Behavior of composite cylindrical shells subjected to nonuniform heating

Nonlinear differential equations describing the thermoelastic behavior of closed orthotropic circular shells under nonuniform heating conditions are obtained; the temperature dependence of the elastic parameters of the material is taken into account. The problem of the stability of a glass-reinforced plastic shell hinged to fixed supports and heated nonuniformly over the thickness is solved. The results of tests on 27–63SV glass-reinforced plastic shells heated and subjected to additional compressive loads at various levels are presented. The theoretical and experimental data are compared.Zukovskii Air Force Engineering Academy. Translated from Mekhanika Polimerov, No. 2, pp. 284–292, March–April, 1971.     

Stability of axially compressed cylindrical composite shells in the presence of nonstationary heating

The problem of smooth cylindrical composite shells uniformly compressed in the axial direction and subjected to nonstationary heating is solved in the linear quasi-static formulation. Expressions are obtained for the critical loads and their regions of application are determined. The calculations are compared with experimental data obtained by linearly heating the outer surface of axially compressed smooth cylindrical shells of glass-reinforced plastic based on phenol-formaldehyde resin.Zhukovskii Central Aerohydrodynamic Institute, Moscow Region. Translated from Mekhanika Polimerov, No. 2, pp. 289–297, March–April, 1973.     

Bending of glass-reinforced plastic beams subjected to a pulsed distributed load created by electromagnetic fields

The behavior of glass-reinforced plastic beams subjected to the action of a pulsed-distributed load is examined. The use of an electrodynamic apparatus producing a powerful magnetic field is described. Procedures for making strain-gauge measurements and recording the forces are outlined. The applicability of the Timoshenko theory to the dynamic bending of glass-reinforced plastic beams is demonstrated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 868–873, September–October, 1974.     

Experimental testing of the applicability of a fourth degree polynomial in describing surfaces of equicritical planar stress distributions in glass-reinforced plastics

The possibility of using a fourth degree polynomial for calculating the anisotropy of glass-reinforced plastics in the planar stress state is evaluated experimentally. The experiments were carried out on industrial specimens of glass-reinforced plastic tubes loaded with an internal pressure, and subjected to an axial tensile force and a torque. Surfaces of equicritical planar stress distribution were constructed for the material of the glass-reinforced plastic tubes. The experimental and theoretical values of the breaking stresses were compared statistically. Most of the experimental values of the breaking stresses were found to lie within the confidence intervals of their theoretical values.S. M. Kirov Timber Technology Academy, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 284–294, March–April, 1970.     

Torsional stability of a glass-reinforced plastic cylindrical shell with an elastic core

The problem of the stability of a glass-reinforced plastic cylindrical shell with an elastic core subjected to twisting moments applied to the edges of the shell is considered. As in various other studies [4–6], the glass-reinforced plastic is treated as an elastically orthotropic material. The core is treated as an isotropic elastic cylinder, whose outer surface is bonded to the shell. Expressions for the critical stresses are obtained for an infinitely long shell and a shell of finite length.Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1082–1086, November–December, 1970.     

Stability of a flexible orthotropic plate with free edges

An investigation is made into the postcritical behavior of rectangular flexible orthotropic plates under the action of distributed and concentrated loads. In particular, glass-reinforced plastic plates with different ratios of the moduli of elasticity are studied. The calculation is performed by the method of successive approximations, using finite differences, on a BESM-2M computer. The solutions obtained are compared with experimental data.Mekhanika Polimerov, Vol. 2, No. 4, pp. 585–592, 1966     

Stability of glass-reinforced plastic shells with allowance for shear stresses

The stability of a cylindrical glass-reinforced plastic shell subjected to external pressure is considered in the geometrically nonlinear formulation with allowance for initial irregularities. The refined shell theory [6, 7], which enables transverse shear strains to be taken into account, is employed. A general algorithm of the solution has been written in ALGOL-60. A numerical solution of the problem has been obtained on a BÉSM-3M computer. Critical loads have been determined over a wide range of variation of the geometrical and physical parameters of the shell. It is established that the difference between the results of the classical and refined theories depends on the thickness, length, and physical parameters of the shell. The classical theory is asymptotically exact as the thickness of the shell tends to zero or the interlaminar shear modulus tends to infinity.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 857–862, September–October, 1969.     

Calculation of the residual stresses in wound glass-reinforced plastics

The effect of the winding and polymerization conditions on the residual stress distribution in wound glass-reinforced plastic cylinders is subjected to a numerical analysis. The calculations are based on the method proposed in [1]. The computer data are examined and the theoretical and experimental results compared.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1026–1030, November–December, 1970.     

Time-temperature superposition applied to the relaxation properties of a glass-reinforced plastic and its matrix

The relaxation behavior in compression of an unsaturated polyester resin and the corresponding glass-reinforced plastic has been investigated. The time-temperature superposition principle is shown to be applicable to the cross-linked polyester resin and the glass-reinforced plastic. The temperature dependences of the shift functionsa _T of the resin and the glass-reinforced plastic are found to satisfy an Arrhenius equation with the constant equal to 21–25 kcal/mole.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 360–363, March–April, 1972.     

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.     

Strength of glass-reinforced plastic rings loaded with internal pressure

The relation between the internal bursting pressure and the thickness of rings made of unidirectional glass-reinforced plastic has been experimentally investigated. It is shown that the carrying capacity of the rings is limited owing to the low strength of the glass-reinforced plastic in compression perpendicular to the fibers.Mekhanika Polimerov, Vol. 4, No. 1, pp. 131–135, 1968     

Apparatus for fatigue testing glass-reinforced plastic specimens in symmetrical tension-compression at acoustic frequencies

The characteristics of an electromechanical apparatus for fatigue testing glass-reinforced plastic specimens in symmetrical tension-compression at loads up to 10–40 kN and acoustic frequencies on the interval 300–5000 Hz are described.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 525–528, May–June, 1972.     

Carrying capacity of thick-walled glass-reinforced plastic rings operating under pressure

Experimental data are presented on the carrying capacity and deformability of thick-walled rings made of unidirectional and two-way glass-reinforced plastic subjected to external and internal pressure. A limitation on the carrying capacity of the rings with increase in relative thickness is noted; an explanation of this effect is offered.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1130–1132, November–December, 1971.     

Dynamic stability of axisymmetrically heated glass-reinforced plastic cylindrical shells bonded to elastic cylinders

The dynamic stability of glass-reinforced plastic shells subjected to the action of a longitudinal pulsating force and an external, uniformly distributed load is examined. The shells are orthotropic, and their elastic properties are temperature-dependent and vary over the thickness of the wall. It is assumed that the elastic cylinder forms a Winkler foundation. Three boundary conditions are investigated.Moscow Institute of Chemical-Machine Building. Translated from Mekhanika Polimerov, No. 2, pp. 331–337, March–April, 1972.     

Strength of reinforced plastics under static loading

The question of the static fatigue of reinforced plastics is considered for plane stress. Relations that predict the static fatigue are given for very simple types of loading. Experimental data are presented for thin-walled tubes of SVAM (5:1) glass-reinforced plastic subjected to long-time tests at constant internal pressure.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 265–273, March–April, 1969.     

Stresses in plastics reinforced with anisotropic fibers and subjected to transverse normal loading

The question of the stress distribution in plastics reinforced with anisotropic fibers and subjected to transverse normal loading is considered. The stresses in the components are determined by the methods of the theory of elasticity using stress functions. The theoretical relations obtained are used to construct diagrams showing the distribution of the tangential, radial, and shear stresses in the composite and the isoclines of the concentration coefficient for a carbon-reinforced plastic. The results obtained for the carbon-reinforced plastic are compared with the analogous results for a glass-reinforced plastic.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 244–252, March–April, 1973.     

Effect of the end conditions on the critical loads for filament-wound glass-reinforced plastic columns

The behavior of glass-reinforced plastic columns with various end conditions has been experimentally investigated. The cross-wound columns had a length to mean diameter ratio of 18–20. Four types of support with different degrees of restraint on end rotation ranging from almost free ends to fixed ends were employed. The possibilities of increasing the critical loads by manipulating the boundary conditions are estimated. Numerical estimates are obtained for the various methods of support. Random imperfections and the number of loadings were not found to have any effect on the critical loads. It is shown that the use of Southwell's method makes it possible to estimate the critical loads for columns with different end conditions from the subcritical loading data.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 54–62, January–February, 1976.     

Effect of climatic loading on the residual stresses and carrying capacity of thick-walled glass-reinforced plastic rings

The effect of climatic loading on the carrying capacity of thick-walled glass-reinforced plastic rings with different residual stress levels has been experimentally investigated. It is established that the rings with the greater residual stress level have a lower maximum breaking load. The carrying capacity of the rings is reduced after simulated aging. This effect is shown to be more sharply expressed in the experiments in which the rings were subjected to dynamic loading.Translated from Mekhanika Polimerov, No. 6, pp. 1132–1134, November–December, 1971.     

Bending of a cantilevered glass-reinforced plastic cylindrical shell weakened by a circular opening

The stress concentration is investigated in the neighborhood of a circular opening in a cantilevered glass-reinforced plastic cylindrical shell with a concentrated load at the free end. The problem is solved by the Bubnov method using a Ural-2 computer. The theoretical results have been checked experimentally on glass-reinforced plastic shells.All-Union Correspondence Polytechnic Institute, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 152–157, January–February, 1970.