(1) Similarly (and not surprisingly) the Dutch artist Gerard Caris always carries a small
pentagonal dodecahedron made up of twelve regular pentagons with him, so that he is always prepared to demonstrate the potentially infinite symmetrical mega-structures which can be made by combining regular pentagons and the solids constructed from them.
The average cell wall thickness ([t.sub.exp]) was calculated first of all using empirical values taken from the thickness of 50 randomly selected cell walls and also using two theoretical models, assuming different cell shapes in a closed-cell foam ([t.sub.theo]): a
pentagonal dodecahedron shape (Model 1) and a tetrakaidecahedral cell shape (Model 2).
Gibson and Ashby [25-27] based their theoretical derivation on the
pentagonal dodecahedron mechanical mode, which is approximative to the actual bubble structure, and then developed the calculation equation (Eqs.