Mechanics of Materials

Gere, James M.; Timoshenko, S.

doi:10.1007/978-1-4899-3124-5

Cited by 1,409 publications

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“…This is in agreement with the theoretical prediction that a freestanding ultrathin graphene sheet is prone to rolling up to form a tubular structure 40 . Scrolling of a sheet-like material is known to enhance the elastic stiffness remarkably 22 . Thus, the fibrous structure resulted from self scrolling of single or few layers of graphene helps maintain elasticity and structural integrity as well when the density of the graphene monolith becomes extremely low.…”

Section: Resultsmentioning

confidence: 99%

“…Superelasticity that has been observed in foams made of carbon-based tubular or fibrillar nanostructures [15][16][17][18][19][20][21] has not been achieved in foams solely based on graphene sheets. Indeed, as the specific elastic bending stiffness of a sheet-like structure is known to be intrinsically inferior to that of its tubular or fibrillar counterparts 22 , previous analysis 13 suggests that it would be highly challenging to realize superelasticity in graphene foams. The ability to maintain structural integrity upon large deformation for graphene monoliths is not only crucial for building new types of flexible electronic devices, such as batteries, supercapacitors, sensors and actuators, but also important for future development of carbon-based biological tissue scaffolds and ultralight cellular materials for mechanical damping and thermal/acoustic insulation.…”

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confidence: 99%

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Biomimetic superelastic graphene-based cellular monoliths

et al. 2012

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Many applications proposed for graphene require multiple sheets be assembled into a monolithic structure. The ability to maintain structural integrity upon large deformation is essential to ensure a macroscopic material which functions reliably. However, it has remained a great challenge to achieve high elasticity in three-dimensional graphene networks. Here we report that the marriage of graphene chemistry with ice physics can lead to the formation of ultralight and superelastic graphene-based cellular monoliths. Mimicking the hierarchical structure of natural cork, the resulting materials can sustain their structural integrity under a load of 450,000 times their own weight and can rapidly recover from 480% compression. The unique biomimetic hierarchical structure also provides this new class of elastomers with exceptionally high energy absorption capability and good electrical conductivity. The successful synthesis of such fascinating materials paves the way to explore the application of graphene in a self-supporting, structurally adaptive and 3D macroscopic form.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Biomimetic superelastic graphene-based cellular monoliths

et al. 2012

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“…The physical properties of the three plates that were chosen are given in Table 2. SS25 and SS60 had a similar Young's modulus (E) whereas the polyurethane (PU) surface had a different Young's modulus. However, the flexural rigidity (Gere and Timoshenko, 1990), which characterizes the bending stiffness of a plate, was of the same order of magnitude for both SS25 and PU (Table 2).…”

Section: Foot Support Surfacementioning

confidence: 94%

“…The Flexural Rigidity (EI) (Gere and Timoshenko, 1990) that characterizes the resistance to bending was computed from the Young's Modulus (E) and the second moment of area (I) ( Table 2) by:…”

Section: Materials Property Determinationmentioning

confidence: 99%

Effects of surface characteristics on the plantar shape of feet and subjects’ perceived sensations

et al. 2009

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Orthotics and other types of shoe inserts are primarily designed to reduce injury and improve comfort. The interaction between the plantar surface of the foot and the load bearing surface contributes to foot and surface deformations and hence to perceived comfort, discomfort or pain. The plantar shapes of 16 participants' feet were captured when standing on three support surfaces that had different cushioning properties in the mid-foot region. Foot shape deformations were quantified using 3D laser scans. A questionnaire was used to evaluate the participant's perceptions of perceived shape and perceived feeling. The results showed that the structure in the mid-foot can change shape, independent of the rear-foot and forefoot regions. Participants were capable of identifying the shape changes with distinct preferences towards certain shapes. The cushioning properties of the mid-foot materials also have a direct influence on perceived feelings. This research has strong implications for the design and material selection of orthotics, insoles and footwear.

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“…The transition to a nonlinear regime is predicted by elasticity theory and can be ascribed to the onset of sizable local deformations originating from the finite size and shape of the indenter. [16][17][18] Importantly, even for large deflections of 50 nm (corresponding to strains of ∼1%), the loading and unloading curves were observed to overlap, indicating fully elastic deformations under these conditions. Further evidence for the excellent resilience of the sheets derives from the fact that the slope of the F(δ) curves does not change after repeated deformations, which proves the absence of permanent damage.…”

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confidence: 99%

Elastic Properties of Chemically Derived Single Graphene Sheets

2008

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The elastic modulus of freely suspended graphene monolayers, obtained via chemical reduction of graphene oxide, was determined through tip-induced deformation experiments. Despite their defect content, the single sheets exhibit an extraordinary stiffness (E ) 0.25 TPa) approaching that of pristine graphene, as well as a high flexibility which enables them to bend easily in their elastic regime. Built-in tensions are found to be significantly lower compared to mechanically exfoliated graphene. The high resilience of the sheets is demonstrated by their unaltered electrical conductivity after multiple deformations. The electrical conductivity of the sheets scales inversely with the elastic modulus, pointing toward a 2-fold role of the oxygen bridges, that is, to impart a bond reinforcement while at the same time impeding the charge transport.Recent experiments have revealed the thermodynamic stability of graphene under ambient conditions, 1-3 which strongly revived the interest in the electrical and mechanical properties of this fascinating carbon nanostructure. Two major methods have been established for the fabrication of graphene monolayers, namely, mechanical exfoliation of graphite 2 and vacuum graphitization of silicon carbide. 3,4 More recently, chemical reduction of graphene oxide (GO) has been reported as an alternative, solution-based route, for obtaining graphenelike sheets which offers the advantages of being cheap and up-scalable. [5][6][7][8] Even though GO is a good insulator, deoxygenation has been shown to substantially enhance its electrical conductivity, albeit the obtained values of ∼1 S/cm remain 2-3 orders of magnitude below that of pristine graphene. 6,7 Due to the limited efficiency of the reduction process, the obtained sheets still contain residual oxygenated functional groups of the starting material. Microscopic studies of the reduced GO also indicate the coexistence of graphitic regions with defect clusters 6,9 in agreement with proposed models. [9][10][11] In addition to its interesting electrical characteristics, this 2D material is expected to have also unique mechanical properties. Recent studies have witnessed its suitability for the fabrication of composites 12,13 and paperlike materials 14 with excellent mechanical properties. However, in order to promote its application in nanotechnology, the mechanical characterization of single sheets is of upmost relevance.Here we present a study of the mechanical and electrical properties of suspended, chemically reduced GO single sheets. Graphite oxide prepared via Hummers method 15 was dispersed in water, deposited onto a Si/SiO 2 substrate, and subsequently reduced by hydrogen plasma treatment. The obtained samples exhibited a high yield of monolayers with lateral dimensions of 0.1-5 µm. Preselected layers were then contacted by standard e-beam lithography with Ti/Au electrodes. In order to freely suspend the layers (Figure 1), the samples were wet etched by buffered hydrofluoric acid, followed by critical point drying to prevent ...

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Mechanics of Materials

Cited by 1,409 publications

References 0 publications

Biomimetic superelastic graphene-based cellular monoliths

Biomimetic superelastic graphene-based cellular monoliths

Effects of surface characteristics on the plantar shape of feet and subjects’ perceived sensations

Elastic Properties of Chemically Derived Single Graphene Sheets

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