Multi-layered, self-actuated devices have been the focus of recent studies due to their ability to exhibit large displacements and achieve complex shapes. Such devices have been constructed using active materials responsive to varying stimuli including electro-active and magneto-active materials to perform useful functions or satisfy objective functions related to target shapes. In this work, the authors seek to study the utility of employing materials responsive to magnetic and electric fields in combination with passive materials, and with varied placement in discrete layers and segments through a flexible beam, to design structures capable of satisfying a variety of objective functions simultaneously. These multi-field responsive composite devices, with greater complexity of the embedded combined actuation mechanisms, are able to achieve a wider variety of target shapes compared to traditional unimorph/bimorph structures actuated by a single-field. Additionally, the increased actuation design space facilitates consideration of a wider range of possible objective functions including those related to power consumption, materials’ cost, and work performed.
Fabrication of these devices for experimentation is both time-consuming and expensive. As a result, this study will utilize an existing one-dimensional model for electromagnetically-actuated composites and expand its features to include segmentation: the arbitrary placement of any active or passive material type in any layer of a given arbitrarily-sized section of the beam. Ultimately, the goal of this study is to analyze the model by varying characteristic features of multi-field actuated, multi-layered, and segmented devices undergoing large displacements under simultaneously applied fields.
Although the model is written arbitrarily for any number of segments, layers within segments, and material types, this study focuses on a base model comprising three material types: electroactive polymer, magneto-active elastomer, and a passive substrate. The initial parameters chosen for the study are the relative lengths (length ratio) of segments, volume of magnetic material, and stiffness of passive material. Two objective functions are chosen. The first is a target shape approximation function, dependent on the errors between the displacements of the computed and the desired shapes. The second calculates a cost based on volume of magnetic material. The effects of the parameters on the objective functions are analyzed by evaluating an array of combinations of parameters; results indicate that each parameter significantly influences the multi-field actuation of the beam, and these correlations are quantitatively analyzed and compared. Concurrently, metrics of power required, structure mass, and other important factors are quantified. As a result, this analysis serves as a precursor to a formal optimization algorithm by determining the usefulness of the chosen objective functions and corresponding input variables for these devices, while also identifying other possible metrics for the design optimization of a multi-field beam.
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