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Cimtec d-3-il16
1. Thigmo-morphogenetic Fiber Composites
Embedded with Shape Memory Alloys
MARIA MINGALLON SAKTHIVEL RAMASWAMY
MSc (Distinction) Emergent Technologies and Design, MArch, Emergent Technologies and Design,
The Architectural Association, London, United Kingdom The Architectural Association, London, United Kingdom
Senior Structural Engineer, ARUP (Montreal), Director & Head of Innovation, KRR Engineering Pvt. Ltd.
Adjunct Professor, McGill University School of Architecture sakthivel@krr.co.in
maria.mingallon@arup.com www.sakthivelramaswamy.com
www.mariamingallon.com
2. The premise of this sensing and
research is to integrate
actuation functions into a fibre composite material
system. Fibre composites, which are anisotropic and heterogeneous, offer the
possibility for local variations in their material properties. Embedded
fibre optics are herein used to sense, while shape memory alloys provide
actuation capabilities to the resulting composite. The definition of the
geometry, inspired by the organization strategies found in biological
composites, complements the functioning of the adaptive material system at both
local and global levels, allowing it to display integrated
functionality.
2 Sakthivel Ramaswamy, Maria Mingallon
31. thank you !
maria.mingallon@arup.com www.sakthivelramaswamy.com
www.mariamingallon.com
sakthivel@krr.co.in
Editor's Notes
This is a render of one of the applications of my thesis project at the AA. The thesis developed a material system able to sense different changes in the environment, interpret these as stimuli and adapt accordingly to a new state of equilibrium. For example,, providing openings to allow for ventilation.
Required??
As we have previously seen, nature makes composites out of fibrous tissues; but it is able to differentiate the various parts of an organism by altering the density and layout of the fibres depending on the function of the element itself. Now, in order to mimic this approach, we decided to use a fibre composite which allows us to integrate shape memory alloys within the matrix of the composite, but at the same time allowed to start from a planar surface and gaining stiffness by means of changing its curvature, or in other words, shaping it as a shell structure but at the same time altering the fibre density. Now this shell morphology also has different zones with higher or lower stiffnesses which again permitted us to position the sma strategically to test the shape change in the building envelope. The illustration you are seeing here features the intended shell before (lower curve) and after actuation by the upper curve. These will be the areas where the smas will be installed since they are the areas capable of taking higher deformation in the shown shell.
This is a diagram featuring the setup of the final prototype in plan view:The smas are represented in blue and are located on the areas with higher degree of flexibility, i.e. at the top four corners of the envelope we have chosenNow our intention was to use fibre optics to sense temperature, humidity and deflection but due to technological constraints and for the purpose of building the prototype, we replaced the fibre optics with a strain gauge to sense deflections and loads and a thermocouple to sense changes in temperature.The strain gauge is shown in blue here and the thermocouple is represented in green. So for example when there is some wind blowing at the corner here, the strain gauge will detect a deflection and trigger a processing unit which will then send a signal to the main controller to start the heating blanket to heat the smas until they reach the actuation temperature and change shape as a result.
This is a picture of the strain gauge used while it was being calibrated
These are the heating blankets used to heat the smasAnd on the side it is the thermocouple used to measure ambient temperature changes but also to monitor the temperature of the smas while they were being heated to their actuation temperatures
These are some pictures showing the process of building the prototype.The shape was built using a mould which was fabricated by CNC milling in a high density polyurethane foam and had to be made out of several pieces due to dimensional restraints. The prototype you are seeing here was 50 x 50 cm, and the process consisted on first laying the glass fibre mat on the mould, then embedding the heating blankets and shape memory alloys as well as the thermocouples and the associated cabling, we then laid the second mat of glass fibres And applied the epoxy resin on the entire model
These are pictures of the setting of the strain gauge with a dummy gauge being installed as well, as you can see here…
These are photograms featuring the shape change of the model during actuationIf we compare these two photographs by looking closely at this corner, we can recognise the change in shape going from here to here where the curvature has increased
This is the final set up with the model on the left hand side of the table, then the thermocouple you can see it here as this green cable,Then the thermocouple processing unit to indicate and control the temperature of the smas, the single input controller unit which is triggers the heating blankets to start heating the smas and the strain gauge processing unit used to detect a deformation in the composite.
This slide features a series of photograpms superimposed to show the shape change during actuation and the associated temperatures the smas were heated at. Overall, the tests performed in the prototype came up much better than we initially thought, The fibre composite we had built was able to deflect quite well under the action of the shape memory alloy. Althought we had tested the actuation stiffeness of the shape memory alloys by means of loading it and measuring the time taken to actuate, we initially thought that when embedded the shape memory alloys were not going to be able to deform as well and as rapidly as when they were just loaded with a point load. However, the tests demonstrated that the resin chosen to built the composite made quite flexible yet strong for the purpose of the prototype and the shape memory alloys were able to deform and change the shape of the prototype as originally intended. One of small complication was the fact that some of the heating blankets, although presented by their manufacturer as well insulated, they were still transmitting certain heat to the composite, which resulted on small burnings on the surface of the model. This is something we are thinking on resolving by using a specifically manufactured product with more reliable insulation.
In terms of the application, our aim was to develop a smart material system for its use in architecture.Now building with a material capable of taking considerably large deformations can be tricky and although there are lots of man-made structures designed and built to ‘move’, certain factors need to be considered in order to integrate movement in a typically static structure. In our case, we chose to built a space frame which instead of being built out of tubular linear elements, it will be built out of a continuous surface, with the smas integrated along its edges. This way when the smas change shape the truss will accommodate that and restructure as if it was a pinned structure. This strategy also allowed us to easily integrate openings in the structure yet using a continuous surface that could be made of a fibre composite.
The following video shows an example of how this deformation will occur and how the openings close and open adapting to different needs. For example, if there is an excess in heat on one side of the structure, façade, or roof system, openings next to that hot point will close and other openings next to a cooler zone will open to let the fresh air come through.
The same strategy can be used to regulate lighting conditions as you can see in this rendering of the intended architectural application
This is another rendering of the intended application featuring an example of what the building envelope would look like
The project was exhibited in New York at the School of Architecture Cooper Union and the Pratt Institute in Brooklyn and we have also published the complete thesis as a book.
