Investigation of dynamic impact responses of layered polymer-graphene nanocomposite films using coarse-grained molecular dynamics simulations

Yang, Zhangke; Chiang, Cho-Chun; Meng, Zhaoxu

doi:10.1016/j.carbon.2022.11.015

Cited by 16 publications

(9 citation statements)

References 71 publications

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“…The bond potential of the bonds connecting the PMMA chains to graphene is consistent with the bond potential of the graphene model. Moreover, the nonbonded interaction between PMMA and graphene is represented by the 12-6 LJ potential, V nb ( r ), observed in previous studies: , V normaln normalb ( r ) = 4 ε [ ( σ r ) 12 − ( σ r ) 6 ] , for 0.25em r < r normalc normalu normalt where r is the distance between a PMMA bead and a graphene bead, and the cutoff distance r cut is equal to 15 Å; ε is the potential well depth of the interaction between PMMA beads and graphene beads; σ is the distance at which V nb ( r ) crosses zero. In our simulations, ε = 1.2 kcal/mol and σ = 4.5 Å, which lead to an interfacial energy of approximately 0.2 J/m 2 , comparable to the experimentally reported value between the PMMA matrix and the graphene sheets .…”

Section: Methodsmentioning

confidence: 99%

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Molecular Dynamics Simulations of Crumpling Polymer-Grafted Graphene Sheets: Implications for Functional Nanocomposites

Liao,

Molares Palmero,

Arshad

et al. 2024

ACS Appl. Nano Mater.

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Polymer-grafted graphene (PgG) sheets are of interest in the development of functional nanocomposite materials for sensing, energy storage, and coatings. Although extensive studies have reported on various physical properties of PgG sheets, our understanding of the fundamental structural behavior of crumpled PgG sheets is still lacking. Here, we perform molecular dynamics (MD) simulations of the crumpling behavior of poly(methyl methacrylate) (PMMA)-grafted graphene (PMMA-g-G) sheets with varying grafting densities based on previously developed coarse-grained (CG) models of PMMA and graphene. The simulation results reveal that the conformation of PMMA-g-G sheets in the initial equilibrium is controlled by the polymer grafting density and can be characterized into three different regimes (i.e., flat, folded, and wrinkled states), where the local distribution of PMMA on the graphene affects the local curvature of the sheet. By analyzing the total potential energy, shape descriptor, and conformation of the system during the crumpling process, it is found that the increase in grafting density reduces the self-adhering and self-folding behaviors of the sheet while making the bending behavior dominate the crumpling process. Moreover, the evaluation of the local curvature, stress distributions, and cross-sectional patterns of crumpled PMMA-g-G sheets further uncovers the reduced degree of mechanical heterogeneity due to the increased grafting density. Our study provides fundamental insights into the conformational behavior of PMMA-g-G sheets in equilibrium and crumpled states in relation to grafting density, which is crucial for establishing the structure–property relationships for leveraging crumpled polymer-grafted sheets in functional nanocomposites.

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Section: Methodsmentioning

confidence: 99%

Section: Overview Of Coarse-grained Modelingmentioning

confidence: 97%

Molecular Dynamics Simulations of Crumpling Polymer-Grafted Graphene Sheets: Implications for Functional Nanocomposites

Liao,

Molares Palmero,

Arshad

et al. 2024

ACS Appl. Nano Mater.

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“…Subsequently, it decreases but maintains a permanent shift, representing the energy dissipated through various molecular mechanisms involved in the plastic deformation of the soft PE matrix and energy dissipation due to the presence of graphene. We computed the dissipation factor 32 for the pristine polyethylene and nanocomposite systems as the ratio between the dissipated energy and total energy. We analyzed the dissipation factor as a function of U p , as depicted in Figure 4.…”

Section: Energy Dissipation During Shock Wave Propagationmentioning

confidence: 99%

“…By confining polymer chains between crystalline domains, the polymer phase's stiffness can be increased, leading to better chain alignment and order, enhancing the degree of crystallinity in the vicinity of the stiff phase, and ultimately improving energy reflection and dissipation. 32 This study also investigated the impact of filler orientation and dispersion in PE-hBN/graphene composites under shock loading conditions, 33 and the study concluded that bicrystalline nanosheets are superior in reinforcing shock strength attenuation in PE-based nanocomposites. The energy dissipation capability of the nanocomposite was found to increase with the misorientation angle of grain boundaries in bicrystalline configurations of graphene and boron nitride nanosheets.…”

Section: Introductionmentioning

confidence: 99%

“…One such factor is the acoustic impedance mismatch at the interface, , directly impacting the heterogeneous mixture’s energy dissipation or shock attenuation. By confining polymer chains between crystalline domains, the polymer phase’s stiffness can be increased, leading to better chain alignment and order, enhancing the degree of crystallinity in the vicinity of the stiff phase, and ultimately improving energy reflection and dissipation . This study also investigated the impact of filler orientation and dispersion in PE-hBN/graphene composites under shock loading conditions, and the study concluded that bicrystalline nanosheets are superior in reinforcing shock strength attenuation in PE-based nanocomposites.…”

Section: Introductionmentioning

confidence: 99%

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Superior Protection Conferred by Multi-Layered Graphene–Polyethylene Nanocomposites under Shock Loading

Singh,

Ranganathan

2023

ACS Appl. Eng. Mater.

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With the emerging need for lightweight, protective materials such as armor, polymer nanocomposites are being continuously developed with tailored properties to enhance energy-absorbing and dissipating capacity. Developing strong and tough materials is of paramount importance within space and weight constraints. Understanding the high-strain rate deformation mechanisms, shock propagation, energy dissipation, and failure is a critical design consideration for armor materials. High-performance natural materials, such as nacre, show remarkable strength and toughness due to their hierarchical layered architecture across multiple length scales. However, such natural materials often experience high impact loads and thus offer good design criteria for artificial armor materials. Here, we report on the shock response of multilayered graphene polyethylene nanocomposites through large-scale coarsegrained molecular dynamics simulations. Simulations for multiple piston speeds (0.3−3.5 km/s) were conducted to study shock propagation, dissipation, and eventual failure. The multilayered organization of graphene significantly increases the impact strength of the composites, as reflected in the spallation strength of the composites. This study also shows the effect of physical grafting of polyethylene chains on shock dissipation and mitigation. The spall strength of the grafted MLG−PE is approximately 10−40% greater than that of its corresponding counterparts. We also elucidated the underlying molecular mechanisms involved in shock deformation. The foremost mechanisms driving dissipation in the grafted composite are the intricate scattering of shock waves at the interface, a substantial difference in the acoustic impedance between graphene and polyethylene, and the occurrence of visco-plastic deformation involving numerous stress-transfer sites. Our research revealed that introducing grafted polymer chains to the fillers results in significant morphological alterations in the polymers, primarily attributed to bond compression, stretching, and bending. The study offers promising design strategies for designing high-performance lightweight materials.

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Insights into the thermomechanical and interfacial behaviors of polymer‐clay nanocomposites via coarse‐grained molecular dynamics simulations

Nie,

Liao,

Ghazanfari

et al. 2024

Polymer Composites

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Polymer‐clay nanocomposites (PCNs) are commonly applied as multi‐functional structural materials with exceptional thermomechanical properties, while maintaining the characteristics of lightweight and optical clarity. In this study, building upon previously developed coarse‐grained (CG) models for nanoclay and poly (methyl methacrylate) (PMMA), we employ molecular dynamics (MD) simulations to systematically investigate the thermomechanical properties of PCNs when arranged in stacked configurations. Incorporating stacked clay nanofillers into a polymer matrix, we systematically conduct shear and tensile simulations to investigate the influences of variations in weight percentage, system temperature, and nanoclay size on the thermomechanical properties of PCNs at a fundamental level. The weight percentage of nanoclay in nanocomposites proves to have a significant influence on both the shear and Young's modulus (e.g., the addition of 10 Wt% nanoclay leads to an increase of 32.6% in the Young's modulus), with each exhibiting greater mechanical strength in the in‐plane direction compared to the out‐of‐plane direction, and the disparity between these two directions further widens with an increase in the weight percentage of nanoclay. Furthermore, the increase in the size of nanoclay contributes to an overall modulus enhancement in the composite while the growth reaches a saturation point after a certain threshold of about 10 nm. Our simulation results indicate that the overall dynamics of PMMA are suppressed due to the strong interactions between nanoclay and PMMA, where the confinement effect on local segmental dynamics of PMMA decays from the nanoclay‐polymer interface to the polymer matrix. Our findings provide valuable molecular‐level insights into microstructural and dynamical features of PCNs under deformation, emphasizing the pivotal role of clay‐polymer interface in influencing the thermomechanical properties of the composite materials.Highlights CG modeling is performed to explore the thermomechanical behavior of PCN. Effects of nanoclay weight percentage and size on modulus are studied. Interface leads to nanoconfinement effect on Tg and molecular stiffness. Correlations between molecular stiffness and modulus are identified. Simulations show spatial variation of dynamical heterogeneity.

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Investigation of dynamic impact responses of layered polymer-graphene nanocomposite films using coarse-grained molecular dynamics simulations

Cited by 16 publications

References 71 publications

Molecular Dynamics Simulations of Crumpling Polymer-Grafted Graphene Sheets: Implications for Functional Nanocomposites

Molecular Dynamics Simulations of Crumpling Polymer-Grafted Graphene Sheets: Implications for Functional Nanocomposites

Superior Protection Conferred by Multi-Layered Graphene–Polyethylene Nanocomposites under Shock Loading

Insights into the thermomechanical and interfacial behaviors of polymer‐clay nanocomposites via coarse‐grained molecular dynamics simulations

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