Sponsored by:
Designing a Sustainable and Affordable Cooling Technology for Mattress
Cameron King, Dio Oey, Lakshmi Prerana Panchumarti, Elijah Tan., Thomas Thwaite, Wendi (Allen) Wu
Feeling
Testing description
Compression and recovery testing were performed to quantitatively determine the “feel” of our matrix layer compared to standard polyurethane foams. Indentation Deflection testing was performed according to ASTM standard D3574. The foam samples were cut to 3in x 4in rectangles, with a thickness of 1in (25mm). The latex and pneumatic foams were doubled to reach 25mm thickness. The matrix was tested with one layer of latex foam and with one layer of pneumatic foam. This was done so that all samples had a thickness of 25mm. The sag factor was determined by measuring the force to compress the foam to 5mm and 12mm and then dividing the 12mm compression force by the 5mm compression force.
The recovery test was performed by compressing the foams using a 9lb dumbbell. The depth of compression was measured using a ruler and the time to return to its initial height was recorded using a 60fps camera. The ruler was placed in the frame of the camera. The time was measured from the time the dumbbell was lifted from the foam and its base reached the initial height. A small button was placed on the top of the foam to better determine the moment the foam returned to its initial height.
Result
The “feel” of our prototype was evaluated using a compression test and a recovery test. These test methods allow us to quantitatively evaluate how the Matrix feels compared to other standard foams. The recovery test measured the time it took for the foam to return to its original thickness after being compressed by a specific load. This method quantifies the “memory foam feel” of each sample. Memory foams are distinguished by their ability to hold shape after a load has been removed. The longer the time for the foam to pop back up, the more memory foam like the sample.
The compression test used measured the indention load deflection, which provides information about the firmness or stiffness of the foam. This test method measures the force required, in Newtons, to compress the foam to 25% and 65% of its original thickness. The ratio of these two compression values is called the sag factor. The sag factor provides information about the “cushioning quality” of the foam. Figure 15 shows the results of the compression and recovery tests.
The Matrix + Pneumatic foam had the closest feel to the other stand-alone foams. The high sag factor combined with the fast recovery time show the matrix + latex was significantly stiffer than the other foams tested. The high sag factor also indicated that the matrix has a high resistance to bottoming out, which is great for consumers who are concerned about support. This was expected as the matrix alone was stiff but and so is the latex foam, so in combination they would result in a stiff/firm layer. We chose the latex foam for our final prototype because it had much better breathability than the pneumatic foam. However, the compression results show that further testing with different foam systems will be important to understand how to combine the matrix with different foams to maximize comfort.
