Deformation mechanisms in cellulose fibres, paper and wood

The use of Raman spectroscopy in probing the deformation mechanisms of cell ulose fibres (regenerated and natural), and two natural cellulose composite systems (wood and paper) is described. It is shown that during tensile def ormation the 1095 cm(-1) Raman band, corresponding to the stretching of the cellulose ring structure, shifts towards a lower wavenumber due to molecul ar deformation. By analysing a number of fibres with different microstructu res this shift is shown to be invaluable in understanding the micromechanis ms of deformation in these materials. Moreover, the rate of Raman band shif t is shown to be invariant with stress for all fibre types, consistent with a fibre microstructure based on a modified series aggregate model. In the composite systems, such as wood and paper, it is shown that the stress-indu ced Raman band shift in the cellulose gives an important insight into their local deformation micromechanics. (C) 2001 Kluwer Academic Publishers.