Prediction of the thermal conductivity of oriented fiberglass plastics

An analytical equation has been derived for calculating the thermal conductivity of fiberglass plastic pipes in the axial direction. The pipes, which represent items with the most general type of reinforcement, were manufactured by uninterrupted slanting and longitudinal-transverse winding. Equations for calculating the thermal conductivity of oriented fiberglass plastics with other types of reinforcement featuring various angles to the direction and plane of reinforcement are particular cases of the derived equation. The results of an experimental check for this equation for calculating the thermal conductivity of epoxy fiberglass plastics are presented.Translated from Mekhanika Kompozitnikh Materialov, Vol. 29, No. 3, pp. 381–386, May–June, 1993.     

Study of the thermophysical and antifriction properties of polyethylene-based compositions

The results of a study of the effect of the filler properties (thermal conductivity, density, particle shape and size, percentage content) on the thermal conductivity of the composite are presented; the factors responsible for the increase in the thermal conductivity of the polymer are indicated. Formulas are recommended for calculating the thermal conductivity of composites based on polyethlene and various fillers.Institute of Polymer Mechanics, Academy of Sciences of the LatvianSSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 259–266, March–April, 1973.     

Effect of extension on the structure and thermophysical properties of kapron (nylon 6)

The effect of extension on the structure and thermal conductivity of kapron has been investigated experimentally in the temperature range +20–130° C. The thermophysical characteristics were determined via a method based on the principle of the regular regime. The structure of the kapron was investigated by infrared spectroscopy and x-ray and microstructural analysis. The mechanical loads produced important structural changes that affected the thermophysical parameters of the kapron.Mekhanika Polimerov, Vol. 4, No. 1, pp. 180–182, 1968     

A generalized thermal conductivity dependence for amorphous polymers

A method of treating the experimental data for the thermal conductivity of amorphous polymers is presented. By means of the proposed method of treatment an invariant thermal conductivity curve for a wide range of temperatures is derived.Moscow Institute of Chemical Engineering. Translated from Mekhanika Polimerov, No. 5, pp. 912–913, September–October, 1972.     

Effect of porosity and component ratio on the thermal conductivity of glass-reinforced plastics

The dependence of the thermal conductivity of glass-reinforced plastics on porosity and component ratio is investigated. The possibility of determining the porosity, specific weight, and resin content of glass-reinforced plastics from their thermal conductivity is confirmed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 487–491, May–June, 1969.     

Correlation between the strength and thermal conductivity of glass-reinforced plastics

The effect of changes in the component ratio and porosity of glass-reinforced plastics on their strength and thermal conductivity is considered. A correlation is shown to exist between the bending strength and thermal conductivity of a glass laminate.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 749–751, July–August, 1969.     

Predicting the porosity of glass-reinforced plastics from their thermal conductivity

The effect of porosity, reinforcement ratio and specific weight on the thermal conductivity of a series of glass-reinforced plastics has been investigated. It is shown that, if the thickness, the weight characteristic (weight per square meter), and the number of layers of reinforcing fabric are known and the thermal conductivities of the components are constant, then the porosity of the glass-reinforced plastic can be predicted from its thermal conductivity. Data on the relation between the specific weight and the thermal conductivity of the glass-reinforced plastics investigated are presented.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 522–525, May–June 1971.     

Thermal conductivity of unidirectionally reinforced hybrid composites

Conclusion The thermal conductivity of organic-glass, organic-carbon, and carbon-glass plastic in dependence on the volumetric content of organic, glass, and carbon fibers was experimentally investigated. The solution for transverse thermal conductivity of unidirectional hybrid composite, obtained in [8] by generalizing the method of self-congruence to the case of a triphase model, is in satisfactory agreement with the experimental data.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 817–822, September–October, 1990.     

Calculation of deformative and thermal properties of multiphase composite materials filled with composite or hollow spherical inclusions by the effective medium method

A theoretical investigation was carried out to examine the possibilities of a structural approach to prediction of elastic constants, creep functions, and thermal properties of multiphase polymer composite materials filled with composite or hollow spherical Inclusions of several types. The problem of determining effective properties of the composite was solved by generalizing the effective medium method, a variant of the self-consistent method, for the case of a four-phase kernel-shell-matrix-equivalent homogeneous medium model. Exact analytical expressions for the bulk modulus thermal expansion coefficient, thermal conductivity coefficient, and specific heat were obtained. The solution for the shear modulus is given in the form of a nonlinear equation whose coefficients are the solution of a system of 12 linear equations.To be presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October 1995.Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 462–472, July–August, 1995.     

Effect of the cellular structure on thermal conductivity of rigid closed-cell foam polymers during long-term aging

The thermal conductivity of rigid closed-cell polyurethane foams during long-term aging has been studied. The similarity between the kinetics of changes in the physical and mechanical characteristics of PU foams on progressive aging is established, which is attributed to the effect of matrix destruction. It is found that rigid foams have cell walls of various strength, whose impact on the kinetics of changes in the physical characteristics of the foams during long-term aging is ascertained. The results of predicting the thermal conductivity of PU foams by the method of temperature-time analogy and establishing the limits of its application are discussed. The research presented is of interest both in determining the foam durability and in replacing freons by alternative, ecologically less harmful blowing agents.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 187–198, March–April, 1999.     

Nonstationary thermal fields in multilayer parachute spaces

The Green's function method, under assumptions which are more general from the point of view of the phenomenological theory of thermal conductivity, is used to construct a closed-form solution to a nonstationary thermal conductivity problem for a conical body cut from a spherical space and truncated by concentric spheres centered at the apex of the cone. In order to construct the Green's function we apply Legendre-Fourier transforms and Fourier — Bessel transforms (for polar axis with n conjugate points). The results of this work have applications to engineering computations.Translated fromVychislitel'naya i Prikladnaya Matematika, No. 69, pp. 77–87, 1989.     

Investigation of the thermophysical properties of polymethyl methacrylate at high hydrostatic pressures

Conclusions 1. The experimentally observed course of heat capacity is explained by competition of contributions from the lattice and defects, on one hand, and from retarded rotators, on the other.2. An equation is proposed which describes the dependence of the thermal conductivity of polymers on pressure and which agrees with experimental data to an accuracy of ±1%.Moscow Chemical Engineering Institute. Translated from Mekhanika Polimerov, No. 5, pp. 845–851, September–October, 1976.     

Residue minimization technique to analyze the efficiency of convective straight fins having temperature-dependent thermal conductivity

In this article, we propose and implement a numerical technique based on residue minimization to solve the nonlinear differential equation, which governs the temperature distribution in straight convective fins having temperature-dependent thermal conductivity. The form of temperature distribution is approximated by a polynomial series, which exactly satisfies the boundary conditions of the problem. The unknown coefficients of the assumed series are optimized using the Nelder–Mead simplex algorithm such that the squared L₂ norm of the residue attains its minimum value within a specified tolerance limit. The near-exact solution thus obtained is further used to calculate the fin efficiency. For the case of constant thermal conductivity, the obtained results are validated with the analytical solutions, while for the case of variable thermal conductivity, the obtained results are corroborated with those previously published in the literature. An excellent agreement in each case consolidates the effectiveness of the proposed numerical technique.     

Control of thermal stresses and displacements in thermoelastic bodies

By developing the method of the inverse thermoelastic and thermal conductivity problem we study problems of optimal control of thermal stresses and displacements in the case of one- and two-dimensional temperature fields. The solution of the optimization problems reduces to solving integral equations of first or second kind for determining the internal heat sources.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 27, 1988, pp. 18–23.     

Predicting certain structural characteristics and physicomechanical properties of glass-reinforced plastics from their thermal activity

A procedure and apparatus for determining the thermal activity of glass-reinforced plastics with one-sided access have been developed. A correlation is established between the interlaminar shear modulus and interlaminar shear strength and the thermal activity of a glass laminate. The effect of structural inhomogeneities and bonding flaws on the thermal activity of a glass-reinforced plastic is investigated and it is shown that the location of an inhomogeneity within the article can be determined.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 128–132, January–February, 1976.     

Effect of electron irradiation on the mechanical and thermal properties of some polymer materials

The effect of electron irradiation on the mechanical properties (deformability) of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide (PI), and Fenilon (Fe) films, as well as the thermal properties (heat conductivity and capacity) of PTFE is studied experimentally. The thickness of the films was 40–50 m. Mechanical tests showed that polyimide films were more resistant to radiation than the other films. The investigation of the changes in the thermal properties of PTFE due to electron irradiation revealed that the phase transitions observed at temperatures of 293 and 303 K in unirradiated PTFE were shifted to lower temperature regions.Abai Alma-Ata State University, Kazakhstan. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 683–689, 1998.     

Nonlocal symmetries. Heuristic approach

A constructive method for constructing nonlocal symmetries of differential equations based on the Lie—Bäcklund theory of groups is developed. The concept of quasilocal symmetries is introduced. With the help of this method nonlocal symmetries of differential equations of the type of nonlinear thermal conductivity and gas dynamics are studied.Translated from Itogi Nauki i Tekhniki, Seriya Sovremennye Problemy Matematiki, Noveishie Dostizheniya, Vol. 34, pp. 3–83, 1989.     

Multicriteria optimization of a composite cylindrical shell subjected to thermal and dynamic actions

Multicriteria optimization of the structure and geometry of a laminated anisotropic composite shell subjected to thermal and dynamic actions is considered. From the known properties of monolayers and the given values of variable structural and geometric parameters, the thermoelastic properties of the layered anisotropic composite are determined. The criteria to be optimized—the natural frequency and the thermal stresses—depend on two variable design parameters, stochastic properties of the composite, and temperature. In the space of the optimization criteria, the domain of allowable solutions and the Pareto-optimal region are found.Translated from Mekhanika Kompozitnykh Materialov, Vol. 40, No. 6, pp. 753–760, November–December, 2004.     

Macrorheological theory of hot compaction of composites

The present work presents the results of mathematical modeling of deformation and thermal processes of compaction of viscous compressible materials. An analytical solution of the problem of one-sided compression and extrusion of powder materials is found which enables us to establish different regimes of compaction and extrusion and to find criterial conditions for their realization at a qualitative level. The numerical analysis of the influence of the nonunifomity of the thermal regime and the conditions of heat transfer on the regularities of compaction nd extrusion of the materials is performed. It is shown how the models developed facilitate the solution of practical problems of producing the concrete items.Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October 1995.Published in Mekhanika Kompozitnykh Materialov. Vol. 31, No. 6. pp. 840–845. November–December, 1995.     

Application of the method of nondestructive control to investigations of thermal characteristics of crystals

Six crystal samples were examined in the form of anisotropic half-spaces with corresponding arrangement of the directions of anisotropy. The heat sources and measurement devices for the excess temperature were moved about the surfaces of the samples in the given directions with identical velocity. The coefficient of thermal conductivity and the bulk thermal capacity of the crystals possessing straight-line anisotropy were determined.Translated from Matematiceskie Metody i Fiziko-Mekhanicheskie Polya, No. 29, pp. 12–16, 1989.