Showing papers on "Young's modulus published in 1992"
TL;DR: In this paper, a new analysis of the deflection of square and rectangular membranes of varying aspect ratio under the influence of a uniform pressure is presented, and the influence on the residual stresses on the deformation of membranes is examined.
Abstract: A new analysis of the deflection of square and rectangular membranes of varying aspect ratio under the influence of a uniform pressure is presented. The influence of residual stresses on the deflection of membranes is examined. Expressions have been developed that allow one to measure residual stresses and Young's moduli. By testing both square and rectangular membranes of the same film, it is possible to determine Poisson's ratio of the film. Using standard micromachining techniques, free-standing films of LPCVD silicon nitride were fabricated and tested as a model system. The deflection of the silicon nitride films as a function of film aspect ratio is very well predicted by the new analysis. Young's modulus of the silicon nitride films is 222 ± 3 GPa and Poisson's ratio is 0.28 ± 0.05. The residual stress varies between 120 and 150 MPa. Young's modulus and hardness of the films were also measured by means of nanoindentation, yielding values of 216 ± 10 GPa and 21.0 ± 0.9 GPa, respectively.
680 citations
TL;DR: Negative Poisson's ratio copper foam was prepared and characterized experimentally as mentioned in this paper, and the transformation into reentrant foam was accomplished by applying sequential permanent compressions above the yield point to achieve a triaxial compression.
Abstract: Negative Poisson's ratio copper foam was prepared and characterized experimentally. The transformation into re-entrant foam was accomplished by applying sequential permanent compressions above the yield point to achieve a triaxial compression. The Poisson's ratio of the re-entrant foam depended on strain and attained a relative minimum at strains near zero. Poisson's ratio as small as -0.8 was achieved. The strain dependence of properties occurred over a narrower range of strain than in the polymer foams studied earlier. Annealing of the foam resulted in a slightly greater magnitude of negative Poisson's ratio and greater toughness at the expense of a decrease in the Young's modulus.
299 citations
TL;DR: A new micromechanical model for the Young's modulus of bone is proposed, which accounts for the anisotropy and geometrical characteristics of the material.
214 citations
TL;DR: In this paper, the properties of nanocrystalline ZnO have been examined using nanindenter techniques to determine hardness, Young's modulus, and strain rate sensitivity.
Abstract: A number of nanocrystalline ceramics have been fabricated by the gas phase condensation technique. The mechanical properties of one of the first ceramics produced by this method, nanophase TiO{sub 2},have been discussed in an earlier study. This paper reports a similar study undertaken to examine the properties of nanocrystalline ZnO. Nanoindenter techniques are used to determine hardness, Young's modulus, and strain rate sensitivity in ultra-fine grained ZnO. Significant properties variations are experienced within a given sample, indicating a large degree of microstructural inhomogeneity. Nevertheless, a distinct evolution in properties can be observed as a function of sintering temperature. Young's modulus and hardness values increase almost linearly with increasing sintering temperature, and, in addition, there also appears to be a linear correlation between the development of the two materials properties. In contrast, strain rate sensitivity is shown to have an inverse dependence on sintering temperature. This dependence appears to be linked to the strong influence of grain size on strain rate sensitivity, so that the lower sintering temperatures, which provide the finer grain sizes, tend to promote strain rate sensitivity. The results of this study are strikingly similar to those obtained earlier for nanophase TiO{sub 2}, and they indicate that themore » earlier results could probably be generalized to a much broader range of nanocrystalline ceramics.« less
153 citations
TL;DR: In this article, the compressive properties of cancellous bone cubes with a large range of densities (relative densities compared with compact bone of 0.04-0.60) were investigated and the exponent relating the Young's modulus to the density was shown to be close to quadratic.
Abstract: Data on the compressive properties of cancellous bone cubes with a large range of densities (relative densities compared with compact bone of 0.04–0.60) show that the exponent relating the Young's modulus to the density is close to quadratic and that it is improbable that the material Young's modulus of our specimens was less than 8 GPa, and was probably considerably higher.
145 citations
TL;DR: In this article, simple, explicit formulae for estimates of the effective elastic moduli of several multiphase composite materials with the Mori-Tanaka method are derived for composites reinforced by aligned or randomly oriented, transversely isotropic fibers or platelets.
Abstract: Simple, explicit formulae are derived for estimates of the effective elastic moduli of several multiphase composite materials with the Mori-Tanaka method. Specific results are given for composites reinforced by aligned or randomly oriented, transversely isotropic fibers or platelets, and for fibrous systems reinforced by aligned, cylindrically orthotropic fibers.
141 citations
TL;DR: In this article, the tensile and impact properties of talc-filled isotactic polypropylene composites were investigated at 0-60 wt% filler contents, and the authors found that the impact strength decreased with increased talc content.
Abstract: Tensile and impact properties of talc-filled isotactic polypropylene composites are investigated at 0–60 wt% filler contents. Tensile modulus registered an increase whereas tensile yield strength and strain-at-break decreased with increasing filler content. Mechanical restraint imposed by the talc particles on the molecular mobility or deformability of polypropylene explained the increase in modulus and decrease in strain-at-break while decrease in tensile yield strength was attributed to decreased crystallinity and formation of stress concentration points around the filler particles. Izod impact strength decreased with increased talc content. Surface modification of talc with a titanate coupling agent LICA 38 enhanced the filler-polymer interaction, further modifying the composite properties consequent upon significant decrease in the stress concentration. Scanning electron microscopic studies revealed better dispersion of surface-modified filler particles in the polymer matrix.
134 citations
TL;DR: In this article, the microhardness of polycrystalline diamond films and several amorphous diamond-like carbon (DLC) films were determined from force-displacement curves obtained using an ultralowload micro-hardness instrument (UMIS‐2000).
Abstract: The microhardness, H, and Young’s modulus, E, of a polycrystalline diamond film and several amorphous diamondlike carbon (DLC) films were determined from force‐displacement curves obtained using an ultralow‐load microhardness instrument (UMIS‐2000). Measurements were made at a constant loading rate of 3 mN/s, to a maximum applied force of 67 and 100 mN with contact force of 0.06 and 1.07 mN, respectively. The diamond film had a surface morphology typical of microwave plasma chemical vapor deposition films (crystallite size 0.5–3 μm), and the force‐displacement curves showed nearly complete elastic behavior. The average values of hardness (80–100 GPa) and modulus (500–533 GPa) are comparable to those of natural (001) diamond reference standards (H=56–102 GPa, E=1050 GPa). The DLC films were prepared by low‐energy ion‐assisted unbalanced magnetron sputtering. By varying the bombarding ion energy, five films were prepared having different sp3/sp2 bonding ratios (3–6), optical gaps (1.2–1.6 eV), and hydrogen ...
128 citations
TL;DR: In this article, the tensile properties of isotactic polypropylene filled with particulate kaolin fillers were evaluated in the composition range 0-60 wt % kaolin. And the authors attributed the restriction on the molecular mobility of the polymer imposed by kaolin particles.
Abstract: Tensile properties of isotactic polypropylene filled with particulate kaolin fillers were evaluated in the composition range 0–60 wt % kaolin. Tensile modulus increased with filler concentration while breaking elongation and tensile strength decreased. The modulus increase was attributed to the restriction on the molecular mobility of the polymer imposed by kaolin particles. The decrease in elongation was also an effect of this restriction coupled with interference to stress transfer by the filler particles. Generation of discontinuity in the composite structure through formation of stress concentration points accounted for the tensile strength decrease. Morphology studies by SEM also indicated the introduction of stress concentration points by the presence of bare and nonadherent kaolin particles and their agglomerates with sharp edges in these composites.
124 citations
TL;DR: The residual stress and Young's modulus of 3C silicon carbide (SiC) epitaxial films were measured by load-deflection measurements using suspended SiC diaphragms fabricated with silicon micromachining techniques as discussed by the authors.
Abstract: The residual stress and Young's modulus of 3C silicon carbide (SiC) epitaxial films deposited on silicon substrates were measured by load-deflection measurements using suspended SiC diaphragms fabricated with silicon micromachining techniques. The film's residual stress was tensile and averaged 274 MPa while the in-plane Young's modulus averaged 394 GPa. In addition, the bending moment due to the residual stress variation through the thickness of the film was determined by measuring the deflection of free-standing 3C-SiC cantilever beams. The bending moment was in the range of 2.6 x 10 exp -8 -4.2 x 10 exp-8 N m.
122 citations
TL;DR: In this paper, it was shown that the effective Young's modulus of a sheet containing holes is independent of the Poisson's ratio of the matrix material and that the elastic moduli of a composite can be found exactly if the shear moduli are all equal; a previously known result.
Abstract: We bring together and discuss a number of exact relationships in two-dimensional (or plane) elasticity, that are useful in studying the effective elastic constants and stress fields in two-dimensional composite materials. The first of these dates back to Michell (1899) and states that the stresses, induced by applied tractions, are independent of the elastic constants in a two-dimensional material containing holes. The second involves the use of Dundurs constants which, for a composite consisting of two isotropic elastic phases, reduce the dependence of stresses on the elastic constants from three independent dimensionless parameters to two. It is shown that these two results are closely related to a recently proven theorem by Cherkaev, Lurie and Milton, which we use to show that the effective Young's modulus of a sheet containing holes is independent of the Poisson's ratio of the matrix material. We also show that the elastic moduli of a composite can be found exactly if the shear moduli of the components are all equal; a previously known result. We illustrate these results with computer simulations, where appropriate. Finally we conjecture on generalizations to multicomponent composite materials and to situations where the bonding between the phases is not perfect.
TL;DR: In this article, a volume element with three cylinders (concentric cylinder assemblage) is considered for the determination of local thermal stresses in a composite, and three different expressions are used to simulate the Young's modulus variations in the interphase, while the Poisson's ratio and coefficient of thermal expansion of the inter-phase region are chosen to be constant.
Abstract: The incorporation of a realistic interphasial region into the micromechani cal analyses of composite systems is critical to the understanding of composite behavior. The interphase is usually modeled as a homogeneous region, despite the fact that it may have spatial property variations. A representative volume element with three cylinders (concentric cylinder assemblage) is considered here for the determination of local thermal stresses in a composite. Three different expressions are used to simulate the Young's modulus variations in the interphase, while the Poisson's ratio and coefficient of thermal expansion of the interphase region are chosen to be constant. The governing field equa tions in terms of displacements are solved in closed form. It is found that, though the solu tion is "dilute," the Young's modulus variations have a distinct effect on the local thermal stresses.
TL;DR: In this paper, the effects of the stacking sequence (orientation of plies adjacent to the 0-deg plies), free surfaces, fiber/matrix interfacial bond strength, initial fiber waviness, resin-rich regions, and nonlinear shear constitutive behavior of the resin on the initiation of fiber microbuckling in thermoplastic composites were investigated using nonlinear geometric and non-linear 2D finite-element analyses.
Abstract: The effects of the stacking sequence (orientation of plies adjacent to the 0-deg plies), free surfaces, fiber/matrix interfacial bond strength, initial fiber waviness, resin-rich regions, and nonlinear shear constitutive behavior of the resin on the initiation of fiber microbuckling in thermoplastic composites were investigated using nonlinear geometric and nonlinear 2D finite-element analyses. Results show that reductions in the resin shear tangent modulus, large amplitudes of the initial fiber waviness, and debonds each cause increases in the localized matrix shear strains; these increases lead in turn to premature initiation of fiber microbuckling. The numerical results are compared to experimental data obtained using three thermoplastic composite material systems: (1) commercial APC-2, (2) QUADRAX Unidirectional Interlaced Tape, and AU4U/PEEK.
TL;DR: In this article, the effect of particle size on the mechanical properties of cured epoxy resins has been studied, where the particle size of the resin was sorted into six groups having different mean sizes ranging from 2-47 μm.
Abstract: Effect of particle size on the mechanical properties of cured epoxy resins has been studied. Resin was filled with angular-shaped silica particles prepared by crushing fused natural raw quartz. These particles were sorted into six groups having different mean sizes ranging from 2–47 μm. Flexural and compressive moduli of the cured epoxy resin slightly decreased with decrease in the particle size of the silica, whereas tensile modulus slightly increased. Flexural and tensile strengths increased with decrease in particle size. Fractured surfaces were observed using scanning electron microscopy to clarify the initiation point of fracture.
TL;DR: A finite element method has been used to investigate the contract stresses due to elastic indentation of coating/substrate systems consisting of a high modulus surface coating on a low modulus substrate as discussed by the authors.
TL;DR: In this article, the mechanical properties of hydrogenated amorphous diamond-like carbon coatings have been studied as a function of the bias voltage in the range 50-500 V.
TL;DR: Isolated bovine retina was taken and a graded traction force applied to determine retinal profile as a function of force, which yields a value of Young's modulus for retina of approximately 2 × 104 Pa, which is about 2 orders of magnitude weaker than typical rubber.
Abstract: The retina can be regarded as an elastic membrane or sheet which stretches and deforms when a force is applied to it. Isolated bovine retina was taken and a graded traction force applied to determine retinal profile as a function of force. The resulting profile can be modelled mathematically and the model then used to determine a value for the elastic constant. The value of the elastic constant obtained by this method is approximately 2 N/m. This value of the elastic constant, combined with the observed retinal thickness, yields a value of Young's modulus for retina of approximately 2 x 10(4) Pa, which is about 2 orders of magnitude weaker than typical rubber. This value can then be used in modelling retinal behaviour in vivo when forces are applied to detached retina.
TL;DR: In this article, a DGEBA/DDA network was used to study the toughening effect due to the introduction of glass beads with different volume fractions, and the influence of surface treatment was also studied by comparing untreated, silane-treated glass beads and beads coated with different thicknesses of an elastomeric adduct.
Abstract: A DGEBA/DDA network was used to study the toughening effect due to the introduction of glass beads with different volume fractions The influence of surface treatment was also studied by comparing untreated, silane-treated glass beads, and beads coated with different thicknesses of an elastomeric adduct The effect of the volume fraction of glass and the surface treatment were discussed in terms of elastic and plastic properties The results were compared with the usual theoretical models Linear elastic fracture mechanics and impact tests were performed to study the crack propagation process The various parameters influenced the deformation mechanism, especially for the coated glass bead composites, for which an optimum thickness was displayed A large improvement in GIc value was obtained with a slight decrease for the stiffness © 1992 John Wiley & Sons, Inc
TL;DR: In this article, the strength and toughness of the recycled polyolefins from municipal solid wastes, composed of 95% polyethylene (PE) and 5% polypropylene (PP), are reinforced with chemico thermomechanical pulp fiber, and the resulting material is formed by compression and in jection molding.
Abstract: In this work recycled polyolefins from municipal solid wastes, composed of 95% polyethylene (PE) and 5% polypropylene (PP), are reinforced with chemico thermomechanical pulp fiber, and the resulting material is formed by compression and in jection molding. Tensile properties are presented as function of fiber concentration, fiber surface treatment with acetic anhydride and phenol-formaldehyde, and sample storage time in water. Strength and toughness of the recycled polyolefins were increased with addi tion of non-treated fiber. Addition of 30% fiber, by weight, in the polymer matrix, in creased its Young modulus up to 150%. Composites with 10 % of treated fiber showed gen erally higher tensile properties than those containing 10 % of non-treated fiber. For composites made with treated fiber, water sorption during storage time was lower and mechanical properties remained higher, compared with composites made from non- treated fiber.
TL;DR: In this paper, a new approach for predicting the Young's modulus of two phase composites has been proposed based on a topological transformation and the mean field theory, which is applied to Co/WCp, Al/SiCp, and glass filled epoxy composites.
Abstract: A new approach for predicting the Young's modulus of two phase composites has been proposed based on a topological transformation and the mean field theory. The new approach has been applied to Co/WCp,Al/SiCp, and glass filled epoxy composites. It is shown that the new theoretical predictions are well within the Hashin and Shtrikman lower and upper bounds (the HS bounds) and are in closer agreement with the experimental results for the corresponding composite systems than both the HS bounds and the predictions of the mean field theory. An advantage of the present approach over other continuum approaches is that it can predict not only the effect of volume fraction of the reinforcing phase, but also the effects of microstructural parameters such as grain shape and phase distribution on the stiffness of composites. It is also shown that the classical linear law of mixtures is a specific case (where the reinforcing phase is continuous and perfectly aligned) of the present approach. In contrast to the...
TL;DR: In this article, metal-containing amorphous hydrogenated carbon (Me-C: H) films were prepared on silicon substrates and the mechanical properties, i.e., microhardness, Young's modulus, and adhesion, were measured with the help of a nanoindenter and scratch tester.
Abstract: Metal-containing amorphous hydrogenated carbon (Me–C: H) films were prepared on silicon substrates. Two kinds of metals (Ti, Ta) were incorporated in the process of reactive rf diode— (13.56 MHz) and DC-magnetron sputtering, respectively. Elastic recoil detection (ERD) and Rutherford backscattering (RBS) of MeV He+ ions were used to determine the hydrogen content and mass density of Me–C: H films. The mechanical properties, i.e., microhardness, Young’s modulus, and adhesion, were measured with the help of a nanoindenter and scratch tester. Results show that (1) the mechanical properties of Me–C: H films depend mainly on metal concentrations. At a certain metal concentration, optimal hardness, Young’s modulus, and critical load were obtained; (2) the M–C: H films with an optimal metal concentration possess similar hardness, Young’s modulus, and higher critical load compared with the corresponding values of diamond-like carbon (a–C: H) films, due to the improvement of the toughness of the films by the incorporation of metals. Therefore, Me–C: H films show high promise of being wear-resistant protective coatings.
TL;DR: In this paper, the compressive strength and modulus of elasticity of concrete specimens made from five types of portland cement, portland blast-furnace slag and air-entraining cement were tested at ages between 1 day and 34 years.
Abstract: Variations in concrete compressive strength, flexural strength, and modulus of elasticity with time are discussed. Concrete specimens made from five types of portland cement, portland blast-furnace slag cement, portland-pozzolan cement and air-entraining cement were tested at ages between 1 day and 34 years. Relationships between the compressive strength at various ages and the 28-day compressive strength are developed for specimens stored in moist and dry environments. Flexural strength and modulus of elasticity are related to the compressive strength.
TL;DR: In this article, the results of ultralow load indentation (nanoindentation) tests carried out on a range of thin film coated systems are reported. And the authors explore the extent to which it is possible to generalize the nanoindentations response of the various systems in terms of the relative mechanical properties of the coating and the substrate.
TL;DR: In this article, single-crystal Brillouin scattering measurements of elastic moduli were performed on an eclogitic omphacite (space group C2/c) with chemical composition close to the diopside (CaMgSiO2O6, 29.9 mol %)-jadeite (NaAlSi2O 6, 57.8 mol %) join.
Abstract: Single-crystal Brillouin scattering measurements of elastic moduli were performed on an eclogitic omphacite (space group C2/c) with chemical composition close to the diopside (CaMgSiO2O6, 29.9 mol %)-jadeite (NaAlSi2O6, 57.8 mol %) join. Prom the 13 elastic moduli measured under ambient conditions we calculate the adiabatic bulk modulus, KS = 130.8 ±0.5 GPa, and the shear modulus, μ = 79.2 ± 0.2 GPa. The magnitudes of all longitudinal elastic moduli (C11, C22, and C33) are inferred to be influenced primarily by the MgO6 and CaO8, or M polyhedra. Although the silica tetrahedra are extremely stiff, the great rotational freedom of these polyhedra yields a mechanical unit (tetrahedral chains) which is relatively compliant. Virtually all of the omphacite moduli are intermediate in value to those for diopside and Jadeite. Most of the moduli for omphacitic pyroxene can be estimated to within several percent by interpolation between the end member elastic moduli weighted according to the molar percentages of diopside and Jadeite.
TL;DR: In this paper, the elastic modulus of CVD diamond has been found to be 1143 GPa and v = 0.0691, which is quite compatible with available experimental evidence.
TL;DR: In this article, the influence of spraying conditions such as spray distance on the magnitude of quenching stress has been studied by measuring the curvature of the substrate during spraying, which suggests that the strength of interlamellar bonding limits the quenched stress at such temperature.
Abstract: In thermal spraying, molten particles strike a solid surface, where they are flattened and quenched within a very short time. Considerable in-plane tensile stress on the order of 100 MPa can develop within each splat during quenching after solidification because thermal contraction of the particle is constrained by the underlying solid. Ni-20Cr alloy and alumina powders have been plasma sprayed in air onto steel substrates that were maintained at about 473 K. The influence of spraying conditions such as spray distance on the magnitude of the quenching stress have been studied by measuring the curvature of the substrate during spraying. Mechanical properties such as Young’s modulus and bend strength of the deposited coatings have also been measured. A strong correlation was found between the quenching stress and the strength of Ni-20Cr coatings, which suggests that the strength of interlamellar bonding limits the quenching stress at such temperature.
TL;DR: In this paper, the rod-like molecule poly-p-phenylene benzobisoxazole (PBO) and the coil-like molecules poly-2,5-benzoxazoles (ABPBO), were spun from polymerization dopes and coagulated at various temperatures.