Effect of fiber tension on the unwinding resistance of hardening layers of glass-reinforced plastic

The shear fracture toughness characteristics of glass-reinforced plastics used for strengthening metal pressure vessels have been determined by testing metal-GRP rings. The shear fracture toughness characteristics are statistically estimated for a unidirectional GRP as a function of the winding tension.K. É. Tsiolkovskii Moscow Aviation Engineering Institute. Translated from Mekhanika Polimerov, No. 5, pp. 935–938, September–October, 1975.     

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.     

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.     

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.     

Statistical characteristics of the mechanical properties of glass-reinforced plastics

A statistical analysis has been made of experimental data on the mechanical properties of a glass-reinforced plastic based on T₁ glass fabric (Soviet standard GOST 8481-61) and IF-ÉD-6 epoxy resin (Elektroizolit Plant, tech. spec. TU 26-59) obtained by testing specimens cut from the waste of wound cylindrical shells. The data obtained can be used for estimating the mechanical reliability of products composed of glass-reinforced plastics of this type.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 131–134, January–February, 1971.     

A rheological model of polymers and glass-reinforced plastics

Network polymers and the corresponding glass-reinforced plastics are investigated for a homogeneous uniaxial state of stress and constant temperature. A physical law relating the high-elastic strain and the stress in explicit form with once-determined structural constants is obtained for the damped (bounded) creep regime. The theoretical solutions are compared with the experimental data for a glass-reinforced plastic based on unsaturated polyester resin and glass mat reinforcement.Institute of Engineering Mechanics, Bulgarian Academy of Sciences, Sofia. Translated from Mekhanika Polimerov, No. 5, pp. 851–857, September–October, 1971.     

Investigation of the anisotropy of the properties of glass-reinforced plastic shells

The load-carrying capacity and deformation of cylindrical and conical glass-reinforced plastic (ÉDT-10 resin) shells loaded in axial compression have been investigated experimentally in relation to the orientation of the fabric reinforcement. The results of the tests are compared with the relations of the theory of elasticity of an orthotropic body.Zhukovskii Central Aerohydrodynamics Institute, Moscow Region; Scientific Research Institute of Production Technology and Organization, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 814–818, September–October, 1969.     

Creep of unidirectional glass-reinforced plastics based on new types of fibers

Theoretical and experimental compressive creep relations for a unidirectional glass-reinforced plastic based on hollow fibers are presented. The agreement between the theoretical and experimental data is shown to be satisfactory. The effect of fiber capillarity on the creep process is unimportant.All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Fiber Glass, Moscow; Institute of Mechanics of Machines and Polymeric Materials, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Mekhanika Polimerov, No. 4, pp. 747–750, July–August, 1971.     

Nonlinear creep of TS8/3-250 glass-reinforced plastic

The creep and recovery of a glass-reinforced plastic are investigated within the frame-work of a nonlinear hereditary model. The material characteristics are determined for the three principal directions. The proportionality of the kernels is established.State Scientific-Research Institute of Machine Science, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 391–397, May–June, 1971.     

Relaxation characteristics of glass-reinforced plastics

A study was made of the relaxation properties of glass-reinforced plastics KAST-V, ÉDF, SVAM, and Textolite. The article gives experimental and theoretical values of the pliabilities and tables of the values of the relaxation properties required for the solution of boundary value problems in viscoelasticity.M. V. Lomonosov State University, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 560–562, May–June, 1970.     

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     

Creep and long-time strength of oriented glass-reinforced plastics in interlaminar shear

The creep and long-time strength in interlaminar shear and the creep in compression in the direction of the reinforcement have been experimentally investigated for certain types of oriented glass-reinforced plastics. The specimens in the interlaminar creep tests took the form of short beams loaded in bending. The experimental creep data for shear and compression are well described by the hereditary theory with a kernel of the Abel type (shear) or in the form of a Rabotnov function (compression). If the stresses are constant in time, good agreement with experiment is also given by Findley's form of the aging theory. A deformation criterion of interlaminar shear strength is also obtained. The experimental curves and values of the creep and long-time strength constants are presented.Translated from Mekhanika Polimerov, No. 6, pp. 1003–1012, November–December, 1971.     

Critical compressive stresses in cylindrical shells composed of orthotropic layers with different orientations

The laws of variation of the strains and critical stresses for smooth thin circular cylindrical glass-reinforced plastic shells based on ÉDT-10P resin have been experimentally investigated at different orientations of the fabric reinforcement. The results of the tests are compared with the theoretical data obtained from the relations of the theory of elasticity of an orthotropic body and orthotropic shells.N. E. Zhukovskii Central Aerohydrodynamic Institute of Production Technology and Organization, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 684–690, July–August, 1973.     

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     

Inelastic constants of oriented glass-reinforced plastic as a function of temperature

Experimental data are compared with theory for certain laws of inelastic deformation of oriented glass-reinforced plastic of the SVAM type at elevated temperatures. The possibility of describing the creep process by means of a nonlinear constitutive equation is considered. The existence of a discrete relaxation-time spectrum is demonstrated in connection with long-term creep. The experimental and theoretical results are compared with allowance for the discrete relaxation-time spectrum. The agreement is shown to be perfectly satisfactory.Mekhanika Polimerov, Vol. 3, No. 2, pp. 279–285, 1967     

Creep strength of anisotropic plates taking account of transverse shear strains

Cylindrical creep buckling of an orthotropic glass-reinforced plastic plate is investigated with consideration of shear creep in the plane xz. In this case the rheology of buckling is not described by the Kirchhoff-Love model, therefore the investigation is carried out using the modified theory of plates [3]. The long-time and instantaneous critical forces are obtained.Mekhanika Polimerov, Vol. 1, No. 5, pp. 114–117, 1965     

Creep of SVAM (5:1)-B in different directions in the plane of the sheet at low stresses

On the basis of an experimental investigation of the creep of SVAM glass-reinforced plastic in different directions it is proposed to calculate orthotropic plates starting from the theory of elasticity of an anisotropic body with allowance for the dependence of the constants on time.Mekhanika Polimerov, Vol. 3, No. 1, pp. 35–40, 1967     

Probability characteristics of the shear modulus of glass-reinforced plastics

The results of tests on wound glass-reinforced plastic specimens based on ÉFB-4 epoxy-phenolic-butyral composition and NS 55/6 glass strand reinforcement with a paraffin finish have been subjected to a statistical analysis with the object of determining the probability characteristics of the shear modulus. The shear modulus is determined for unidirectional structures and structures with reinforcement ratios of 1:1, 1:2, and 3:2. The results of the tests are used to determine the mathematical expectation, variance, and probability density function of the shear modulus.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 1, pp. 160–162, January–February, 1973.     

Elastoplastic stability of glass-reinforced plastic plates with a central metal layer

The problem of the stability of a three-layer plate with a central plastic layer of metal sandwiched between elastic glass-reinforced plastic outer layers is considered. The presence of a metal layer restrains the development of creep strains in the glass-reinforced plastic and makes it possible to neglect the viscous strain components. The general equations of the problem are obtained, and the approximate Il'yushin formulation [1] is considered. An example is presented for a rectangular plate in pure shear. It is shown that the elastic anisotropic layers play the part of a load-relieving system for the central plastic layer [3], which results in an increase in the over-all critical load for the layered plate.Kalinin Polytechnic Institute. Translated from Mekhanika Polimerov, No. 5, pp. 909–915, September–October, 1969.     

Creep equations for orthotropic material based on the theory of local deformations

By introducing a time factor into the local deformation function, the theory of local deformations can be used to unite the theories of plasticity and creep. The local deformation function is taken as a rheological dependence in the form of an integral equation, and it is assumed to vary in a way that depends on the direction relative to the principal isotropic axes. Thus, equations are obtained for an orthotropic material with nonlinear creep. The relations obtained also allow for the variation of Poisson's ratio with time. It is shown that special cases of these expressions were previously used to describe the creep of glass-reinforced plastics at low stresses.Mekhanika polimerov, Vol. 1, No. 1, pp. 44–49, 1965