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.     

Calculation of the residual stresses and strains in wound reinforced-plastic products

A method is proposed for determining the residual stresses and strains in wound glass-reinforced plastic products. The fabrication process is divided into five stages: winding, heating polymerization, cooling, and removal from the mandrel. The initial stresses that develop during winding and the subsequent stress increment associated with heating are taken into account. Polymerization is treated as a process during which the mechanical and thermophysical properties of the material change. Chemical shrinkage of the resin and its filtration through the fiberglass are disregarded. Equations are derived for the residual radial and peripheral stresses in the finished product, for the residual change in inside diameter, and for the temperature at which the product is released from the mandrel during the cooling process. The experimental data relating to two types of wound products are discussed. The results of a computation of the residual stresses and the residual changes in inside diameter are compared with the experimental data.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 134–139, January–February, 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     

Residual stresses in glass-reinforced plastics parts

The determination of the residual stresses in glass-reinforced plastics elements is considered. It is shown that these stresses reach appreciable values and should be taken into account in strength calculations. Quantitative data are supplied for a series of materials. At normal operating temperatures the residual stresses are stable.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1117–1119, November–December, 1969.     

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.     

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.     

Residual stresses in glass-reinforced polyethylene

The variation of the axial and radial components of the residual stresses in fiber-reinforced polyethylene with distance from the fiber has been investigated. It is shown that, irrespective of the agent employed, coupling leads to an increase in stresses. The values obtained for the residual stresses are compared with the adhesion strength determined by the shearing method. The effect of a structure-forming agent on the residual stresses is investigated.Mendeleev Moscow Chemical Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 722–724, July–August, 1971.     

Experimental study of the effect of technological parameters on the residual stresses in thin-walled coiled parts

The effect of the parameters of heat treatment and programmed winding under tension on the residual stresses in thin-walled coiled parts made from glass plastic by the "dry" winding of a heated glass strip on an unheated mandrel is studied experimentally. The effect of the thickness of the parts on the maximum radial residual stresses is considered. A method is proposed for regulating the residual stresses in parts with very thick walls.Translated from Mekhanika Polimerov, No. 1, pp. 75–80, January–February, 1972.     

Residual stress distribution in different types of adhesion joints

The results of a photoelastic investigation of the distributions of shrinkage and temperature residual stresses in glued joints and coatings are compared. The degree of nonuniformity of the residual stress distribution over the length and thickness is determined as a function of the scale factor. It is shown that the bulk of the residual stresses in metal joints glued with K-115 epoxy adhesive are temperature stresses, which may reach 130 kgf/cm². The shrinkage and temperature residual stress distributions are similar in character.Kucherenko Central Scientific-Research Institute of Building Structures. Translated from Mekhanika Polimerov, No. 4, pp. 738–742, July–August, 1971.     

Thermoelastic problem for a circular cylinder of reinforced multilayer material

The temperature stresses and displacements are determined in an elastic circular cylinder of reinforced multilayer material. The relationship between the displacements of the inside and outside surfaces of the cylinder and the radial stresses and the mechanical and thermophysical properties of the components, the reinforcement ratio, and the ratio of the radii is investigated. The results are used to interpret the behavior of wound glass-reinforced plastic products under varying temperature conditions and during the curing stage.Mekhanika Polimerov, Vol. 3, No. 1, pp. 136–141, 1967     

Analysis of the technological stresses in wound components made out of composites during the whole duration of the preparation process

Conclusions The application of a discrete winding scheme and the relationships of the theory of filtration consolidation and the theory of unstable viscoelastic media to the calculation of the technological stresses allows one to take account of the most important technological factors and to describe the overall process involved in the preparation of wound components from laminar composites. The power winding stage and the nonisothermal heat-treatment stage make the greatest contribution to the magnitude of the technological stresses.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 500–508, May–June, 1980.     

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.     

Taking account of heat transfer in locally heated thermoelastic plates made out of composite materials

Conclusions The proposed approach to the determination of the thermal stress state of thin plates made out of composite materials permits taking into account the effect of the coefficient of heat transfer from a region of local heating outside of it. The significant effect of heat transfer from the heating zone on the temperature field and the stresses indicates the necessity of taking it into account in connection with calculations on the strength of composite plates subjected to local heating.Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 1027–1030, November–December, 1979.     

Variation of the residual stresses during the fabrication of thick-walled wound glass-reinforced plastic articles

The results of an experimental investigation of the development of the residual stresses in thick-walled glass-reinforced plastic cylinders during the fabrication process are presented. The variation of the stresses from the beginning of winding to removal of the cyclinders from the mandrel is examined.Translated from Mekhanika Polimerov, No. 2, pp. 355–357, March–April, 1974.     

Formation of residual stresses in components made out of laminated and fibrous composites during the hardening process

Conclusions The application of the theory of the viscoelasticity of unstable media to the calculation of the residual stresses enables one to reveal effects due to the change in the properties of a solidifying binder under different sets of operating conditions for the technological process. At the same time, it once again confirms that thermal shrinkage makes a significantly larger contribution to the magnitude of the residual stresses than chemical shrinkage. The absolute values of the stresses are in satisfactory agreement with results that were obtained using simpler calculational schemes.Moscow Power Institute. Translated from Mekhanika Polimerov, No. 5, pp. 790–795, September–October, 1976.     

Experimental study of the effect of the technological factor of rolling-in (packing) on the physicomechanical properties of glass plastic

Conclusions 1. The rolling-in (packing) of wound glass-plastic objects is a favorable technological factor, improving the homogeneity of the material, increasing the elastic and strength characteristics of the glass plastic, and reducing the thermal expansion coefficients and macroscopic residual stresses due to the thermal shrinkage of the objects.2. However, extremely large packing forces may reduce certain of the mechanical characteristics of the material, chiefly the strength and modulus relating to interlayer shear.Moscow Power Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1043–1047, November–December, 1976.     

Effect of technological factors on the mechanical reliability of structures made from composites

Research on the effect of technological factors on the strength of reinforced-plastics structures is reviewed. Attention is concentrated on structures in the form of bodies of revolution fabricated by the winding technique. The influence of the winding parameters and the curing regime on the residual stresses is discussed. Data on the variation of the mechanical properties of the resin in the course of the curing process are examined. The contributions of chemical and thermal shrinkage to residual stress formation are compared. Methods of reducing the residual stresses are considered.Presented at the 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 3, pp. 529–540, May–June, 1972.     

Comparison of methods of investigating the components of the elongation of textile fibers

Resolving the elongation of textile fibers into its components (rapidly disappearing, slowly disappearing, and residual) provides valuable information on the mechanical properties and makes it possible to predict a series of mechanical characteristics of the fabrics into which they are made. The optimal methods of determining these components are established.Moscow Textile Institute. Translated from Mekhanika Polimerov, No. 3, pp. 444–450, May–June, 1972.     

Determination of the residual stresses in wound glass-reinforced plastic rings

The stresses that develop during winding in wound glass-reinforced plastic rings change during polymerization, when the modulus of elasticity in the radial direction is reduced by heating. Further changes occur in connection with cooling and removal from the mandrel. The theoretical relations obtained for determining these stresses are found to be confirmed by experiment.Bauman Moscow Higher Technical College. Translated from Mekhanika Polimerov, No. 5, pp. 892–898, September–October, 1969.     

Effect of heat treatment on the distribution of residual stresses and the properties of epoxy polymers

Conclusions The analysis of the experimental data showed that heat treatment results in a reduction in the stressed state of a polymer, which affects the tensile strength of the material to a greater degree than the compressive strength. During heat treatment, significant changes take place in sections of the polymer damaged by the effect of residual compressive stresses and sections in which the residual stresses change sign. The quantitative relations in the change in the tensile strength of the material in these two sections make it possible to explain the mechanism of the effect of heat treatment and to predict its character.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 787–790, September–October, 1986.