High modulus polypropylene fibers. I. Mechanical properties

Analysis of the static and dynamic elastic moduli of a one-coat rendering mortar with laboratory and in situ samples

Evolution of microstructures at a wide range of solidification cooling rate in a Ni-based superalloy

A comparison of Young's moduli and Poisson's ratios obtained from ultrasonic laboratory measurements with static moduli obtained under identical stress conditions shows that the Young's moduli are 1 to 6 times higher under ultrasonic loading conditions. A comparison of these two laboratory measured quantities with log derived moduli measured at 20 KHz indicates that Eultrasonic> Esonic > Estatic, The clay content and porosity of the samples varied from 1 % to 54.5% and 3% to 17.5%, respectively. This clearly suggests that a wide variety of sandstones behave in a viscoelastic manner. The magnitude of the variation with frequency is a function of the clay content, grain size, shape of intergranular contacts, mineralogy and fluid saturations. A model is presented that describes this observed viscoelastic behavior. The measured static moduli are a function of the sample length. This effect is investigated in some detail. The reported static moduli were obtained at L/d ratios of 2. When comparing log measurements to core, two inherent problems were encountered: depth correlation and sample size. These effects need to be properly accounted for when comparing logs with cores.

Polymeric materials are known to be more or less dispersive and absorptive. Dispersion has a consequence that the dynamic modulus is frequency dependent, and absorption is exhibited by the fact that these materials have the ability to absorb energy under vibratory motion. The phenomenon of dispersion in conjunction with the powerful notion of complex Modulus of Elasticity (MOE), permits to establish the relation between the real and the imaginary components of the MOE, that is, respectively the Storage and loss moduli. The loss factor is simply determined through taking the Ratio of these two MOE components. The theoretical background for the interrelations between the Storage modulus and the loss modulus is found in the Kramers-Kronig relations. However, due to the mathematical difficulties encountered in using the exact expressions of these relations, approximations are necessary for applications in practical situations. On the other hand, several simple models have been proposed to explain the viscoelastic behavior of materials, but all fail in giving a full account of the phenomenon. Among these models, the standard viscoelastic model, better known as the Zener model, is perhaps the most attractive. To improve the performance of this model, the concept of fractional derivates has been incorporated into it, which results in a four-parameter model. Applications have also shown the superiority of this model when theoretical predictions are compared to experimental data of different polymeric materials. The aim of this article is to present the results of applying this model to rubber, both natural and filled, and to some other selected more general polymer.

Effects of iron particles’ volume fraction on compression mode properties of magnetorheological elastomers

The structure, thermodynamics, and slow activated dynamics of the equilibrated metastable regime of glass-forming fluids remain a poorly understood problem of high theoretical and experimental interest. We apply a highly accurate microscopic equilibrium liquid state integral equation theory, in conjunction with naïve mode coupling theory of particle localization, to study in a unified manner the structural correlations, thermodynamic properties, and dynamic elastic shear modulus in deeply metastable hard sphere fluids. Distinctive behaviors are predicted including divergent inverse critical power laws for the contact value of the pair correlation function, pressure, and inverse dimensionless compressibility, and a splitting of the second peak and large suppression of interstitial configurations of the pair correlation function. The dynamic elastic modulus is predicted to exhibit two distinct exponential growth regimes with packing fraction that have strongly different slopes. These thermodynamic, structural, and elastic modulus results are consistent with simulations and experiments. Perhaps most unexpectedly, connections between the amplitude of long wavelength density fluctuations, dimensionless compressibility, local structure, and the dynamic elastic shear modulus have been theoretically elucidated. These connections are more broadly relevant to understanding the slow activated relaxation and mechanical response of colloidal suspensions in the ultradense metastable region and deeply supercooled thermal liquids in equilibrium.

Dynamic and static elasticity of the resting skeletal muscle of the frog have been studied as a function of the sarcomere length. Isolated intact fibres as well as glycerol extracted fibres show a resting tension starting at 2.05 microns sarcomere length and increasing approximately exponentially to 2 . 10(4) N/m2 at 3.0 microns sarcomere length. Differences between the two types of preparation were seen in the dynamic experiments. The dynamic Young's modulus of intact fibres (recorded at 1 Hz and small amplitudes) increased from 2 . 10(5) N/m2 at 2.1 microns sarcomere length to 2.5 . 10(6) N/m2 at 2.9 microns while the static modulus varied from 5 . 10(3) N/M2 to 3 . 10(5) N/m2, the dynamic modulus at small amplitudes was equivalent to the modulus of the short range elasticity (SRE). The range of the SRE did not depend on the sarcomere length and amounted to about 5 nm per sarcomere. The dynamic modulus strongly depended on the amplitude: at large amplitudes the muscle became less stiff by a factor of 10 to 20. This tendency levelled off at about 10 Hz by a strain-induced relaxation process. The dynamic modulus of the glycerol extracted fibres were nearly of the same magnitude as the static modulus, there was neither evidence for an SRE nor for a significant amplitude-dependence of the dynamic modulus. For interpreting the results we propose to further develop the meander model of muscle (Pechhold et al. 1977 b).

Evaluating the elastic characteristics of reservoir's rocks is crucial for the oil and gas sector to reduce risks throughout drilling and production operations. Elastic parameters are essential for prediction of wellbore stability, estimation of in-situ stresses, optimization of drilling performance and design of hydraulic fracturing. Depending on the type of formation, Elastic parameter is varied dramatically. Thus, a precise way to identify these characteristics is needed. Inaccurate assessment of elastic characteristics can result in excessive expenditure and inappropriate field development plans. Static elastic modulus (Est) can be determined through laboratory testing. Although laboratory measurement is the most precise approach to determine the elastic modulus, it requires a continuous core sample to acquire a complete profile of the formation's elastic characteristics. However, just a portion of the well is typically sampled for cores. On the other hand, wireline log data is applied to determine the dynamic modulus (Edyn), allowing for continuous assessment of elastic properties. Numerous characteristics of the rock, including consolidation, pore pressure and lithology affect the dynamic modulus. Thus, it needs to be converted to Static elastic modulus by empirical formulae. Several empirical equations have been proposed to convert dynamic Young's modulus to static Elastic modulus. Nevertheless, the validity of these relationships is restricted and exclusive to certain areas. This research seeks to establish a relationship between Dynamic modulus and static Elastic modulus for sandstone formation of Rumaila oil field. The suggested correlation provides accurate predictions of the static elastic modulus for the complete sandstone segment. The newly created correlation performed better than the previous correlations in predicting static elastic modulus with average absolute error of 8.69 %, and correlation coefficient of 0.9848. The newly established empirical correlation can assist geo-mechanical engineers in estimating continuous profile of the sandstone formation's static modulus.

CORRIGENDUM

The elastic modulus of cement paste is the key parameter for characterizing the mechanical response of concrete. In modern concrete technology, the admixtures are often used to enhance the performance of concrete. This paper introduces a nondestructive testing method to evaluate the dynamic elastic modulus of cement paste. Moreover, the effect of water-cement ratio and conventional admixtures on the dynamic elastic modulus of cement paste is investigated, in which three kinds of admixtures are taken into account including Viscosity Modifying Admixture (VMA), Silica Fume (SF), and Shrinkage-Reducing Admixture (SRA). The results from experimental investigation indicate that the dynamic elastic modulus of cement paste increases with decreasing water-cement ratio. The addition of SF increases the dynamic elastic modulus, however, the overdosage of VMA causes its reduction. SRA reduces the elastic modulus at early age without affecting the elastic modulus at later period.

The gelation of gellan gum solutions was investigated by means of sound velocity and viscoelastic measurements. The molecular weights determined by light-scattering measurements were 21.7 × 104 at 25.0 °C (the ordered state) and 9.47 × 104 at 40.0 °C (the disordered state), and the ratio is 2.29, supporting the scheme of conformational transition of gellan gum between a double helix and a single coil. Sound velocity measurements were performed in the concentration range from 0.05 to 2.4% at 25 and 35 °C. The decrease in the sound velocity difference between the solutions and pure solvents, ΔV, at 25 °C was observed in a fairly narrow concentration range of 0.70–1.0%, and this decrease indicates a dehydration of gellan molecules followed by the conformational change of random coil to helix. The effects of gellan concentration on gelation were examined viscoelastically in the concentration range from 0.85 to 4.85% at 25 °C. The crossover concentration of gelation where the equivalent power-law behaviors of the storage modulus, G′, and the loss modulus, G″, appeared against the angular frequency was about 3.1%. Gelation curves of the complex moduli and ΔV curves were examined as a function of time by quenching from 35 to 25 °C. Two distinct processes were observed in the gelation curve of G′ and G″. On the other hand, only a single process, which corresponds to the first process in the gelation curve, was observed in the ΔV curve. The results were explained as indicating that the first process was attributable to the conformational change from coils to helices of gellan molecules, and the second process to the development of aggregates of helices or the formation of bundles of helices resulting in gelation.

Because of its biodegradable trait, starch has been widely used as the raw material for packaging. Effects of different thermal treatment methods (high temperature-high pressure heating (HH), microwave heating (MH) and alkali heating (AH) with and without glycerol on physical properties of high amylose maize starch films (HASFs) were investigated in this study. HASFs under HH had highest elongation at break (E%), and lowest tensile strength (TS), modulus of elasticity (EM) and opacity (OC). HASFs under MH had highest TS, water holding capacity (WHC) and OC, and lowest thickness (TN), E%, solubility in water (SW) and solubility in oil (SO), while HASFs under AH had highest TN, EM, SW and SO, and lowest WHC. Compared with water, plasticized HASFs with glycerol had higher TN，E%, WHC, SW and OC, and lower TS, EM and SO. XRD results revealed the V-type polymorph and the difference in intensity of diffraction peaks of HASFs under three methods. This study would be helpful to design and prepare HASFs.

This study explored coconut shells in developing Al-Cu-Mg based nanocomposites for fabricating mould parts. The aim is to engineer alternate way through which income can be generated from agricultural wastes and recycling of industrial waste like aluminium cans. Al-Cu-Mg based nanocomposites were produced and characterised. Effects of carbonised and uncarbonised coconut shell nanoparticle (UCSNP) additions on properties of Al-Cu-Mg nanocomposites were compared. Maximum tensile strength was obtained at 10%vol uncarbonised coconut shell nanoparticle additions to Al-Cu-Mg. Increase in tensile strength and elastic modulus were noted with carbonised coconut shell reinforced Al-Cu-Mg nanocomposites against the decrease in the elastic (Young’s) modulus of the UCSNP/Al-Cu-Mg nanocomposites. Despite highest tensile strength of 10%volUCSNP/Al-Cu-Mg, 10%volCCSNP/Al-Cu-Mg nanocomposite is ranked as the best material in this study due to its optimum combination of properties including tensile strength, elastic modulus, tensile strain, impact energy and hardness values. Hence, it has been selected for fabricating open die mould parts to be used in compression sheet forming process for fabricating polymeric standard samples for tensile flexural analyses. Keywords: Al-Cu-Mg, Coconut, Shell, Nanoparticles, Mould fabrication

Tensile and dynamic mechanical properties of improved ultrathin polymeric films for magnetic tapes are presented. These films include poly(ethylene terephthalate) or PET, poly(ethylene naphthalate) or PEN, and aromatic polyamide (ARAMID). PET film is currently the standard substrate used for magnetic tapes; thinner tensilized‐type PET, PEN, and ARAMID were recently used as alternate substrates with improved material properties. The thickness of the films ranges from 6.2 to 4.8 μm. Young's modulus of elasticity, F5 value, strain‐at‐yield, breaking strength, and strain‐at‐break were obtained at low strain rates by using a tensile machine. Storage (or elastic) modulus, E′, and the loss tangent, tan δ, which is a measurement of viscous energy dissipation, are measured by using a dynamic mechanical analyzer at temperature ranges of −50 to 150°C (for PET), and −50 to 210°C (for PEN and ARAMID), and at a frequency range of 0.016 to 29 Hz. Frequency–temperature superposition was used to predict the dynamic mechanical behavior of the films over a 28 decade frequency range. Results show that ARAMID and tensilized films tend to have higher strength and moduli than standard PET and PEN. The rates of decrease of storage modulus as a function of temperature are lower for PET films than those for PEN and ARAMID films. Storage modulus for PEN films are higher than that for PET films at high frequencies, but this relationship reverses at low frequencies. ARAMID has the highest modulus and strength among the films in this study. The relationship between polymeric structure and mechanical properties are also discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2225–2244, 2002

Abstract. The accuracy of ground deformation modelling at active volcanoes is a principal requirement in volcanic hazard mitigation. However, the reliability of such models relies on the accuracy of the rock physical property (permeability and elastic moduli) input parameters. Unfortunately, laboratory-derived values on representative rocks are usually rare. To this end we have performed a systematic laboratory study on the influence of pressure and temperature on the permeability and elastic moduli of samples from the two most widespread lithified pyroclastic deposits at the Campi Flegrei volcanic district, Italy. Our data show that the water permeability of Neapolitan Yellow Tuff and a tuff from the Campanian Ignimbrite differ by about 1.5 orders of magnitude. As pressure (depth) increases beyond the critical point for inelastic pore collapse (at an effective pressure of 10–15 MPa, or a depth of about 750 m), permeability and porosity decrease significantly, and ultrasonic wave velocities and dynamic elastic moduli increase significantly. Increasing the thermal stressing temperature increases the permeability and decreases the ultrasonic wave velocities and dynamic elastic moduli of the Neapolitan Yellow Tuff; whereas the tuff from the Campanian Ignimbrite remains unaffected. This difference is due to the presence of thermally unstable zeolites within the Neapolitan Yellow Tuff. For both rocks we also find, under the same pressure conditions, that the dynamic (calculated from ultrasonic wave velocities) and static (calculated from triaxial stress-strain data) elastic moduli differ significantly. The choice of elastic moduli in ground deformation modelling is therefore an important consideration. While we urge that these new laboratory data should be considered in routine ground deformation modelling, we highlight the challenges for ground deformation modelling based on the heterogeneous nature (vertically and laterally) of the rocks that comprise the caldera at Campi Flegrei.