Axial mechanical properties and robust optimization of foam-filled hierarchical structures

Abstract

In this study, two novel foam-filled hierarchical structures are proposed, namely foam-filled square hierarchical tubes (FSHT) and foam-filled circular hierarchical tubes (FCHT). First, dynamic FEA models of the foam-filled hierarchical tubes are established by LS-DYNA and validated against experimental data. The mechanical behaviors of the foam-filled hierarchical tubes under axial load are investigated. The results show that novel foam-filled hierarchical tubes have better crashworthiness performances than conventional foam-filled square tubes (FST) and foam-filled circular tubes (FCT). Then, the theoretical solution of energy absorption is developed, and its accuracy is validated. Next, the design parameters (foam density and thin-wall thicknesses) of FSHT and FCHT are analyzed by orthogonal array design, and the effects of design variables on crashworthiness are studied. Finally, to obtain the optimal design parameters of FSHT and FCHT, the robust optimization method considering the manufacturing uncertainty is implemented by employing the interval uncertainty model (IUM) and the feedforward neural network (FNN). Structures obtained with the proposed robust optimization method are of more stable performance compared with the traditional deterministic optimization counterparts. The findings provide a hybrid design combining hierarchical tubes with foam fillers with superior crashworthiness performance for energy-absorbing devices, and the robust optimization method can be used to design efficient lightweight crashworthy structures.