Relationship between the rheological characteristics of teflon determined for different loading regimes and temperatures

Specimens of teflon investigated in the temperature range from –40 to +60°C at various strain rates and in various loading regimes are used to demonstrate the relationship between changes in the theological properties of a material at constant standard loading rates (in the =vt regime) and the rheological characteristics determined by acoustic methods.Mekhanika Polimerov, Vol. 3, No. 4, pp. 619–624, 1967Presented on 3 February 1967 at the 4-th All-Union Conference on Strength and Plasticity, Moscow.     

Dynamic properties of teflons obtained under various molding conditions

The natural frequencies and decrements, velocities of sound, dynamic moduli of elasticity, and Poisson's ratios of teflon specimens have been investigated in relation to the nature of the starting powder and molding conditions. The optimal dynamic characteristics are determined and it is shown that chey can be used to optimize the molding conditions and control the quality of teflon products.Mekhanika Polimerov, Vol. 2, No. 6, pp. 917–922, 1966     

Equations for determining the deformation of filled polytetrafluoroethylene materials

Experimental data are given on the deformation of polytetrafluoroethylene (teflon) filled with S-1 colloidal graphite. Design equations are proposed for estimating the deformation of filled teflon materials in relation to the percentage of filler in the mixture, compressive stress, and test duration.Mekhanika Polimerov, Vol. 1, No. 3, pp. 57–62, 1965Communication II. For Communication I see [1].     

Verification of the hypothesis of the existence of a potential with reference to teflon

In establishing the rheological relations describing the behavior of materials during deformation it is often very useful to employ a potential function. The hypothesis of the existence of a potential is verified in relation to the deformation of teflon in a complex state of stress.Scientific-Research Institute of Mathematics and Mechanics, Leningrad Zhdanov State University. Translated from Mekhanika Polimerov, No. 3, pp. 565–567, May–June, 1969.     

Creep of certain polymers under hydrostatic pressure

The problems of an experimental investigation of polymer creep under omnidirectional hydrostatic pressure are considered. The method of investigation is discussed, and the loading devices are described. The results of tests on low-pressure polyethylene and teflon are reported.Mekhanika Polimerov, Vol. 4, No. 2, pp. 232–236, 1968     

Effect of hydrostatic pressure combined with uniaxial tension on certain physical properties of polymers

The residual changes in the density and swelling properties of high-density polyethylene, teflon, PVC, and ebonite after extension under hydrostatic pressure have been investigated. It is shown that in this case the density of all the materials tested is higher and the swelling lower than in the case of uniaxial tension alone. This effect of hydrostatic pressure is attributable to the creation of favorable conditions for the healing of cracks formed in the deformation process.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1018–1023, 1967     

Investigation of the Poisson's ratio of certain crystalline polymers under a constant compressive load

The results of an investigation of the Poisson's ratio in compression for two crystalline polymers, low-density polyethylene and teflon, are given. The effect of time under load and temperature on the value of the Poisson's ratio is examined.Mekhanika Polimerov, Vol. 1, No. 4, pp. 43–46, 1965     

Deformation of elastic polyurethanes with a bimodal cellular structure

This article examines the cellular structure and mechanical properties of elastic foamed polyurethanes with a bimodal cellular structure (BFPUs). It is shown that the sizes of the oval cells (3–12 mm) in the elastic foamed polyurethenes that are studied are a tenth of an order greater than the sizes of the polyhedral cells (0.1–0.6 mm). Conversely, for rigid foamed polyurethanes, the polyhedral cells are more than a tenth of an order larger than the oval cells (microcells). The equations of the compression curve of BFFUs are found, and it is established that the deformation of BFPUs is determined by the deformation function of the cellular structure and the viscoelastic properties of the polymer matrix. The deformation functions of the cellular structure and the relaxation properties of BFPUs are determined. It is shown that choosing BFPUs with a cellular structure improves the comfort properties of the foamed material: the softness coefficient increased by 8–19% in the investigated case, while the support coefficient increased by 15–35%.Paper presented at the IX International Conference on the Mechanics of Composite Materials (Riga, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 3, pp. 330–339, May–June, 1996.     

Rationalization of the shape of wound membrane shells of revolution composed of high-modulus material

A method of designing composite membrane shells of revolution under axisymmetric loading is described. The properties of the shell material are analyzed. It is shown that for shells of high-modulus material in the presence of tensile membrane stresses the fibers fail in the matrix. A fiber arrangement and shell geometry ensuring isotensoid properties are proposed for this case. A technological and weight analysis is presented.S. Ordzhonikidze Moscow Aviation Institute. Translated from Mekhanika Polimerov, No. 5, pp. 822–828, September–October, 1975.     

Some aspects of the behavior of shock-compressed polymers

The changes in the properties of certain polymeric materials subjected to the action of plane shocks of varying amplitude are discussed. Three loading techniques are employed — single, multiple, and high-frequency multiple loading — each accompanied by a different rise in the temperature of the polymeric material. The results show that the change in physicomechanical properties also varies with the loading technique.Volgograd Polytechnic Institute. Translated from Mekhanika Polimerov, No. 1, pp. 76–80, January–February, 1970.     

Effect of technological factors on the structure and properties of Eskaplen film material

The effect of the composition of the solvents, the concentration of the solutions, and the rate of film formation on the structure and properties of Eskaplen film material obtained on the basis of SKI-3 isoprene rubber hydrochloride has been investigated. The properties of the film material are shown to depend on the structure that develops during the film-forming process.Moscow Technologic Institute of the Meat and Dairy Industry. Translated from Mekhanika Polimerov, No. 1, pp. 8–13, January–February, 1973.     

Effect of small additives of oligomer on the viscoelastic properties of carbon fiber plastics

The viscoelastic properties of carbon fiber composites whose phenol-formaldehyde matrix is modified by thermodynamically incompatible isocyanate derivatives have been investigated. Data are given on fiber wetting (Table 11), internal stress (Table 2), viscoelastic properties (Fig. 1), and tensile strength (Fig. 2). The modified composites are strengthened by the addition of 0.5–4% oligomer additive. This process involves the formation of a two-phase structure, in which the additive phase microparticles act as a polymer filler. Due to selective interactions, the intermediate layer formed at the fiber-binder interface leads to changes in the viscoelastic properties and tensile strength of the matrix and improved maintenance characteristics for the material as a whole.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 4, pp. 440–445, July–August, 1993.     

Theoretical model of the anisotropy of low-cycle deformability of glass-fiber reinforced plastics

Conclusion A theoretical model is suggested for the anisotropy of low-cycle deformability of glass plastics determined by the anisotropy of the deformational properties of the material in short-term static tension (compression). The effect of the anisotropy of cyclic loss of strength of the deformational properties is taken into account by the introduction of the characterizing function which is taken to be independent of the mechanical properties of the material and of the conditions of low-cycle loading.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 437–442, May–June, 1985.     

Creep of polymer materials under periodically varying loads

A method is proposed for constructing the creep curves of a material whose nonlinear memory properties are described by Rozovskii's nonlinear integral equation [2] (with allowance for the stress dependence of the relaxation time) under given periodic loading from known creep curves recorded at constant stress. In deriving the theoretical relation certain simplifying assumptions are made (the creep strain accumulated in 1–2 cycles is small, no vibration [4–6]). An experimental check shows that the proposed method can be used to predict the behavior of a material under periodic loading with an accuracy sufficient for practical purposes.Mekhanika Polimerov, Vol. 2, No. 3, pp. 330–336, 1966     

Effect of the properties of the material of the buckling of a plate

In [2] it was shown with reference to the cylindrical bending of a plate that the Kirchhoff-Love hypothesis is asympototically accurate for determining the critical load irrespective of the properties of the material. However, the question of the dependence of the critical load on the material properties was left unexplored. This question is now numerically investigated. Curves characterizing the variation of the critical load with relative shear modulus are presented.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 355–357. March–April, 1969.     

Hardness of polymers

Hardness was measured on a Rockwell type instrument modified to measure the depth of the unrecovered indentation. The indentors were balls of various diameters and cones with various vertex angles. The hardness of the following materials was investigated: aminoplast (amino resin), K-17-2, FKP-1, polymethylmethacrylate (plexiglas), polyvinyl chloride (PVC), polyethylene, and teflon. The hardness is related to the strength and elastic characteristics.Mekhanika Polimerov, Vol. 2, No. 3, pp. 337–349, 1966     

Estimation of the stability of the strength of glass-reinforced plastics in conical shells

On the basis of a statistical analysis of the test data it is shown that there is a difference between the mechanical characteristics (in tension and compression) of laminated glass-reinforced plastics obtained under laboratory and industrial conditions by impregnation under pressure in a closed mold. The stability of the strength properties of the glass-reinforced plastic in various conical shells, produced in large batches, is considered. Certain experimental relations between the material properties and the total number of shells produced are also established.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 102–108, January–February, 1970.     

Free vibrations of a viscoelastic beam

The method of averaging is used to investigate the free transverse vibrations of a viscoelastic beam supported at the ends. The material properties of the beam are described by a certain nonlinear integral equation of Volterra type.Institute of Mechanics and Seismic Stability of Structures, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Mekhanika Polimerov, No. 4, pp. 752–756, July–August, 1971.     

State of stress of flexible viscoelastic plates with an opening

The problem of the state of stress of flexible plates with an opening is investigated with allowance for the viscoelastic properties of the material. The basic equations and the corresponding boundary conditions are formulated. The boundary value problem is solved by numerical integration. The effect of the creep properties of the material on the stress redistribution in the plate is investigated with reference to polymethyl methacrylate. It is shown that the angle of rotation, the ring moment, and the ring forces at the edge of the opening vary with time and as a function of the load.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 4, pp. 708–713, July–August, 1971.     

Stability of a transversely isotropic cylindrical shell in axial compression

The problem of the stability of a transversely isotropic cylindrical shell subjected to axial compression is considered with the aid of three-dimensional linearized equations for small subcritical strains. Transcendental equations are obtained for the critical loads corresponding to axisymmetric and nonaxisymmetric deformation. It is shown that in the case of the axisymmetric buckling mode the Kirchhoff-Love hypothesis is asymptotically exact irrespective of the properties of the material. The dependence of the critical load on the properties of the shell material is investigated numerically. Graphs of the variation of the critical load with relative shear modulus are presented.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1064–1068, November–December, 1969.