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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative porosity characterization of composite materials by means of ultrasonic attenuation measurements (1992)
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 1-8 
    Details
    ISSN: 1573-4862
    Keywords: Composite materials ; graphite/epoxy ; porosity ; ultrasonic attenuation ; image analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Ultrasonic techniques utilizing a pair of transducers in a combination of pulse-echo and through-transmission modes were developed. Two types of methods were discussed for determination of material attenuation in composites: direct or absolute methods for materials with low signal loss, and indirect or relative methods for materials with higher signal loss. In all cases, transfer functions of the transducers and specimen surfaces were taken into consideration so that the measurement system is self-calibrated. Void content was measured by means of microscopic image analysis of photomicrographs of the specimen cross-sections and a correlation of material attenuation with porosity was established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566012
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  • 2
    Electronic Resource
    Electronic Resource
    Micromechanical analysis of nonlinear thermal deformation of filamentary metal matrix composites (1991)
    Springer
    Computational mechanics 9 (1991), S. 17-26 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A micromechanical model was developed to predict the thermomechanical deformation of unidirectional filamentary metal matrix composites. The composite is represented by two concentric cylinders, the inner one simulating the fiber and the outer one the matrix. Both elastic and elastic-plastic analyses were performed. In the model the fiber was assumed to be linear-elastic and the matrix a work-hardening elastoplastic material. The elastoplastic analysis was based on the deformation theory of plasticity in conjunction with the von Mises yield criterion. The matrix cylinder in the model was divided into a number (N) of concentric layers with each layer having different values of tangent modulus and Poisson's ratio depending on the amount of plastic deformation. An elastic analysis of a composite cylinder with (N+1) layers was then performed and served as a subroutine for a computer program. The computer program was applied to the study of thermal deformation in the longitudinal and transverse directions of a filamentary silicon carbide/aluminum composite subjected to thermal cycling up to 177°C (350°F). Longitudinal and transverse thermal strains were measured using strain gages. The critical temperature at which the strain-temperature curves become nonlinear was experimentally determined and predicted by the model. Above this critical temperature the longitudinal thermal expansion coefficient decreases while the transverse one increases. The complete three-dimensional state of stress in the fiber and the matrix was computed. It was determined that in addition to the longitudinal stresses high transverse stresses were also developed in the matrix. The experimental thermal strain curves verified the theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369912
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  • 3
    Electronic Resource
    Electronic Resource
    Strain analysis of composites by moiré methods (1973)
    Springer
    Experimental mechanics 13 (1973), S. 246-252 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Moiré techniques were developed, adapted and applied to the determination of strain fields in filamentary composite laminates. Conventional techniques, using 1000 line-per-inch (Ipi) arrays bonded or photoprinted onto the specimen, were applied to glass-epoxy and boron-epoxy specimens with holes and cracks. Techniques for tenfold fringe multiplication were also applied to glass-epoxy and boron-epoxy laminates with holes. A reflective surface of glass-like smoothness was produced on the specimen and a 500 dot-per-inch grid photoprinted on it. A rigid distortion-free camera was used for recording replicas of the specimen grid by projection photography. These replicas were analyzed with a 200 line-per-millimeter (5080 Ipi) grating for reconstruction of moiré-fringe patterns. These patterns were analyzed by graphical and mechanical differentiation using second-order moiré. Strain distributions and strain-concentration factors were in very good agreement with theoretical and other experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02322621
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  • 4
    Electronic Resource
    Electronic Resource
    Holographically determined isopachics and isochromatics in the neighborhood of a crack in a glass composite (1980)
    Springer
    Experimental mechanics 20 (1980), S. 53-56 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The isochromatic and isopachic fringes are obtained holographically in the neighborhood of a central crack in a tensile, orthotropic glass-composite plate. The general inability to separate the principal stresses or strains from such information alone under anisotropic conditions is discussed, as are the results relative to fracture-mechanics implications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321034
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of fracture toughness by photoelastic coating (1987)
    Springer
    Experimental mechanics 27 (1987), S. 10-13 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The photoelastic-coating method was applied to the determination of fracture toughness in aluminum plates. The specimens were plates with a central transverse crack. Determinations were made first by the compliance method. The specimens were loaded statically to failure. The opening displacement across the crack was measured with a clip gage. In using this photoelastic-coating method, the stress-intensity factor was obtained in terms of the radius and fringe order of various isochromatic fringe loops using an extrapolation law. An apparent stress-intensity factor was obtained from several isochromatic fringe patterns away from the crack tip and then extrapolated to the crack tip to determine the true value. Results obtained by the photoelastic-coating method are higher than those obtained by the compliance method for all loads, due to the bluntness of the crack tip in the first set of specimens. Theoretical predictions fall between the compliance method and photoelastic-coating results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02318857
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal stress analysis of a silicon carbide/aluminum composite (1991)
    Springer
    Experimental mechanics 31 (1991), S. 202-208 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermal deformations and stresses were studied in a silicon-carbide/aluminum filamentary composite at temperatures up to 370°C (700°F). Longitudinal and transverse thermal strains were measured with strain gages and a dilatometer. An elastoplastic micromechanical analysis based on a one-dimensional rule-of-mixtures model and an axisymmetric two-material composite cylinder model was performed. It was established that beyond a critical temperature thermal strains become nonlinear with decreasing longitudinal and increasing transverse thermal-expansion coefficients. This behavior was attributed to the plastic stresses in the aluminum matrix above the critical temperature. An elastoplastic analysis of both micromechanical models was performed to determine the stress distributions and thermal deformation in the fiber and matrix of the composite. While only axial stresses can be determined by the rule-of-mixtures model, the complete triaxial state of stress is established by the composite cylinder model. Theoretical predictions for the two thermal-expansion coefficients were in satisfactory agreement with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02326060
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamic compressive behavior of thick composite materials (1998)
    Springer
    Experimental mechanics 38 (1998), S. 172-180 
    Details
    ISSN: 1741-2765
    Keywords: Thick composites ; strain rate effects ; dynamic response ; compressive testing of composites ; falling weight impact ; split Hopkinson pressure bar ; compressive properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of strain rate on the compressive behavior of thick carbon/epoxy composite materials was investigated. Falling weight impact and split Hopkinson pressure bar systems were developed for dynamic characterization of composite materials in compression at strain rates up to 2000 s−1. Strain rates below 10 s−1 were generated using a servohydraulic testing machine. Strain rates between 10 s−1 and 500 s−1 were generated using the drop tower apparatus. Strain rates above 500 s−1 were generated using the split Hopkinson pressure bar. Unidirectional carbon/epoxy laminates (IM6G/3501-6) loaded in the longitudinal and transverse directions, and $$[(0_8 /90_8 )_2 /\bar 0_8 ]_s $$ cross-ply laminates were characterized. The 90-deg properties, which are governed by the matrix, show an increase in modulus and strength over the static values but no significant change in ultimate strain. The 0-deg and cross-ply laminates show higher strength and ultimte strain values as the strain rate increases, whereas the modulus increnases only slightly over the static value. The increase in strength and ultimate strain observed may be related to the shear behavior of the composite and the change in failure modes. In all cases, the dynamic stress-strain curves stiffen as the strain rate increases. The stiffening is lowest in the longitudinal direction and highest in the transverse direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325740
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of shear modulus of single fibers (1999)
    Springer
    Experimental mechanics 39 (1999), S. 284-286 
    Details
    ISSN: 1741-2765
    Keywords: Fiber ; shear ; characterization ; composite ; torsion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A technique was developed for determining the longitudinal shear modulus of uniform diameter single fibers. A length of single fiber suspended from one end and with a weight attached at the other end was used as a torsional pendulum. Its longitudinal shear modulus can be experessed as a function of the frequency of oscillation of the torsional pendulum. Tests were conducted on five different types of fibers: carbon, Kevlar 49, silicon carbide, K-glass fibers and G-glass fibers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02329806
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  • 9
    Electronic Resource
    Electronic Resource
    Wave propagation in transversely impacted composite laminates (1979)
    Springer
    Experimental mechanics 19 (1979), S. 9-16 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental investigation was conducted to determine wave-propagation characteristics, transient-strain distributions and residual properties for unidirectional and angle-ply boron/epoxy and graphite/epoxy laminates impacted with silicon-rubber projectiles at velocities up to 250 ms−1 (820 ft/s). Tests were conducted at normal and 45-deg oblique impact. Strain signals obtained from surface and embedded strain gages were recorded and analyzed to determine the types of waves, propagation velocities, peak strains, strain rates and attenuation characteristics. The predominant wave is a flexural on propagating at different velocities in different directions. The flexural wave velocity is higher in the higher-modulus direction. In general, measured wave velocities were higher than theoretically predicted. The amplitude of the in-plane wave is less than ten percent of that of the flexural wave. Peak strains and strain rates in the transverse to the (outer) fiber direction are much higher than those in the direction of the fibers. Strain rates up to 640 s−1 were measured. Under oblique 45-deg impact, the flexural wave is still the predominant one. Peak strains under this oblique impact range between 36 and 56 percent of those under normal impact of the same velocity. Residual elastic properties and strength were measured around the point of impact. The most significant result was a reduction in the transverse strength of the unidirectional laminates. The dynamics of impact were also studied with high-speed photography. The projectile is completely flattened within 50–70 μs and the total contact time is of the order of 300 μs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02327764
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  • 10
    Electronic Resource
    Electronic Resource
    Shrinkage stresses around rigid inclusions (1962)
    Springer
    Experimental mechanics 2 (1962), S. 240-244 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The objective of this paper is the presentation of methods to study shrinkage stresses in matrices cast around rigid inclusions. The method of casting plastic specimens around glass inclusions and analyzing the resulting isochromatic fringe patterns is briefly discussed. An alternate method for the study of the relative or dimensionless stress distribution using rubber models with inserted inclusions is also, presented. A partial solution to the stress distribution between two inclusions was obtained. The generality of the method and its applicability to any matrix material are emphasized. It is pointed out that the stress field obtained corresponds to the thermal-stress field produced by a difference in the coefficients of thermal expansion of the matrix and the inclusion material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02326722
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