Here is a video that describes how photo elasticity can be done with a camera and computer screen and a polarizing filter or polarizing sunglasses.
I am working on a project with Dr. Ergun Akleman to create 3D structures from 2D structures. I have managed to create a structure that can fold from a 2D shape to a tetrahedron. A video of the structure unfolding is given here: https://www.youtube.com/watch?v=evGOyAA_JfA&feature=youtu.be. Some pictures of the structure are given below:
The current project is looking at creating a shape memory polymer that mimic the behavior of blooming flower tea. A video that describes how blooming flower tea is made is given here: http://www.youtube.com/watch?v=TLCnHcmhezw. This is a type of tea called “art” tea and consists of tea leaves in a compact structure that folds over a flower and opens up when exposed to hot water. A picture of the blooming flower tea is given here:
Some inspiration for this project also comes from origami robots. MIT and Harvard have created an origami robot that can assemble itself and move from a 1-Dimensional structure. A video of the robot is given here: http://www.tested.com/tech/robots/463382-brief-mit-origami-robot-walks-away-laser-cutter/.
In order to work on this project, I have tried some flower baking molds at various degrees of temperatures. However, there is some difficulty in obtaining the proper folding technique for the opening of the flower. The picture below depicts a flower from the baking mold. I have made one with a glass transition at 70 C and one with a glass transition at 30 C. Since the flower from the baking mold is very flat on the back, the structure does not yield to folding in very well.
Next I tried laser-cutting a flat 2D shape of a flower and folding it in. Pictures of the flat 2D shape are given below.
I have uploaded a video of the shape memory polymer flower blooming here: https://www.youtube.com/watch?v=y7iQLhYO4_U&feature=youtu.be
I have currently made some hexagonal chiral structures that incorporate color change. Below are pictures of two of these structures that incorporate different color changes.
I have also been experimenting with using fabric with the colored polymer. Below are pictures of fabric incorporated into the polymer.
I recently used a laser-cutter to create a spiral and auxetic shape in the shape memory polymer. After cutting, I placed the material in a hot water bath whose temperature was above 70 deg C. Then applied pressure with my hands and cooled under cold water from the faucet. The results of the spiral and the auextic shapes are given below.
Here is a video of the uncurling of the auxetic amp using a hair dryer: https://www.youtube.com/watch?v=nZGNkn1s4F0&feature=youtu.be
The laser-cutter leaves some burnt edges of shape memory polymer. Also, the integral line segments in the auxetic shape were quite small so did break off when trying to pull them out. For future work, some sanding along the edges could be done to decrease the edge effects from the laser cutter. However, the shape change produced is the desired effect.
In order to utilize a shape memory alloy, the properties of the alloy need to be known. Charlotte Lelieveld from the TU Deflt has done work in creating smart composites materials, i.e. materials that incorporate shape memory alloys and shape memory polymers (1-2). Pictures of her work is given below:
In order for me to create a similar, I need to know the properties of both the shape memory alloy and shape memory polymer. The properties of relevant importance to me are listed below:
Shape Memory Alloys (3):
1. Density (g/cc): 6.5
2. Electrical Resistivity (micro Ohms/cm): 76 (Martensite)/82 (Austenite)
3. Thermal Conductivity (W/m deg C): 18
4. Elastic Modulus (GPa): 40 (Martensite)/75 (Austenite)
5. Specific Heat Capacity (J/kgK): 322
The power to heat the SMA strips, can be found through estimating the energy by (1):
E = Power*time = mass*Specific Heat Capacity* change in temperature
The power may be calculated from Joule’s law:
P = Voltage^2/Resistance
The resistance in each wire is given by:
R = resistivity * length/cross-sectional area
1. Lelieveld, C. M. J. L. (2013). Smart Materials For The Realization Of An Adaptive Building Component. Ph.D. doctoral Thesis, Delft University of Technology.
Currently, I am working on incorporation of heating through electronic sources. I have made a sample that contains 20 guage nichrome wire from Jacobs. The data on the wire is given below:
From this data, I used Mathematica to curve fit to a second order polynomial. The equation for the polynomial is given as: Amps = 7.55359*10^-6*T^2+0.00549092*T+2.47994. An image of the curve fit data is given below:
For the 20 guage nichrome wire, a temperature of 30 deg C can be obtained with the application of 2.65 Amps. The sample with the nichrome wire, as well as, a sample that contains carbon black, and a sample that contains embedded shape memory alloy is seen in the picture below:
Note that the weight percentage of carbon black is too high, and the sample created was a gummy consistency.