Showing papers on "Volume fraction published in 1970"

Theory of magnetic suspensions in liquid crystals

Abstract: The present paper discusses some properties of small, elongated particles suspended in a nematic or cholesteric phase, with low concentrations (typical volume fraction occupied by the particle f ≊ 10-3). We find that in most cases the particle axis should be locked and parallel to the local nematic axis n(r). If such colloidal suspensions could be made successfully with magnetic grains, it should be possible to prepare « ferronematics » or « ferrocholesterics », where locally all particles are magnetized in one direction (colinear to n), and also « compensated » materials with no spontaneous magnetization. These three types of samples should all show remarkable distorsions and phase changes in low external fields H. Similar effects are expected under electric fields with colloidal suspensions of polar rod molecules such as helical polypeptides.

Structure and properties of thermal-mechanically treated 304 stainless steel

Abstract: Mechanical and thermal-mechanical treatments of 304 stainless steel enables yield strengths of over 200,000 psi to be obtained with elongations better than 10 pct. Electron microscopy, X-ray, and magnetic techniques show that during deformation, strain induced γ → ∈ → α transformation occurs with further thermal nucleation of α achieved by aging up to 400°C. The yield strength is linearly proportional to the amount of ° irrespective of the treatment used to form α. The yield strength is given by αy = 225f + 48.65 ksi, where ƒ is the volume fraction of martensite. Softening occurs by aging at 500°C and above due to a decrease in percent α which may occur by renucleation of γ. The system is an unusual form of composite strengthening; hard martensite particles are formed within the austenite, and the percent α (and thereby the mechanical properties), can be controlled by the mechanical/thermal-mechanical processing.

A systematic investigation of elastic moduli of Wc-Co alloys

Abstract: Measurements of Young’s modulus, shear modulus, compression modulus, and Poisson’s ratio on WC-(1 ~ 30) wt pct Co alloys were carried out by dynamic resonance method. The effects of volume fraction of the WC phase, the carbon content, and the WC particle-size on the elastic moduli were investigated in some detail. The result shows that the various elastic moduli of the alloys depend solely on volume fractions of the constituent phases and they invariably fall within Hashin and Shtrikman’s bounds. Moreover, the moduli are found to be approximated by Paul’s “strength of materials” type formulas. It is concluded that elastic behavior of the alloys can be essentially predicted on the basis of a simplified geometrical model of WC particles embedded in continuous cobalt matrix.

Thermal expansion of boron fiber-aluminum composites

Abstract: The linear thermal expansion of silicon carbide coated boron (BORSIC®) aluminum composites was measured as a function of volume fraction fiber and angle with respect to the fiber axis. The measurements were made with a standard quartz tube-type dilatometer at a heating rate of 150°C per hr. Measurements were made between 25° and 300°C on 2024 aluminum alloy-BORSIC and 1100 aluminum alloy-BORSIC composites in the 0 and 90 deg fiber orientation as a function of volume fraction fiber. The axial test results are compared with several models found in the literature which predict composite thermal expansion. These predictions yield values which are higher than the measured expansion coefficients of the 0 deg composites. The discrepancy is assumed to be related to yielding in the matrix. The 90 deg composites are found to agree with the transverse thermal expansion coefficient relationship of Schapery (also Levin) which employs the Poisson ratio for each phase and the composite. The expansion coefficients of 2024 aluminum alloy-BORSIC composites containing 54 pct by volume fiber are given for fiber orientations of 0, 15, 30, 45, 60, 75, and 90 deg.

Tensile properties and equilibrium swelling of plasticized amorphous polyurethane rubbers

Abstract: Incorporation of plasticizers or other inert, liquid diluents causes a profound weakening of rubbers. The modulus of elasticity and tensile strength decrease approximately with the square of the gel fraction v0 of rubber which was present at the time of formation of the three-dimensional network. Equlibrium swelling of plasticized rubbers is well represented by v2m = kv0, where v2m is the volume fraction of rubber network in the swollen state, at equlibrium, and k a constant equal to v2m for the unplasticized rubber. This swelling law is independent of the way in which v0 is obtained; inert liquid diluents, comprising molecularly dispersed compounds, as well as suspensions of insoluble liquids, gases, and chemically inert, solid fillers yield the same relation. Further, it is independent of the chemical nature of solvent and rubber. It appears that also the mechanical properties of foams, liquid-filled foams, and plasticized elastomers containing the same volume fraction of network rubber are very similar.

The average volume of martensite plates during transformation

Abstract: Using quantitative metallography the average volumes of the martensite plates have been measured in Fe-23.8Ni-0.42C and Fe-28.5Ni-0.4C after varying degrees of transformation. Over a range of volume fraction transformed from 0.07 to 0.55 (the highest volume fraction sample upon which measurements could be made), the average volume of the martensite plates is constant. Fisher’s equation, which predicts a decrease in the average volume by two orders of magnitude over the experimental range of transformation, is not substantiated by the present experiments chiefly because the influence of autocatalysis is neglected in its derivation.

Attempt for the diffused interphase layer determination from the volume changes of microheterogeneous polymer mixtures

Abstract: For the experiments there have been prepared such microheterogeneous mixtures of isotactic polypropylene with polyethylene and of polyvinylchloride with polyethylene which contained maximum 60 volume per cent of dispersed phase component (iPP; PVC respectively) at 160°C for various diffusion times, whereat with sufficient exactness the tetrahedric lattice model could be applied. From the dependence of the mixture excess volume on dispersed phase volume fraction, calculated from additive and real densities, the volume fraction at the maximum dilatation (Φ m ) was determined. At supposing theFickian course of the mutual diffusion, it was possible to calculate the thickness of the interphase layer. It was stated that for both polymer pairs the diffusion after 15 min had been practically stopped. This phenomenon, which could be explained by the kinetic hindrances during the interpenetration of the different nature polymer segments, is resulting in the deviation from theFickian course of diffusion.

The recrystallization characteristics of moderately deformed aluminum

Abstract: The early stage of isothermal recrystallization of moderately deformed, polycrystalline alloys of zone-refined aluminum containing 20 and 45 at. ppm of Au has been studied by quantitative metallography. The basic structural parametersXv, the volume fraction recrystallized, andSv, the grain boundary area per unit volume, were measured on specimens annealed for different times at specific temperatures in the range 80° to 187°C. Both the maximum, Gm, and the average,\(\bar G\), growth rates of the recrystallizing grains were also determined. All results could be interpreted in terms of a site-saturated, matrix grain edge nucleation at zero time with subsequent two-dimensional growth perpendicular to the nucleated edge controlling recrystallization kinetics. An equation relatingSv toXv was derived and found to describe the experimental data quite well. Experimentally, the ratio\(G_m /\bar G\) was 2.6 and the activation energy for growth was 25,700 cal per mole.

Application Of Incremental Damage Theory ToGlass Particle Reinforced Nylon 66 Composites

Abstract: In this paper, tensile tests are carried out on seven kinds of glass particle reinforced nylon 66 composites in which a particle volume fraction is varied in 0%, 10%, 20% and 30%, and glass particles treated or untreated with silan-coupling are used. The stress-strain response of the composites depends on both the particle volume fraction and the treatment of interface between the particles and matrix. Young's modulus and Poisson's ratio are characterized by only the particle volume fraction, while tensile strength is described as a function of the particle volume fraction and interface treatment. With increasing particle volume fraction, the tensile strength increases first and then becomes constant in the interface-treated composites, and decreases in the interface-untreated conventional composites. Numerical analysis is also carried out on stress-strain response and damage behavior of the seven kinds of composites. The stress-strain relations of the interface treated composites are explained only by influence of particle volume fraction while those of the conventional composites are characterized by considering the particle volume fraction and interfacial debonding between the particles and matrix.

Thermal Expansion of Extruded Graphite‐ZrC Carbide Composites

Abstract: The thermal expansion of extruded graphite‐ZrC composites was measured over the temperature range 20°–2500°C and over a composition range 0–0.4 volume fraction of carbide, for directions parallel and transverse to the extrusion axis. The thermal‐expansion furnace was a 4‐in.‐i.d. by 60‐in.‐long horizontal graphite resistance heater in which a 30‐in.‐long sample was passively heated. Measured thermal expansion of the composite are compared with those calculated. Calculations using elastic‐constant data of the composite material are in good agreement with the measurements.

Elastic properties of model two-phase continuous composites

Abstract: The dynamic elastic moduli were measured on macroscopic models simulating two-phase microstructures where the second phase was present as a continuous, isotropic network Using open-pore polymer foams with higher-moduli, infiltrating matrices, the composite moduli were found to be linear with volume fraction of the network phase Variations of network cell size or surface area indicated that the moduli increased with increasing interfacial area, but only when interphase wetting was present and matrix contraction upon solidification occurred Metallic foams with a lower moduli matrix produced moduli that were compatible with existing bounding theories for composites

Strengthening of copper with tantalum (continuous) filaments

Abstract: Composites of copper reinforced with 0003 in diam continuous tantalum filaments have been fabricated up to 038 volume fraction using the infiltration technique Their elastic modulus, ultimate tensile strength, and yield strength have been found to be linear functions of the volume fraction of the filaments (V f ) The filaments elongated continuously until fracture occurred at the ultimate tensile strength of the composite given byS c =S f V f +σ″ m where σ″ m is the flow stress of the matrix at the fracture strain of the composite andS f is the ultimate tensile strength of the filament It has been shown that the tensile strength of not only Ta−Cu but other ductile filament-ductile matrix systems can also be closely predicted

Reaction kinetics and product formation in the heterogeneous polymerisation of 2,6‐dimethylphenol

Abstract: In the oxidative condensation of 2,6-dimethylphenol catalysed by copper compounds, poly(2,6-dimethylphenylene oxide) was formed as a particulate solid in both pyridine and pyridine-methanol mixtures. No quinone was produced when the volume fraction of pyridine exceeded 15%. The rate of polymerisation was independent of monomer concentration and first order with respect to catalyst concentration. This first-order dependence ceased when catalyst concentrations exceeded 4 × 10−2 molar. Above this concentration the polymerisation rate is probably controlled by mass transfer of oxygen from the gas to the liquid phase. The rate of polymerisation increased as the volume fraction of methanol increased. A reaction mechanism is proposed to account for the kinetics; this involves a reversible step. Particle sizes of the dispersed polymers have been measured. Heterogeneous systems can be used to produce polymers of higher molecular weights than those obtained in solution systems.