Search results for "volume fraction"

Model of the mechanical response of short flax fiber reinforced polymer matrix composites

2011

Abstract Natural-fiber-reinforced short-fiber composites are finding more applications lately, therefore there is a need for estimation of the mechanical properties of such composites based on the properties of the constituents. The fibers themselves also possess complicated internal structure, resulting in anisotropy of their properties. Taking into account the internal structure of bast fiber, we evaluate the elastic properties of a composite unit cell, consisting of a fiber of average length and matrix according to the fiber volume fraction in the composite. The unit cell properties are used to estimate the stiffness of a misaligned short-fiber composite by means of orientation averaging…

Ein unabh�ngiges Verfahren zur Messung der Zusammensetzung von Gasgemischen mit Hilfe der Gaschromatographie

1977

The volume fraction of gas mixtures may be measured gas chromatographically by application of the 100% method, provided they can be separated. In case of gases it is not necessary to calibrate with another method. The specific character of the detector signals can be eliminated by measurements with pure components. The procedure is compared with the Scholander method. In case of O2/N2 mixtures the results agree within reproducibility, but in case of O2/CO2/N2 mixtures a systematic deviation of the CO2 fractions to smaller values is found as concerns the Scholander method. A gas mixture with 5.6 Vol% CO2 shows a difference of approximately 0.3 Vol%. The gas chromatographic method is almost 1…

Statics and Dynamics of Bidisperse Polymer Melts:  A Monte Carlo Study of the Bond-Fluctuation Model

1998

As a first step toward the computer simulation of polydisperse polymeric melts, a lattice model containing two types of chains with lengths N1 = 20 − x and N2 = 20 + 4x (0 ≤ x ≤ 10 ) is studied. This variation of x, together with the fixed composition of 80% of short and 20% of long chains, leads to a polydispersity of 1 ≤ Nw/Nn ≤ 2 (Nw, Nn:  weight-, number-average chain lengths). To represent dense melts, the bond-fluctuation model at a volume fraction, φ = 1/2, of occupied lattice sites is used. The simulation treats both the athermal case (chain connectivity and excluded volume interaction only) and a thermal case, where additionally a choice for the bond length and bond angle potential…

1985

Using a self-constructed light scattering apparatus, the pressure dependence of the demixing temperature of solutions of PVC 20 000, PVC 37 000 and PVC 70 000 in THE/water was determined up to 1 000 bar for different compositions of the mixed solvent. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) In contrast to the thetasolvents o-xylene and phenetole, the solubility decreases with increasing pressure for all molecular weights and compositions under investigation typically by about 1 K/100 bar. The evaluation of the experimental findings demonstrates that the volume fraction of the nonsolvent in the mixed solvent, φ, is the variable that governs ph…

Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition p…

2010

The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition…

Ripening-dominated crystallization in polydisperse hard-sphere-like colloids

2009

We report on the crystal growth scenario in gravity-matched, polydisperse hard-sphere-like colloids at increasing particle concentration. In the fluid-crystal coexistence region, the crystal size as a function of time shows two separate regimes corresponding to crystal growth and crystal ripening. At higher supersaturation the crystal size grows according to the same power law through the whole experimental window of a few days: crystal growth and ripening merge together. We show that our observations cannot be explained by considering the slowing down of single-particle dynamics due to increasing volume fraction. We suggest that size fractionation occurring at the crystal-fluid interface i…

Surface-directed spinodal decomposition: modelling and numerical simulations

1997

We critically review the modelling and simulations of surface-directed spinodal decomposition, namely, the dynamics of phase separation of a critical or near-critical binary mixture in the presence of a surface with a preferential attraction for one of the components of the mixture.

Influence of the electrical interface properties on the rheological behavior of sonicated soy lecithin dispersions

2006

A significant effect, on the rheological behavior, due to the electrical properties of vesicles formed from concentrated soy lecithin dispersions have been studied in this work. The rheopectic behavior of concentrated soy lecithin dispersions (120, 150, 180, 210 and 240 g L−1) prepared by swelling–light sonication–freezing–unfreezing procedure is studied and it is specially emphasized on the transition under steady shear from lamellar phase of planar sheets to closed structures as multilamellar vesicles. Samples have been exposed to a different number of sonication cycles (from 0 to 100) and the changes in the hysteresis loop area, the apparent viscosity and the electrophoretic mobility hav…

Climatology of the average water-soluble volume fraction of atmospheric aerosol

2007

The average water-soluble volume fraction of atmospheric aerosol particles was inferred from measurements at three different locations across Central Europe. Together with a comprehensive literature review these data sets are classified into four aerosol types. The classified data are parameterized as a function of particle size using a logarithmic normal distribution function, which seems most appropriate to represent the hygroscopicity maximum in the accumulation size range. This parameterization can be used as a simplified input parameter for various model calculations. In addition, a summary on water-soluble volume fractions and hygroscopic growth factors is presented along with a short…

Vanadium Carbide Dissolution during Austenitisation of a Model Microalloyed FeCV Steel

2005

High performance commercial micro alloyed steels contain elements such as vanadium, which leads to a fine dispersion of vanadium carbide precipitates. The precipitation state, in terms of volume fraction and size distribution, plays a significant role in final mechanical properties of the material. Different austenitisation heat treatments were performed on a model ternary alloy FeCV. Precipitation states were characterised combining different experimental techniques. TEM was used to identify the chemical composition of observed precipitates. ICP mass spectroscopy was performed to measure the volume fraction of precipitates. The size distribution was studied by SEM. Results are characterist…