Nondestructive methods of determining the dielectric constants of anisotropic polymeric materials

Procedures for determining the principal constants of the dielectric constant tensor of anisotropic polymeric materials are described. It is shown that the simplest solution of the problem corresponds to the use of external measuring capacitors. Two variants of measuring apparatus for determining the principal constants of the ε tensor and the anisotropy coefficient of polymeric materials are described with reference to block diagrams. The results of testing laboratory models are presented.     

Variation in the optical properties of polymeric film materials under static and cyclic loading (review)

Conclusion At the present time, use of optical methods in analyzing the structure of polymeric materials reduces, with rare exception, only to the method of the low-angle scattering of polarized light. Orientation phenomena and supramolecular structures, whose dimensions exceed the length of the light wave, are studied using this method. The potentials of optical methods are not fully utilized, however, in studying heterogeneities commensurate with, or smaller than the wavelength, and it is precisely microcracks, micropores, and the dispersed phase in a polymeric mixture that exhibit these dimensions. The high sensitivity of optical methods to these heterogeneities, and the possibility of using the Burger-Beer law for polymeric films ensures the widespread use of light-scattering and spectral-transparence methods for the structural analysis of heterogeneous materials (polymeric mixtures, filled composite materials), and also in studying pores and fatigue damage in polymeric films, and in exposing the most heavily loaded zones in articles.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 35–56, January–February, 1989.     

Effect of hydrostatic pressure on certain thermodynamic properties of polymeric materials

By means of a thermodynamic approach it is demonstrated that the mechanical properties of homogenous polymeric materials depend only on specific volume. Expressions are derived for the entropy and volume coefficient of thermal expansion as functions of hydrostatic pressure and temperature. It is shown that for both crystalline and amorphous polymeric materials the bulk modulus depends on reduced temperature.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 825–829, September–October, 1970.     

Some features of the frictional behavior of polymeric crystalline materials

The coefficients of friction for thin polymeric films are calculated, and it is shown that the coefficient of friction of the films is much less than that of a homogenous block. This may be due to some features of the antifriction properties of polymeric crystalline materials.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1053–1058, November–December, 1972.     

Effect of electrophysical activation of components on adhesive interaction in polymer composites

The key problem in designing polymeric composites is ensuring a sufficiently strong adhesive bond between the polymer and the filler (or the reinforcement). One method for strengthening the intermolecular interaction at the phase interface is electrophysical activation of the particle surface. We have investigated the absorption activity and adhesiveness of powdered inorganic fillers and polymeric binders with triboelectric activation and activation in a corona discharge. We consider a broad class of disperse materials. We show that electrophysical activation of powdered materials causes changes in the concentration of donor and acceptor centers on the particle surface and in the adsorption activity of the materials as a whole. The presented results can be used for goal-directed selection of the most effective method of activation for disperse materials; they also are evidence for the important role of adsorption forces in the adhesion phenomenon.Report presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 734–741, November–December, 1995.     

高体积百分比颗粒增强聚合物材料的有效粘弹性性质

聚合物材料通常表现为粘弹性性质．为了改进聚合物材料的力学性能,通常将某种无机材料以颗粒或纤维的形式填充到聚合物中,从而得到增强、增韧的聚合物基复合材料．提出了一个新的细观力学模型,用于预测颗粒增强聚合物复合材料的有效粘弹性性质,尤其针对高体积百分比的颗粒夹杂复合材料,该方法基于Laplace变换和双夹杂相互作用的弹性模型．计算了玻璃微珠/ED-6复合材料的有效松弛模量以及恒应变率下的应力应变关系．计算结果表明在高体积百分比下该文方法比基于Mori Tanaka方法预测的粘弹性效应明显减弱．     

Testing methods for predicting the life of polymeric materials

On the assumption that the performance of polymeric materials can be predicted only on the basis of long-time tests under conditions similar to those that obtain in practice, the authors consider creep, stress relaxation, and dynamic measurements at various temperatures and frequencies. Theoretical methods of estimating the life of polymeric materials are investigated with allowance for changes in the physical and chemical structure of the polymer and the nonconstancy of the activation energy of the relaxation processes over a broad temperature interval.Lenin Moscow State Pedagogical Institute, Laboratory of Problems Polymer Physics. Translated from Mekhanika Polimerov, No. 2, pp. 212–220, March–April, 1971.     

Structure and properties of magnetic fibrous polymeric materials

Characteristic features of the filtration of liquids by magnetic fibrous polymeric materials (MFPM) are addressed; these materials are a set of fibers of a polymeric material containing a ferritic filler; they are adhesively bound at points of their intersection. It is demonstrated that variations in structural parameters (fiber thickness, distribution of fiber throughout the material, and its concentration), as well as the degree and direction of magnetization of the MFPM exert an influence on the efficiency of the liquid filtration. Optimum parameters for MFPM designed to purify liquids of ferromagnetic and nonmagnetic contaminants are given.A paper 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. 3, pp. 291–297, May–June, 1995.     

A general modelling framework and specific mechanical approaches to simulate curing phenomena in polymers

Polymers are employed as adhesives, filling or sealing materials, among others. Within these applications, a chemical reaction (e.g. polymerization) leads the materials to cure from a liquid to a solid. In this contribution, first a general continuum mechanical modelling framework for the simulation of curing phenomena is highlighted. It takes into account the main chemical, thermal and mechanical phenomena of polymeric curing processes. Secondly, different mechanical models to capture the mechanical behaviour of polymeric curing processes are regarded. It is shown that elastic, viscoelastic and viscoplastic models at large deformations can be employed. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some aspects of the behavior of shock-compressed polymers

The changes in the properties of certain polymeric materials subjected to the action of plane shocks of varying amplitude are discussed. Three loading techniques are employed — single, multiple, and high-frequency multiple loading — each accompanied by a different rise in the temperature of the polymeric material. The results show that the change in physicomechanical properties also varies with the loading technique.Volgograd Polytechnic Institute. Translated from Mekhanika Polimerov, No. 1, pp. 76–80, January–February, 1970.     

Temperature dependence of Young's modulus and the absorption coefficient of certain polymeric materials

The procedure and the results are described of the experimental determination of Young's modulus and the absorption coefficient as a function of temperature of polymeric materials, polystyrene foam, polyarylite, and others, obtained in dynamic investigations.     

Numerical modeling of large strain behavior of polymeric crushable foams

This paper describes a constitutive law modeling isotropic polymeric foam materials. Focus has been placed on modeling the relative density dependency effect on polymeric foams subjected to large deformations using uniaxial and hydrostatic compressive hardening laws. The constitutive model is written in terms of the rotated Kirchhoff stress and of its conjugate logarithmic, or Hencky, strain measure. A numerical scheme for solving the constitutive model is described and implemented using both the finite element and the element-free Galerkin methods, in a Total Lagrangian finite strain framework. The imposition of the unilateral contact with friction and the essential boundary conditions are obtained by applying the Augmented Lagrangian method. Numerical examples are presented in order to attest the performance of the proposed constitutive model.     

Investigation of the relation between the depth of penetration and indentation diameter in polymer hardness measurements

It has been experimentally demonstrated that for polymeric materials the area of the indentation should not be calculated from the depth of penetration of the spherical indenter, since this gives hardness values that are too low. It is shown that when the surface of a polymeric specimen is indented by a rigid ball, the effect of the spherical stress tensor on the yield point is important; the average stress on the contact area at the beginning for forced high-elastic deformation is close to the compressive yield stress of the polymeric material and considerably higher than its tensile yield stress.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 995–998, November–December, 1971.     

Polymer friction

The results of research on the antifriction properties of polymeric materials and expressions for calculating their coefficient of friction are presented. The effect of the mechanical properties of the materials on their antifriction characteristics is discussed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 421–429, May–June, 1975.     

The use of polymers for model investigations based on dynamic photoelasticity

The possibility of taking the inelastic characteristics of polymeric and nonpolymeric materials into account in the photoelastic modeling of dynamical problems has been investigated. The proposed method is an approximate one based on the use of the Kelvin-Voigt model for both types of materials. The results of comparative experimental investigations of certain plane dynamical problems are presented and the experimental and theoretical data are compared.B. E Vedeneev All-Union Scientific-Research Institute of Hydraulic Engineering, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 456–465, May–June, 1972.     

On phenomenological and micro-mechanical models in finite elasticity and viscoelasticity for rubber-like materials

The structure of rubber-like materials is characterised through chain-like macromolecules which are linked together at certain points. This special structure leads to a completely random three-dimensional network [5]. There are several phenomenological based models and micro-mechanically motivated network models for elastic and viscoelastic polymeric materials which have been proposed in the literature [4]. The aim of the research work is to give an overview of various phenomenological and micro-mechanical models for elastic and viscoelastic processes at large deformations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Time-temperature superposition. Review

Experimental attempts to confirm the applicability of time-temperature superposition as a means of predicting the deformation of polymeric materials are reviewed. Examples of the use of the method for the accelerated testing of amorphous and crystalline thermoplastics, thermosets, and composites are presented. The review is confined to the class of thermorheologically simple bodies and isothermal deformation regimes.     

Machines for physicomechanical testing of polymeric materials

Two tensile-testing machines are described for physicomechanical tests of polymeric materials with deformation up to 100 and 1,000% in which the conditions of deformation are assigned directly to the measurement base of the specimen by using an automatically regulated electric drive, ensuring parity of the measured quantity (force, elongation, or stress) with the requisite preset functional controller.     

Effect of hydrostatic pressure on the viscosity of failure of polymeric materials

Conclusions A setup and method were developed for studying the effect of hydrostatic pressure on the characteristics of the crack resistance of polymeric materials. The viscosity of failure of material K-4I based on butyl rubber was determined in a wide range of rates of crack propagation and hydrostatic pressures. It was found that an increase in the hydrostatic pressure increases the resistance to crack propagation in a polymeric material. The pressure-time analogy method, where the dependences of the viscosity of failure on the rate of crack growth are parallelly shifted to the value of the pressure-time shift and a generalized curve is formed, can be used for taking the effect of the pressure into consideration.Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 973–977, November–December, 1986.     

Review of recent scientific publications in the field of polymer mechanics

The results of research in polymer mechanics carried out by the authors or with their direct participation during the last 5 years are briefly reviewed. The following questions are covered: theory and methods of solution of problems of polymer mechanics, statistical methods in polymer mechanics, the experimental investigation of the properties of polymeric materials, and the reflection of the theory and methods of polymer mechanics in the textbooks.