Morphing of bistable variable stiffness composites using distributed MFC actuators

The use of piezoelectrically controlled bistable composite laminates for morphing applications has received increased attention in recent years. So far, most existing investigations have explored the possibility to trigger snap-through using large-sized piezoelectric Macro Fibre Composite (MFC) actuators bonded at the centre of the bistable laminate. However, bonding large-sized MFCs at the centre of the plate leads to flattening of the midsection of the laminate, which can result in the loss of bistability. This study presents an alternative approach of bonding distributed smaller MFCs over the entire surface of the laminate and investigate the resulting stable shapes and the change in snap-through voltages. Self-resetting piezoelectrically controlled active laminates where the MFC patches are distributed over the laminate surface have been investigated. A semi-analytical model using the Rayleigh-Ritz technique is developed to account for the distributed actuation system. Results from the proposed semi-analytical framework are verified using a corresponding finite element model. The bistable shapes, as well as the snap-through and snap-back voltages, are calculated for different distributed MFC configurations and are compared with a single MFC laminate system. Snap-through voltage predictions from the proposed semi-analytical formulation and the finite element model are compared with the experimental results for a single MFC patch available from the literature. Further, the possibility to tailor the snap-through voltages of the proposed laminate-MFC configuration is explored by replacing conventional cross-ply laminates with variable stiffness (VS) laminates generated from curvilinear fibre alignments. A finite element parametric study is performed by tailoring the VS fibre orientation parameters to achieve a bistable laminate-MFC configuration with lower snap-through requirements where the designed laminate is actuated with distributed MFC patches.