Controlling the Bending Response of a Multi-Layer Composite Module

Controllable bending stiffness and damping has significant applications in soft robotics, especially for soft slender manipulator arms inspired by octopus tentacles. The bending moment on a solid slender beam is balanced by the sum of moments generated by internal stresses. Resulting stresses are not controllable and decided by the bending curvature, area moment of inertia and elastic modulus of the beam. On the other hand, if a beam is a composite of multiple layers, the internal stresses caused by an external load could be related to the friction force between layers. Thus, the bending response of such a composite beam could be controlled by changing the normal pressure between layers. Based on this fundamental concept, we study a multi-layer structure, which is able to achieve variable bending stiffness and damping using several ways to modulate the friction force between layers. We perform static and dynamic tests to determine how normal inter-layer pressure, which can be controlled using various techniques, corresponds to changes in stiffness and damping ratio values. Finally, we describe the design and fabrication of a prototype composite beam comprising multiple thin layers suspended in an elastomeric substrate. Wall et. al. [1] studied using vacuum pressure to change the bending stiffness of a multilayer structure. In this work, we focus on the application of electrostatic force to modulate the normal pressure between layers by charging flexible electrodes on each sheet and compare our results with the vacuum-driven approach.