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.     

Structural residual stresses in oriented glass-reinforced plastics

A previously proposed method is used to obtain expressions for calculating the residual stresses as a function of the physicomechanical properties of the polymer matrix and the reinforcement ratio. The calculation results are presented and the corresponding state of stress and strain analyzed. There are considerable deviations (in the magnitude and distribution of the stresses) from models that neglect or only take partly into account the interaction of the fibers.Moscow Ordzhonikidze Aviation Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1051–1058, November–December, 1968.     

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.     

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 residual stresses on the strength of oriented glass-reinforced plastics

The effect of structural residual stresses on the strength of a glass-reinforced plastic loaded along and across the fibers is investigated. It is established that the residual stresses lead to an increase in the strength of the glass-reinforced plastic across the fibers and to cracking of the polymer matrix in tension along the fibers, but have practically no effect on the combined deformation of the matrix and the fibers in compression.Moscow Ordzhonikidze Aviation Institute. Translated from Mekhanika Polimerov, No. 3, pp. 475–480, May–June, 1969.     

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.     

Investigation of internal stresses in glass-reinforced plastics

The strength properties of and internal stresses in epoxy and epoxyphenol resins and GRPs based on them are investigated using an optical method of determining internal stresses. The GRPs had tape and fabric reinforcement. Compared with the internal stresses in unplasticized specimens, the stresses in pure resin films and in GRPs based on plasticized resins are found to be smaller. It is shown that the distribution of internal stresses in GRPs is anisotropic. The highest internal stresses are observed in tape-reinforced GRPs in a direction normal to the fibers. Glass reinforcement in two directions at right angles reduces the internal stresses in GRPs as compared with pure resin films. In both reinforced and unreinforced films, the internal stresses depend on the curing conditions.Mekhanika polimerov, Vol. 1, No. 1, pp. 82–88, 1965     

Coefficients of thermal expansion of unidirectional glass-reinforced plastics

In order to verify the theoretical formulas for calculating expansion coefficients the author has conducted tests on AG-4S unidirectional glass-reinforced plastics. The coefficients have been determined along and across the reinforcement at temperatures from 20 to 100° C. The experimental data are compared with the theoretical calculations. The anisotropy of thermal expansion, the scatter of the experimental data, and the temperature dependence of the expansion coefficients are discussed.Mekhanika Polimerov, Vol. 4, No. 3, pp. 568–570, 1968     

Theory of shrinkage stresses in oriented glass-reinforced plastics

The problem of shrinkage stress distribution in glass-reinforced plastics is examined on the basis of an improved model under certain assumptions concerning the nature of the curing process. Cylindrical tubes of epoxy glass-reinforced plastic are investigated under stepped temperature conditions.Mekhanika Polimerov, Vol. 1, No. 6, pp. 61–68, 1965     

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     

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.     

Determination of residual stresses in plastics

A method is proposed for calculating the residual stresses in hot-molded plastics parts. Data are presented for a polyester glass-reinforced plastic.Mekhanika Polimerov, Vol. 3, No. 5, pp. 827–832, 1967     

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.     

Change in the degree of anisotropy of unidirectional glass-reinforced plastics during winding

The change in the degree of anisotropy of the principal elastic and strength properties of unidirectional glass-reinforced plastics during the winding process is described. Two such materials — LSB-F and LSO-R-2M — have been experimentally investigated. The anisotropy of the elastic properties is characterized by the parameter and that of the strength properties by the parameter =/_r.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 953–956, September–October, 1970.     

Resistance of wound glass-reinforced plastics to failure by unwinding

The debonding of wound glass-reinforced plastics is examined from the statistical standpoint. The statistical stress intensity distribution function characterizing the fracture toughness is obtained. The effect of defect size on the critical nominal stresses is discussed.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 5, pp. 881–885, September–October, 1969.     

Relationship between strength characteristics of unidirectional glass-reinforced plastics and their composition

The article discusses the effect of the amount of binder present and the porosity of the glass reinforced plastic on the usable strength of the glass fibers, the tensile strength, and the elasticity module in stretching. It is shown that a relationship exists over the whole range tested between the volume ratio of the components (binder and glass fiber), certain strength characteristics, and porosity. A method is suggested for the comparison of glass-reinforced plastics according to their usable fiber strength which can be used for the selection of the best binder, the glass material, the glass composition, glass fibers, the lubricant, the technological scheme, etc.Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 477–480, May–June, 1970.     

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.     

Determination of the magnitude and distribution of the initial stresses in glass-reinforced plastics

The stresses that develop in the resin at and near the glass-resin interface during the curing of polyester and epoxy glass-reinforced plastics have been experimentally studied by the photoelastic method. The volume state of stress in three mutually perpendicular directions in various sections and in the danger zones is qualitatively and quantiatively described. It is established that the stresses investigated may be the cause of cracking that reduces the tightness and strength of the glass-reinforced plastic.I. M. Gubkin Moscow Institute of the Petrochemical and Gas Industry. Translated from Mekhanika Polimerov, No. 4, pp. 661–667, July–August, 1973.     

Determination of the magnitude and distribution of the initial stresses in glass-reinforced plastics

Photoelastic stress analysis is used to demonstrate the effect of coupling agents on the residual microstresses, i.e., the stresses that develop at near the glass-resin interface during the curing of polyester and epoxy glass-reinforced plastics and, as a rule, remain throughout the life of the product. Coupling agents of different chemical composition applied to the surface of the glass fibers have different effects on the components of the state of stress and thus can act as a powerful regulating factor.