摘要:

Solutions of seven polymeric sizing agents, viz., four kinds of poly vinyl alcohols (PVAs), carboxy methyl starch (CMS), and sodium polyacrylate (PA) in addition to their binary mixtures, at a concentration of 10%–-were rheologically characterized at 80°C. It was found that: (1) all these solutions behaved as non-Newtonian shear thining fluids that displayed measurable thixotropic character, and (2) the apparent viscosity, at a constant shear rate, and the extent of thixotropy depended both on the kind of sizing agent and on the composition of the binary mixtures. The flow behavior index and the shear thining index of each solution, as deduced from the power law, were estimated, and hence the degree of pseudoplasticity and the flow properties of each solution were evaluated.

ISSN:0360-2559    

DOI:10.1080/03602559608000590

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The increasing societal awareness of, and preoccupation with recycling of materials poses a technological problem for composites, in terms of both recycling of products and reuse of waste constituent materials. Although economical, the resin transfer molding (RTM) process generates substantial amounts of waste fabric that is traditionally discarded. In this paper the reuse of scrap fabric through the fabrication of preform material and its subsequent processing through RTM is discussed. Performance levels achieved through the use of glass and hybrid carbon-glass secondary level recyclate preforms are reported and are shown to have considerable potential for further development. Dynamic mechanical analysis is also used to assess the viscoelastic behavior of the specimens.

ISSN:0360-2559    

DOI:10.1080/03602559608000591

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Neutrons from a americium-beryllium source with a source strength of 5 Ci have been examined for shielding using a borated polymer composite formulated of baryte and quartz as strengtheners. It is observed that there is a considerable dose reduction and spectral hardening leading to energy degradations. Various sources of americium have been tried with a target nucleus of beryllium in this experiment for a qualitative estimation of dose reduction. The peaks in the spectra reveal the residual carbon6C12nucleus due to excited neutrons. Use of boron for neutron capture capability and low-Z element polymers for high elastic scattering cross section has contributed to the energy reduction as per the spectrum.

ISSN:0360-2559    

DOI:10.1080/03602559608000592

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Rice straw pulp has been bleached by a nonconventional fourstage method using organic solvents in the bleaching solutions. Methanol, ethanol, acetone, and dioxane, 10%, 30%, and 50% by volume were mixed with water as bleaching media in the first-stage process. Effects of kind and percentage of the organic solvent in the bleaching mixtures on the physical characterization of the bleached pulps and of the paper sheets were studied. Results are discussed on the basis of changing the physicochemical properties of the media by varying the solvent content in the bleaching mixture.

ISSN:0360-2559    

DOI:10.1080/03602559608000593

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Bamboo-plastic composite (BPC) was prepared under Co-60 gamma radiation with Talla bamboo of Bangladesh using methyl methyacrylate (MMA) as the bulk monomer combined with methanol at different proportions. Skin, and middle and inner portions of bamboo were longitudinally separated and were used for making the BPC. The polymer loading increased very slightly and the tensile strength (TS) of the composite was enhanced by 9%–12%. However, incorporation of some additives such as NVP, TPGDA, TMPTA, LiNO3, and urea to the bulk monomer enhanced the TS values further. Lithium yielded the highest TS values, increased by 43%, and bending strength (BS), increased by 59%. When urea was mixed with lithium, the corresponding TS value increased to 48% with the middle part of the bamboo. Water absorption was low with BPC compared to the untreated bamboo.

ISSN:0360-2559    

DOI:10.1080/03602559608000594

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Instability of the plane interface between two viscoelastic (Maxwellian) superposed conducting fluids in the presence of suspended particles and variable horizontal magnetic field in porous medium is studied. The cases of two fluids of uniform densities, viscosities, magnetic fields, and suspended particles number densities separated by a horizontal boundary; and of exponentially varying density, viscosity, suspended particles number density, and magnetic field are considered. It is found that the stability criterion is independent of the effects of viscoelasticity, medium porosity, and suspended particles but is dependent on the orientation and magnitude of the magnetic field. The magnetic field succeeds in stabilizing a certain range of wavenumbers which were unstable in the absence of the magnetic field. The system is found to be stable for potentially stable configuration/stratifications. The growth rates are found to increase (for certain wavenumbers) and decrease (for other wavenumbers) with the increase in kinematic viscosity, suspended particles number density, magnetic field, medium permeability, and stress relaxation time.

ISSN:0360-2559    

DOI:10.1080/03602559608000595

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Results of computer simulation of static mechanical behavior of a body consisting of ∼1000 hard elastic particles have been invoked to discuss some problems of mechanics of disordered (amorphous) and ordered (crystal) bodies: the glass-liquid transition, irreversible deformation (plasticity in a solid and flow in a liquid states), and intermediate (like liquid crystal) state. It has been shown that the existence of two states, solid and liquid; the condition of transition between them; and the fundamental mechanical properties of a solid body, viz., plasticity, strain softening, and localization of deformation within the shear bands, are controlled by the number of physical contacts between the particles, spatial distribution of contacts, and their disintegration under shear deformation. Systems of rigid particles are in a solid or a liquid state depending on the number of interparticle contacts. Solid (glass or crystal) and liquid states were determined from the ability of a system to resist shape change under external force. As a criterion of the liquid-to-glass transition the equality of the number (translational and rotational) of degrees of freedom, ℱ and the number of constraints of these motions, 𝒞, was used (ℱ = 𝒞). A system is solid if ℱ < 𝒞 and is liquid if ℱ > 𝒞. In systems of rigid particles, constraints are due to mechanical contacts (𝒞1) and/or chemical bonds between the particles (𝒞2). Glasses were classified as mechanical (granular systems and metallic glasses) if 𝒞 ≥ 𝒞2, chemical (nonorganic glasses) if 𝒞1≥ 𝒞2, and combined (polymer glasses) if 𝒞1∼ 𝒞2. Some results of computer imitation confirming the transition criterion are presented. Irreversible deformation of the particle assemblies in the liquid state, unlike in the solid one, showed the following features: extremely low yield stress, absence of change in the number of interparticle contacts and the volume of the system during flow, and random distribution of local strains. Shear strain of the liquid assemblies is governed by particle rotation and consists in the changes of particle orientation, while shear strain of a glassy solid is due to the disintegration of interparticle contacts. A relationship between distribution function of particle orientation and shear strain of the body is found. Crystals of rigid elliptic particles are anisotropic and demonstrate solidlike, liquidlike, or intermediate behavior in different directions depending on the arrangement and ellipse eccentricity. Validity of the geometrical concepts for developing the theory of a condensed state is based on the assumption that any interaction potential can be decomposed into two components: hard repulsion and soft attraction, which are responsible for various properties of the materials.

ISSN:0360-2559    

DOI:10.1080/03602559608000596

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0360-2559    

DOI:10.1080/03602559608000597

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor