Circumventing Snap-Through Instability Through Alternate Loading Strategies

Morphing structures are structures that change shape or state to change their operating characteristics or respond to changes in environmental conditions. Thin unsymmetric cross-ply fiber reinforced composites exhibit multiple stable shapes as they are cooled from the curing temperature to room temperature due to induced residual stresses and geometric nonlinearities involving significant out-of-plane deflections. Such composites exhibit dramatic snap-through instabilities when transformed from one equilibrium position to another if triggered with force, piezoelectric materials like Microfiber composites (MFC), Shape Memory Alloys, or any other stimuli. As both shapes are stable in nature, they do not require any additional holding forces to maintain a particular shape making them attractive for applications in deployable and morphing structures. Although the snap-through process is an inherently dynamic process that encounters instability after the limit point, it has been demonstrated earlier that a complete quasi-static transition between the two stable shapes can be alternatively achieved by suitable loading strategies. In this work, we explore suitable loading mechanisms to can lead to a quasi-static snap-through by means of external moments. A new strategy is suggested, where the composite is first subjected an inward moment in two opposite edges, and then opposite moments are applied to the other orthogonal edges. Through our alternative multi-loading strategy proposed in this work, we have obtained quasi-static snap-through, thus circumventing the instability process. We further carry out an extensive parametric study to explore how such quasi-static transitions evolve with change in fiber orientation angles in fiber reinforced composite laminates.