Modelling the elastic properties of cellulose nanopaper

Highlights: • The elastic modulus of cellulose nanopaper is successfully predicted from a fibrous network model. • Stiff nanopapers require strong and dense networks of long, thin, stiff and straight nanofibres. • The elastic modulus of the model is related to the stress state in the network. The elastic modulus of cellulose nanopaper was predicted using a two-dimensional (2D) micromechanical fibrous network model. The elastic modulus predicted by the network model was 12 GPa, which is well within the range of experimental data for cellulose nanopapers. The stress state in the network revealed both tensile and compressive stresses during elastic deformation of the model. The length, diameter, waviness and elastic modulus of the cellulose nanofibres were varied in the model and their effect on the elastic modulus of fibrous networks was studied. It was found that high values of elastic moduli of cellulose networks could be obtained for long, thin and straight nanofibres of high stiffness. The effect of inter-fibre bonding and network density was also investigated. Increasing fibre-fibre interactions facilitated stress transfer in cellulose networks and led to a higher elastic modulus of the nanopaper. Denser networks also resulted in a higher elastic modulus due to an increasing number of nanofibres and inter-fibre bonds.