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  • 1
    Electronic Resource
    Electronic Resource
    The effect of coating on the stiffness and toughness of encapsulated fiber composites (1988)
    Springer
    Colloid & polymer science 266 (1988), S. 1110-1125 
    Details
    ISSN: 1435-1536
    Keywords: Encapsulatedfiber composites ; stiffness andtoughness ; four-phasemodel ; elasticmoduli ; coatingproperties
    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 The effect of the coating of the fiber on the stiffness and toughness of composite materials is presented in this paper. The type of composite material considered is of a macroscopically isotropic composite medium containing coated fibers. The models used to simulate such materials consists of: the cylindrical fiber, a cylindrical annulus of the coating, an annulus of the matrix enveloped by an infinite region of an equivalent composite consisting of a transversely isotropic material and representing the real composite with dispersed coated fibers. Solutions for the longitudinal, transverse and shear elastic moduli in the four-phase model were established assuming linear elastic conditions. The results were found to depend on the extent and the mechanical properties of the coating. The stiffness and toughness of the composite were evaluated in models representing plane-stress equatorial sections of the representative volume element of the real material according to the Hashin-Rosen model. The stiffness of the fiber composites was studied by varying the rigidity and the extent of the fiber-coating in the model and evaluating its influence on the overall mechanical behavior of the model. On the other hand, the toughness of the composite was evaluated by the method of caustics in models made of composite PMMA plates with PMMA inclusions coated with a ductile annulus. Interesting results were derived concerning the influence of the soft annulus on the mechanical behavior of the composite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01414401
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  • 2
    Electronic Resource
    Electronic Resource
    Antiplane shear crack in an infinite plate with a circular inclusion (1985)
    Springer
    Archive of applied mechanics 55 (1985), S. 295-306 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Übersicht Es wird der Einfluß untersucht, den ein elastischer, kreisförmiger Einschluß aus verschiedenem Material in einer unendlichen Platte mit einem Riß, welche einer longitudinalen Schubspannung unterworfen ist, auf den Spannungszustand der Platte ausübt. Die vorgeschlagene Methode benutzt komplexe Variablen in Zusammenhang mit der Muskhelishvilischen Technik und gibt für den Spannungszustand in der Platte interessante Resultate. Numerische Ergebnisse wurden gefunden, um den Einfluß der Inhomogenität auf die Spannungsintensitätsfaktoren des Risses zu bestimmen.
    Notes: Summary The effect of an elastic circular inclusion of a different material on the stress state of a single-cracked infinite sheet subjected to anti-plane shear is investigated. The proposed method makes use of complex variables in conjunction with Muskhelishvili's technique and has given interesting results for the stress field in the cracked plate. Numerical results, derived from this technique, investigate the influence of the regional inhomogeneity, produced by the inclusion in the structure, on the variation of stress-intensity factors at the crack tips.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538224
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  • 3
    Electronic Resource
    Electronic Resource
    The stress intensity variation of an orthotropic perforated plate containing an internal crack (1993)
    Springer
    Archive of applied mechanics 63 (1993), S. 242-252 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Das elastische Problem einer unendlichen, orthotropen Platte mit verschiedenen Wurzeln ihrer charakteristischen Gleichung wird im Falle, daß die Fasern senkrecht zu einem inneren Riß verlaufen und daß sie durch ein elliptisches Loch geschwächt sind, im Rahmen der Lekhnitskii-Theorie gelöst. Die Platte wird im Unendlichen einer vorgeschriebenen Spannung unterworfen, während die Randbedingungen an den Rißflanken, am Lochrand und im Unendlichen gegeben sind. Mit Hilfe der Methode der komplexen Variable wird die Lösung des Problems zurückgeführt auf die Berechnung von Cauchy-Integralen der analytischen Funktionen des Problems. Die numerische Lösung des Problems zeigt eine starke Abhängigkeit von Mode-I-Spannungsintensitätsfaktoren (SIF) an den Rißspitzen von der Rißlänge oder des Ligaments zwischen der Rißplatte und dem Loch. Weiterhin wurde gezeigt, daß Orthotropie starken Einfluß auf die Spannungsintensität hat. Diese Beobachtungen stehen in voller Übereinstimmung mit Resultaten aus der Arbeit [1] über ein ähnliches Problem für eine orthotrope Platte, wo allerdings die Wurzel der charakteristischen Gleichung identisch sind.
    Notes: Summary The elastic problem of an infinite orthotropic plate with different roots of its characteristic equation, when the fibers are oriented perpendicularly to an internal crack, and is weakened by an elliptic hole, is solved using Lekhnitskii's theory. The plate is subjected to prescribed stresses at infinity, while the boundary conditions are given at the flanks of the crack, at the rim of the perforation and at infinity. Using the complex-variable method, the solution of the problem is reduced to the evaluation of Cauchy-type integrals concerning the analytic functions of the problem. The numerical solution of the problem revealed an intense variation of mode-I stress intensity factors (SIF) at the crack tips due to the increase of either the crack length, or the distance of the near-by rack tip from the center of the hole. Furthermore, it was found that orthotropy strongly influences the intensity of stresses at the crack tips. These findings are in complete agreement with results given in a previous work by the authors, concerning a similar problem for an orthotropic plate, which, however, constitutes a special case, where the material presents equal roots for its characteristic equation [1].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00793891
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  • 4
    Electronic Resource
    Electronic Resource
    The averaged mechanical properties of prismatic lattice formed by ellipsoidal inclusions (1999)
    Springer
    Archive of applied mechanics 69 (1999), S. 240-256 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The objective of this paper is to evaluate the averaged elastic properties of 3-D grained composites in which identical inclusions form a prismatic network interacting with the matrix material. The inclusions are of ellipsoidal shape with transverse circular sections located at the nodes of a doubly-periodic lattice with an orthogonal elementary cell. When the arrays of inclusions are set at equal spacings in normal directions through the thickness of the matrix, the material formed is an anisotropic composite with tetragonal symmetry at planes transverse to the fiber axis. The longitudinal and transverse elastic and shear moduli as well as the longitudinal Poisson's ratios of such composites are evaluated in this paper. The averaged properties are studied in terms of the aspect ratio and volume fraction of the inclusions as well as the relative rigidity of the constituent phases. Employing the Eshelby's theory for the stress field around a single ellipsoidal inhomogeneity, which is surrounded by the effective anisotropic material, and considering the Mori-Tanaka's concept for the mutual interaction of the neighboring inclusions, we may evaluate the averaged elastic properties of grained composites with aligned ellipsoidal inclusions at finite concentrations. The results provided in a closed-form solution concern the stiffness of 3-D grained composites with parallely dispersed ellipsoidal inclusions forming a prismatic network inside the principal material. It is shown that the stiffness is affected by both the geometry of the inclusions and their concentration. The use of different composite models in the analysis shows that intense variations of stiffness occur mainly in hard composites weakened by soft ellipsoidal inclusions. These findings come in full verification with experimental or theoretical results from the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050217
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  • 5
    Electronic Resource
    Electronic Resource
    Crack bifurcation modes in composite plates under impact (1986)
    Springer
    International journal of fracture 32 (1986), S. 71-92 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On a soumis à des tractions par impact des plaques fissurées comportant des inclusions élastiques circulaires ancrées dans une matrice. On discute ici de l'influence de l'inclusion sur la propagation d'une fissure de bord initiale. On a essayé deux types d'éprouvettes, comportant respectivement des inclusions dures ou tendres, noyées dans une matrice tendre ou dure. On montre que, systématiquement, la fissure en propagation fait état de bifurcations dans la zone de mésophase située entre la matrice et les inclusions circulaires. Dans les deux types d'éprouvettes, on a constaté qu'il était courant que la fissure initiale subisse un phénomène de séparation. Pour définir le champ de contraintes déterminant, on a évalué les facteurs dynamiques d'intensité des contraintes à différentes positions de la fissure, ainsi que les vitesses de la fissuration suivant la fissure principale suivant ses branches au cours de la propagation. On observe que l'amorçage de la fissure dans les plaques tendres comportant des inclusions dures est suivi d'une émission d'ondes de Rayleigh qui contribuent à déterminer le mode de rupture du composite. On a également utilisé des tracés isochromatiques pour simuler le champ de contrainte, en figeant la fissure en cours de propagation et en procédant à une analyse photo-élastique. Ces approximations ont conduit à des résultats satisfaisants dans le cas de fissures qui s'avancent dans des plaques composites.
    Notes: Abstract Cracked plates with bonded elastic circular inclusions inside a matrix were subjected to an impact tensile loading. The influence of the inclusion on the propagation of an initial edge-crack was discussed in this paper. Two types of specimens were tested, that is with hard or soft inclusions surrounded by soft or hard matrices respectively. It has been shown that bi-, or tri-furcations of the propagating crack have persistently occured at the region of mesophase between matrix and circular inclusions. The phenomenon of splitting of the initial crack was common in both types of specimens. For the definition of the prevailing stress field, the dynamic stress intensity factors were evaluated at different positions of the crack, as well as the crack-velocities along the main crack or its branches during their propagation. It was observed that the crack initiation in soft plates with hard inclusions was followed by the emission of Rayleigh waves, which contributed to the mode of fracture of the composite. Isochromatic patterns were also used to simulate the stress-field of the propagating cracks against the inclusions at distinct time-instants where the propagating crack was frozen at this instant and static photoelastic analysis was applied. These approximations gave satisfactory results with the cracks advancing inside the composite plates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019785
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  • 6
    Electronic Resource
    Electronic Resource
    The strain-hardening effect in HRR plane fields according to T-criterion (1994)
    Springer
    International journal of fracture 67 (1994), S. 117-132 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The strain-hardening effect on fracture is investigated with the aid of the T-criterion using HRR stress fields [1–3] around a crack tip in a power hardening material. Using the appropriate components of strain energy density for the elastic-plastic as well as a nearly elastic expression of the T-criterion, we find the fracture angles, as well as fracture stresses in materials possessing an elastic extended up to a perfectly plastic behavior, by considering plane mixed-mode deformation at the crack tip. Significant influence of the strain hardening coefficient, n on the fracture stress, as well as the hardening parameter α mainly appeared in plane strain conditions. This phenomenon was observed almost independently of the solution applied, which provides a nearly elastic or an elastic-plastic expression of the T-criterion describing the fracture conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019598
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