Design of orthotropic parts of complex shape by the method of nonplanar sections

Procedures based on the hypothesis of nonplanar sections are used to derive equations for determining the normal stresses at an arbitrary point of a body of complex shape in tension and bending. The anisotropy of the material properties is taken into account by introducing a variable modulus of elasticity. The theoretical results have been checked experimentally.Gor'kii Zhadanov Polytechnic Institute. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 351–354, March–April, 1969.     

Ultrasonic determination of the stiffness characteristics of an orthotropic material with imperfect elasticity

The propagation parameters of ultrasonic vibrations in an orthotropic material with imperfect elasticity have been measured. The results of the measurements are used to calculate the complex stiffness characteristics, and the correspondence between the nature of the anisotropy and the adopted model is examined. The anisotropy of the inelastic properties is investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 195–206, March–April, 1973.     

Investigation of the performance of composite shells under repeat internal pressure

The effect of the winding material and its thickness on the residual strains and the mode of failure of a composite shell is analyzed. The results of low-cycle fatigue tests on composite shells are presented.P. I. Baranov Central Institute of Aircraft Engine Building. Translated from Mekhanika Polimerov, No. 6, pp. 1060–1065, November–December, 1973.     

Effect of anisotropy on the cyclic deformation and heating of SVAM-type glass-reinforced plastics

The effect of anisotropy of the mechanical properties on the cyclic deformation and heating of 1:1 and 5:1 SVAM-type glass laminates has been investigated for symmetrical tension-compression and pulsating tension and compression. It is shown that on the main part of the fatigue curve, depending on the anisotropy and the cyclic stress level, the temperature may be stabilized. At the same time, fracture is invariably accompanied, under fixed experimental conditions, by a rise in temperature to a certain value that depends only on the anisotropy property of the glass-reinforced plastic, the strain also reaching critical values that are determined by the cycle asymmetry and the anisotropy property of the material.Institute of Mathematics and Mechanics, Academy of Sciences of the Armenian SSR, Erevan. Translated from Mekhanika Polimerov, No. 5, pp. 898–903, September–October, 1971.     

Method of the anisotropy potential in the linear mechanics of polymers

The potential of the displacements due to the anisotropy of the physical properties of a material (the anisotropy potential) is used in order to reduce the solution of the linear statistical boundary problem of elasticity theory and that of the linear creep of homogeneous anisotropic bodies to two simpler problems: one involving an anisotropic medium, and the other involving an equation analogous to the Poisson equation.S. M. Kirov Ural Polytechnic Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 1, pp. 24–31, January–February, 1972.     

Supermolecular structure of teflon and its role in the manufacture of metal-polymer antifriction materials

The question of the formation of supermolecular structures in teflon is considered. It is shown that during processing they become oriented, causing anisotropy of the material properties. The realtive rheological characteristics of the anisotropic materials are given as a function of the directionality of the force field. Specimens are obtained on the basis of the experimentally determined laws and certain properties of a polymer-metal antifriction material consisting of a high tin, porous bronze impregnated with teflon are investigated.Institute of the Chemistry of High Molecular Compounds, AS UkrSSR, Kiev. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1122–1124, November–December, 1968.     

A complex approach to evaluation of the strain-strength properties in stretching of KMU-8 carbon-filled construction plastic

Conclusion The detailed study of the mechanical properties of KMU-8 CFRP in stretching characterizes it as a construction material with high anisotropy of the elastic and strength properties. The accurate determination of the properties of the monolayer allows subsequently calculating the elastic characteristics based on the theory of laminated plastics with a precision sufficient for engineering and construction calculations. The calculated strengths should be estimated with consideration of the specific features of strain and failure of the carbon-filled plastic.Translated from Mekhanika Kompozitnykh Materialov, No. 4, pp. 488–499, July–August, 1993.     

Consideration of nonelastic losses in the determination of rigidity parameters of anisotropic polymers by ultrasonic methods

The propagation of oscillations in an orthogonally anisotropic medium with losses is investigated, using Hooke's law with complex coefficients. Functions are derived relating the complex modules of an orthotropic body to the parameters of propagation of ultrasonic oscillations. The effect of nonelastic anisotropy on the mechanical properties of the material is investigated. Equations are derived for the transition from complex modules to complex technical characteristics.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 32–38, January–February, 1972.     

Low-cycle fatigue of a composite substance containing a dispersed filler in cyclic compression

Conclusions 1. The lifetime of a composite material having a dispersed filler has been examined under conditions of low-cycle compression.2. It has been shown that, in distinction from materials of fibrous structure, the lifetime of this material is determined, not by a breakdown in the continuity of structure, but the deformability of the polymer matrix.3. The absence of a correlation between the static and fatigue strengths of composite mateials from cold and hot curing is caused by the different effect of the structure of the cured binder as a component of the material on the ultimate static characteristics and creep, whose relaxation character is more clearly expressed.4. Creep of the binder and the strength of the microspheres are the main factors which determine the lifetime of the material in question in cyclic compression.All-Union Scientific-Research Institute of Synthetic Resins, Vladimir. Translated from Mekhanika Polimerov, No. 4, pp. 653–657, July–August, 1978.     

Technological anisotropy of chaotically reinforced glass-fiber-resin materials

The authors investigate the strength properties of chaotically reinforced glass-fiber-resin materials in compression-molded and injection-molded artifacts of complex shape and also the density, water absorption, and binder content in various zones in the artifacts. They find anisotropy to be present in the strength indices, owing to orientation of the reinforcing elements during flow of material in the mold. They determine the coefficients of anisotropy of the strength (these are defined as the ratios of the strength in the flow direction to the strength in a perpendicular direction). They suggest a method of estimating the degree of orientation of the reinforcing elements in artifacts made of nonoriented glass-fiber-resin materials.All-Union Scientific-Research Institute of Glass-Fiber-Reinforced Plastics and Glass Fiber, Moscow Region. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 507–515, May–June, 1973.     

Numerical characteristics of the degree of anisotropy of the mechanical properties of materials

Conclusions 1. A unique procedure for determination of the numerical characteristics of the degree of anisotropy of the strength and deformation properties of materials is proposed.2. The concepts of the deformability surface and the anisotropy surface of the deformability permit representing graphically the deformation properties of materials.3. The system of integral characteristics of the mechanical properties of materials opens up new possibilities in connection with the analysis and optimization of different reinforcement schemes.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 601–609, July–August, 1978.     

Dispersed failure of an anisotropic flywheel

Based on a hereditary damage model of solids, the strength of a cylindrically anisotropic flywheel is calculated. By using a failure criterion, the location and time of initial failure is determined in relation to an anisotropy parameter, for which the ratio of rigidities in the tangential and radial directions is taken. The process of dispersed failure depends on the expansion intensity of the damaged zone. The boundary of the zone is the failure front, whose equations of motion are obtained in the cases of absence and presence of a residual strength for the material behind the failure front. In the second case, the damaged material is modeled by an isotropic elastic medium with considerably reduced values of strength and rigidity characteristics, and variations in the pressure on the failure front are also determined. Graphs of the radial coordinate of failure front as a function of time are constructed and analyzed for different values of the anisotropy parameter, the degree of residual strength and density behind the failure front, and proportions of geometrical sizes of the flywheel. The critical failure times are found. A system of restrictions on the values of mechanical and geometrical parameters is revealed which makes possible the realization of the process of dispersed failure investigated.Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 1, pp. 93–108, January–February, 2005.     

A type of mechanically anisotropic,optically sensitive material

The technology for obtaining a mechanically anisotropic, optically sensitive material that can be used in photoelastic stress analysis is described. The mechanically anisotropic, photoelastic materials obtained by this method (method 3) are free of initial birefringence, have a sufficiently high degree of mechanical anisotropy, and possess high optical sensitivity. The elastic and piezooptic properties of specimens of orthotropic material have been investigated and it has been found that the isochromatics (lines of equal path differences ) are lines of equal principal strain differences. Experimental results are presented for the stress distribution in an orthotropic disk compressed by a pair of opposing concentrated forces.Translated from Mekhanika Polimerov, No. 5, pp. 835–839, September–October, 1971.     

Determination of the maximum stresses in a cantilever composed of material with deformation anisotropy

The results of a theoretical investigation of the state of stress of a cantilever with allowance for deformation anisotropy are presented. Expressions for determining the bending stresses in a beam with a profile having a specific radius of curvature at the support are obtained on the basis of the hypothesis of broken-line (cylindrical) sections. The expressions obtained are extended to the case of a beam made of material with viscoelastic properties. A numerical example is given.Institute of Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. Translated from Mekhanika Polimerov, No. 3, pp. 453–458, May–June, 1976.     

The anisotropy of compact bone material

From the measurements of the main elements of the microstructure of compact bone material, it is concluded that the theoretical model of a transtropic material can be applied to bone tissue. This conclusion is confirmed by the experimental data obtained on compression. The correlation connection between the ultimate strength of compact bone material and the elasticity modulus has been found. It is shown that the anisotropy of the compact material is satisfactorily described by the tensor formula.Scientific-Research Institute of Medical Radiology, Academy of Medical Sciences of the USSR, Obninsk. S. M. Kirov Leningrad Order of Lenin Wood Technology Academy. Translated from Mekhanika Polimerov, No. 4, pp. 711–716, July–August, 1972.     

Stress concentrations around openings in transversely isotropic shells

A method of investigating stress concentrations around openings in shells made of a transversely isotropic material (oriented glass-reinforced plastic [5]) is described. The use of a Timoshenko-type theory makes it possible to take into account the effect of tangential shearing stresses and the anisotropy of the elastic properties of the shell in a direction normal to the middle surface. A complex form of the resolvents of this theory, constructed in [6], is employed.Physicomechanical Institute, Academy of Sciences of the Ukrainian SSR, L'vov. L'vov Franko State University. Translated from Mekhanika Polimerov, No. 6, pp. 1076–1081, November–December, 1970.     

Mechanical properties of blends of liquid crystalline copolyesters with polyprophylene

Conclusions A significant effect of the addition of LCP on the mechanical properties and their anisotropy has been established. Already, if one considers the shape of curves of the stress-strain relationship it can be seen that curves typical for semicrystalline polymers (pure polypropylene) with clearly visible yield point and significant cold drawing leading to an anisotropic stiffening are changing into curves without yielding and with a brittle failure (LC-rich blends). Generally, the tensile elasticity modulus increases with increasing LCP content for both MD and TD. The maximum value of anisotropy of elastic properties was noted for a rather low content of LCP (c = 5%). On the contrary, the stress at yield decreases with increasing LCP content. The same was observed for the strain at yield but in both cases an important increase of anisotropy has taken place. Consequently, the total elongation during drawing (strain at break) showed a drastic decrease for blends with higher LCP content (about 60–80 times). The addition of the LCP to polypropylene has led to a stiffness increase (higher elasticity modulus) but simultaneously to a considerable plasticity decrease. As a confirmation of these observations, there served also the creep test where a decrease of the creep compliance (by two times) for LC-rich blends as compared with pure PP was noted.It also should be emphasized that, generally, a smaller effect of LCP content on the elastic deformation was noted than that on the time dependent effects (nonelastic creep deformation).Published in Mekhanika Kompozitnykh Materialov, Vol. 30, No. 4, pp. 442–450, July–August, 1994.     

Thermoelastic stresses in a nonuniform orthotropic cylinder

The stress distribution in a cylinder with cooling nonuniform with respect to the circumferential coordinate is investigated. The nonuniformity of the mechanical properties of the material in this direction is taken into account. Numerical results obtained at values of the parameters characteristic of wound glass-reinforced products are discussed.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 3, pp. 560–563, May–June, 1975.     

Fracture toughness characteristics of laminated composites

Parameters characterizing the resistance of laminated composites to interlaminar fracture are discussed. The properties of the specific interlaminar fracture work, i.e., the amount of work spent on the formation of a unit of new surface of interlaminar crack, were examined. Taking account of the anisotropy of the material, this work may be characterized using a matrix. Upon change in the direction of crack growth, the matrix elements are transformed similarly to the components of a symmetrical second rank tensor. An interpretation is offered for the matrix elements. The proposed theoretical model was in accord with our experimental results.Moscow Engineering Institute. Technical University, Russia. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 21–31, January–February, 1996.     

Contact problems for beams and plates with low shear stiffness

The low shear stiffness and strength of unidirectionally reinforced plates and beams predetermines the choice of calculation model in specific problems [4]. The contact problem is considered for a glass-reinforced plastic plate resting on a Winkler foundation; the deformation properties of the plate are described by the equations of an orthotropic material; the investigation is based on generalized applied theories of the Timoshenko and Ambartsumyan types [5–8], which permit the high shear compliance of thin-walled structures to be taken into account.L'vov Polytechnic Institute; Ivan Franko Institute of Petroleum and Gas. Translated from Mekhanika Polimerov, No. 4, pp. 715–720, July–August, 1970.