Abstract
dc:description.abstractThin Shells are widely used structural elements but are often limited to simple geometries. Special geometric designs can optimise performance through light yet stiffer shell structures. Creasing is one such method that has attracted a lot of traction lately. Many of these structures are underpinned by motion localised within creases, albeit some that exhibit soft modes of deformation from facet bending, leading to non-rigid Origami. These non-rigid Origami structures offer several functional behaviours such as tunable stiffness, deployability, and shape morphing. As such, the potential use of creased shells in a range of applications is intriguing. However, of dominant interest in this thesis is analysing the geometric and mechanical fundamentals of a crease in a shell instead of developing a particular solution. In analysing non-rigid Origami to qualify for practical applications, non-isometric mechanical models are crucial to determine the shape and mechanics of the resulting structure. The simplification of finite element modelling proposed in this thesis offers a solution that can capture the geometric intricacies and mechanics of non-rigid Origami which are not captured by simple isometric models, with computational efficiency. This validated FEM has been used to explore the geometry and mechanics of simple but interesting non-rigid Origami structures throughout the thesis, and compared against simple analytical models. A straight crease embedded in a thin metal sheet serves as a starting point for exploring non-rigid Origami. This is approached by classifying the problems based on the location of the crease ends, and geometric constraints. Simple energy arguments along with experimental and finite element models are utilised to capture the underlying mechanics. It is found that the geometry of the creased sheets with a single straight crease depends on the location of the crease end, the extent of the sheet, the thickness of the sheet, and the degree of deformation or the fold-angle. Following this, a similar approach is employed to investigate curved creases. Unlike straight creases, the creasing method influences the deformation of the sheet with a curved crease, the effect of which is explored using differential geometry and simple plate buckling analogy where a good agreement with finite element models are observed. This reveals that a curved crease introduces mechanical frustration in one way or the other. The finite element solutions capture the many nuances in geometry of the curved creased sheets that analytical models with isometric assumption overlook. Finally, a posteriori from the two single crease studies are utilised to explore several cases of intersecting creases and understand their geometry and force-displacement mechanics. A parametric study revealed the geometric and material parameters that affect the bistability of mulitply-creased sheets, which can then be fine tuned to suit a wide range of applications. Throughout this thesis, the intention has been to pursue simple analytical methods supported by informal/formal observations obtained from small-scale physical experiments, to derive generalised insights and relationships. These will serve as a building block for applications of non-rigid Origami using straight/curved creases. Insights into the straight and curved creases and associated compliance and bistability from this study can be leveraged by engineers for a range of novel technologies from nano-scale air vehicles, developable mechanisms, switches, actuators to macro-scale satellite technologies.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2023
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Mierunalan, Seyon
- Advisor dc:contributor.advisor
-
- Seffen, Keith
Subjects
dc:subject × 8Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.108161
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/367645