Crashworthiness Optimization Design Of Composite Thin-walled Structures

The automotive crash safety has always been as one of the major concerns of researchers in national or aboard. Furthermore, improving buffering and energy absorption capability of energy-absorbing structures of vehicle is a key part of safety issues. While with the rise and rapid development of composite, it has been widely used in automotive field to replace traditional metal materials because of its excellent properties including high specific energy absorption and strength. So it is necessary to investigate crashworthiness of composite structures. This article employed theoretical analysis, experiment analysis and finite element simulation methods to study and analyze the compression energy absorption capacity of composite thin-walled tubes, and found some factors which affects its energy absorption capacity and conducted optimization design for composite tubes with the goal of maximum specific energy absorption. The main work of this paper is as follows:(1) Basic theory of composite mechanics and classical theory of cylindrical laminated shell were introduced. Mechanical analysis for composite tubes was conducted. A brief introduction of optimization design theory was given and the optimization problem of crashworthiness was defined.(2) The impacts of trigger structure, lay-up condition and foam filler on energy absorption capacity and failure mode of composite tubes was investigated by quasi-static axial compression tests. The following conclusions were obtained: Performing chamfering could effectively decrease the initial peak load; Adding a certain number of axial layers could effectively increase the SEA of the tube; Foam filler could improve the SEA of the tube.(3) Based on experimental results, LS-DYNA was used to establish the numerical models of composite tubes. Failure parameters in MAT54 was determined. Then multi-layer shell elements was used to model the failure models of composite tubes.(4) Energy absorption capacity of metal and composite thin-walled structures with the same geometry was compared and the influence rule of the impacts of geometry was analyzed by numerical simulation methods. The results suggest that because of the difference between the failure modes of GFRP and aluminum tubes, the GFPR circular tube shows the best performance in terms of energy absorption than that of the tapered tubes and the square tube. While for aluminum tubes, the tapered tube is the best. And then optimization design was conducted for the diameter, wall thickness and lay-up condition of composite tubes with the goal of maximum specific energy absorption. The results show that appropriately increase the wall thickness and decrease the diameter of the tube could improve its SEA.