Bimodal cellular poly(methyl methacrylate) with micron and nano sized (300 to
500 nm) cells with up to 5 weight percent of sepiolite nanoparticles and
porosity from 50 weight percent to 75 weight percent are produced by solid
state foaming. Uniaxial compression tests are performed to measure the effect
of sepiolite concentration on the elastic modulus and the yield strength of the
solid and cellular nanocomposites. Single edge notch bend tests are conducted
to relate the fracture toughness of the solid and cellular nanocomposites to
sepiolite concentration. The relative modulus is independent of sepiolite
content to within material scatter when considering the complete porosity
range. In contrast, a mild enhancement of the relative modulus is observed by
the addition of sepiolite particles for the foamed nanocomposites with a
porosity close to 50 percent. The relative compressive strength of the cellular
nanocomposites mildly decreases as a function of sepiolite concentration. A
strong enhancement of the relative fracture toughness by the addition of
sepiolites is observed. The enhancement of the relative fracture toughness and
the relative modulus (at 50 percent porosity) can be attributed to an improved
dispersion of the particles due to foaming and the migration of micron sized
aggregates from the solid phase to the microcellular pores during foaming