Comparison of the crashworthiness of 3D printed circular multi-cell structures with graded height and different numbers of feders

Purpose The purpose of this study is to investigate the crashworthiness performance of bio-inspired circular multi-cell tubes with graded wall heights and different feder arrangements for automotive safety applications. Inspired by the morphology of turtle shells, the study aims to maximize energy absorption (EA) and specific energy absorption (SEA) while minimizing peak crash force (PCF) to enhance passenger safety. It seeks to determine the optimal geometric parameters of lightweight PLA + structures produced via 3D printing technology to achieve superior impact resistance. Design/methodology/approach Energy-absorbing tubes were manufactured using Fused Deposition Modeling (FDM) with sustainable PLA + filament. A Taguchi L9 orthogonal array experimental design was used to minimize the number of experiments. The study analyzed four control parameters: number of feders, side-by-side feder arrangement, height difference between inner/outer cylinders and tube thickness. Quasi-static axial compression tests were conducted to evaluate deformation behavior. Performance indicators, including SEA, EA, PCF and Crash Force Efficiency (CFE), were analysed using Signal-to-Noise (S/N) ratios to determine optimal geometric configurations. Findings Results indicate that tube thickness and side-by-side feder arrangement significantly influence total EA and CFE. The graded height design successfully controlled initial deformation stages. Taguchi analysis identified the F6S3T2H2 configuration as optimal for maximum energy dissipation capacity. Conversely, the F4S1T1H6 design demonstrated the lowest PCF, offering a smoother crushing behavior beneficial for reducing deceleration risks. Increasing the number of side-by-side feders improved structural stability and CFE significantly, while single-feder designs exhibited lower performance due to crack propagation during crushing. Originality/value This paper presents a novel energy absorber design combining turtle-shell-inspired morphology with graded height differences and specific feder arrangements. It uniquely applies the Taguchi method to optimize these geometric parameters for PLA + structures produced via FDM. The study provides valuable experimental data on the crashworthiness of graded multi-cell structures, offering a lightweight solution for enhancing passive safety systems in the automotive industry. It specifically highlights the critical role of feder arrangement in maintaining structural integrity under load.