Session: 13-11-02: Friction, Fracture, and Damage II

Paper Number: 168129

Fracture Toughness Prediction of Graphene With a Substrate 

Two-dimensional (2D) materials, such as, graphene, hBN, silicene, and transition-metal dichalcogenides (TMDCs) have presented exceptional electrical, optical, and mechanical properties in their atomic thin layers. Transition-metal tellurides, as the relatively heavier members of the TMDC family, are the only TMDCs with a stable metalloid chalcogen (tellurium). In particular, molybdenum ditelluride (MoTe₂) show a variety of layer-dependent intrinsic material properties with their tunable and reversible polymorphic features. It is crucial to accurately characterize the material properties of MoTe₂, especially fracture toughness, which directly impacts the fabrication of MoTe₂ based devices and their resultant reliability and durability.

In-plane failure of 2D materials refers to the bonding breaking processes at the in a nanometer to sub-micron domain, which have been quantified by a variety of parameters numerically through the literature. Molecular dynamics (MD) simulations and density functional theory (DFT) calculations have been extensively adopted to investigate the intrinsic strength of 2D materials and the bond breaking processes under a variety of external loadings. When subjected to laboratory-based nano-mechanical testing such as in situ Transmission electron microscopy (TEM) testing, Atomic Force Microscopy (AFM) deflection testing, etc, the in-plane dimensions of the 2D material samples are often on the micron scale while their thickness is in sub-nanometer domain. Meanwhile, the 2D material samples often contain pre-existing flaws and irregular edges. Therefore, fracture toughness can provide a more practical measure to the in-plane failure of 2D materials subject to the loading conditions.

In this study, finite element analysis (FEA) is employed to investigate the Mode I fracture behavior of MoTe₂ , both with and without the consideration of a supporting substrate. Multi-layer MoTe₂ is modeled as a continuum thin film. The Griffith’s criterion with be considered under the linear elastic fracture mechanics (LEFM) assumption. A center-through crack will be considered to analyze the creak propagation and evaluate the fracture toughness. Using the Separating Morphing and Adaptive Remeshing Technology (SMART) in ANSYS, the crack growth is simulated without a pre-defined crack path. This adaptive remeshing technique will simultaneously generate a denser mesh near the propagating crack tips, ensuring the accuracy of stress concentration calculation and crack propagations.  Our results predicted the stress concentration at the crack tip and elucidated the crack propagation with and without the substrate. The relation between fracture toughness and MoTe₂ thickness, crack length, external loading are predicted. The role of the substrate in the load transfer are explored. The fracture toughness of single layer and multi-layer MoTe₂ are predicted and compared with experimental results.

This study established a robust and efficient computational fracture mechanics framework to predict and analyze the fracture toughness of 2D materials through integration with laboratory nanomechanical testing.

Presenting Author: Jingzhe Qiao Clemson University

Presenting Author Biography: Jingzhe is a Ph.D. student in the School of Mechanical and Automotive Engineering, Clemson University. His research area is multi-scale, multi-physics simulations of materials and structures.

Authors:

Jingzhe Qiao Clemson University
Zhewen Yin University of South Florida
Michael Cai Wang University of South Florida
Huijuan Zhao Clemson University