Showing papers on "Young's modulus published in 1998"
TL;DR: In this paper, the stiffness of single-walled carbon nanotubes is estimated by observing their freestanding room-temperature vibrations in a transmission electron microscope, assuming that the vibration modes are driven stochastically and are those of a clamped cantilever.
Abstract: We estimate the stiffness of single-walled carbon nanotubes by observing their freestanding room-temperature vibrations in a transmission electron microscope. The nanotube dimensions and vibration amplitude are measured from electron micrographs, and it is assumed that the vibration modes are driven stochastically and are those of a clamped cantilever. Micrographs of 27 nanotubes in the diameter range 1.0--1.5 nm were measured to yield an average Young's modulus of $〈Y〉=1.25 \mathrm{TPa}.$ This value is consistent with previous measurements for multiwalled nanotubes, and is higher than the currently accepted value of the in-plane modulus of graphite.
1,621 citations
TL;DR: In this paper, the mechanical behavior of multi-walled carbon nanotube/epoxy composites was studied in both tension and compression, and it was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression.
Abstract: The mechanical behavior of multiwalled carbon nanotube/epoxy composites was studied in both tension and compression. It was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression. In addition, it was found that the Raman peak position, indicating the strain in the carbon bonds under loading, shifts significantly under compression but not in tension. It is proposed that during load transfer to multiwalled nanotubes, only the outer layers are stressed in tension whereas all the layers respond in compression.
1,617 citations
TL;DR: In this article, a theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described, and the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA).
Abstract: A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young’s modulus, and Poisson’s ratio for ideal polycrystalline TiSi2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young’s modulus for single crystal TiSi2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the ...
1,469 citations
TL;DR: In this paper, the elastic properties of thin gelatin films were investigated with the atomic force microscope (AFM) with the major aim of this study was to investigate the influence of the film thickness on the apparent elastic (Young's) modulus.
Abstract: The elastic properties of thin gelatin films were investigated with the atomic force microscope (AFM). The degree of swelling and thus the softness of the gelatin can be tuned by immersing it in mixtures of propanol and water. Therefore, we have chosen gelatin films as a model system to characterize the measurement of elasticity of thin and soft samples. The major aim of this study was to investigate the influence of the film thickness on the apparent elastic (Young's) modulus. Thus, we prepared wedge-shaped samples with a well-defined thickness of up to 1 μm. The Young's modulus of our samples was between 1 MPa and 20 kPa depending on the degree of swelling. The elasticity was calculated by analyzing the recorded force curves with the help of the Hertz model. We show that the calculated Young's modulus is dependent on the local film thickness and the applied loading force of the AFM tip. Thus, the influence of the hard substrate on the calculated softness of the film can be characterized as a function of...
638 citations
TL;DR: In this article, the elastic properties of an individual multi-wall boron nitride (BN) nanotube were determined from the thermal vibration amplitude of a cantilevered BN and the axial Young's modulus was found to be 1.22 ± 0.24 TPa.
542 citations
TL;DR: In this paper, the authors examined the work done during indentation using dimensional analysis and finite element calculations for conical indentation in elastic-plastic solids with work hardening, and proposed a method for estimating the hardness and modulus of solids using instrumented indentation with conical or pyramidal indenters.
Abstract: The work done during indentation is examined using dimensional analysis and finite element calculations for conical indentation in elastic-plastic solids with work hardening. An approximate relationship between the ratio of hardness to elastic modulus and the ratio of irreversible work to total work in indentation is found. Consequently, the ratio of hardness to elastic modulus may be obtained directly from measuring the work of indentation. Together with a well-known relationship between elastic modulus, initial unloading slope, and contact area, a new method is then suggested for estimating the hardness and modulus of solids using instrumented indentation with conical or pyramidal indenters.
518 citations
TL;DR: In this article, the authors used micro-Raman spectroscopy to monitor the cooling-induced compressive deformation of carbon nanotubes embedded in an epoxy matrix, and derived the Young's modulus of single and multi-wall carbon nano-tubes from a concentric cylinder model for thermal stresses.
Abstract: Micro-Raman spectroscopy is used to monitor the cooling-induced compressive deformation of carbon nanotubes embedded in an epoxy matrix. Young’s modulus of single- and multiwall nanotubes may then be derived from a concentric cylinder model for thermal stresses, using the D*-band shift for each tube type. The resulting values of the elastic moduli are in very good agreement with predicted theoretical values, and with the published experimental data set of Treacy et al., Nature (London) 381, 678 (1996).
517 citations
TL;DR: In this article, the authors combine the results of available investigations to develop best-fit relationships between (1) shear wave velocity and equivalent N60 from Becker penetration tests; (2) normalized shear modulus and shear strain; and (3) damping ratio and hear strain.
Abstract: Two of the most important parameters in any dynamic analysis involving soils are the shear modulus and the damping ratio. Because both shear modulus and damping are strain dependent, curves must be developed to define their variation with shear strain. Fifteen studies (including this one) now provide results from tests on a wide variety of gravels. This paper combines the results of available investigations to develop best-fit relationships between (1) shear wave velocity and equivalent N60 from Becker penetration tests; (2) normalized shear modulus and shear strain; and (3) damping ratio and shear strain. The mean curve for the normalized shear modulus reported for gravelly soil in this study falls near the mean curve reported for sands by Seed and Idriss (1970). The normalized shear modulus curve is dependent on confining pressure, but essentially independent of sample disturbance, relative density, and gradation. The mean damping ratio curve falls toward the lower range of the data reported by Seed and...
399 citations
TL;DR: In this article, it was shown that Young's modulus increases with decreasing tube diameter and decreases with increasing tube helicity, and the variation in modulus is attributed to differences in torsional strain, the dominant component of the total strain energy.
Abstract: We report in detail that unlike other materials, carbon nanotubes are so small that changes in structure can affect the Young’s modulus. The variation in modulus is attributed to differences in torsional strain, which is the dominant component of the total strain energy. Torsional strain, and correspondingly Young’s modulus, increases significantly with decreasing tube diameter and increases slightly with decreasing tube helicity.
372 citations
TL;DR: This article derived scaling relationships for conical indentation in elastic-plastic solids with work hardening, and examined the relationships between hardness, contact area, initial unloading slope, and mechanical properties of solids.
Abstract: We derive, using dimensional analysis and finite element calculations, several scaling relationships for conical indentation in elastic-plastic solids with work hardening. Using these scaling relationships, we examine the relationships between hardness, contact area, initial unloading slope, and mechanical properties of solids. The scaling relationships also provide new insights into the shape of indentation curves and form the basis for understanding indentation measurements, including nano- and micro-indentation techniques. They may also be helpful as a guide to numerical and finite element calculations of indentation problems.
332 citations
TL;DR: In this article, a new type of bamboo fiber-reinforced polypropylene (PP) composite was prepared and its mechanical properties were tested, and it was found that with 24 wt % of such MAPP being used in the composite formulation, the mechanical properties of the composite such as the tensile modulus, the Tensile strength, and the impact strength all increased significantly.
Abstract: A new type of bamboo fiber-reinforced polypropylene (PP) composite was prepared and its mechanical properties were tested. To enhance the adhesion between the bamboo fiber and the polypropylene matrix, maleic anhydride-grafted polypropylene (MAPP) was prepared and used as a compatibilizer for the composite. The maleic anhydride content of the MAPP was 0.5 wt %. It was found that with 24 wt % of such MAPP being used in the composite formulation, the mechanical properties of the composite such as the tensile modulus, the tensile strength, and the impact strength all increased significantly. The new composite has a tensile strength of 32–36 MPa and a tensile modulus of 5–6 GPa. Compared to the commercially available wood pulp board, the new material is lighter, water-resistant, cheaper, and more importantly has a tensile strength that is more than three times higher than that of the commercial product. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1891–1899, 1998
TL;DR: It was found that composites with smaller hydroxyapatite particles had higher torsional modulus, tensile modulus and tensile strength, but lower strain to failure, and dynamic mechanical analysis is useful in studying the viscoelastic behaviour of the composite.
TL;DR: In this paper, the authors used scanning force microscopy (SFM) for probing micromechanical properties of compliant polymeric materials, such as polyisoprene rubbers, elastic polyurethanes, and hard surfaces of polystyrene and polyvinylchloride (PVC).
Abstract: Scanning force microscopy (SFM) was used for probing micromechanical properties of compliant polymeric materials. Classic models of elastic contacts, Sneddon's, Hertzian, and JKR, were tested for various indentation depths and for a variety of polymeric materials. We selected extremely compliant polyisoprene rubbers (Young's modulus, E = 1−3 MPa), elastic polyurethanes (E = 5−50 MPa), and hard surfaces of polystyrene (PS) and polyvinylchloride (PVC) (E = 1−5 GPa). Both Sneddon's and Hertzian elastic models gave consistent and reliable results in the range of indentation depths up to 200 nm which are close to JKR solution. Close correlation is observed between absolute values of elastic moduli determined by SFM and known values for bulk materials.
TL;DR: Inherent and stress state-induced anisotropy in the elastic deformation properties of granular materials were investigated experimentally as mentioned in this paper, where very small strain-amplitude cyclic normal stresses were applied in the vertical and horizontal directions at various isotropic and anisotropic stress states.
TL;DR: In this paper, the effects of environmental conditions and mechanical damage on the tensile stiffness and strength of two natural fibers, flax and nettle, are investigated, and the effect of fiber damage is also significant.
Abstract: The effects of environmental conditions and mechanical damage on the tensile stiffness and strength of two natural fibers, flax and nettle, are investigated. Flax and nettle both contain cellulosic fiber bundles in the outer layer of the plant, each bundle comprising many individual cells bonded together. Novel experimental equipment is designed and constructed to measure, under varying environmental conditions, the static and dynamic tensile moduli and the strength of individual fiber cells. As previous work has shown, the tensile modulus is dependent on environ mental relative humidity, but the effect of fiber damage is also significant. There is a correlation between the extent of damage, measured as the proportion of the fiber showing as bright under a polarizing microscope, and the modulus. When the effect of damage is taken into account, there is a consistent relationship between modulus and relative humidity.
TL;DR: In this article, a theory is proposed to explain the discrepancy between theoretical modulus predictions and experimental modulus measurements, which effectively reduces the aspect ratio and the volume fraction of the inclusion.
Abstract: Recent experiments on layered silicate-elastomer nancomposites by Burnside and Giannelis have shown that there is a discrepancy between theoretical modulus predictions and experimental modulus measurements. A theory is proposed to explain this discrepancy. We hypothesize that the discrepancy is due to imperfect bonding between the matrix/inclusion interface which effectively reduces the aspect ratio and the volume fraction of the inclusion. We use a simple interface model to quantify the imperfect interfacial bonding. From this model, we introduce the concept of the effective aspect ratio and effective volume fraction of the inclusions. These effective quantities depends on a single material parameter, namely, the constant interfacial shear stress, τ. The interfacial shear stress for the elastomer-silicate nanocomposites is found by fitting the theory to the experimentally measured modulus of Burnside and Giannelis. The interfacial shear stress is in the range of thousands of Pascals. For the elastomer-silicate nanocomposite systems considered here, the interfacial shear stress can be decomposed into two parts; intrinsic shear stress τ i and frictional shear stress τ f . The intrinsic interfacial shear stress τ i depends only on the volume fraction of inclusions and decreases with increasing volume fraction of inclusions. On the other hand, the frictional shear stress τ f is found to increase linearly with the applied strain. Since the mean stress is also proportional to the applied strain, this gives rise to an effective coefficient of friction, which is found to be 0.0932 for the nanocomposite system considered here.
TL;DR: In this paper, a morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies, which revealed that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal and transverse directions.
Abstract: Morphological survey on new PBO fiber (Zylon®) was conducted by X-ray and transmission electron microscopic studies. Crystal size, orientation of the crystal, fibrils, microvoids, and fine structure were discussed. It was found that the molecule in the fiber showed high orientation (more than 0.99 in Hermann's orientation function for heat-treated fiber) and relatively small crystal sizes in the longitudinal (160 A) and the transverse (110 A) directions. Crystal modulus estimated by extrapolation to perfect orientation on the plot of the fiber modulus as a function of fiber orientation (Northolt's method) shows discrepancy from the crystal modulus directly obtained by X-ray scattering. This discrepancy means that the Northolt's model is insufficient to describe the Young's modulus of PBO fiber. Microvoids elongated to the fiber direction were examined by small-angle X-ray scattering and transmission electron microscopic methods. The diameter of the microvoids was 20 A to 30 A and the fiber had a very thin microvoids-free layer (0.2 μm). Preferential orientation of the a-axis of crystal in the fiber was also confirmed. Summarizing these results, a structure model of the PBO fiber was proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 39–48, 1998
TL;DR: In this article, the elastic properties of transition metal carbides, nitrides and carbonitrides are reviewed and a comparison of the evaluation methods for Young's modulus as a function of the sample porosity is made.
TL;DR: In this article, tension-tension, load-controlled fatigue results extending to over 100 000 cycles for electron-beam-evaporated copper are reported, fabricated as a single tensile coupon with hundreds of grains across the width but only one or few through the thickness supported on a silicon frame.
TL;DR: In this article, a functionally graded composite is prepared and the spatial gradation of Young's modulus in the functionally graded material (FGM) is measured using optical interferometry and cracks are mapped in the FGM under quasi-static loading conditions with cracks oriented perpendicular to the direction of the elastic gradient and near the interface of the graded and the homogeneous portions of three-point bending specimens.
TL;DR: A method is introduced to measure internal mechanical displacement and strain by means of MRI to provide a means for remote palpation and elasticity quantitation in deep tissues otherwise inaccessible to manual palpation.
Abstract: A method is introduced to measure internal mechanical displacement and strain by means of MRI. Such measurements are needed to reconstruct an image of the elastic Young's modulus. A stimulated echo acquisition sequence with additional gradient pulses encodes internal displacements in response to an externally applied differential deformation. The sequence provides an accurate measure of static displacement by limiting the mechanical transitions to the mixing period of the simulated echo. Elasticity reconstruction involves definition of a region of interest having uniform Young's modulus along its boundary and subsequent solution of the discretized elasticity equilibrium equations. Data acquisition and reconstruction were performed on a urethane rubber phantom of known elastic properties and an ex vivo canine kidney phantom using <2% differential deformation. Regional elastic properties are well represented on Young's modulus images. The long-term objective of this work is to provide a means for remote palpation and elasticity quantitation in deep tissues otherwise inaccessible to manual palpation.
TL;DR: In this article, the authors studied the phenomena of piling up and sinking up of surface profiles in conical indentation in elastic-plastic solids with work hardening using dimensional and finite-element analysis.
Abstract: The phenomena of the 'piling up' and 'sinking-in' of surface profiles in conical indentation in elastic-plastic solids with work hardening are studied using dimensional and finite-element analysis The degree of sinking in and piling up is shown to depend on the ratio of the initial yield strength Y to Young's modulus E and on the work-hardening exponent n The widely used procedure proposed by Oliver and Pharr for estimating contact depth is then evaluated systematically By comparing the contact depth obtained directly from finite-element calculations with that obtained from the initial unloading slope using the Oliver-Pharr procedure, the applicability of the procedure is discussed
TL;DR: In this paper, a series of thermal barrier coatings were produced by plasma spraying ZrO 2 +8wt%Y 2 O 3 (PYSZ) to a thickness of about 2 mm, some six to eight times thicker then state of the art coatings currently in service.
Abstract: The thermophysical and mechanical properties of plasma-sprayed thermal barrier coatings are very strongly dependent on the microstructure, and this may be controlled by manipulating the parameters controlling the plasma spray process. A series of coatings was produced by plasma spraying ZrO 2 +8wt%Y 2 O 3 (PYSZ) to a thickness of about 2 mm, some six to eight times thicker then state of the art coatings currently in service. A controlled variation of plasma spray parameters was carried out to produce a range of different microstructures that could be related to material properties and these in turn correlated with the process variables. The particular properties studied were the thermophysical properties, diffusivity and expansion, and the mechanical properties, modulus, strain to failure and flexural strength measured in four point bend.
TL;DR: In this article, stress-to-strain differential values were measured in tensile testing at various stages of deformation in both austenitic and martensitic states of a near-equiatomic NiTi shape memory alloy as a measurement of the moduli of elasticity for the two phases.
TL;DR: In this article, it was shown that the frequency dependences of all complex moduli (shear, Young's, etc.) and complex Poisson's ratios of real solid materials can be determined by transforming the causal and real relaxation and creep responses, respectively, from the time-domain into the frequency domain.
TL;DR: In this article, the second and third order elastic constants of tellurite glass at room temperature have been derived from the longitudinal and shear sound velocities and density of the glass.
TL;DR: In this paper, the effects of the filler content and size on the mechanical properties such as tensile modulus, Ec, yield strength, σyc, and impact strength, SIC, of glass bead-filled polypropylene (PP) composites have been investigated employing an Instron materials tester and a Ceast impact tester at room temperature.
Abstract: The effects of the filler content and size on the mechanical properties such as tensile modulus, Ec, yield strength, σyc, and impact strength, SIC, of glass bead–filled polypropylene (PP) composites have been investigated employing an Instron materials tester and a Ceast impact tester at room temperature. With increasing concentration of glass beads, Ec and SIC increase, but σyc decreases non–linearly, within a filler volume fraction range of 0%−20%; under the same test conditions, the values of EC and σyc for PP with bigger beads are somewhat lower than those of PP with smaller ones; the maximum values of SIC for the composites are about 1.4 times as high as the unfilled PP; the interface between the matrix and the beads is a weak bond. The results indicate that the stiffness and the toughness of the PP composites are effectively improved by addition of glass beads.
TL;DR: A system capable of measuring the elastic modulus of small tissue samples was developed and preliminary elasticity measurements on canine kidney samples are presented and discussed.
TL;DR: Ultrasound properties of rabbit and human skin tissues under transverse stress have been studied in vitro over the frequency range from 15 MHz to 40 MHz and results show that backscattering coefficients only exhibit minor variation with strain.
Abstract: Ultrasound properties of rabbit and human skin tissues under transverse stress have been studied in vitro over the frequency range from 15 MHz to 40 MHz. B-scan images show significant increases in average dermal grey-scale levels for increasing strain. Quantitative measurements show that ultrasound attenuation coefficients decrease significantly with increasing strain. A linear decrease of 0.109 dB/mm/strain% in rabbit skin and 0.069 dB/mm/strain% in human breast reduction skin was observed at 30 MHz. Experimental results show that backscattering coefficients only exhibit minor variation with strain. The speed of sound in human skin appears to be age-dependent. The viscoelastic and mechanical properties of skin, including stress relaxation, creep and Young’s modulus as a function of strain were also studied.
Patent•
12 May 1998
TL;DR: In this article, an anisotropic conductive adhesive film contains a first insulating adhesive layer, a second insulating layer whose modulus of elasticity after curing is less than or equal to that of the cured first layer, and electrically conductive particles which are dispersed in at least either the first or second layer.
Abstract: An anisotropic conductive adhesive film contains a first insulating adhesive layer, a second insulating adhesive layer whose modulus of elasticity after curing is less than the modulus of elasticity of the cured first insulating adhesive layer, and electrically conductive particles which are dispersed in at least either the first insulating adhesive layer or the second insulating adhesive layer.