The Integrated Design Method Of Carbon Fiber 3D Printing Crash Box

The automobile crash box can absorb the collision energy effectively when the low-speed collision occurs,so that it can reduce the damage probability of some high-cost parts such as the front longitudinal beam and protect the passengers.The performance of the automobile crash box determines the safety and maintenance cost of the vehicle in low-speed collision.In order to design and manufacture the crash box with objective performance.In this thesis,taking the advantages of material designability in 3D printing,the material-structure-performance integrated design method for the crash box is studied.Aiming at the desired performance of the crash box,the parameters of the required materials and structrues are deduced,then the performance of the crash box is optimized and the parameters of better-performance materials and structures are calculated.In terms of crash box material,this thesis investigated the carbon fiber reinforced nylon 3D printing composite materials and their preparation methods and printing process.Then this thesis measured the mechanical parameters of the 3D printing material with 5%-15% carbon fiber proportion by mechanical tests and summarized the material properties model according to the changes of material mechanics parameters.In terms of crash box structure,taking the honeycomb structure for the structure of the crash box,this thesis built the finite element model by testing and simulation comparison and demonstrated the correctness of 3D printing material parameters.This thesis selected 4 kinds of honeycomb structures and deduced the formulas of their relative densities.This thesis kept the same relative densities for these honeycomb structures by using the CAD parameterized method and simulated the in-plane compression by the finite element model to compare the energy absorption capacities.The results showed that the Kagome honeycomb performs the best in these 4 honeycomb structures with the carbon fiber 3D printing material.Therefore,this thesis took it for the crash box structure.Considering the material-structurer-performance integrated design,this thesis conducted the sensitivity analysis for the Kagome structure to find out the key design variables,and concluded the main energy absorption pattern of the Kagome structure and the impact trend of the material and structural paramters on energy absorption capacities.Taking the SEA(specific energy absorption)of a certain crash box as the objective performance,this thesis established a response surface model with structure and material parameters as the design variables by combining CATIA and ABAQUS in Isight and got the structure and material parameters with the NSGA-II genetic algorithm when the crash box meet the objective performance.On this basis,this thesis continued to optimize the crash box performance.The optimized crash box can meet the RCAR low-speed collision rules with lighter weight and higher SEA.The thesis proved that 3D printing can be adopted to introduce material design variables and realize the material-structure-performance integrated design of the automobile crash box.The required structure and material parameters can be deduced by making the crash box meet the objective performance with the method of material-structure-performance integrated design,so that the design ideas of crash boxes are expanded.