A multiscale crack-bridging model of cellulose nanopaper

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.

Comparison of tension wood and normal wood for oxidative nanofibrillation and network characteristics

“…A similar phenomenon has been observed previously (Jonasson et al 2020) and indicates the importance of pretreatment before homogenization to obtain enhanced network properties. Enhanced toughness, which was observed in the TW CNF networks, has also been observed for nanofibril networks of high-DP CNFs, both experimentally (Henriksson et al 2008;Fukuzumi et al 2013) and theoretically (Meng et al 2017). The nanofibril length is preserved in these CNFs (Shinoda et al 2012) and thus supports network formation, resulting in a higher elongation before failure.…”

Biomimetic composites with enhanced toughening using silk-inspired triblock proteins and aligned nanocellulose reinforcements

“…The pullout process is restrained by bonding between fibrils, and a significant mechanism in cellulose nanomaterial toughening is an extrinsic one because of the bridging effect by fibers behind the crack tip. It seems, therefore, that our triblock spidroin proteins were able to enhance this effect by efficiently locking fibers in place, which modeling also suggests should result in increased toughness ( 33 ). This prediction fits with the observation that fibers that toughened with proteins showed relatively blunt fracture surfaces of fibril bundles, with qualitatively smaller and fewer regions of pullout than the other samples (Fig.…”

Mechanically Robust Antibacterial Nanopapers Through Mixed Dimensional Assembly for Anionic Dye Removal

“…Another work reported by Fryczkowska et al investigated the physico-chemical and transport properties of GO/Cellulose membranes [21]. Meng et al shredded light on toughening mechanism of cellulose nanopaper by developing a multiscale crack-bridging model [22]. Meng et al also developed a theoretical model to understand the effect of nano-fiber alignment in fracture toughness of CNF nanopaper [23].…”