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  • Chemical Engineering  (3)
  • Poisson's ratios  (2)
  • composites  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Spectral decomposition of the compliance fourth-rank tensor for orthotropic materials (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 289-306 
    Details
    ISSN: 1432-0681
    Keywords: Key words Spectral decomposition ; compliance tensor ; orthotropic medium ; Euler angles ; elastic strain energy ; Poisson's ratios ; quasi-isotropic medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The compliance tensor related to orthotropic media is spectrally decomposed and its characteristic values are determined. Further, its idempotent tensors are estimated, giving rise to energy orthogonal states of stress and strain, thus decomposing the elastic potential in discrete elements. It is proven that the essential parameters, required for a complete characterisation of the elastic properties of an orthotropic medium, are the six eigenvalues of the compliance tensor, together with a set of three dimensionless parameters, the eigenangles θ, ϕ and ω. In addition, the intervals of variation of these eigenangles with respect to different values of the elastic constants are presented. Furthermore, bounds on Poisson's ratios are obtained by imposing the thermodynamical constraint on the eigenvalues to be strictly positive, as specified from the positive-definite character of the elastic potential. Finally, the conditions are investigated under which a family of orthotropic media behaves like a transversely isotropic or an isotropic one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004199900066
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The homogenization method for the study of variation of Poisson's ratio in fiber composites (1998)
    Springer
    Archive of applied mechanics 68 (1998), S. 281-295 
    Details
    ISSN: 1432-0681
    Keywords: Key words Homogenization method ; Poisson's ratios ; fiber composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Materials with specific microstructural characteristics and composite structures are able to exhibit negative Poisson's ratio. This fact has been shown to be valid for certain mechanisms, composites with voids and frameworks and has recently been verified for microstructures optimally designed by the homogenization approach. For microstructures composed of beams, it has been postulated that nonconvex shapes (with reentrant corners) are responsible for this effect. In this paper, it is numerically shown that mainly the shape, but also the ratio of shear-to-bending rigidity of the beams do influence the apparent (phenomenological) Poisson's ratio. The same is valid for continua with voids, or for composites with irregular shapes of inclusions, even if the constituents are quite usual materials, provided that their porosity is strongly manifested. Elements of the numerical homogenization theory and first attempts towards an optimal design theory are presented in this paper and applied for a numerical investigation of such types of materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050165
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The adhesion coefficient of fiber-reinforced polymers evaluated by dynamic measurements (1982)
    Springer
    Colloid & polymer science 260 (1982), S. 837-841 
    Details
    ISSN: 1435-1536
    Keywords: Adhesion coefficient ; composites ; fibers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A theoretical model, consisting of a series of infinite concentric cylinders surrounding a fiber in a composite material, was introduced in this paper to give a quantitative account of interface phenomena, already experimentally observed. A series of specimens, conveniently designed to represent the theoretical model, were subjected to dynamic modes of loading to measure the amount of adhesion between fibers and matrices by means of an adhesion coefficient developed in the theory. It was found that theoretical results for the adhesion between matrix and filler were compatible with the structural characteristics of the specimens tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01419093
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of moisture absorption on the thermomechanical properties of particulates (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 394-403 
    Details
    ISSN: 1435-1536
    Keywords: Moisture absorption ; particulates ; composites ; glass transition temperatured
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Water absorption in particulate composites at ambient temperature influences their thermomechanical properties. Second Fick's law of diffusion was used in this paper to predict the diffusion coefficient of the composite materials tested. In all cases the matrix material was a diglycidyl ether of bisphenol-A polymer cured with 8 phr triethylene tetramine and filled with iron particles with an average diameter 150 μm at five distinct volume fractionsv f =0, 0.05, 0.10, 0.16 and 0.20. The modification of the modulus of elasticity, ultimate stress, breaking strain and breaking energy due to moisture absorption was examined. Moreover, differential scanning calorimetry was used to study the influence of the time exposure into water and the filler concentration of the particulates on their glass transition temperature. Finally, the void occupancy in the composite was evaluated from free volume considerations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418212
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  • 5
    Electronic Resource
    Electronic Resource
    Crack propagation modes in fiber and particulate composites in the microstructure (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 610-625 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The influence of the hard or soft inclusions and the mesophase layers in either a soft-hard-soft or hard-soft-hard combination of biphase plates submitted to dynamic tensile loads on the fracture mode and bifurcation process in both phases was investigated in this paper. It was assumed that the soft or hard matrix is infolding the hard or soft inclusion of the plate, so that the plate constitutes a meridional section of the representative volume element of a unidirectional fiber composite, or a principal section of a particulate. The influence of the mechanical properties of either phase on the crack propagation velocity and the initiation of crack bifurcation was studied by using high-speed photography and dynamic caustics. The results showed that the propagating crack tended to bifurcate either in the brittle or in the mesophase layer under certain conditions of propagation velocity. It was shown that bifurcation of a propagating crack depends on the elastic moduli and Poisson's ratios of the phases, as well as on the extent of the mesophase layer, which depended on the adhesion quality of phases.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280910
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The gel-phase modulus of high-impact polystyrene from dynamic mechanical spectroscopy (1988)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 9 (1988), S. 229-236 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: High-impact polystyrene (HIPS) constitutes a mechanically attractive composite, consisting of a glassy matrix and a rubberlike particle phase (gel phase). Dynamic mechanical spectroscopy was performed for the polystyrene matrix for three different types of HIPS as well as for the concentrated gel-phase material, at the vicinity of the respective glass-transition temperatures (Tg). An approximate estimation of the gel-phase modulus was attempted by using known mechanical models. A comparison with experiments was also made. The modulus of the composite was found to be lower than the theoretical lower bound for particulate composites. This was attributed to a separate phase between gel particles and the matrix. A diffusion-type variation of the modulus of this mesophase layer was estimated, and a correlation between calculated fitting parametric exponents and impact behavior of HIPS was found. Moreover, the Tgs of the materials under investigation were also measured with two independent methods. It was found that all types of HIPS presented higher Tgs than the pure matrix by 5 to 10°C with the highest Tg found being that of the gel-enriched material. The shift of Tgs to higher temperatures was attributed to an eventual increase of the effective cross-link density of the matrix because of grafting.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750090310
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamic mechanical properties of particulates: Application to iron-epoxy composites (1986)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 7 (1986), S. 1-8 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The dynamic mechanical properties of composite materials, consisting of an epoxy matrix filled with iron particles, were determined over a temperature range. The storage- and loss moduli were evaluated in a Dynastat apparatus, with the parameters being the volume fraction of filler and the test frequency. A theoretical model was developed for comparing the experimental results with the theoretical predictions. A satisfactory correlation was obtained for the glassy region of the composite.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750070102
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    Paper (German National Licenses)
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