Design and Analysis of Multi-Patch Composite Plates for a High Multi-Stability of a Morphing Skin

The morphing structures are a significant research area in engineering industry, especially, the fields of aerospace and aircraft which aim at improving performance over a wider range of normal operating conditions. The most challenging design requirement of a morphing structure is a skin, which exhibits both in-plane compliance and out-of-plane stiffness. An asymmetric composite laminate is as good candidate for achieving a morphing skin. By curing the unidirectional composite laminate at elevated temperature and cooling at room temperature, a phenomenon of bi-stability is mainly caused by the mismatch in the thermal expansion coefficients of lamina within the laminate. In practical applications, a single bi- stable composite cannot fulfil multi-stable configurations required for a multifunctional surface. For this reason, a number of bi-stable composite laminates is connected together as continuous surface for showing a higher degree of multi-stability.

In this dissertation, the model of Multi-Stable Composite Surface (MCS) is presented by tailoring bi-stable composite patches together in a (m×n) grid form, and then the model is extended to connect a mix of bi-stable and mono-stable composite patches. This new modification on the model reduced the interactions between adjacent bi-stable composite patches in order to show more distinct stable shapes. Based on these results, a novel connection approach is presented by introducing a flexible aluminum strip between connected bi-stable composite patches. This Multi-Stable Hybrid Surface (MHS) shows a theoretical maximum 2𝑛 stable configuration for 𝑛 number of bi-stable composite patches. These stable configurations are interesting shapes that may be used to create a large multi- stable surface as a useful device in a morphing skin application. Finally, potential applications of multi-stable hybrid surfaces are introduced. This work could be used as a guideline for design of a large multi-patch morphing skin in order to improve the multi- functional structures.