E²F – Designing Deployable Folded Plate Structures
Motivation
A key advantage of the construction principle of folding is that it combines two fundamental technical functionalities, namely the transformability and the inclusion of statically usable stiffness. By inserting fold lines, a flat panel with a thin cross section can be converted into a heavy-duty structure. In addition these structures can be convertible, provided that the fold lines have been designed appropriately. There is a distinction between rigid foldings as a structural morphology principle for self-supporting light-weight structures and deployable foldings as a construction principle for transformable structures. Both properties – reinforcement and deployability – predestine foldable structures for applications in architecture and engineering.
Objectives
Deployable foldings form a connection between architecture and mechanical engineering by, in technical terms, combining the central aspects of construction, statics and kinematics. The design and construction of such structures demand knowledge transfer across traditional disciplinary boundaries. The objective of the research project is to enable the specific technical application of deployable foldings in architecture and engineering. For that purpose a specific design and development process has to be provided.
Approach
The problems occurring during the design and development process have to be identified and the requirements for the utilized methods need to be defined. Only then, missing methods and tools can be developed. Initially, an overview of the technically usable folding patterns and the tasks, which need to be accomplished, needs to be created. The first subgoals are the respective classification as well as the mutual allocation of tasks and potential solutions. The more in-depth study of applicable deployable foldings discusses the coherence between typical properties and the application of these foldable structures in structural and mechanical engineering designs. The focus lies on foldings in the construction industry and related disciplines such as automotive or mechanical engineering, where, among others, the influences on the folding process and the load-bearing behavior need to be examined.
Classifying convertible folds
Within the framework of market analyses and literature research, examples for transformable structures in technical applications are gathered. Subsequently, the analysis of similarities and distinctions can identify characteristic features that are suitable to describe and classify foldings consistently. In doing so, the focus should lie on foldable structures made from rigid, stiff surfaces with non-negligible, definite thicknesses. The systematic description and classification of foldings is a requirement for the development of a specific design and development process. In order to ensure a complete classification, deployable foldings from mechanical engineering, architecture and structural engineering need to be gathered systematically. The identification of characteristics requires knowledge about geometry and tessellation as well as construction and motion technology.
Classifying potential tasks
Foldings can be utilized to accomplish different types of tasks. These tasks include, among other things, the reduction of required space, for example for temporary pavilions, or the shift in effective surface, for example for facades, that adapt to the time of day and the climate situation. Besides the mere purpose, the tasks, that need to be accomplished, can be differentiated further by geometric or kinematic criteria. A systematic collocation and classification of the problems solvable by foldings is missing thus far. The identification of the present tasks and the describing boundary conditions leads to a systematic characterization of the respective task. Task classes have been defined using the descriptions. Furthermore, new potential combinations of task properties are examined to reveal further task classes and therefore new application areas for foldings.
Analysis of specific technical problems for the development of convertible folds
Many deployable originate from origami. Flexible models made from paper, a material with negligible thickness, are capable of absorbing or even resisting torsions and restraints. The considered foldable structures are composed of rigid materials with a definite thickness. The fact that the kinematic properties might vary, poses a special challenge. A key task of the complex folding structures lies in the development of details and hinges as well as in the manufacturing and the assembly process. The goal is to systematically attain knowledge about the difficulties occurring while developing convertible foldable structures. These difficulties are also the reason why deployable foldable structures are only used sporadically so far.
Assigning specific problems to established development processes
For structural approaches and methodical designing of foldable structures, previously formulated development processes can be applicable. However, these do not consider the special requirements of foldable structures that result from the interaction of various disciplines and areas of application. The assembled specific problems of foldable structures are assigned to established development processes. Based on the classification, the most suitable development process is chosen as a foundation for a specific development process.
Formulating and verifying the specific development process
A specific, customized development process supports the architects and engineers in all phases of the project. They are guided by existing guidelines and processes from engineering and architecture. The development process is expanded by further boundary conditions and requirements specific to foldings. Explicit definitions of the working steps and the respective interfaces are supposed to enable a continuous and selective application of the process steps. The formulated, specific process constitutes a hypothesis that needs to be verified for applicability. A qualitative assessment takes place through specific definition of tasks and their solving during workshops. The results and the feedback are incorporated into the process development.
Methods and tools for the development of convertible folds
In the various fields of engineering there are different methods available for the individual steps of the development process and the various aspects of designing. These aspects include approaches to determine requirements, catalogs for the selection of physical effects, procedures for dimensional synthesis of mechanisms or analytical methods such as the finite elements method and the multibody simulation. The suitability of these methods as well as the associated tools for an efficient development and designing of transformable structures are examined. In doing so, on the one hand it is necessary to examine whether the range of functions of the associated tools is appropriate and on the other hand determine the specific problems and at which particular moment of the development process they can be utilized effectively. This will reveal, if the existing methods have to be adjusted or redeveloped in order to perform the according steps in the development process.
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