Instability and softening in a continuous bi-rod

We present a continuous bi-rod structure composed of two flanges and a pleated web. The structure is characterised by an instability mechanism that couples axial contraction and twisting. In so doing, the latter can be controlled by the former. Moreover, a remarkable softening response is observed immedi-ately after the critical state. A custom testing machine has been designed and manufactured in order to experimentally investigate the mechanical response of the continuous bi-rod. Full scale finite element simulations have been also performed to provide a deeper understanding of the relative contribution of the flanges and the pleated web to the observed mechanical response. The features exhibited by the continuous bi-rod pave the way for innovative technological applications in areas of growing interest (e.g., compliant mechanisms, morphing and deployable structures).(c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).