Theoretical Kelvin Foam in 3D
Polyurethane foams are, by design, as fine as possible so it is not easy to see their structure. This app allows you to explore a good, theoretical approximation of a real PU foam. You can see the foam from all directions. Using a mouse and controls you can make it smaller or bigger, change the opaqueness/thickness of its wall, the thickness of struts and even its anisotropy - exactly as you can do it in real life.
Credits
A big Thank You to prof. Steven Abbott for designing and developing the app.
We have 15 bubbles assembled into a small blob of foam. The bubbles are tetrakaidecahedra (14 faces), also known as truncated octahedra, with 4- and 6-edged faces and are one of the Archimedean solids. They are able to tesselate, to fill space. Lord Kelvin pointed out that they made a good approximation to an ideal foam, and so this foam is called a Kelvin foam. A more perfect foam was defined by Denis Weaire and Robert Phelan. The Weaire-Phelan foam was made of a dodecahedron and a different tetrakaedecahedron with a mix of 5- and 6-edged faces. Despite the kind help of Guy Inchbald, an expert in 3D shapes, I decided not to implement one because for our purposes, the Kelvin foam is good enough.
To get a better look at the foam from whatever angles interest you, use your mouse to zoom in, rotate (left click) and pan (right click). You can also use the Control sliders to change the opacity of the walls (to simulate changing walls thickness), thickness of struts or elongation of the cells.
The three key features are:
- The foam walls (or faces) make up the bulk of the surface area of each bubble but account for a tiny % of the foam material.
- The struts (or Plateau borders as some purists call them) contain a large fraction of the foam material. Material drainage runs along these borders when the foam is growing. The borders are curved triangles in cross-section.
- The nodes or vertices. These are where the struts meet. In reality they have a size bigger than just the borders coming together. You will see it better when you take a flight through a model open cell foam in the video below.