A microstructure-based constitutive model of anisotropic cellulose nanopaper with aligned nanofibers

Endowed with excellent mechanical properties, cellulose nanopaper provides a promising design strategy for addressing the dilemma between the strength and toughness of engineering materials. Anisotropic nanopaper with highly aligned nanofibers can achieve high mechanical properties. In this paper, we develop a multiscale tension-shear model that correlates both the strength and toughness with the microstructure to quantitatively understand the exceptional properties of anisotropic cellulose nanopaper. By formulating a relationship between the interfacial macroscopic performance and nanoscale parameters involving the self-healing of hydrogen bonds, we establish a microstructure based constitutive model of cellulose nanopaper to describe its nonlinear mechanical behavior. It is theoretically suggested that engineering the nanofiber size enables cellulose nanopaper to realize strengthening and toughening. Meanwhile, multiple mechanical properties of the nanopaper can be simultaneously enhanced by increasing the hydrogen bond density. A scaling relation is proposed to correlate the mechanical properties of cellulose nanopaper with the microstructure parameters. The developed model predictions agree well with the relevant experimental data. The constitutive model can also be extended to describe the mechanical response of cellulose bulk materials. This work can not only help understand the fundamental deformation mechanisms of cellulose nanopaper, but also help design high-performance nanocellulose structural materials. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Cellulose nanopaper, endowed with excellent mechanical properties, can achieve strengthening and toughening by adjusting nanofiber size and increasing hydrogen bond density. This study quantitatively understands its outstanding performance through a multiscale model and proposes a scaling relation related to microstructure parameters.