Compensation of thermal stresses in glass-fiber-reinforced plastic articles by the layerwise winding method

The contact pressures which must be created during winding with layerwise hardening in order to compensate radial stresses on the contact surfaces of the layers are determined. The tensions realizing the necessary pressures are calculated. The relations obtained are checked experimentally.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 640–645, July–August, 1972.     

Mechanical properties of a carbon-fiber-reinforced plastic and the residual stresses in wound components made out of combined composites

A technique for calculating the residual stresses in wound components made out of mixed carbon-fiber-and glass-fiber-reinforced plastics and the results of the calculations are presented. The effect of the conditions under which the components are wound on the magnitude and nature of the residual stresses distribution in components made out of combined composites is investigated. The results of the calculations are compared with the experimental values.Translated from Mekhanika Polimerov, No. 6, pp. 996–1004, November–December, 1975.     

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.     

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.     

Modeling the mean stresses in structural elements made of fiber composites

Conclusions The results of solution of the above-examined problems show that the method proposed here makes it possible to satisfactorily (with an error smaller than 5% for the maximum stresses) recalculate the mean stresses obtained in models made of fiber composites (such as by the photoelastic method) for the corresponding full-scale parts. The method does not require special election of the model materials, which is its main advantage and makes it easy to use.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 495–500, May–June, 1990.     

Calculation of stresses in multilayer cylindrical articles made of variously combined composite materials

Both residual and working stresses are analyzed which appear in thick-walled cylindrical articles made of variously combined composite materials. A conservative homogeneous difference scheme is constructed for a "throughway" numerical integration of the resolvent equation in the Lamé problem of a compound cylinder. With the aid of this equation, the stress distribution is analyzed for multilayer structures with various ratios of layer thicknesses and various layer sequences.     

Nonsymmetrical temperature fields and stresses in cylinders made of nonuniform composites

The class of problems for determining nonsymmetrical temperature fields and stress in thick-walled hollow nonuniform cylinders is considered. A resolution set of differential equations is constructed for determining steady-state temperature fields, stresses, and displacements in asymmetrically heated cylinders which are arbitrarily nonuniform with respect to thickness with one plane of elastic symmetry. An approach is suggested for effective numerical solution of this class of problems. Problems are analyzed for thick-walled cylinders whose relative volume content of reinforcing elements varies in the radial direction. Known relationships of composite mechanics are used in order to find effective mechanical and thermophysical parameters for the material. Examples are provided for solving specific problems which point to the requirement of considering nonuniformity with respect to thickness.To be presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 494–500, July–August, 1995.     

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.     

Calculation of the deflection of a composite pipeline made by winding tubes

An estimate of the stress state of polymer cellular (hollow) pipe members is proposed, which is based on averaged components of the displacement vector. A calculation algorithm is presented that takes into account the effect of action of soil on the pipe surface where the normal displacements are positive.     

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.     

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.