Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150049

150049 - Microstructure and Dynamics of Nanocellulose Network: Insights Into the Deformational Behaviors 

Cellulose nanocrystals (CNCs) thin films draw considerable interest in engineering and technological applications due to their excellent mechanical and physical properties, which are closely linked to their dynamic and microstructural features. To better understand these properties, we employ coarse-grained molecular dynamics (CG-MD) simulations to investigate the dynamics and microstructural changes in CNC films under deformation. Our results reveal that the Young’s modulus of CNC films can be quantitatively predicted by a power-law scaling relationship with initial packing density, where higher density leads to increased modulus and strength. By evaluating the local molecular stiffness during the deformation process, we find that CNC films with higher density exhibit a greater degree of dynamic heterogeneity, which is significantly reduced under deformation. Furthermore, our findings show that randomly oriented CNCs align more with the direction of applied stress, leading to higher free volume and porosity during deformation. However, the dynamics of CNCs are influenced more by local packing and density than by CNC orientation.

Expanding our investigation to cellulose-based bulk materials composed of disordered CNCs forming a porous network microstructure, we find that increasing density and cohesive interaction between CNCs enhances the shear modulus and yield stress of the bulk system, strongly dependent on the cohesive energy density. By evaluating the local molecular stiffness, we observe that the bulk CNC system becomes more dynamically heterogeneous with increasing density and cohesive interaction, akin to glass-forming liquids. This influence on shear modulus and dynamic heterogeneity of bulk CNCs is more pronounced with variations in density due to the high rigidity of CNCs and the high porosity of the network microstructure. Our comprehensive analysis highlights the importance of cohesive interactions and their impact on mechanical properties. Higher cohesive interaction strength results in enhanced mechanical properties, as evident from the increase in shear modulus and yield stress, quantitatively captured by examining the cohesive energy density. This multiscale modeling approach provides a pathway for the rational design of nanocellulose-based materials with desirable mechanical properties for various engineering applications.

Our findings elucidate the mechanical performance of CNC thin films and networks under deformation, emphasizing the role of microstructural and dynamic factors in determining their mechanical properties. These insights are crucial for advancing the application of CNCs in various engineering fields, significantly contributing to the science and engineering of renewable materials. Through detailed simulations and analyses, we offer fundamental insights into the deformational mechanisms of CNC films and networks, aiding in the advancement of cellulose-based material design for enhanced mechanical performance.

Presenting Author: Zhaofan Li Iowa State University

Presenting Author Biography: Zhaofan Li is currently a Postdoctoral Scholar in the Aerospace Engineering Department at Iowa State University. He received his Ph.D. in Civil Engineering from North Dakota State University. His research focuses on establishing a multi-scale materials-by-design framework by integrating theories (i.e., soft matter physics, mechanics, continuum theories), computational techniques (i.e., molecular dynamics, coarse-grained modeling, and machine learning), and experiments to facilitate the design and development of high-performance structural materials.

Authors:

Wenjie Xia Iowa State University
Zhaofan Li Iowa State University