3D printing will revolutionize the manufacturing industry. Significant advances in computer aided design, additive manufacturing and materials science have opened up the possibilities of self-assembly systems, self-healing and material property alterations. Printing layer by layer allows complex geometries to be built, previously difficult under conventional manufacturing routes. This paper is a review of the current materials available for 3D printing that enable the emergence of 4D printing, a ‘smart material’ that responds in a programmed way to an external stimuli. The outlook is towards potential space applications, in all areas including deployable structures, antennas and medical supplies.

Additive manufacturing — A review of 4D printing and future applications

Review: A review of active structural control: challenges for engineering informatics

https://www.iri.upc.edu/files/scidoc/786-Tensegrity-frameworks:-Static-analysis-review.pdf

Tensegrity frameworks: Static analysis review.

This dissertation presents Thrust Network Analysis,
a new methodology for generating compression-only vaulted surfaces
and networks. The method finds possible funicular solutions under
gravitational loading within a defined envelope. Using projective
geometry, duality theory and linear optimization, it provides a
graphical and intuitive method, adopting the same advantages of
techniques such as graphic statics, but offering a viable extension
to fully three-dimensional problems. The proposed method is
applicable for the analysis of vaulted historical structures,
specifically in unreinforced masonry, as well as the design of new
vaulted structures. This dissertation introduces the method and
shows examples of applications in both fields. Thrust Network
Analysis, masonry, historic structures, compression-only
structures, limit analysis, equilibrium analysis, funicular design,
form-finding, structural optimization, Gothic vaults, reciprocal
diagrams.

Thrust Network Analysis : exploring three-dimensional equilibrium

Metamaterials exhibit properties beyond those exhibited by conventional materials in conventional scenarios. These have been investigated both theoretically and experimentally at length. In many cases the underpinning physical understanding of metamaterials has greatly preceded our ability to manufacture constituent structures. However, the development of additive manufacturing techniques gives new possibilities for the fabrication of complex metamaterial structures, many of which cannot be realised through conventional fabrication methods. The literature to date contains contributions from a diverse group of researchers from the physical sciences, mathematics, and manufacturing technology in the creation of metamaterials for electromagnetic, acoustic and mechanical applications. It is proposed that additive manufacturing holds the key to realise the capabilities of this vibrant research community and permit the creation of new paradigms in fundamental structures but also exploitation through application. For this purpose, a literature review is presented which identifies key advances in metamaterials alongside additive manufacturing and proposes new opportunities for researchers to work together through intra/inter disciplinary research to realise structures which exhibit extraordinary behaviour(s). This review represents a comprehensive account of the state-of-the-art in the production of such metamaterials using additive manufacturing methods and highlights areas, which, based on trends observed in the literature, are worthy of further research and require a coordinated effort on behalf of the afore mentioned disciplines in order to advance the state-of-the-art.

Additive manufacturing of metamaterials: A review

https://www.fernandofraternaliresearch.com/publications/Tensegrity_Bridge_2014.pdf

Minimum mass design of tensegrity bridges with parametric architecture and multiscale complexity

We give an algorithm for solving the form-finding problem, that is, for finding stable placements of a given tensegrity structure. The method starts with a known stable placement and alters edge lengths in a way that preserves the equilibrium equations. We then characterize the manifold to which classical tensegrity systems belong, which gives insight into the form-finding process. After describing several special cases, we show the results of a successful test of our algorithm on a large system.

/pdf/a-marching-procedure-for-form-finding-for-tensegrity-2luazl1h8j.pdf

A marching procedure for form-finding for tensegrity structures

Tensegrity systems are prestressed frameworks composed of bars and cables. A particular elastic tensegrity system is examined. This system can be bistable in two fundamentally different ways, one depending on its geometric dimensions, and the other one depending on the initial deformation, or prestrain, of the elastic elements. A reduced-order semi-analytical model is derived, and its predictions are verified with a full-order numerical model. In particular, the critical geometry and prestrain at which the system switches from one regime to another are determined. This case study provides a benchmark and new insights on this class of structures.

/pdf/bistable-regimes-in-an-elastic-tensegrity-system-fkc12niazl.pdf

Bistable Regimes in an Elastic Tensegrity System

Large deployable space structures are mission-criti cal technologies for which deployment failure cannot be an option. The difficulty to full y reproduce and test on ground the deployment of large systems dictates the need for e xtremely reliable architectural concepts. In 2010, ESA promoted a study focused at the pre-development of breakthrough architectural concepts offering superior reliabilit y. The study, which was performed as an initiative of ESA Small Medium Enterprises Office (http://www.esa.int/SME/), by Kayser Italia at its premises in Livorno (Italy), with Uni versita' di Roma TorVergata (Rome, Italy) as sub-contractor and consultancy from KTH (Stockholm, Sweden), led to the identification of an innovative large deployable structure of “ten segrity” type, which achieves the required reliability because it permits a drastic reduction in the number of articulated joints in comparison with non-tensegrity architectures. The i dentified target application was in the field of large antenna reflectors. The project focu sed on the overall architecture of a deployable system and the related design implicatio ns. With a view toward verifying experimentally the performance of the deployable structure, a reduced-scale breadboard model was designed and manufactured. A gravity off-loading system was designed and implemented, so as to check deployment functionality in a 1-g environment. Finally, a test campaign was conducted, to validate the main design assumptions as well as to ensure the concept’s suitability for the selected target appli cation. The test activities demonstrated satisfactory stiffness, deployment repeatability, a nd geometric precision in the fully deployed

http://www.spacearchitect.org/pubs/AIAA-2012-3601.pdf

On an innovative deployment concept for large space structures

The present paper explores the capabilities of a tensegrity-inspired tower with regard to frequency tuning by shape morphing. To change the configuration of the proposed structure, shape-memory-alloy (SMA) actuators are used. This actuation principle also takes advantage of the variation of the elastic modulus of SMAs associated with the martensitic transformation. The temperature modulation of the SMA wires is successfully achieved by Joule heating, through a proportional-integral-derivative controller, to change between a low-temperature shape and a high-temperature shape. The implementation of a short-time-Fourier-transform control algorithm allows for the correct identification of the dominant input frequency, associated with the dynamic excitation. This information is used to automatically change the configuration of the structure in order to shift its natural frequency away from that of the dynamic excitation. With this frequency tuning, one obtains a reduction of the accelerations throughout the structure up to about 80%. The good performance of the proposed control approach gives promising indications regarding the use of tensegrity systems, in combination with SMAs, for shape-morphing applications, and, in particular, for self-tuning structures.

/pdf/design-and-experimental-testing-of-an-adaptive-shape-1pfz80mmt3.pdf

Andrea Micheletti

Papers

Minimum mass design of tensegrity bridges with parametric architecture and multiscale complexity

A marching procedure for form-finding for tensegrity structures

Bistable Regimes in an Elastic Tensegrity System

On an innovative deployment concept for large space structures

Design and experimental testing of an adaptive shape-morphing tensegrity structure, with frequency self-tuning capabilities, using shape-memory alloys