Abstract Recent microscale ballistic experiments have revealed that multilayer graphene membranes exhibit exceptionally high ballistic limit velocity and specific penetration energy. A key feature contributing to the exceptional performance of these systems is the cone wave that develops at impact, which propagates radially at a very high speed for ultra-light and stiff graphene membranes, distributing the kinetic energy of the projectile away from the impact zone. Current theories on ballistic impact consider infinitely wide membranes, and atomistic simulations involve very small projectiles and specimen dimensions, and thus cannot ascertain whether microscale ballistics observations are scalable and size-independent. Here, we discover a particular size effect due to the reflection of cone wave that has not been previously observed or considered. We present molecular dynamics simulations showing that there exists a critical membrane size below which the cone wave reflections from the boundaries induce perforation; a phenomenon that is particularly relevant for microballistic testing of graphene membranes. We present an analytical relationship, verified by simulation data, which predicts the critical membrane size simply as a function of the projectile size, membrane thickness and the ratio of the projectile and membrane densities. Our findings provide timely guidance for future microscale experiments and atomistic simulations for accurate characterization of the impact performance of 2D nanomaterials.
Last. Sinan Keten(NU: Northwestern University)H-Index: 34
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Abstract Graphene oxide (GO) shows promise as a nanocomposite building block due to its exceptional mechanical properties. While atomistic simulations have become central to investigating its mechanical properties, the method remains prohibitively expensive for large deformations and mesoscale failure mechanisms. To overcome this, we establish a coarse-grained (CG) model that captures key mechanical and interfacial properties, and the non-homogeneous effect of oxidation in GO sheets. The CG mode...
Predicting the macroscopic fracture energy of highly cross-linked glassy polymers from atomistic simulations is challenging due to the size of the process zone being large in these systems. Here, we present a scale-bridging approach that links atomistic molecular dynamics simulations to macroscopic fracture properties on the basis of a continuum fracture mechanics model for two different epoxy materials. Our approach reveals that the fracture energy of epoxy resins strongly depends on the functi...
Last. Sinan Keten(NU: Northwestern University)H-Index: 34
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Polymers reinforced with multi-layer graphene (MLG) phases are promising candidates for new materials with high modulus, strength and toughness. Drawing inspiration from nacre's layered “brick and mortar” structure, here we propose molecular scale design strategies to improve the mechanical performance of MLG–polymer layer-by-layer nanocomposites. We present a coarse-grained molecular dynamics (CG-MD) study of interfacial failure mechanisms of MLG domains embedded in a poly(methyl methacrylate) ...
Abstract Transverse impact behaviour of graphene sheet (GS) has been studied using molecular dynamics (MD) simulations. One, two and three layers of GS have been impacted with a fullerene rigid projectile in the impact velocity range: 3.5–7.5 km/s. LAMMPS is used for MD simulations using the AIREBO force field. Kinetic energy, displacement, velocity and perforation resistance force of the projectile have been investigated to understand the perforation mechanics of GS. In-plane axial-wave and out...
Abstract Despite its importance, the mechanical behavior of graphene under the impact of projectiles has rarely been studied due to experimental and computational difficulties. Here, we simulated the impact of silica and nickel projectiles with a supersonic initial velocity on graphene. Then we analyzed the impact by using ReaxFF reactive force field method, which is capable of describing the entire system. During the process of projectile penetration, we identified various atomistic features, s...
Last. Sinan Keten(NU: Northwestern University)H-Index: 34
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Multi-layer graphene assemblies (MLGs) or fibers with a staggered architecture exhibit high toughness and failure strain that surpass those of the constituent single sheets. However, how the architectural parameters such as the sheet overlap length affect these mechanical properties remains unknown due in part to the limitations of mechanical continuum models. By exploring the mechanics of MLG assemblies under tensile deformation using our established coarse-grained molecular modeling framework,...
Understanding the deformation mechanisms in multilayer graphene (MLG), an attractive material used in nanodevices as well as in the reinforcement of nanocomposites, is critical yet challenging due to difficulties in experimental characterization and the spatiotemporal limitations of atomistic modeling. In this study, we combine nanomechanical experiments with coarse-grained molecular dynamics (CG-MD) simulations to elucidate the mechanisms of deformation and failure of MLG sheets. Elastic proper...
#1Fernando Soto(UCSD: University of California, San Diego)H-Index: 22
#2Aída Martín(UCSD: University of California, San Diego)H-Index: 22
Last. Joseph Wang(UCSD: University of California, San Diego)H-Index: 173
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Acoustically triggered microcannons, capable of loading and firing nanobullets (Nbs), are presented as powerful microballistic tools. Hollow conically shaped microcannon structures have been synthesized electrochemically and fully loaded with nanobullets made of silica or fluorescent microspheres, and perfluorocarbon emulsions, embedded in a gel matrix stabilizer. Application of a focused ultrasound pulse leads to the spontaneous vaporization of the perfluorocarbon emulsions within the microcann...
Layered assemblies of polymers and graphene derivatives employ nacre’s tested strategy of intercalating soft organic layers with hard crystalline domains. These layered systems commonly display elastic properties that exceed simple mixture rule predictions, but the molecular origins of this phenomenon are not well understood. Here we address this issue by quantifying the elastic behavior of nanoconfined polymer layers on a model layered graphene-polymer nanocomposite. Using a novel, validated co...
#1Eric D. Wetzel(ARL: United States Army Research Laboratory)H-Index: 26
#2Radhakrishnan Balu(ARL: United States Army Research Laboratory)H-Index: 7
Last. Todd D. Beaudet(ARL: United States Army Research Laboratory)H-Index: 5
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Abstract The remarkable properties of graphene, including unusually high mechanical strength and stiffness, have been well-documented. In this paper, we combine an analytical solution for ballistic impact into a thin isotropic membrane, with ab initio density functional theory calculations for graphene under uniaxial tension, to predict the penetration resistance of multi-layer graphene membranes. The calculations show that continuous graphene membranes could enable ballistic barriers of extraor...
#1Andrew L Bowman(ERDC: Engineer Research and Development Center)
#2Edwin P. Chan(NIST: National Institute of Standards and Technology)H-Index: 23
Last. John K. Newman(ERDC: Engineer Research and Development Center)H-Index: 3
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Recent nanoscale ballistic tests have shown the applicability of nanomaterials for ballistic protection but have raised questions regarding the nanoscale structure-property relationships that contribute to the ballistic response. Herein, we report on multimillion-atom reactive molecular dynamics simulations of the supersonic impact, penetration, and failure of polyethylene (PE) and polystyrene (PS) ultrathin films. The simulated specific penetration energy (Ep*) versus impact velocity predicts t...
The development of armour systems with higher ballistic resistance and light weight has gained considerable attention as an increasing number of countries are recognising the need to build up advanced self-defence system to deter potential military conflicts and threats. Graphene is a two dimensional one-atom thick nanomaterial which possesses excellent tensile strength (130 GPa) and specific penetration energy (10 times higher than steel). It is also lightweight, tough and stiff and is expected...
Abstract We simulated ballistic impact tests of multilayer polyurea/silicon-carbide (SiC) nanostructures using molecular dynamics (MD). First, we conducted density functional theory calculations to obtain accurate parameters to model the nonbonded interactions of the polyurea/SiC interface and subsequently investigated the influence of interfacial adhesion on the impact response. Our MD simulations demonstrate that the ballistic limit velocity and the specific penetration energy of the polyurea/...
Abstract Multilayer graphene sheets (MLGSs) are promising nano-reinforcements that can effectively enhance the properties of polymer matrices. Despite many studies on MLGSs-reinforced polymer nanocomposites, the effect of wrinkles formed in MLGSs on the reinforcement effect and the viscoelastic properties of polymer nanocomposites has remained unknown. In this study, building upon previously developed coarse-grained models of MLGSs and poly(methyl methacrylate) coupled with molecular dynamics si...
Last. Xiaohu Yao(SCUT: South China University of Technology)H-Index: 14
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Abstract Incorporating graphene nanosheets into a polymer matrix is a promising way to utilize the remarkable electronic, thermal, and mechanical properties of graphene. However, the underlying mechanisms near the graphene-polymer interface remain poorly understood. In this study, we employ coarse-grained molecular dynamics (MD) simulations to investigate the nanoscale mechanisms present in graphene-reinforced polycarbonate (GRPC) nanocomposites and the effect of those mechanisms on GRPC’s mecha...
#1Xing Yang(NUAA: Nanjing University of Aeronautics and Astronautics)H-Index: 1
#2Bin Zhang(NUAA: Nanjing University of Aeronautics and Astronautics)H-Index: 4
Abstract The transverse impact responses of three kinds of bilayers (h-BN/h-BN, graphene/graphene, and hybrid graphene/h-BN) twisted at various angles (0°∼30°) are investigated by molecular dynamics simulations, which explore the nano-projectile penetrates the layers at a series of velocities (1∼12 km/s). For each twisted bilayer, the critical penetration velocity shows no evident differences (