Creep Behavior of Graphene Oxide, Silk Fibroin, and Cellulose Nanocrystal Bionanofilms

Abstract

Graphene oxide (GO), silk fibroin (SF), and cellulose nanocrystal (CNC) nanocomposite is a novel biomaterial with superior mechanical properties. Elevated temperature nanoindentation experiments using constant load hold method are performed to investigate temperature-dependent mechanical and creep behavior of the GO–SF–CNC nanocomposite. Hardness and reduced modulus of GO–SF–CNC are determined from experiments at 25, 40, 60, 80, and 100 °C, and yield strength and creep coefficients are predicted from finite element analysis using two-layer viscoplasticity theory. Results show that increasing the temperature from 25 to 80 °C, hardness, reduced modulus, and yield strength of GO–SF–CNC nanocomposite dramatically increase by 112%, 40%, and 140% respectively, and creep displacements during constant load hold reduce by 53%. It is attributed to increasing in crystallizations in the nanocomposite because of increasing in β-sheet formations of SF material and reduction in water molecules in CNC material. However, at 100 °C, the mechanical properties deteriorate, and creep displacements increase because of water evaporation from the nanocomposite, making it weaker. Hardness-to-yield strength ratio is found within 1.84–2.06. Maximum creep exponent is 2.9 at 40 °C, which reduces to 2.06 at 80 °C and again increases to 2.27 at 100 °C. © 2022 Wiley-VCH GmbH.