Quantifying the relationships between the mechanical properties and geometrical parameters of graphene platelet films based on finite element simulations

Qi, Penghao ORCID: https://orcid.org/0000-0003-2901-1443 2025. Quantifying the relationships between the mechanical properties and geometrical parameters of graphene platelet films based on finite element simulations. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Multilayer graphene platelet films (MGPFs) are highly promising materials due to their exceptional mechanical, electrical, and chemical properties, making them suitable for a wide range of advanced applications, including flexible electronics, energy storage, and nano-engineered composites. However, their macroscopic mechanical properties, particularly their elastic behavior and deformation mechanisms, are highly sensitive to multiscale geometric structures, such as individual platelets size, area fraction, and the number of stacked layers. While molecular dynamics (MD) and atomic analysis methods can capture complex behaviors at the atomic or molecular level, they are limited by computational scale and efficiency, preventing a complete analysis of the material properties of their representative structural units. Similarly, traditional finite element methods struggle to capture intricate interlayer behaviors and complex arrangements at the microscale. Consequently, a quantitative understanding of how these microstructural features influence the macroscopic mechanical performance of MGPFs remains a major challenge, which significantly hinders the optimal design and practical application of high-performance MGPF-based systems. In this work, we propose a computational method based on equivalent mechanical transformation and have developed a realistic three-dimensional (3D) stochastic periodic representative volume element (RVE) modelling framework to analyse the mechanical behaviour of MGPFs. By incorporating realistic geometric randomness and multi-scale platelet arrangements, the RVE models enable detailed finite element simulations that capture the mechanical properties of macroscopic MGPFs. By incorporating realistic geometric randomness and multiscale flake arrangements, our RVE model enables detailed finite element simulations that accurately and efficiently predict the macroscopic mechanical properties of MGPFs. As far as we know, this is currently the only simulation method based on a finite element model that bridges the microstructure and macroscopic properties of macroscopic graphene films. The study focuses first on systematically quantifying the influence of geometric parameters on five independent elastic constants of MGPFs, including in-plane and out-of-plane stiffness components. The results reveal that the dimensionless platelet size, graphene area fraction, and number of layers significantly alter the effective stiffness and elastic anisotropy. Detailed parametric studies establish predictive relationships between these geometric descriptors and the macroscopic elastic behavior. Additionally, the impact of defects—such as missing or misaligned graphene platelets—is examined, offering insight into how local structural discontinuities can dominate global mechanical performance. These findings are validated through comparison with available experimental data and provide a generalizable modeling approach applicable to other laminated materials with nacre-like structures. Beyond elasticity, this research also investigates the bending stiffness of MGPFs, which plays a critical role in their functional reliability, especially in applications involving large-scale deformation such as flexible circuits and bendable sensors. Conventional two-dimensional (2D) models often fail to capture the intrinsic three-dimensional architecture and interlayer mechanical interactions of MGPFs, leading to potentially inaccurate predictions of their flexural behavior. To overcome this limitation, the previously established three-dimensional stochastic RVE modeling framework was adapted and refined to enable accurate simulation of bending stiffness. By introducing targeted modifications—such as boundary conditions and load application schemes suitable for out-of-plane deformation—the original model was extended to capture bending responses across a wide range of microstructural configurations. The resulting stiffness values were normalized with respect to the theoretical bending stiffness of an idealized monolithic graphene film, thereby enabling meaningful comparisons and quantitative analysis of the influence of geometric parameters on the flexural performance. The analysis reveals that reduced platelet overlap, uneven defects and decreased graphene platelets size significantly reduce bending stiffness, underscoring the critical importance of microstructural control. These insights offer concrete guidelines for tuning the flexibility of MGPFs and similar nanostructured laminates for targeted applications. A preliminary discussion on the failure behavior of MGPFs is also conducted within the finite element framework. While failure mechanisms in microscale and nanoscale graphene materials are often explored using molecular dynamics (MD) simulations or density functional theory (DFT), these atomistic methods are limited in scale and unsuitable for macroscopic systems. As emphasized earlier, finite element methods provide irreplaceable advantages for modeling larger-scale MGPF systems. Therefore, it remains necessary to construct FEM-based approaches capable of simulating the failure behavior of MGPFs under various structural configurations. Although comprehensive failure analysis lies beyond the primary scope of this study, a simplified interlayer failure model was incorporated into the FEM framework to capture the essential features of delamination and interfacial damage. Through proof-of-concept simulations on selected configurations, the feasibility of this method was demonstrated. These preliminary findings validate the use of FEM for failure modeling in layered graphene systems and underscore the need for future development of advanced multiscale damage models. This initial investigation lays the groundwork for future studies focused on durability, damage evolution, and failure mechanisms in layered graphene-based materials. In summary, this research presents a unified and versatile modeling framework for analyzing the elastic response, bending stiffness, and preliminary failure behavior of MGPFs. The insights obtained contribute to a deeper understanding of structure–property relationships in multilayer graphene composites and provide a solid foundation for the rational design and optimization of next-generation graphene-based materials in both structural and functional applications.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Engineering
Uncontrolled Keywords:	1. Graphene 2. Nacre-like structure 3. Finite element analysis 4. Mechanical properties 5. Multiscale simulation 6. Structural analysis
Date of First Compliant Deposit:	2 March 2026
Last Modified:	02 Mar 2026 13:05
URI:	https://orca.cardiff.ac.uk/id/eprint/185261

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