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.     

Adhesion bond and temperature stresses at the polymer - filler interface in polyethylene composites

The temperature stresses in polyethylene composites with fibrous fillers have been estimated. It is shown that they do not represent a threat to the adhesion bond or the cohesion strength of the components of the systems investigated. Model experiments have revealed the presence of an adhesion interaction between the filler and the matrix in the composite itself and have made it possible to estimate the actual threat posed by the temperature stresses. The mechanism of action of the filler particles on the thermal expansion of the composite is explained.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1049–1056, November–December, 1970.     

Investigation of the temperature residual stresses and strains in thick-walled wound reinforced plastic products

The kinetics of the temperature residual stresses and strains in thick-walled reinforced-plastic cylinders and rings have been experimentally investigated employing a special procedure for continuously monitoring the internal strains and stresses in the various zones of the semifinished product during the heat treatment stage. The effect of the resin polymerization (polycondensation) temperature and the mandrel material on the magnitude and distribution of the temperature stresses is considered. The total residual stresses have been determined by a nondestructive strain-gauge method with differentiation of the components.Translated from Mekhanika Polimerov, No. 6, pp. 1040–1046, November–December, 1971.     

Residual stresses in plastic rings reinforced with glass and manufactured with consolidation of the various layers

The residual stresses in thin-wall plastic rings reinforced with glass and prepared by the method of consolidating the layers in combination with various winding regimes have been studied experimentally. It is shown that variation of the winding regime from one layer to another can change the distribution of the stresses through the thickness of the ring.Moscow Energy Institute. Translated from Mekhanika Polimerov, No. 1, pp. 174–176, January–February, 1972.     

Effect of fillers and solvents on the properties of polystyrene coatings

The mechanism of coating formation from solutions of atactic polystyrene in xylene and carbon tetrachloride has been investigated. It has been established that, as the filler content increases, in coatings formed from polystyrene solutions containing an evaporating solvent the growth of the internal stresses and the thermophysical characteristics is characterized by similarity of slope, as distinct from the case of coatings obtained from systems containing a polymerizing solvent. It is shown that the nature of the solvent has an important effect on the character of the interaction at the polymer—filler interface and on the structure and properties of the coatings.Kucherenko Central Scientific-Research Institute of Structural Design. Institute of Physical Chemistry, AS USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1127–1129, November–December, 1968.     

A refined model for three-point bending of sandwich panels. 1. Deflections and bending stresses

Design formulas for the flexural characteristics of sandwich panels under three-point loading by point forces, taking into account local effects, have been derived. Transverse deformation of the normal in the modified model is deduced in terms of the difference between deflections of face layers. It is considered that the rotation of the normal depends also on shear of the filler. The deflections, local curvatures, and bending stresses, dependent on the face-layer thicknesses and transverse characteristics of the filler, are studied. The danger of initial failure caused by the local moment stresses at the central panel section is shown. Comparative estimates refining the conventional designs are established.Institute of Polymer Mechanics, Latvian Academy of Sciences, Riga LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 6, pp. 747–767, November–December, 1997.     

Initial stresses in filament-wound reinforced-plastic rings

Methods of experimentally determining the initial stresses in filament-wound GRP rings are examined and the effect of winding tension is investigated. It is shown that by varying the winding tension it is possible to exercise a considerable degree of control over the magnitude and distribution of the initial stresses.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 505–511, May–June, 1969.     

Experimental determination of residual stresses in wound unidirectional glass-reinforced plastics

The residual stresses in prestressed ring-shaped systems of wound unidirectional glass-reinforced tape have been investigated experimentally. The relation between the residual stress and the winding force has been established. A decrease in the specified prestress is demonstrated. The results of tensile tests on free rings of wound glass-reinforced tape are presented.Mekhanika Polimerov, Vol. 2, No. 1, pp. 123–129, 1966     

Mechanical properties and internal shear stress field in reinforced media as a function of the type of microstructure

The effect of type of microstructure and volume content of filler and binder on the internal stress field and shear modulus has been analyzed for various composite materials. There is an "optimum" filler content at which the maximum stresses in the structure are lowest. A quantitative estimate is obtained for the error of the approximate formulas for the shear modulus of various types of structure.Mekhanika Polimerov, Vol. 3, No. 4, pp. 667–670, 1967     

Effect of a filler on the strength properties of thermosets

The effect of a filler on the strength properties of polymers in tension is investigated. The thermostructural stresses that develop in the composite during cure are taken into account. Relations are given for the strength of the filled polymer as a function of the percentage filler content. In the process of analyzing the thermostructural stresses an analytic expression is obtained for the linear expansion coefficient of the composite with allowance for the structural distribution of the components. Calculated values of the strength and thermostructural stresses are presented for composites with different filler contents. The theoretical determination of the strength of filled polymers is compared with the results of experimental investigations of composites based on epoxy resin filled with quartz dust.Leningrad Mechanical Institute. Translated from Mekhanika Polimerov, No. 1, pp. 97–101, January–February, 1973.     

Winding glass-reinforced plastic rings under programmed tension

The strength, stiffness, and initial stresses of glass-reinforced plastic rings wound under variable tension in accordance with five different programs are considered. The relative thickness of the rings was 0.15–0.20. It is shown that the law of variation of the tension on the tape during winding has an important effect on the investigated parameter.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 361–364, March–April, 1971.     

Variation of certain transverse characteristics over the thickness of wound glass-reinforced plastic rings

The variation of certain transverse characteristics over the thickness of wound glass-reinforced plastic rings has been experimentally determined under normal conditions and at the polymerization temperature of the material investigated. The characteristics in question are used in investigating the state of stress of the ring and the initial fabrication stresses.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 165–167, January–February, 1970.     

Elastic and Sorption Characteristics of an Epoxy Binder in a Composite During Its Moistening

Results of an experimental investigation into the elastic and sorption characteristics of a model composite material (CM) — epoxy resin filled with LiF crystals — during its moistening are presented. Properties of the binder in the CM with different filler contents (v _f = 0, 0.05, 0.11, 0.23, 0.28, 0.33, 0.38, and 0.46) were evaluated indirectly by using known micromechanical models of CMs. It was revealed that, for the CM in a conditionally initial state, the elastic modulus of the binder in it and the filler microstrain (change in the interplanar distance in the crystals, measured by the X-ray method) as functions of filler content had the same character. The elastic modulus of the binder in the CM with a low filler content was equal to that for the binder in a block; the elastic modulus of the binder in the CM decreased with increasing filler content. The maximum (corresponding to water saturation of the CM) stresses in the binder and the filler microstresses as functions of filler content were of the same character. Moreover, the absolute values of maximum stresses in the binder and of filler microstresses coincided for high and low contents of the filler. At v _f = 0.2–0. 3, the filler microstrains exceeded the stresses in the binder. The effect of moisture on the epoxy binder in the CM with a high filler content was not entirely reversible: the elastic characteristics of the binder increased, the diffusivity decreased, and the ultimate water content increased after a moistening-drying cycle.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 499–511, July–August, 2005.     

Inertia effects in circular squeeze film bearing using Herschel–Bulkley lubricants

Recent engineering trends in lubrication emphasize that in order to analyze the performance of bearings adequately, it is necessary to take into account the combined effects of fluid inertia forces and non-Newtonian characteristics of lubricants. In the present work, the effects of fluid inertia forces in the circular squeeze film bearing lubricated with Herschel–Bulkley fluids with constant squeeze motion have been investigated. Herschel–Bulkley fluids are characterized by an yield value which leads to the formation of a rigid core in the flow region. The shape and extent of the core formation along the radial direction is determined numerically for various values of Herschel–Bulkley number and power-law index. The bearing performances such as pressure distribution and load capacity for different values of Herschel–Bulkley number, Reynolds number, power-law index have been computed. The effects of fluid inertia and non-Newtonian characteristics on the bearing performances have been discussed.     

Effect of fillers on the viscosity and viscoelasticity of low-density polyethylene melts. Communication 1

An investigation of low-density polyethylenes filled with up to 30% by volume dispersed particles, has shown that for both the matrix and the composites the apparent viscous flow activation energy does not depend on the shear stresses and increases starting from a certain filler concentration at which the conformation range in the matrix is depleted. The dependence of the relative viscosity of the compositions on the volume filler content is satisfactorily described by an equation that contains the reduced filler concentration, defined as the ratio of the nominal filler concentration to the limiting concentration at which the adsorption layers on the particles extend throughout the matrix. The thickness of the polymer layer adsorbed on the particles must be determined from the specific exterior particle surface, with allowance for the volume of the polymer in the sorption space of the porous filler.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 478–486, May–June, 1976.     

Mechanism by which tension on the fibrous filler affects the structure and the strength of wound glass-plastics

Conclusions 1. We have studied how the structure of glass-plastics wound with twisted threads is affected by tension on the fibrous filler. The trend of changes in fiber content and porosity, as well as an increasingly nonuniform distribution of the reinforcing filler over the thickness, has been established.2. The effect of a nonuniform filler distribution over the thickness on the tensile strength has been evaluated. The calculated and the experimental curve of strength as a function of the tension have been compared, the former taking into account variable porosity, fiber content, and nonuniformity of fiber distribution over the thickness.3. It has been demonstrated that the change in the strength characteristics of a wound glass-plastic as a function of the tension on the reinforcing filler during winding is due to a combined complex effect of such factors as the overall fiber content and porosity, a nonuniform fiber distribution over the thickness, the fiber orientation, and the degree of mechanical damage in threads due to their interaction with the active components of the winding machine.Report presented at the Third All-Union Conference on Polymer Mechanics. Riga, November 10–12, 1976.Translated from Mekhanika Polimerov, No. 3, pp. 439–444, May–June, 1977.     

Results of an experimental investigation of the residual stresses in wound glass-reinforced plastics

The results of an experimental investigation of the residual stresses in wound glass-reinforced plastic rings are presented. The residual stresses were determined by the Davidenkov method. The dependence of the maximum tensile and compressive circumferential stresses on ring thickness and polymerization temperature is investigated. The experimental data are compared with the results of calculations based on the theory proposed in [1, 2].Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1116–1119, November–December, 1970.     

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     

Calculation of the residual stresses in wound glass-reinforced plastic parts when the material characteristics vary over the thickness

The thermoelastic residual stresses in anisotropic rings and cylinders with characteristics that vary over the thickness are determined. The calculation of the stresses in wound glass-reinforced plastic parts is illustrated by examples.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga, Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 686–691, July–August, 1971.     

Stability of cylindrical casings of fiberglass plastic having an elastic filler under the action of axial compression,external pressure,and twisting

The stability of orthotropic cylindrical casings containing a filler is studied under the action of axial compression, external pressure, or twisting. Analogies with plates are established for sufficiently stiff fillers. Simple formulas are obtained for calculating critical stresses which are convenient for practical application.Translated from Mekhanika Polimerov, No. 3, pp. 484–489, May–June, 1974.