Deformation micromechanics of natural cellulose fibre networks and composites

The deformation micromechanics of cotton and flax single natural cellulose fibres in relation to their use in cellulose-based networks and composite materials is reported. The deformation of such fibres induces a shift in the 1095 cm-1 Raman band, corresponding to the ring structure of the particular polymorph, which can be calibrated against strain. It is shown that this band shift can be used to monitor the deformation micromechanics of fibrous networks (cotton paper) and the composite micromechanics of single natural cellulose fibre unidirectional composites. The shear lag approach of Cox [Br. J. Appl. Phys. 3 (1952) 72] is investigated for the fibrous network and composite materials. For the network it is demonstrated that this theory does not apply since bonding across the end modifies the stress transfer by ‘shear-lag’. For the natural fibre composites it is thought that bonding occurs across the ends, also modifying this effect, but other possibilities are discussed in detail.