Showing papers on "Elastic modulus published in 2006"
TL;DR: In this article, an analytic approach was proposed to determine the tension and bending rigidities of CNTs directly from the interatomic potential, which is useful in the study of multi-wall carbon nanotubes.
Abstract: Young's modulus and the thickness of single wall carbon nanotubes (CNTs) obtained from prior atomistic studies are largely scattered. In this paper we establish an analytic approach to bypass atomistic simulations and determine the tension and bending rigidities of graphene and CNTs directly from the interatomic potential. The thickness and elastic properties of graphene and CNTs can also be obtained from the interatomic potential. But the thickness, and therefore elastic moduli, also depend on type of loading (e.g., uniaxial tension, uniaxial stretching, equibiaxial stretching), as well as the nanotube radius $R$ and chirality when $Rl1\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. This explains why the thickness obtained from prior atomistic simulations is scattered. This analytic approach is particularly useful in the study of multiwall CNTs since their stress state may be complex even under simple loading (e.g., uniaxial tension) due to the van der Waals interactions between nanotube walls. The present analysis also provides an explanation of Yakobson's paradox that the very high Young's modulus reported from the atomistic simulations together with the shell model may be due to the not-well-defined CNT thickness.
625 citations
TL;DR: In this article, the effect of the particle size on the mechanical properties of polymeric composites reinforced with spherical particles was investigated and it was found that particle sizes at micro scale have little influence on the Young's modulus of the composite and that Youngs modulus increases as the size of particles decreases at nano scale.
464 citations
TL;DR: In this article, the in-plane elastic properties of carbon nanotubes are calculated using a composite cylinders micromechanics technique as a first step in a two-step process.
433 citations
TL;DR: A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses and glass-forming liquids is presented in this article, where it is found that the elastic moduli of BMGs have correlations with the glass transition temperature, melting temperature, mechanical properties, and even liquid fragility.
Abstract: A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses (BMGs) and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have correlations with the glass transition temperature, melting temperature, mechanical properties, and even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough correlation with a weighted average of the elastic constants for the constituent elements. Although the theoretical and physical reasons for the correlations are to be clarified, these correlations could assist in understanding the long-standing issues of glass formation and the nature of glass and simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist in selecting alloying components for controlling the elastic properties and glass-forming ability of the BMGs and thus can guide BMG design. As case study, we report the formation of the families of rare-earth-based BMGs with controllable properties.
427 citations
TL;DR: In this article, the mechanical properties of expanded graphite (EG) reinforced nanocomposites were investigated as a function of particle concentration and processing technique, and it was found that EG reinforced nano-composites showed higher elastic modulus than neat epoxy.
424 citations
TL;DR: In this article, a mechanics model of micro-crack toughening is presented, which predicts the magnitude of microcracks as well as the existence of R-curve effects.
Abstract: A mechanics model of microcrack toughening is presented. The model predicts the magnitude of microcrack toughening as well as the existence of R-curve effects. The toughening is predicated on both the elastic modulus diminution in the microcrack process zone and the dilatation induced by microcracking. The modulus effect is relatively small and process-zone-size-independent. The dilatational effect is potentially more substantial, as well as being the primary source of the R curve. The dilatational contribution is also zone-size-dependent. The analysis demonstrates that microcrack toughening is less potent than transformation toughening.
421 citations
TL;DR: In this article, the elastic moduli of ultrathin poly(styrene) and poly(methylmethacrylate) (PMMA) films of thickness ranging from 200 nm to 5 nm were investigated using a buckling-based metrology.
Abstract: The elastic moduli of ultrathin poly(styrene) (PS) and poly(methylmethacrylate) (PMMA) films of thickness ranging from 200 nm to 5 nm were investigated using a buckling-based metrology. Below 40 nm, the apparent modulus of the PS and PMMA films decreases dramatically, with an order of magnitude decrease compared to bulk values for the thinnest films measured. We can account for the observed decrease in apparent modulus by applying a composite model based on the film having a surface layer with a reduced modulus and of finite thickness. The observed decrease in the apparent modulus highlights issues in mechanical stability and robustness of sub-40 nm polymer films and features.
406 citations
TL;DR: In this article, the effect of external magnetic field on the elastic modulus of magnetoelasts has been investigated and a phenomenological approach was proposed to describe the dependence of the elastic properties on the magnetic induction.
376 citations
TL;DR: In this article, the elastic modulus of intact rock is used for many rock engineering projects, such as tunnels, slopes, and foundations, but due to the requirements of high-quality core samples and associated sophisticated test equipment, instead the use of empirical models to obtain this parameter has been an attractive research topic.
357 citations
TL;DR: In this paper, the effect of nano-alumina on the elastic modulus and compressive strength of cement composite, cylindrical specimens ( Φ 20 × 40 mm) with different volume fractions of nano alumina at different curing days (3 days, 7 days, 28 days).
332 citations
TL;DR: In this article, the authors proposed a Single Walled Carbon Nanotube (SWCNT) finite element (FE) model, based on the use of non-linear and torsional spring elements, to evaluate its mechanical properties.
TL;DR: In this article, a nanoscale silver paste containing 30-nm silver particles that can be sintered at 280degC was made for interconnecting semiconductor devices, which produced a microstructure containing micrometer-size porosity and relative density of around 80%.
Abstract: A nanoscale silver paste containing 30-nm silver particles that can be sintered at 280degC was made for interconnecting semiconductor devices. Sintering of the paste produced a microstructure containing micrometer-size porosity and a relative density of around 80%. Electrical and thermal conductivities of around 2.6times105 (Omegamiddotcm)-1 and 2.4W/K-cm, respectively, were obtained, which are much higher than those of the solder alloys that are currently used for die attachment and/or flip-chip interconnection of power semiconductor devices. The sintered porous silver had an apparent elastic modulus of about 9GPa, which is substantially lower than that of bulk silver, as well as most solder materials. The lower elastic modulus of the porous silver may be beneficial in achieving a more reliable joint between the device and substrate because of increased compliance that can better accommodate stress arising from thermal expansion mismatch
TL;DR: Data indicate that, besides the chemical properties of the polyelectrolytes, the substrate mechanics of PEM films is an important parameter influencing cell adhesion and that PEM offer a new way to prepare thin films of tunable mechanical properties with large potential biomedical applications including drug release.
Abstract: Mechanical properties of model and natural gels have recently been demonstrated to play an important role in various cellular processes such as adhesion, proliferation, and differentiation, besides events triggered by chemical ligands. Understanding the biomaterial/cell interface is particularly important in many tissue engineering applications and in implant surgery. One of the final goals would be to control cellular processes precisely at the biomaterial surface and to guide tissue regeneration. In this work, we investigate the substrate mechanical effect on cell adhesion for thin polyelectrolyte multilayer (PEM) films, which can be easily deposited on any type of material. The films were cross linked by means of a water-soluble carbodiimide (EDC), and the film elastic modulus was determined using the AFM nanoindentation technique with a colloidal probe. The Young's modulus could be varied over 2 orders of magnitude (from 3 to 400 kPa) for wet poly(l-lysine)/hyaluronan (PLL/HA) films by changing the ED...
TL;DR: In this article, an experimental research was performed on the complete compressive stress-strain relationship for concrete after heating to temperatures of 100-800 °C, where the shape varying with temperature was considered.
TL;DR: The hypothesis that Eeff of gecko setae falls within Dahlquist's criterion for tack is tested, the validity of a model of setae as cantilever beams is evaluated, and highly linear forces of deformation under all compression conditions support the cantilevers model.
Abstract: Conventional pressure sensitive adhesives (PSAs) are fabricated from soft viscoelastic materials that satisfy Dahlquist's criterion for tack with a Young's modulus (E) of 100 kPa or less at room temperature and 1 Hz. In contrast, the adhesive on the toes of geckos is made of beta-keratin, a stiff material with E at least four orders of magnitude greater than the upper limit of Dahlquist's criterion. Therefore, one would not expect a beta-keratin structure to function as a PSA by deforming readily to make intimate molecular contact with a variety of surface profiles. However, since the gecko adhesive is a microstructure in the form of an array of millions of high aspect ratio shafts (setae), the effective elastic modulus (E(eff)) is much lower than E of bulk beta-keratin. In the first test of the E(eff) of a gecko setal adhesive, we measured the forces resulting from deformation of isolated arrays of tokay gecko (Gekko gecko) setae during vertical compression, and during tangential compression at angles of +45 degrees and -45 degrees . We tested the hypothesis that E(eff) of gecko setae falls within Dahlquist's criterion for tack, and evaluated the validity of a model of setae as cantilever beams. Highly linear forces of deformation under all compression conditions support the cantilever model. E(eff) of setal arrays during vertical and +45 degrees compression (along the natural path of drag of the setae) were 83+/-4.0 kPa and 86+/-4.4 kPa (means +/- s.e.m.), respectively. Consistent with the predictions of the cantilever model, setae became significantly stiffer when compressed against the natural path of drag: E(eff) during -45 degrees compression was 110+/-4.7 kPa. Unlike synthetic PSAs, setal arrays act as Hookean elastic solids; setal arrays function as a bed of springs with a directional stiffness, assisting alignment of the adhesive spatular tips with the contact surface during shear loading.
TL;DR: In this article, the mechanical and viscoelastic behavior of nanocomposites was investigated using a servohydraulic testing machine and a dynamic mechanical analyzer, respectively, and it was found that the addition of clay particles improved both the elastic modulus and storage modulus of pure epoxy significantly.
TL;DR: In this paper, the first-order Raman spectra of diamond anvils were investigated at pressures up to 310GPa and the high-frequency edge of the Raman band, which corresponds to Raman shift of the anvil culet due to the normal stress, was calibrated against the sample pressure derived from the equation of state of Pt.
Abstract: In order to develop an optical method for pressure determination in the multimegabar region, the first-order Raman spectra of diamond anvils were investigated at pressures up to 310GPa The high-frequency edge of the Raman band, which corresponds to the Raman shift of the anvil culet due to the normal stress, was calibrated against the sample pressure derived from the equation of state of Pt The obtained pressure dependence of the edge frequency demonstrates the reliability of this diamond anvil Raman gauge Up to the maximum pressure of this study, the relation between Raman frequency and normal stress at the diamond anvil culet is formally similar to the equation of state of a hydrostatically compressed isotropic elastic body having a bulk modulus of K0=547(11)GPa and a pressure derivative of the bulk modulus K0′=375(20)
TL;DR: In this article, two different approaches for modeling the behavior of carbon nanotubes are presented, one based on homogenization and the other based on finite element models, where the interatomic interactions due to covalent and non-covalent bonds are replaced by beam and spring elements, respectively, in the structural model.
TL;DR: This work reports on the mechanical properties of silver nanowires with a unique fivefold twin structure using a lateral force atomic force microscopy (AFM) method in which wires are held in a double-clamped beam configuration.
Abstract: To exploit the novel size-dependent mechanical properties of nanowires, it is necessary for one to develop strategies to control the strength and toughness of these materials. Here, we report on the mechanical properties of silver nanowires with a unique fivefold twin structure using a lateral force atomic force microscopy (AFM) method in which wires are held in a double-clamped beam configuration. Force-displacement curves exhibit super elastic behavior followed by unexpected brittle failure without significant plastic deformation. Thermal annealing resulted in a gradual transition to weaker, more ductile materials associated with the elimination of the twinned boundary structure. These results point to the critical roles of microstructure and confinement in engineering the mechanical properties of nanoscale materials.
TL;DR: In this paper, the authors used the Young's modulus of natural fibres for changes in moisture content and density that occur as a result of processing and found that the Halpin-Tsai equation predicted the experimental data most accurately for the NFRT created for this study.
Abstract: Natural fibre reinforced thermoplastics (NFRT) are increasingly used in a variety of commercial applications, but there has been little theoretical modeling of structure/property relationships in these materials. In this study, micromechanical models available in the short fibre composites literature were used to predict the stiffness of some commercially important natural fibre composite formulations. Also included are equations that correct the Young’s modulus of natural fibres for changes in moisture content and density that occur as a result of processing. Hemp fibres, hardwood fibres, rice hulls, and E-glass fibres were blended into high-density polyethylene in mass fractions of 10–60-wt%. The Young’s modulus of these composites was compared to theoretical values generated by the rule of mixtures, Halpin–Tsai, Nairn’s generalized shear-lag analysis and Mendels et al. stress transfer (micromechanical) models. Based on a sum of errors squared criterion, the Halpin–Tsai equation was found to predict the experimental data most accurately for the NFRT created for this study.
TL;DR: In this article, a unified equation for yield strength, elastic modulus, ultimate strength and ultimate strain of stainless steel at elevated temperatures is proposed, which is shown that the proposed equation accurately predicted the test results.
TL;DR: In this article, the elastic constants were determined using the WIEN2K computational implementation of the full-potential linear-augmented plane wave (FLAPW) method and the generalized gradient approximation (GGA).
TL;DR: In this paper, the Hartree-Fock (HF) method and the density functional theory (DFT) were used to calculate anisotropic elastic constants of titanium diboride, TiB 2.
TL;DR: In this paper, two series of linear low density polyethylene (LLDPE)/SiO2 nanocomposites were prepared, and the effect of nanoparticles on crystallinity, and hence to the morphology of the materials was studied.
TL;DR: In this article, the Young's modulus and calorimetry measurements were carried out on films of PVA-based composites reinforced with different types of nanotubes and an unmistakable correlation between polymer ordering and reinforcement was found.
TL;DR: In this paper, the elastic modulus and failure behavior of polyurea-formaldehyde shelled microcapsules were determined through single-capsule compression tests, and the average capsule shell wall modulus was 3.7 GPa regardless of whether the capsule was tested immersed or dry.
Abstract: The elastic modulus and failure behavior of poly(urea-formaldehyde) shelled microcapsules were determined through single-capsule compression tests. Capsules were tested both dry and immersed in a fluid isotonic with the encapsulent. The testing of capsules immersed in a fluid had little influence on mechanical behavior in the elastic regime. Elastic modulus of the capsule shell wall was extracted by comparison with a shell theory model for the compression of a fluid filled microcapsule. Average capsule shell wall modulus was 3.7 GPa, regardless of whether the capsule was tested immersed or dry. Microcapsule diameter was found to have a significant effect on failure strength, with smaller capsules sustaining higher loads before failure. Capsule size had no effect on the modulus value determined from comparison with theory.
TL;DR: In this article, the compositional dependences of elastic moduli are found to be anomalous considering the elastic modulus of the alloying elements, and the role of interatomic interactions in designing ductile metallic glasses is suggested.
Abstract: Fracture in compression has been investigated in Fe65Mo14C15B6 bulk amorphous steel doped with lanthanides to provide systematic variations of the elastic moduli. An onset of plasticity is observed as Poisson’s ratio approaches 0.32 from below. Combining with previous analysis reported by Lewandowski et al. [Philos. Mag. Lett. 85, 77 (2005)] using single-composition results from different sources, the findings are in support of universal critical Poisson’s ratio for plasticity in metallic glasses. The compositional dependences of elastic moduli are found to be anomalous considering the elastic moduli of the alloying elements. The role of interatomic interactions in designing ductile metallic glasses is suggested.
TL;DR: In this article, the authors carried out systematic creep tests after different times of rest and over sufficiently long times with pasty materials of various internal structures in a Couette geometry and showed that for a stress below the yield stress these materials remain solid but undergo residual, irreversible deformations over long time which exhibit some trends typical of aging in glassy systems.
Abstract: We carried out systematic creep tests after different times of rest and over sufficiently long times with pasty materials of various internal structures in a Couette geometry. From an analysis of the data taking into account the inertia of the system and the heterogeneous distribution of stress, we show that: (i) for a stress below the yield stress these materials remain solid but undergo residual, irreversible deformations over long time which exhibit some trends typical of aging in glassy systems; (ii) as a result of thixotropy (or aging) in the solid regime the elastic modulus increases logarithmically with the time of rest; (iii) in the liquid regime the effective behavior of the material can be well represented by a truncated power-law model; (iv) a fundamental parameter of the solid-liquid transition is a critical effective shear rate (associated with the yield stress) below which the material cannot flow steadily.
TL;DR: In this article, a servo-hydraulic testing machine was used to study the strain-rate dependent behavior of concrete in tension and the effect of temperature and moisture content on the strain sensitivity of concrete.
TL;DR: In this article, a multi-layered model for frictionless contact analysis of functionally graded materials (FGMs) with arbitrarily varying elastic modulus under plane strain-state deformation has been developed.