A multiscale crack-bridging model of cellulose nanopaper. (June 2017)

• Record Type: Journal Article
• Authors: Meng, Qinghua; Li, Bo; Li, Teng; Feng, Xi-Qiao
• Is Part Of: Journal of the mechanics and physics of solids. Volume 103(2017:Jun.)
• Page Start: 22
• Page End: 39
• Publication Date: 2017-06
• Subjects: Cellulose nanopaper -- Fracture toughness -- Crack-bridging model -- Cohesive law -- Hydrogen bond; Mechanics, Applied -- Periodicals; Solids -- Periodicals; Mechanics -- Periodicals; Mécanique appliquée -- Périodiques; Solides -- Périodiques; Mechanics, Applied; Solids; Periodicals; 531.05
• DOI: 10.1016/j.jmps.2017.03.004
• Languages: English
• ISSNs: 0022-5096

Abstract

Highlights: Multiscale crack-bridging model for predicting the fracture toughness of cellulose nanopaper. Cohesive law considering the hydrogen bonds on cellulose nanofibril interfaces. Optimal nanofibril sizes that achieve a higher fracture toughness of nanopaper. Unified law for the fracture toughness of nanopaper in terms of microstructure and material parameters. Abstract: The conflict between strength and toughness is a long-standing challenge in advanced materials design. Recently, a fundamental bottom-up material design strategy has been demonstrated using cellulose nanopaper to achieve significant simultaneous increase in both strength and toughness. Fertile opportunities of such a design strategy aside, mechanistic understanding is much needed to thoroughly explore its full potential. To this end, here we establish a multiscale crack-bridging model to reveal the toughening mechanisms in cellulose nanopaper. A cohesive law is developed to characterize the interfacial properties between cellulose nanofibrils by considering their hydrogen bonding nature. In the crack-bridging zone, the hydrogen bonds between neighboring cellulose nanofibrils may break and reform at the molecular scale, rendering a superior toughness at the macroscopic scale. It is found that cellulose nanofibrils exhibit a distinct size-dependence in enhancing the fracture toughness of cellulose nanopaper. An optimal range of the length-to-radius ratio of nanofibrils is required to achieve higher fracture toughness of cellulose nanopaper. A unified law is proposed to correlate the fracture toughness of cellulose nanopaper with its microstructure and material parameters. The results obtained from this model agree well with relevant experiments. This work not only helps decipher the fundamental mechanisms underlying the remarkable mechanical properties of cellulose nanopaper but also provides a guide to design a wide range of advanced functional materials.