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  • Engineering  (9)
  • Polymer and Materials Science  (6)
  • 1
    Electronic Resource
    Electronic Resource
    The flammability of polyacrylonitrile and its copolymers IV. The flame retardant mechanism of ammonium polyphosphate (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 18 (1994), S. 307-312 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Ammonium polyphosphate is shown to be an effective flame retardant for homopolymeric and selected fibre-forming copolymers of acrylonitrile. Compared with other phosphates and phosphorus-containing species, it significantly increases both limiting oxygen index and char levels. The mechanism of retardancy is shown to be both physical and chemical in character. When heated to 300°C, the polyphosphate melts and converts to polyphosphoric acid which acts as a physical barrier to surface polymer oxidation and promotes nucleophilic oligomerization of pendant, adjacent nitrile groups. A reduction in the activation energy of this first stage of acrylic polymer degradation suggests that the favoured decomposition route gives rise via oligomerization to char-promoting precursors. Char analyses indicate an empirical formula of C30H13N7P2, which compares favourably with that of a proposed phosphorylated, polynuclear, aromatic heterocyclic structure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fam.810180506
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  • 2
    Electronic Resource
    Electronic Resource
    Probabilistic approach for transport of contaminants through porous mediaPaper presented at the ASME Winter Annual Meeting, December 1987. (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1431-1451 
    Details
    ISSN: 0271-2091
    Keywords: Probabilistic diffusion-convection equation ; Gaussian field approach ; Random walk method ; Fluctuation Peclet number ; Porous media ; Two-phase system ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The channels formed between individual particles in porous media have variable dimensions and orientations. The porosity, permeability and its anisotropy exhibit random spatial distributions. The probabilistic approach can effectively describe the transport of contaminants through porous media and is analysed in this paper. Numerical results are obtained by considering (I) random dispersion coefficients without and with spatial structure, (II) random time distribution of concentration at the inlet boundary, (III) random velocity distribution in the flow field without and (IV) with variable dispersion coefficient, (V) non-linearity of the governing equation and (VI) anisotropy of the dispersion coefficient. Two methods are used for probabilistic predictions: (1) Gaussian field approach in conjunction with Monte Carlo method and (2) random walk method. The input random parameters are assumed to have normal and log-normal distributions according to available experimental data. The probability distribution functions of the contaminant concentration at different locations within the flow domain are calculated and compared with the input distributions as a function of the mean and fluctuation Peclet numbers. The one-dimensional case is analysed in detail and the illustrative numerical predictions are compared with analytical and experimental results. The extension to a two-dimensional domain is discussed in the last part of this paper.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650091202
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Melting Behaviour on Upward Flame Spread of Thermoplastics (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 21 (1997), S. 1-6 
    Details
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of melting behaviour on upward flame spread of thermoplastic materials when subjected to small ignition sources and considered to suffer no external flux was studied using large-scale tests. For moderate fire conditions the cone calorimeter was utilized, with the sample set in a vertical orientation to study the melting behaviour of the specimens. Under these conditions the results indicate that the melting behaviour significantly affects upward flame spread behaviour. A pool of the melt which formed at the base of the vertically oriented sample tested creates a pool fire which then controls the fire growth and flame spread. In contrast, it was found that some thermoplastic materials which have higher glass transition temperatures or undergo a special pyrolysis process such as depolymerization, intumescing or charring do not experience significant melting behaviour when exposed to the same thermal insult. As a result, they behave very differently in terms of upward flame spread. The study also indicates that the melting behaviour of thermoplastic materials is an important characteristic in fires which should be taken into account in the development of modelling, in particular for upward flame spread models. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    A probabilistic method for field solutions in two-phase flows (1993)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 16 (1993), S. 65-81 
    Details
    ISSN: 0271-2091
    Keywords: Probabilistic numerical method ; Neumann expansion method ; Fluid flow ; Solid-liquid two-phase flow ; Stochastic process ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Solid-particle motion and related transport phenomena in two-phase flow are fluctuating processes in space and time. A deterministic method can describe only partially the intrinsic physics of these processes. In this paper, the fluctuations of the flow parameters are modelled by considering the spatial correlations, and a probabilistic computational method for two-phase flow is presented. The probabilistic governing equations have been discretized in space using a finite volume method, and then solved by applying the Neumann expansion method. This last method is time efficient, and its convergence can be guaranteed even for large fluctuations. A liquid-solid particle mixture flow in a circular pipe is taken as an example. Computational results illustrate the merit of the probabilistic approach for the prediction of two-phase flow phenomena.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650160105
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  • 5
    Electronic Resource
    Electronic Resource
    TREATMENT OF BODY-FORCE VOLUME INTEGRALS IN BEM BY EXACT TRANSFORMATION FOR 2-D ANISOTROPIC ELASTICITY (1997)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 89-109 
    Details
    ISSN: 0029-5981
    Keywords: BEM ; numerical fracture mechanics ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the Boundary Element Method (BEM) based on the direct formulation, body-force effects manifest themselves as an additional volume integral term in the Boundary Integral Equation (BIE). The numerical solution of the integral equation with this term destroys the notion of the BEM as atruly boundary solution method. This paper discusses the treatment of this volume integral for two-dimensional anisotropic elasticity with body-forces present. The analytical basis for transforming this integral exactly into boundary ones is presented for geometrically convex regions. This restores the application of the BEM to such problems as a truly boundary solution technique. Numerical examples are presented to demonstrate the veracity of the transformation and implementation. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    A six-node finite element for plate bending (1985)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 21 (1985), S. 131-143 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A six-node plate bending element has been developed by employing mixed formulation based on a modified Hellinger-Reissner principle and the Reissner-Mindlin plate bending theory. The numerical result indicates that, among the types of assumed independent transverse shear strains considered, a combination of 2α version with either 5α version or 6α version is free of spurious kinematic modes and leads to accurate and reliable solutions even for very thin plates.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620210111
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  • 7
    Electronic Resource
    Electronic Resource
    A hybrid finite element method for heterogeneous materials with randomly dispersed rigid inclusions (1995)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 38 (1995), S. 1635-1653 
    Details
    ISSN: 0029-5981
    Keywords: hybrid method ; heterogeneous materials ; random distribution ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A hybrid finite element approach is proposed for the mechanical response of two-dimensional heterogeneous materials with linearly elastic matrix and randomly dispersed rigid circular inclusions of arbitrary sizes. In conventional finite element methods, many elements must be used to represent one inclusion. In this work, each inclusion is embedded inside a polygonal element and only one element is required to represent one inclusion.In numerically approximating stress and displacement distributions around the inclusion, classical elasticity solutions for a multiply-connected region are employed. A modified hybrid functional is used as the basis of the element formulation where the displacement boundary conditions of the element are automatically considered in a variational sense.The accuracy and efficiency of the proposed method are demonstrated by two boundary value problems. In one example, the results based on the proposed method with only 64 hybrid elements (450 degrees of freedom) are shown to be almost identical to those based on the traditional method with 2928 conventional elements (5526 degrees of freedom).
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620381004
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  • 8
    Electronic Resource
    Electronic Resource
    In situ studies of epitaxial silicon growth by gas source molecular beam epitaxy (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 7 (1997), S. 215-224 
    Details
    ISSN: 1057-9257
    Keywords: silicon ; epitaxy ; kinetics ; dynamics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The value of in situ monitoring to study growth dynamics and surface reaction kinetics in a gas source molecular beam epitaxy process is illustrated with reference to the growth of Si films on Si(001) substrates using a beam of disilane (Si2H6). By using a combination of reflection high-energy electron diffraction (RHEED) and reflection anisotropy spectroscopy (RAS), we show first how morphological (long-range order) and local electronic structure effects can be separated in the evaluation of growth dynamics. This involves the measurement of step density changes by RHEED concomitantly with the variation in domain coverage on the Si(001) (2×1)+(1×2) reconstructed surface by RAS. This approach is then extended to investigate the kinetics of hydrogen desorption, which is the rate-limiting step in Si growth from Si2H6. It is shown that over a significant temperature range, zeroth-order kinetics are obeyed and this is explained on the basis of a step-mediated desorption process. Finally we show how this influences the growth rate on substrates of differing degrees of vicinality. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    A semi-analytic method for dynamic response analysis based on Gurtin's variational principle (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 297-306 
    Details
    ISSN: 1069-8299
    Keywords: semi-analytic method ; dynamic response ; convolution ; variational principle ; series ; finite element method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the paper a semi-analytic approach for solving dynamic response problems is developed which is based on Gurtin's convolution-type variational principle. A finite element discretization in the space domain and a series representation in the time domain are considered. This approach overcomes the shortcomings of existing methods yet utilizes their advantages for solving dynamic response problems. The example of a beam shows that this new approach is a very effective method in obtaining solutions for dynamic response problems. The paper also concentrates on utilizing time domain series for various boundary conditions, so that solutions calculated by this approach have a very high accuracy and efficiency.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640110403
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  • 10
    Electronic Resource
    Electronic Resource
    Matrix-size interactions in epoxy-glass fibers composites in relation to mechanical relaxations and effects of thermal aging (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1771-1777 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study was carried out to examine the effect of removing the size from the surface of glass fibers in order to determine its role with respect to thermoxidative aging. Dynamic mechanical relaxation data have revealed that mechanical losses were always greater than the calculated upper bound values. The effects of removing the size from the surface glass fibers for epoxy matrix composites were found to be completely different when a fluoroligomer was used to modify the resin. Contrary to the case of the conventional epoxy resin, the characteristics of the composites containing fluoroligomer-modified resin were found to be insensitive to the removal of the size from the glass fibers surface. The presence of the size on the surface of the fibers provides an interlayer that degrades through the formation of more lightly crosslinked products than the matrix, thereby providing a large increase in dynamic mechanical losses after thermal aging. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070551307
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