Mechanical characterization of bistable laminates for very small aircraft morphing applications

This work is concerned with the mechanical characterization of bistable composite plates in order to investigate their nonlinear behavior dependence on mechanical factors, e.g. strain, stress trends and potential energy. The bistable laminates have two stable shapes that are actuated by a variety of mechanisms (piezoelectric ceramic based actuators, shape memory alloys or thermal actuation) to induce "snap-through" between states. These composite structures are receiving interest in several aeronautic applications such as shape changing applications without the need of servoactivated control systems. Scope of the work is to describe the "0" strain-stress status of the asymmetric bistable laminates, immediately after the manufacturing process. An experimental testing is carried out with the purpose of collecting enough data for the numerical and analytical analyses. Numerical simulations based on Finite Element Models (FEM) are used to study strain and stress fields of the laminates and successively to validate semi-analytical results. By the Classic Plate Lamination Theory (CLPT), an analytical model is developed to provide an interpretation of the bistability phenomenon. The experimental results, with FE and CLPT models, help to understand the relation between the mechanical features of the composite laminate and the bistability phenomenon. This paper reports on detailed nonlinear characterization of bistable plates using numerical, analytical and experimental data in order to provide a starting point for future works characterizing bistable strain-stress evolution over the time.