Date of Award

5-2025

Document Type

Thesis

Degree Name

Master of Engineering (ME)

Department

Mechanical Engineering

Committee Chair/Advisor

Zhaoxu Meng

Committee Member

Lihua Lou

Committee Member

Yifan Zhang

Abstract

Graphene exfoliation is a critical step in the fabrication of high-quality graphene

layers. However, the underlying fracture mechanisms remain poorly understood. In this

work, I employed coarse-grained (CG) molecular dynamics (MD) simulations to

investigate how factors such as interfacial binding energy, substrate cohesion, temperature,

peeling mode, and edge defects influence the outcome of the exfoliation process. To model

polymer-assisted mechanical exfoliation, I used a finite-size system in which multilayer

graphene (MLG) is sandwiched between two thin polymer films. Leveraging the

spatiotemporal efficiency of the CG model, I performed fifty simulation iterations per

parameter set and analyzed the results from a probabilistic perspective.

The simulation results reveal that interfacial adhesion plays a pivotal role in

determining exfoliation failure modes—governing whether the failure occurs through

adhesive separation at the polymer–graphene interface or through successful exfoliation of

graphene layers. At low interfacial binding energies, adhesive failure is predominant. As

the interfacial binding energy increases, the failure mode shifts toward layer separation

within MLG. A sharp transition zone exists between these regimes, where the probability

of exfoliating different numbers of graphene layers becomes highly sensitive to interfacial

adhesion strength.

Additionally, I found that temperature, substrate adhesion, and peeling mode can

modulate this transition. Notably, corner peeling introduces greater localized stress

compared to side peeling, enabling monolayer exfoliation under conditions where

interfacial and cohesive energies are comparable.

To further investigate the role of edge defects, I modified the CGMD model by

introducing edge cracks in MLG, which was treated as a stand-alone system. By

systematically varying the crack length and model dimensions, I found that longer edge

cracks significantly reduce the exfoliation force required for layer separation, while shorter

cracks demand higher forces to initiate fracture. These results suggest that edge crack

defects can be deliberately engineered to improve exfoliation efficiency and enable higher

control over the location and propagation of fractures.

Overall, this thesis provides new insights into the underlying mechanics of

graphene exfoliation, establishing a computational modeling-based probabilistic

framework for predicting failure modes. The findings demonstrate how interfacial

adhesion, peeling configuration, and defect engineering can be strategically manipulated

to optimize exfoliation outcomes and facilitate the reliable production of high-quality

graphene for a wide range of advanced applications.

Author ORCID Identifier

0009-0007-1810-152X

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