Showing papers on "Elastic modulus published in 2014"
TL;DR: An ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film that enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.
Abstract: Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.
1,199 citations
TL;DR: It is reported that the two-dimensional elastic modulus of graphene is maintained even at a high density of sp(3)-type defects, which provides important basic information for the rational design of composites and other systems utilizing the high modulus and strength of graphene.
Abstract: It is important from a fundamental standpoint and for practical applications to understand how the mechanical properties of graphene are influenced by defects. Here we report that the two-dimensional elastic modulus of graphene is maintained even at a high density of sp(3)-type defects. Moreover, the breaking strength of defective graphene is only ~14% smaller than its pristine counterpart in the sp(3)-defect regime. By contrast, we report a significant drop in the mechanical properties of graphene in the vacancy-defect regime. We also provide a mapping between the Raman spectra of defective graphene and its mechanical properties. This provides a simple, yet non-destructive methodology to identify graphene samples that are still mechanically functional. By establishing a relationship between the type and density of defects and the mechanical properties of graphene, this work provides important basic information for the rational design of composites and other systems utilizing the high modulus and strength of graphene.
549 citations
TL;DR: In this article, the 2D elastic modulus of CVD monolayer MoS2 and WS2 was investigated and it was shown that the moduli of their bilayer heterostructures are comparable to the corresponding bilayer homostructure, implying similar interactions between the hetero monolayers as between homo monlayers.
Abstract: Elastic properties of materials are an important factor in their integration in applications. Chemical vapor deposited (CVD) monolayer semiconductors are proposed as key components in industrial-scale flexible devices and building blocks of two-dimensional (2D) van der Waals heterostructures. However, their mechanical and elastic properties have not been fully characterized. Here we report high 2D elastic moduli of CVD monolayer MoS2 and WS2 (∼170 N/m), which is very close to the value of exfoliated MoS2 monolayers and almost half the value of the strongest material, graphene. The 2D moduli of their bilayer heterostructures are lower than the sum of 2D modulus of each layer but comparable to the corresponding bilayer homostructure, implying similar interactions between the hetero monolayers as between homo monolayers. These results not only provide deep insight into understanding interlayer interactions in 2D van der Waals structures but also potentially allow engineering of their elastic properties as desired.
454 citations
TL;DR: High 2D elastic moduli of CVD monolayer MoS2 and WS2 (∼170 N/m) are reported, which is very close to the value of exfoliated MoS1 andWS2 monolayers and almost half thevalue of the strongest material, graphene.
Abstract: Elastic properties of materials are an important factor in their integration in applications. Chemical vapor deposited (CVD) monolayer semiconductors are proposed as key components in industrial-scale flexible devices and building blocks of 2D van der Waals heterostructures. However, their mechanical and elastic properties have not been fully characterized. Here we report high 2D elastic moduli of CVD monolayer MoS2 and WS2 (~ 170 N/m), which is very close to the value of exfoliated MoS2 monolayers and almost half the value of the strongest material, graphene. The 2D moduli of their bilayer heterostructures are lower than the sum of 2D modulus of each layer, but comparable to the corresponding bilayer homostructure, implying similar interactions between the hetero monolayers as between homo monolayers. These results not only provide deep insight to understanding interlayer interactions in 2D van der Waals structures, but also potentially allow engineering of their elastic properties as desired.
411 citations
TL;DR: In this paper, a macroscopic compression test utilizing a simple custom-built instrument was employed to measure polydimethylsilox-ane (PDMS) elastic modulus.
Abstract: A macroscopic compression test utilizing a simple custom-built instrument was employed to measure polydimethylsilox- ane (PDMS) elastic modulus. PDMS samples with varying crosslinking density were prepared with the elastomer base to the curing agent ratio ranging from 5 : 1 to 33 : 1. The PDMS network elastic modulus varied linearly with the amount of crosslinker, ranging from 0.57 MPa to 3.7 MPa for the samples tested. PDMS elastic modulus in MPa can be expressed as 20 MPa/PDMS base to curing agent ratio. This article describes a simple method for measuring elastic properties of soft polymeric materials. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41050.
391 citations
TL;DR: In this paper, the authors combine short and long-chain alginates to reduce the viscosity of pregel solutions and synthesize homogeneous hydrogels of high ionic cross-link density.
Abstract: The development of hydrogels for cartilage replacement and soft robotics has highlighted a challenge: load-bearing hydrogels need to be both stiff and tough. Several approaches have been reported to improve the toughness of hydrogels, but simultaneously achieving high stiffness and toughness remains difficult. Here we report that alginate-polyacrylamide hydrogels can simultaneously achieve high stiffness and toughness. We combine short- and long-chain alginates to reduce the viscosity of pregel solutions and synthesize homogeneous hydrogels of high ionic cross-link density. The resulting hydrogels can have elastic moduli of ∼1 MPa and fracture energies of ∼4 kJ m–2. Furthermore, this approach breaks the inverse relation between stiffness and toughness: while maintaining constant elastic moduli, these hydrogels can achieve fracture energies up to ∼16 kJ m–2. These stiff and tough hydrogels hold promise for further development as load-bearing materials.
344 citations
TL;DR: New analytical solutions and closed-form relationships for predicting the elastic modulus, Poisson׳s ratio, critical buckling load, and yield (plateau) stress of cellular structures made of the diamond lattice unit cell are presented.
Abstract: Cellular structures with highly controlled micro-architectures are promising materials for orthopedic applications that require bone-substituting biomaterials or implants The availability of additive manufacturing techniques has enabled manufacturing of biomaterials made of one or multiple types of unit cells The diamond lattice unit cell is one of the relatively new types of unit cells that are used in manufacturing of regular porous biomaterials As opposed to many other types of unit cells, there is currently no analytical solution that could be used for prediction of the mechanical properties of cellular structures made of the diamond lattice unit cells In this paper, we present new analytical solutions and closed-form relationships for predicting the elastic modulus, Poisson׳s ratio, critical buckling load, and yield (plateau) stress of cellular structures made of the diamond lattice unit cell The mechanical properties predicted using the analytical solutions are compared with those obtained using finite element models A number of solid and porous titanium (Ti6Al4V) specimens were manufactured using selective laser melting A series of experiments were then performed to determine the mechanical properties of the matrix material and cellular structures The experimentally measured mechanical properties were compared with those obtained using analytical solutions and finite element (FE) models It has been shown that, for small apparent density values, the mechanical properties obtained using analytical and numerical solutions are in agreement with each other and with experimental observations The properties estimated using an analytical solution based on the Euler–Bernoulli theory markedly deviated from experimental results for large apparent density values The mechanical properties estimated using FE models and another analytical solution based on the Timoshenko beam theory better matched the experimental observations
315 citations
TL;DR: It is demonstrated that the incorporation of carbon nanofibers into porous chitosan scaffolds improved the properties of cardiac tissue constructs, presumably through enhanced transmission of electrical signals between the cells.
301 citations
TL;DR: Most hydrogels have poor mechanical properties, severely limiting their scope of applications, but here a hybrid hydrogel, consisting of hydrophilic and crystalline polymer networks, achieves an elastic modulus of 5 MPa, a strength of 2.5 MPa and a fracture energy of 14 000 J m-2 while maintaining physical integrity in concentrated electrolyte solutions.
Abstract: Most hydrogels have poor mechanical properties, severely limiting their scope of applications. Here a hybrid hydrogel, consisting of hydrophilic and crystalline polymer networks, achieves an elastic modulus of 5 MPa, a strength of 2.5 MPa, and a fracture energy of 14 000 J m−2, while maintaining physical integrity in concentrated electrolyte solutions.
275 citations
TL;DR: It is concluded that it is possible to describe the elastic properties of the cell body by means of an effective elastic modulus, used in a self-consistent way, when using the brush model to analyze data collected with a dull AFM probe.
262 citations
TL;DR: A remarkably facile one-pot synthetic strategy based on polymerization-induced phase separation (PIPS) to generate nanostructured PEMs that exhibit an unprecedented combination of high modulus and ionic conductivity that holds tremendous potential to advance lithium-ion battery technology by enabling the use of lithium metal anodes or to serve as membranes in high-temperature fuel cells.
Abstract: The primary challenge in solid-state polymer electrolyte membranes (PEMs) is to enhance properties, such as modulus, toughness, and high temperature stability, without sacrificing ionic conductivity. We report a remarkably facile one-pot synthetic strategy based on polymerization-induced phase separation (PIPS) to generate nanostructured PEMs that exhibit an unprecedented combination of high modulus and ionic conductivity. Simple heating of a poly(ethylene oxide) macromolecular chain transfer agent dissolved in a mixture of ionic liquid, styrene and divinylbenzene, leads to a bicontinuous PEM comprising interpenetrating nanodomains of highly cross-linked polystyrene and poly(ethylene oxide)/ionic liquid. Ionic conductivities higher than the 1 mS/cm benchmark were achieved in samples with an elastic modulus approaching 1 GPa at room temperature. Crucially, these samples are robust solids above 100 °C, where the conductivity is significantly higher. This strategy holds tremendous potential to advance lithiu...
TL;DR: Ti-6Al-4V cellular solids with high strength, low modulus and desirable deformation behavior could be fabricated through the cell shape design using the electron beam melting (EBM) technique.
TL;DR: In this paper, a method to design manufacturable extremal elastic materials is presented, which is shown to be close to the theoretical limit given by mathematical bounds, and the deviations are due to the imposed manufacturing constraints.
TL;DR: A multifrequency force microscopy method that enables simultaneous mapping of nanomechanical spectra of soft matter surfaces with nanoscale spatial resolution and provides the peak force and the indentation of the Young's modulus.
Abstract: A method that combines high spatial resolution, quantitative and non-destructive mapping of surfaces and interfaces is a long standing goal in nanoscale microscopy. The method would facilitate the development of hybrid devices and materials made up of nanostructures of different properties. Here we develop a multifrequency force microscopy method that enables simultaneous mapping of nanomechanical spectra of soft matter surfaces with nanoscale spatial resolution. The properties include the Young's modulus and the viscous or damping coefficients. In addition, it provides the peak force and the indentation. The method does not limit the data acquisition speed nor the spatial resolution of the force microscope. It is non-invasive and minimizes the influence of the tip radius on the measurements. The same tip is used to measure in air heterogeneous interfaces with near four orders of magnitude variations in the elastic modulus, from 1 MPa to 3 GPa.
TL;DR: In this article, the authors used finite element modeling to predict the effect of variation in the struts diameter on the elastic modulus as well as collapse stress of cellular lattice structures.
TL;DR: In this paper, a broad range of hydrophobic monolithic silica aerogels and xerogels made from polyethoxydisiloxane precursors were synthesized and the effects of density on the mechanical, microstructural, and thermal properties were studied.
TL;DR: In this paper, a combination of experimental measurements and numerical simulations are used to characterize the mechanical and electrochemical response of thin film amorphous Si electrodes during cyclic lithiation.
Abstract: A combination of experimental measurements and numerical simulations are used to characterize the mechanical and electrochemical response of thin film amorphous Si electrodes during cyclic lithiation. Parameters extracted from the experiment include the variation of elastic modulus and the flow stress as functions of Li concentration; the strain rate sensitivity; the diffusion coefficient for Li transport in the electrode; the free energy of mixing as a function of Li concentration in the electrode; the exchange current density for the Lithium insertion reaction; as well as reaction rates and diffusion coefficients characterizing the rate of formation of solid-electrolyte interphase layer at the electrode surface. Model predictions are compared with experimental measurements; and the implications for practical Si based electrodes are discussed.
TL;DR: Results indicated that the presence of PEG not only improves PLA processing but also leads to relevant surface, geometrical and structural changes including modulation of the degradation rate of PLA-based 3D printed scaffolds.
TL;DR: The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys.
TL;DR: In this article, a review of the properties of graphene lattice lattice is presented, including the in-plane tensile response and the free-standing indentation response, based on multiscale levels: including quantum mechanical and classical molecular dynamics simulations and parallel continuum models.
Abstract: Recent progress of simulations/modeling at the atomic level has led to a better understanding of the mechanical behaviors of graphene, which include the linear elastic modulus E, the nonlinear elastic modulus D, the Poisson’s ratio ν, the intrinsic strength σint and the corresponding strain eint as well as the ultimate strain emax (the fracture strain beyond which the graphene lattice will be unstable). Due to the two-dimensional geometric characteristic, the in-plane tensile response and the free-standing indentation response of graphene are the focal points in this review. The studies are based on multiscale levels: including quantum mechanical and classical molecular dynamics simulations, and parallel continuum models. The numerical studies offer useful links between scientific research with engineering application, which may help to fulfill graphene potential applications such as nano sensors, nanotransistors, and other nanodevices.
TL;DR: The microstructure and mechanical properties of the CoCrCuFeNiNb high-entropy alloy coating prepared by plasma transferred arc cladding process were investigated in this article, where two phases were found in the prepared coating with Nb: one is face-centered-cubic solid solution phase; the other is the Laves phase of (CoCr) Nb type.
Abstract: The microstructure and mechanical properties of the CoCrCuFeNiNb high-entropy alloy coating prepared by plasma transferred arc cladding process were investigated. Two phases are found in the prepared coating with Nb: one is face-centered-cubic solid solution phase; the other is the Laves phase of (CoCr) Nb type. The nano-indentation testing indicates that the microhardness (H), elastic modulus (E), the hardness/modulus of elasticity ratio (H/E ratio) and high resistance to plastic deformation (H3/E2) of the coating with Nb are 6.13 GPa, 221 GPa, 0.028 and 4.7 × 10− 3 respectively. The CoCrCuFeNiNb coating displays excellent wear and corrosion resistance. The wear resistance of the coating with Nb is about 1.5 times higher than that of the coating without Nb under the same wet sand rubber wheel abrasion testing conditions. Compared with the coating without Nb and as-cast 304 stainless steel, the coating with Nb shows the lowest icorr values in polarization curves and the highest fitted Rf values in EIS plots in 6N hydrochloric acid solution.
TL;DR: In this paper, a medium theory of elasticity is presented, which extends previous approaches by incorporating the effect of compression, of amplitude e, allowing one to describe quantitative features of sound propagation, transport, the boson peak, and elastic moduli near the elastic instability occurring at a compression ec.
Abstract: Connectedness and applied stress strongly affect elasticity in solids. In various amorphous materials, mechanical stability can be lost either by reducing connectedness or by increasing pressure. We present an effective medium theory of elasticity that extends previous approaches by incorporating the effect of compression, of amplitude e, allowing one to describe quantitative features of sound propagation, transport, the boson peak, and elastic moduli near the elastic instability occurring at a compression ec. The theory disentangles several frequencies characterizing the vibrational spectrum: the onset frequency where strongly-scattered modes appear in the vibrational spectrum, the pressure-independent frequency ω* where the density of states displays a plateau, the boson peak frequency ωBP found to scale as , and the Ioffe–Regel frequency ωIR where scattering length and wavelength become equal. We predict that sound attenuation crosses over from ω4 to ω2 behaviour at ω0, consistent with observations in glasses. We predict that a frequency-dependent length scale ls(ω) and speed of sound ν(ω) characterize vibrational modes, and could be extracted from scattering data. One key result is the prediction of a flat diffusivity above ω0, in agreement with previously unexplained observations. We find that the shear modulus does not vanish at the elastic instability, but drops by a factor of 2. We check our predictions in packings of soft particles and study the case of covalent networks and silica, for which we predict ωIR ≈ ωBP. Overall, our approach unifies sound attenuation, transport and length scales entering elasticity in a single framework where disorder is not the main parameter controlling the boson peak, in agreement with observations. This framework leads to a phase diagram where various glasses can be placed, connecting microscopic structure to vibrational properties.
TL;DR: In this paper, a comprehensive characterization of the stress, elastic modulus, hardness and adhesion of ALD aluminum oxide (Al2O3) films grown at 110-300°C from trimethylaluminum and water is presented.
TL;DR: In this article, a single-crystal CoCrFeNiAl03 high-entropy alloy (HEA) was synthesized by Bridgman solidification and the growth direction of the singlecrystal product mainly focused on the orientation.
TL;DR: Covalent monolayer sheets in 2 hours: spreading of threefold anthracene-equipped shape-persistent and amphiphilic monomers at the air/water interface followed by a short photochemical treatment provides access to infinitely sized, strictly monolayered, covalent sheets with in-plane elastic modulus in the range of 19 N/m.
Abstract: Covalent monolayer sheets in 2 hours: spreading of threefold anthracene-equipped shape-persistent and amphiphilic monomers at the air/water interface followed by a short photochemical treatment provides access to infinitely sized, strictly monolayered, covalent sheets with in-plane elastic modulus in the range of 19 N/m.
TL;DR: In this article, the structural and elastic properties of Ca-Pb intermetallic compounds were investigated by using the first-principles calculations based on density functional theory, and the calculated equilibrium structural parameters were in good agreement with the available experimental data.
TL;DR: The fluctuation spectrum reveals an additional mode that is attributed to diffusion of structural defects in the column-like aggregates in the LCLC disodium cromoglycate and the elastic moduli and viscosity coefficients are measured.
Abstract: Using dynamic light scattering, we study orientational fluctuation modes in the nematic phase of a self-assembled lyotropic chromonic liquid crystal (LCLC) disodium cromoglycate and measure the Frank elastic moduli and viscosity coefficients. The elastic moduli of splay (K1) and bend (K3) are in the order of 10 pN while the twist modulus (K2) is an order of magnitude smaller. The splay constant K1 and the ratio K1/K3 both increase substantially as the temperature T decreases, which we attribute to the elongation of the chromonic aggregates at lower temperatures. The bend viscosity is comparable to that of thermotropic liquid crystals, while the splay and twist viscosities are several orders of magnitude larger. The temperature dependence of bend viscosity is weak. The splay and twist viscosities change exponentially with the temperature. In addition to the director modes, the fluctuation spectrum reveals an additional mode that is attributed to diffusion of structural defects in the column-like aggregates.
TL;DR: In this paper, the elastic moduli depend on the angle of inclination of the ligaments with respect to the grid of lines connecting the centers of the rings of a hexachiral and tetrachiral honeycomb.
TL;DR: In this paper, the porosity of boron carbide was measured and the effect of porosity on mechanical properties (hardness, fracture toughness, and elastic modulus) was investigated.
Abstract: The densification behavior of boron carbide without sintering additives is reported for temperatures in the range of 1100 °C to 1800 °C by spark plasma sintering (SPS) technique together with the sintering parameters (Holding Time and Pulsed DC). The influence of porosity on mechanical properties (hardness, fracture toughness and elastic modulus) of boron carbide prepared by SPS is measured. Pulsed DC current is found to play a dominant role in the densification of boron carbide and in achieving near theoretical density at lower sintering temperature compared to conventional sintering techniques. Hardness, fracture toughness and elastic modulus of fully dense B 4 C are measured as 37.2 GPa, 2.8 MPa.m 1/2 and 570 GPa respectively. Microstructural analysis indicates the presence of deformation twins in boron carbide grains.
TL;DR: This work explores the interplay of giant elastic anisotropy and geometrical frustration imposed by boundary conditions in droplets, demonstrating spontaneous formation in the nematic phase of chiral patterns from achiral building blocks and of central line defects and surface faceting in the columnar phase.
Abstract: Confined liquid crystals (LC) provide a unique platform for technological applications and for the study of LC properties, such as bulk elasticity, surface anchoring, and topological defects. In this work, lyotropic chromonic liquid crystals (LCLCs) are confined in spherical droplets, and their director configurations are investigated as a function of mesogen concentration using bright-field and polarized optical microscopy. Because of the unusually small twist elastic modulus of the nematic phase of LCLCs, droplets of this phase exhibit a twisted bipolar configuration with remarkably large chiral symmetry breaking. Further, the hexagonal ordering of columns and the resultant strong suppression of twist and splay but not bend deformation in the columnar phase, cause droplets of this phase to adopt a concentric director configuration around a central bend disclination line and, at sufficiently high mesogen concentration, to exhibit surface faceting. Observations of director configurations are consistent with Jones matrix calculations and are understood theoretically to be a result of the giant elastic anisotropy of LCLCs.