Scaling Laws of Strength and Toughness in Cellulose Nanofiber Networks from Scale-Bridging Simulations

Cellulose nanofiber networks hold significant potential to reconcile the conflict between strength and toughness. Nevertheless, how their strength and toughness quantitatively scale with microstructural features remains elusive. In this work, we reveal a scale-bridging supercoarse-grained (SCG) approach that can reconstruct experimental stress-strain curves by identifying representative effective microstructural geometries. Then, from a cascade of SCG simulations, we have rationally derived a set of microstructure-based scaling laws that correlate strength and toughness with nanofiber geometries, which also unify a wide range of literature findings. For demonstration, our method can treat micrometer-scale systems containing experimental fiber diameters ranging from 11 to 113 nm. Importantly, the parameters of our SCG models are systematically obtained from sublevel coarse-grained and atomistic simulations. Our current work not only provides critical insights on general scale-bridging modeling techniques but also establishes a deeper quantitative understanding of the design and interpretation of nanocellulose-based strong and tough materials.