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991.
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The change in polystyrene (PS) layer thickness, which has been simultaneously determined during post-yield deformation, shows
that crazing is the basic mechanism of toughening in all laminated films, and that shear deformation supplements the contribution
of crazing especially for samples with high polyethylene (PE) volume fractions. Crazes formed in PS layers in the laminated
films are slender and regular compared with the short and lenticular crazes formed in bulk PS film. When PE volume fraction
increased, craze advance speed decreased because of the reduction of the stress concentration effect at craze tips. The life-time
of the first mature craze to be formed at a given strain rate increased with PE volume fraction because the PE supporting
the mature crazes could effectively inhibit craze rupture and blunt out the propagating crack by absorbing the stored elastic
energy in the PS layer that would have been dissipated as fracture surface energy. 相似文献
995.
996.
A. Sadananda Chary S. Narender Reddy T. Chiranjivi 《Journal of Materials Science》1989,24(6):2199-2202
Dielectric properties, dielectric constant (k), dielectric loss (tan δ) and a.c. conductivity (σ) in the solution-grown single crystals of RbNO3 are presented from room temperature to about 200°C covering the frequency range 102 to 105 Hz. A broad peak observed in tan δ-frequency data between 103 and 105Hz is thought to be due to impurity-vacancy dipoles. The sudden rise of three parameters near 160°C is attributed to the known
phase transition from trigonal to CsCl structure. 相似文献
997.
998.
999.
A model of the electronic structure of graphite-like carbon films, describing the semiconductor properties of this material, is presented. Spectra of optical constants of microcrystalline carbon films in the region λ = 0.4–8.0 μm were studied by the spectral ellipsometry and IR reflection methods. A number of distinctive features of the spectra, associated with both the appearance of C---C- and C---Hn-type bonds and direct energy gaps, were found. Analysis of the optical data using the proposed model makes possible a common interpretation of our results and literature data. Values of a parameter Θ, which is an averaged qualitative parameter of structural distortions within carbon microcrystallites as compared with crystalline graphite, are determined from comparison of theoretical results and experimental data. 相似文献
1000.
Summary If the roots of the characteristic equation of the governing differential equation for the stress function of an orthotropic plate under generalized plane stress conditions are equal classical solutions of anisotropic elasticity theory do not hold anymore. The general form of the stress function for such orthotropic materials is discussed and the exact solution is given for the plate with an elliptic opening loaded in tension.Comparison of the stress distribution for the material with distinct characteristic roots indicated that in produces much higher stress concentrations than the model with equal roots. For the latter case solution of any boundary value problem may be obtained very easily through an existing solution for the isotropic material.Given also that there are several problems involving stress concentrations in orthotropic plates as yet unsolved, the analysis presented here might be of considerable help in the, designing of the structure of composite laminates.With 8 Figures 相似文献