– We have two main goals: development of an algorithm to identify extreme mechanical properties of tensegrity metamaterials and conducting laboratory studies of samples of these materials manufactured through 3D printing – explains Anna Al Sabouni-Zawadzka, PhD, from the Faculty of Civil Engineering, project leader.

The result should be obtaining at least two gradient (of changing parameters) tensegrity metamaterials of extreme mechanical properties, and also determination of their potential applications in civil engineering. They could be used as various types of vibration damping elements, e.g. vibration isolation mats. The WUT team also wants to develop a database with results of laboratory tests conducted on 3D printed elements. It would be useful for researchers and engineers studying vibration isolation elements.

From a module to a metamaterial

This should be the result. How to get that? Since metamaterials are artificial structures, it means that their properties can be controlled. We know they are special and this exceptional character is mainly the result of their shape and structure at the level greater than molecular level (and less because of their chemical and phase composition). In the project, researchers are concentrating on this main aspect.

Let us have a closer look at what tensegrity is. In simple terms, it is a special type of trussed structure made of compressive elements and tensile elements connected in such way that the whole structure is very stable and durable. Tensegrity takes advantage of the self-tension state, which means that the compression and tension forces are in perfect balance.

– Tensegrity can be used in many branches – points out Anna Al Sabouni-Zawadzka, PhD. – We can use them in load-bearing parts of buildings or foot bridges, as well as in flexible structures, such as moving facades or foldable columns. Aviation and space engineering are also important fields of application, where ultralight tensegrity structures are used as elements of antennas or rovers. On a smaller scale, tensegrity structures may be combined to make module structures, like metamaterials which are the subject of this project.

How can we get a metamaterial? It’s easiest to build it from basic tensegrity modules (these are, for example, simplex modules made on the basis of regular prisms). Modules are the smallest, elementary particles of the material. They may be placed in various ways - depending on the properties of a given structure. In a mathematical model, supercells may be established – in the end, the obtained metamaterial, regardless of the number of supercells, will have exactly the same properties.

– These are preliminary studies which I published in the paper ”High-Performance Tensegrity-Inspired Metamaterials and Structures”, but they were about structures without gradation – explains Anna Al Sabouni-Zawadzka, PhD. – In literature, there are no studies on tensegrity metamaterial tests of variable parameters.

Theory and practice

– Our research will cover 3D structure and should lead to development of a new algorithm for analysis of smart metamaterials of changeable mechanical properties – describes Anna Al Sabouni-Zawadzka, PhD. – Metamaterials will have a cell structure and will be based on regular tensegrity modules of changeable geometrical proportions, various bonding methods, changeable stiffness. We will analyse various methods of obtaining gradient (i.e., of changing parameters) properties and their impact on extreme properties of tensegrity structures.

Special attention is paid to these properties since they allow to have a structure which in one way will have large load bearing and will be stiff under an applied load (e.g., vertically) and under a load in another direction (e.g., horizontal) will be very flexible. It is significant, for example, in case of mats damping seismic vibrations.

Development of an algorithm is the first (theoretical) aim of the project. The second aim is practical - checking if the algorithm is working.

– We have planned laboratory tests on samples of single modules and tensegrity metamaterials manufactured through 3D printing.

The project ”Numerical and experimental tests of gradient tensegrity metamaterials of extreme mechanical properties” is implemented through a grant of the National Science Centre within the programme SONATA 18.