Transient creep of glass-reinforced plastic

Short-time (up to 30 min) creep tests on SVAM glass-fiber orthotropic material at 20°C have shown that it is subject to creep even at room temperature. At the same time, the behavior of this material in creep is observed to be markedly anisotropic.Mekhanika Polimerov, Vol. 1, No. 2, pp. 47–54, 1965     

Plane-stress creep of a glass-reinforced plastic

The creep behavior of an orthotropic glass-reinforced plastic based on Polimal'-109 resin and 19-S4 glass fabric is described. A special device for testing tubular specimens in plane-stress creep has been designed. The loading conditions include combined torsion and tension, internal pressure, and loading along the principal directions of anisotropy. Constitutive equations describing creep and recovery are proposed for the two-dimensional case.Warsaw. Translated from Mekhanika Polimerov, No. 3, pp. 398–410, May–June, 1971.     

Some creep properties of AG-4V glass-reinforced plastic

Creep test results for AG-4V glass-reinforced plastic in compression are presented for the temperature range 20–150° C. Some qualitative and quantitative characteristics of the dependence of strain on temperature, stress, and orientation are noted.Mekhanika Polimerov, Vol. 1, No. 5, pp. 30–33, 1965     

Effect of “rest” on creep of glass-reinforced plastic SVAM

The effect of rest on creep of glass-reinforced plastic SVAM is investigated. It is shown that for the cyclic loading regime used (24-h load, 24-h rest) the effect of rest is closely related with orientation of the specimen and with the magnitude of the load.Institute of Mechanics, Academy of Sciences of the Armenian SSR, Erevan. Translated from Mekhanika Polymerov, No. 3, pp. 547–550, May–June, 1974.     

Experimental determination of the transverse shear modulus of a wound glass-reinforced plastic in creep

It is proposed to determine the interlayer shear modulus in creep starting from the results of bending tests on simply supported beams with a concentrated load. It is assumed that the increase in deflection with time is caused by interlayer creep. The data of creep tests on wound glass-reinforced plastic beams are presented and used to determine the long-time interlayer shear modulus.Leningrad. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 370–372, March–April, 1969.     

Stability of glass-reinforced plastic columns

The stability of circular columns of unidirectional glass-reinforced plastic (EF-32-301) is investigated for two types of end conditions: hinged at both ends and one end hinged, the other fixed. The experimental data are compared with theory [1]. A relationship is established between the change in reduced length and the shear parameter.Institute of Hydrodynamics, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 906–910, September–October, 1968.     

Finite-difference method of solving the bending problem for glass-reinforced plastic plates with allowance for creep

A new finite-difference method is proposed for solving the bending problem as it applies to thin rectangular orthotropic plates of linear hereditary material. The proposed method makes it possible to obtain a closed approximate solution in explicit form for a series of finite-difference systems of equations corresponding to the problem of the bending of plates of orthotropic glass-reinforced plastic with allowance for the rheological properties of the material under various boundary conditions.Institute of Cybernetics and Computer Center, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Mekhanika Polimerov, No. 6, pp. 1075–1082, November–December, 1969.     

Bending of prestressed glass-reinforced plastic beams

Initial waviness of the fibers and prestressing are investigated in relation to their effect on flexural stiffness and strength for beams with low shear strength. It is shown that prestressing the reinforcement increases the flexural stiffness but at the same time adds to the shear correction as a result of an increase in the modulus of elasticity E_x in the direction of reinforcement and the insensitivity of the shear modulus G_xz to prestress. It is established that prestressing increases the shear strength and the degree of anisotropy . Materials of two types are investigated: unidirectional (AG-4S) and cloth-reinforced (SKT-11).Mekhanika Polimerov, Vol. 3, No. 5, pp. 888–893, 1967     

Dynamic stability of glass-reinforced plastic shells

The problem of the dynamic stability of circular-cylindrical glass-reinforced plastic shells subjected to external transverse pressure is examined in the nonlinear formulation. After the Lagrange equations have been constructed, the problem reduces to the integration of a system of ordinary differential equations with aperiodic coefficients. The integration has been carried out numerically on a computer for various loading rates and shell parameters. Analogous problems for isotropic metal shells were examined in [1–4]. A review of the subject may be found in [5].Mekhanika Polimerov, Vol. 4, No. 1, pp. 109–115, 1968     

Stability of cylindrical glass-reinforced plastic shells

The stability of cylindrical shells in axial compression has been experimentally investigated. The glass-reinforced plastic shells were fabricated in various ways: by winding glass strand, from glass cloth, and by a combination of the first two methods. The buckling mode and critical load were determined as functions of the ratio of shell radius to shell thickness. A statistical analysis of the test data leads to a formula with an empirical coefficient for use in practical stability calculations.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 5, pp. 886–891, September–October, 1969.     

Creep buckling of glass-reinforced plastic cyclindrical shells

The buckling modes of cylindrical shells made of a polymeric composite with creep properties are considered. The initial imperfections of the shell are characterized by a Fourier series. The time dependence of a large number of harmonics of the Fourier series is investigated by means of nonlinear equations of the Timoshenko type. It is established that some are damped, while others grow at an ever-increasing rate. It is shown that in the course of time the effective shape of the deflections is transformed and at the critical moment the shell buckles in a mode that differs from the shape of the initial deflections.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 697–703, July–August, 1971.     

Mechanical properties of a hollow-fiber glass-reinforced plastic

The strength and elastic properties of a hollow-fiber glass-reinforced plastic are investigated together with the effect of temperature, and long-time and cyclic loading on its mechanical characteristics. The instantaneous moduli of elasticity and the creep kernel parameters are obtained on the basis of the creep diagrams.Translated from Mekhanika Polimerov, No. 2, pp. 341–345, March–April, 1971.     

Optimal reinforcement of a glass-reinforced plastic plate

Relations are derived for the optimal arrangement of the reinforcement in a rectangular glass-reinforced plastic plate supported at the edges and stressed in uniaxial compression by a short-term or long-term, uniformly distributed load. (The optimal arrangement is understood to be that which maximizes the critical load.)All-Union Scientific-Research Institute of Railroad Transport, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 741–744, July–August, 1969.     

Effect of aging on creep of SVAM glass-reinforced plastic in tension with allowance for the orientation of the fibers

The author presents the results of an experimental study of the effect of aging under room conditions on the creep deformation of SVAM glass-reinforced plastic. It is established that with prolongation of the aging period up to two years the resistance of the material to creep deformation increases. The effect of aging is investigated in relation to anisotropy.Mekhanika Polimerov, Vol. 1, No. 6, pp. 20–29, 1965     

Correlation analysis and strength of glass-reinforced plastic pipe

The correlation between certain input characteristics of glass cloth reinforced plastic pipe and product quality is evaluated. The almost total lack of both interfactor and multiple correlation is noted. The parameters that should be controlled in manufacturing pipe for purposes of obtaining the necessary correlation are listed.Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1014–1019, November–December 1968.     

Nonlinear creep of a glass fabric-reinforced plastic in several complex states of stress

Tensile, compressive, torsional, and combined creep tests have been performed on tubular specimens of a glass fabric-reinforced plastic. The sign of the normal stress has been found to have an important influence on the development of the shear creep strains. The rheological parameters of the material necessary for approximating the test curves have been determined and the results of the calculations compared with experiment.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 212–218, March–April, 1973.     

Fracture of a glass-reinforced plastic in cyclic tension-compression

Uniaxial tension-compression tests have revealed the existence of a correlation between the static and cyclic deformation characteristics of a glass-reinforced plastic. The possibility of calculating the cyclic lifetime from the static test data using Bailey's rule and Zhurkov's equation for the time dependence of the strength has been investigated. A method of allowing for the particular characteristics of the fatigue fracture of a reinforced material, based on the correlation between the static and cyclic deformation, is proposed and is found to lead to a considerable improvement in the convergence of the theoretical and actual cyclic lifetimes.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 654–662, July–August, 1971.     

On the theory of anisotropic creep of unidirectional glass-reinforced plastics

The basic relations of the theory of anisotropic creep of unidirectional glass-reinforced plastics (GRPs) in a three-dimensional stress state are found using a model of a material with inhomogeneous structure and the rheological properties of the resin. These relations are suitable for investigating the stress state of GRPs for resin stresses not exceeding certain values. The phenomena of simple creep and stress relaxation are studied with reference to a unidirectional GRP with an epoxy-maleic resin matrix.Mekhanika Polimerov, Vol. 1, No. 2, pp. 64–69, 1965     

Some features of the unwinding of glass-reinforced plastic rings

The reasons for the nonhomogeneity of the material of wound glass-reinforced plastic tubes are discussed. Formulas are given for constructing the shrinkage or temperature stress diagrams for nonhomogeneous tubes by the unwinding method.S. M. Kirov Ural Polytechnic Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 6, pp. 1076–1081, November–December, 1973.