Dynamic Characteristics and Energy Harvesting from Bi-stable Composite Plates

The bi-stable composite structures are a group of composite materials which have different applications, especially in morphing structures, because of having two stable states and no need to spend any energy to stay in each one of these stable modes. So, they have attracted the attention of many researchers and aerospace forums. The bi-stability property of these laminates is caused by the application of thermal residual stresses and the existence of differences in the mechanical characteristics of the constituent layers. Bi-stable composite sheets can be divided into laminates with straight fibers, laminates with curved fibers hybrid laminates, and mosaic laminates. The most common type of bi-stable laminates is bi-stable composite sheets with straight fibers. Unlike laminates with straight fibers, laminates with curved fibers have variable extension, bending, and extension-bending coupling stiffness. By adjusting the effective angles in bi-stable composite laminates with curved fibers, the design goals can be met. Hybrid bi-stable composite laminates are created by combining bi-stable composite laminates with metals. Also, mosaic bi-stable composite laminates are created by connecting a number of bi-stable composite laminates and composite laminates with a symmetrical arrangement.

Snap-through between stable states, which is a non-linear phenomenon, causes the bi-stable composite laminate to experience a large deformation during the jump. This special feature differentiates bi-stable composite laminates from other composite counterparts. Another important application of the bi-stable composite laminates is their use in energy harvesting systems. One of the limitations of the linear energy harvesting systems is their narrow frequency bandwidth. The snap-through phenomenon, the nonlinear behavior of bi-stable composite laminates and also the presence of various non-linear vibration regimes motivated researchers to use them as appropriate candidates to substitute linear energy harvesters. Also, due to the occurrence of large deformations during the snap-through process, energy harvesting systems based on the bi-stable composite laminates have the ability to produce more power than their linear counterparts.

In our research group at Isfahan University of Technology (IUT), many studies have been conducted on static, dynamic behavior and vibration energy harvesting of different types of bi-stable composite laminates. These studies have included carrying out experimental tests, developing semi-analytical models for small to medium sized laminates, developing a geometrically exact model for laminates with arbitrary dimensions, developing a comprehensive formulation of finite element method, as well as modeling and simulation in ABAQUS and ANSYS commercial software. In the experimental studies carried out by our group, the force and the base acceleration required for snap-through between stable states have been obtained in static and dynamic analyses, respectively. Also, in experimental tests, various non-linear vibration regimes were observed. In part of the experimental studies, the effect of the presence of magnets on the dynamic response of bi-stable composite laminate with straight fibers was investigated. The results showed that adding magnets to the laminate reduced the base acceleration required for snap-through. Our experimental and analytical studies show that laminate hybridization increases the required force for snap-through. Therefore, hybrid bi-stable composite laminates perform better in applications such as aerospace morphing structures than traditional bi-stable composite laminates. The accuracy of numerical models was measured with the help of experimental results. The obtained results showed a good agreement between numerical models and experimental tests.