase;(2)the filling of aluminum foam can significantly improve the energy-absorbing capacity of the energy-absorbing structure,and the positive gradient of aluminum foam filling is better than the negative gradient and single density aluminum foam in improving the energy-absorbing capacity of the energy-absorbing structure.Finally,the multi-objective optimal design of the energy-absorbing structure is carried out,and the sample points are established by DOE design experiments,and the data sample points of different models are obtained by Abaqus simulation and experiments,and a double high-precision proxy model with the maximum specific energy absorption SEA and the minimum initial peak collision force PCF as the evaluation index is constructed based on the response surface function method.The NSGA-Ⅱ multiobjective genetic algorithm was used to optimize the design parameters and obtain the optimal solution of the Pareto front,and the multi-objective optimization toolbox in Design-expert was used again to optimize and verify the results.The optimal solution of the multi-objective optimization problem obtained is ρ=0.5g/cm3,the lay-up method is[±87°/±16°/±15°/±89°],the optimal ideal value of SEA is 18.2J/g,the optimal value of PCF is 18230 N,and the errors of SEA and PCF corresponding to the two optimization methods are 2.109% and 4.1828% respectively,which meet the design requirements.This thesis provides theoretical data to support the design and engineering application of the impact resistance of CFRP thin-walled tubes with internal filling of gradient foam aluminum structure.