Tensile properties of cellulose acetate butyrate composites reinforced with bacterial cellulose

Composites of cellulose acetate butyrate reinforced with cellulose sheets synthesised by Gluconacetobacter xylinus were produced by solvent evaporation casting. The composites contained 10% and 32% volume cellulose, and showed a Young's modulus of 3.2 and 5.8 GPa, and a strength of 52.6 and 128.9 MPa, respectively, in tensile tests. Stress-strain curves showed bi-phasic material characteristics, with an initial linear behaviour, followed by yielding, and a second linear phase until fracture. Cyclic tensile loading-unloading experiments at incremental strain revealed an increasing elastic modulus after each straining step. A simple analytical model demonstrated that the observed increase of the elastic modulus can be explained by reorientation of the initially random oriented cellulose fibrils due to straining. (C) 2004 Elsevier Ltd. All rights reserved.