Date of Award
Master of Science (MS)
Oliver J Myers
Thin bistable composite laminates can be used for shape morphing applications by virtue of their material properties and asymmetric ply layup. These laminates are called bistable because they can be snapped into two or more stable shapes. A single bistable patch can result in simple cylindrical shapes and when multiple such patches are assembled into a single multi-patch laminate they result in more complex and multiple stable shapes that can find wide practical use in shape morphing applications. To be able to design such multi-patch laminates we need to have models that can predict the stable shapes of such laminates based on the input of laminate parameters which includes but is not limited to variables like patch shape and size, number of plies, ply thickness, material properties, etc. These models can then be used to establish a design method based on optimization to solve the inverse problem of solving for the laminate parameters given a specific target shape(s).The curing and snap through of these laminates could be simulated using Finite Element analysis to solve for the stable shapes. But due to the large computational costs associated with simulating multi-patch laminates, using FEA in the optimization model is not preferred and alternate surrogate models need to be considered. Analytical models exist that can approximate the stable shapes of the laminates from the input of material properties and laminate geometry. These models correlate with FEA and experiments to a satisfactory degree and could be used for design purposes. Additionally, machine learning is also considered as an approach to solve the problem since it is data driven and a computationally cheaper tool as compared to FEA. In this research, the aforementioned surrogate models are explored and their feasibility to design multi-patch laminates are investigated. The most suited model is then used to design a four-patch grid laminate targeting a specific shape(s). Additionally, this research delves into the novel idea of designing Kirigami composites. Kirigami is an ancient art of paper cutting which is popularly used to make decorative shapes. Using this method, simple cut patterns can be made on a 2D sheet to yield complex 3D shapes. Thus, the disparate concepts of Kirigami and bistability could be integrated to achieve unprecedented shape morphing capabilities. Current work in this area investigates the geometry and simulation of the curing and snapping process of Kirigami composites using FEA and correlates them with experimental results. In this study, the surrogate models discussed earlier are extended to develop an approach to compute the shapes of these laminates in a computationally cheaper method.
Biju, Jebin, "Surrogate Modeling of Single, Multi-Patch and Kirigami Composite Laminates for Design Purposes" (2021). All Theses. 3521.