Nanocomposites obtained by casting a mixture of a latex and a n aqueous suspension of cellulose whiskers have been studied. Their mechanical properties (e.g. shear modulus) are found to increase by more than three orders of magnitude in the rubbery state of the polymer matrix, when the whisker content is 6 wt%. This large and unusual effect is discussed on the basis of different types of mechanical models, including semi-phenomenological and numerical finite element calculations. It is concluded that cellulose whiskers form a rigid network linked by hydrogen bonds. The formation of this network is assumed to be governed by a percolation mechanism.

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This paper deals with the inflation of elastic membranes of general shapes in the context of thermoforming of heated polymeric sheets against relatively cold moulding surfaces. A previous paper (1) has dealt with axisymmetric problems. As before, both theoretical and experimental investigations are reported. The theoretical part consists of a self-contained finite element formulation for large deformation, free and constrained inflation of isotropic elastic membranes. The computer program developed on the basis of presented formulation is applied to free and constrained inflation of plane elliptical membranes of aspect ratios 2 and 4. The material model adopted is that of a single constant neo-Hookean elastic material. The constrained analyses are carried out for inflation against: (a) cylindrical walls (90 degree elliptical cones), (b) 60 degree elliptical cones, and (c) horizontal plates. Separate analyses are performed by assuming the contact to be either slipless or frictionless. The theoretical results are compared with the experimental ones for free inflation and constrained inflation cases (a) and (c).