Effects of interface properties on the mechanical properties of bio-inspired cellulose nanocrystal (CNC)-based materials

Abstract

Cellulose nanocrystals (CNCs) is a new family of cellulose materials with outstanding mechanical and chemical properties that have been successfully demonstrated to have potential for many applications. Understanding the mechanical behavior of individual CNCs and their interaction at nanoscale is very important for improving the manufacturing process and mechanical performance of the resulting materials at macroscale. However, due to time and length scale limitations for both, experimental observations and atomistic modeling, predicting the mechanical performance of a system consisting of many CNCs is still challenging. We present a coarse-grained model of CNCs based on both mechanical properties and crystal-crystal interactions to overcome this limitation. Parametrization of the model is carried out in comparison with all-atom (AA) molecular dynamics and experimental results of some specific mechanical and interfacial tests. Subsequently, verification is done with other independent tests. In particular, we note that the parameters of the model can be calibrated to capture the properties of both twisted and untwisted CNC interface without sacrificing the mechanical properties of the individual particle. Finally, we analyze the effect of interface properties on the mechanical performance of CNC-based materials including, bending test of a crystalline bundle, tensile test and fracture in two representative bioinspired architectures. The results revealed different failure mechanisms depending upon the interfacial configuration. For instance, well-aligned CNCs lead to a more brittle and catastrophic failure mechanism, whereas naturally twisted interfaces promote toughening mechanisms that helps attained optimal mechanical performance.