Crashworthiness analysis and multi-objective optimization design for foam-filled spiral tube

•A novel foam filled spiral tube (FFST) was firstly presented and manufactured by 3D printing.•Crashworthiness characteristics of FFSTs were systematically investigated.•A theoretical prediction model to predict the mean crush force of FFSTs was proposed and validated.•Multi-objective optimization design and comparison on FFSTs were conducted. Thin-walled structures, due to their favorable mechanical properties and exceptional energy absorption capabilities, find extensive applications across various engineering fields. This study, drawing inspiration from natural spiral structures, introduces a novel foam-filled spiral tube (FFST) to further enhance the crashworthiness of thin-walled structures. The spiral tubes (STs) and random foam are additively manufactured. Quasi-static compression tests are undertaken to investigate the energy absorption properties of STs, foam and FFSTs. Unlike conventional methods, this study adopts micro-computed tomography (micro-CT) technology to understand the mechanisms of interaction between the foam and ST. The parametric study is performed based on the finite element model to evaluate the influence of meso‑structure properties of tubes and foam fillers on the crashworthiness and deformation modes. The experimental results indicate that an increase in the wall thickness of both the ST and foam leads to a simultaneous increase in specific energy absorption (SEA) and initial peak crushing force (IPCF). Conversely, a decrease in the wavelength and an increase in the amplitude of waves results in the reduction of both SEA and IPCF, along with an enhancement of crushing force efficiency (CFE). Micro-CT images indicate mutual extrusion between the foam and ST and with a reduction in wavelength, the number of folds in the samples increased, thus enhancing the energy-dissipation capacity. The numerical results reveal a strengthening of interaction between the foam and ST with decreasing wavelength and increasing foam cell wall thickness. A theoretical model is proposed for predicting the plateau stress of FFSTs based on the energy conservation principle and the plastic hinge theory. Comparisons between theoretical and test results exhibit good agreement. Comparing the FFST obtained through multi-objective optimization design with an ST featuring same structural parameters, it is observed that the IPCF increases by 8.00 %, SEA increases by 18.10 %, and the undulation of load-carrying capacity (ULC) decreases by 31.96 %. Finally, thr