Mechanics of cellulose nanopaper using a scalable coarse-grained modeling scheme

Cellulose, the abundantly available and sustainable biopolymer, exhibits intrinsic mechanical properties superior to many high-performance structural materials. The exceptional mechanical properties of cellulose-based materials inherently hinge upon their bottom-up hierarchical material structure starting from cellulose molecular chains to large scale fibers. However, fully atomistic simulation of such materials at experimental sample dimension becomes computationally prohibitive for the exploration of mechanics involving length scale effects. To address this challenge, here we develop a bottom-up, scalable coarse-grained (CG) modeling scheme of cellulose materials to study the deformation and failure mechanism of cellulose-based materials with insight of the interplay among cellulose building blocks at different length scales, starting from molecular chain, to nanofiber, and finally to microfiber scales. After studying the response of cellulose fibers under different loadings such as shearing and opening, this CG scheme is applied to study the deformation process of a cellulose nanopaper under tension, thus revealing the nanoscale failure mechanism otherwise impossible by atomistic simulations. In addition, the CG model also predicts the strength and stiffness of the nanopaper with respect to varying fiber lengths. Given its scalable nature, such a CG modeling scheme can be readily adapted to study the mechanical behaviors of other cellulose-based materials with mechanistic insight from molecular scale, and thus holds promise to foster the design of cellulose-based high-performance materials.