Elastic constants of glass-reinforced plastics with anisotropic structure

The macroscopic elastic constants of plastics reinforced in one direction are calculated by solving the statistical boundary value problem of the theory of elasticity. The results obtained and the method proposed in [15] are used to compute the macromoduli of GRP with an anisotropic layered structure created by an orthogonal arrangement of unidirectional tapes and to compute the moduli of elasticity of a unidirectional layered material with random deviations of the layers from the direction of preferred orientation.V. A. Steklov Mathematical Institute, Academy of Sciences of the USSR, Sverdlovsk Branch. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 631–637, July–August, 1968.     

Strength of glass-reinforced plastics in the complex stress state

A new criterion of strength is proposed for anisotropic materials of the glass-reinforced plastic type. This criterion takes into account not only the different ultimate strengths in tension and compression in each direction but also the dependence of the ultimate shear strengths on the sign (direction) of the shear stresses. The criterion is given in tensor invariant form, so that it can be rewritten for any direction of the glass fibers. The criteria proposed by other authors, in particular, R. Hill's condition of plasticity [1], follow from the new generalized criterion as special cases. The results of experiments conducted both by the authors of the present article and by other investigators provide good confirmation of the proposed criterion.Mekhanika Polimerov, Vol. 1, No. 2, pp. 70–78, 1965     

Experimental methods of investigating the state of stress of glass-reinforced plastic shells

A method of testing glass-reinforced plastic shells under external hydrostatic pressure is described together with a procedure for determining the elastic properties of the material of which the shell is composed. Test data on the strength and stability of shells subjected to external hydrostatic pressure are presented.Leningrad. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 157–163, January–February, 1969.     

Statistical characteristics of the mechanical constants of glass-reinforced plastics

The results of statistical treatment of experimental data on the physicomechanical properties of glass-reinforced plastics, based on alkali-free, aluminoborosilicate glass fibers (composition NS-55/6) with paraffin as lubricant and epoxyphenolbutyral composition EFB-4, obtained from tensile tests on flat specimens prepared by "wet" winding on a mandrel, are given. The data can be used for evaluating the effect of the scatter of the mechanical constants of a composite material on the efficiency of a structure and its elements.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1125–1128, November–December, 1972.     

Elastic and strength characteristics of a glass-reinforced plastic in compression

The elastic constant and strength characteristics in compression have been experimentally determined for a cold-cured glass-reinforced plastic in the direction of all three principal axes of anisotropy. It is shown that the elastic constants obtained satisfy the constraints imposed on orthotropic materials by the thermodynamic relations.Translated from Mekhanika Polimerov, No. 5, pp. 866–869, September–October, 1970.     

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     

Experimental-theoretical analysis of the state of stress and strain of stiffened glass-reinforced plastic shells subjected to local loads

The state of stress and strain of stiffened glass-reinforced plastic shells subjected to local loads applied to the stiffeners is investigated with allowance for interlaminar shear strains over the thickness of the glass-reinforced plastic. The solution is based on Vlasov's semimembrane theory. A comparative experimental-theoretical investigation has been made using models subjected to radial and axial loads and twisting moments.     

Effect of temperature and anisotropy on the elastic constants of oriented glass-reinforced plastics

The experimental temperature dependence of the modulus of elasticity and Poisson's ratio are presented for SVAM oriented glass-reinforced plastic. The possibility of treating SVAM sheet as orthotropic at elevated temperatures is demonstrated.Institute of Chemical Physics, AS USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1026–1032, November–December, 1968.     

Procedure for determining the elastoplastic anisotropy constants and creep characteristics of glass-reinforced plastics

The dependence of the parameters of the static stress-strain and creep diagrams on the gage width and length of the specimen has been experimentally investigated. Other technical factors — the accuracy with which the specimen is mounted in the grips or wedges, the transverse strain distribution, and Saint Vanant's principle — are also considered. Recommendations are given for selecting the principal dimensions of test specimens of composites with various structures.State Scientific-Research Institute of Machine Science, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 747–754, July–August, 1970.     

Elastic constants of randomly reinforced plastics

A previously developed [4] general method of solving the nonlinear (in the statistical sense) boundary value problem of the theory of elasticity is used to determine the macroscopic moduli of elasticity of randomly reinforced plastics whose structure is simulated by a two-phase microinhomogeneous medium. The macroscopic modulus is represented in the form of a series composed of the sum of the mean value of the modulus and a sequence of corrections that take into account the central moments of the distribution of elastic constants. The limits of convergence of this series are established. The values of the macroscopic moduli for a glass-reinforced plastic obtained by calculation are compared with the experimental data.Mekhanika Polimerov, Vol. 3, No. 2, pp. 259–265, 1967