Microstructural changes of filled rubber-like materials under cyclic loading

The concept of network decomposition has vastly been used in many micro-mechanical models describing stress-softening of rubber-like materials in the first loading cycle as for example the Mullins-effect. Nevertheless, this concept highly simplifies the rubber matrix by decomposing it into two parallel networks that have no interactions with each other. In order to take into account the interactions between these networks some further extensions to the network decomposition concept seem necessary. To this end, a third network is introduced and the concept of rubber cell is proposed and developed. Using this concept, the influence of the filler network on elasticity of the two networks can be predicted by considering the cell as a RVE. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Amplitude-dependent phenomena of filler-reinforced rubber: Experiments,modelling and simulation

It's a matter of common knowledge, that carbon black-or silica-loaded elastomers show a pronounced nonlinearity when excited with dynamic deformation amplitudes, namely the Payne-effect. Furthermore, several experiments prove a very complex history-dependence and significant recovery-behaviour of this effect. In the present paper, a few experimental results of dynamical measurements on filler-loaded rubber are shown with importance attached to the complicated history dependence. In order to describe the depicted phenomena, a model, based on intrinsic time scales is presented with corresponding simulation results. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Viscosity,rubber elasticity,and viscoelasticity of concentrated polymer solutions

The results of a comparative investigation of the effect of the nature of the polymer and the solvent on the viscosity, rubber elasticity, and viscoelasticity of concentrated polymer solutions in the region of linear mechanical behavior are presented. It is established that in the case of nonpolar polymers the solvent affects only the free volume of the solution, whereas for polar polymers it also affects the entanglement network. This leads to the equality of the viscosities of solutions of nonpolar polymers in different solvents when compared in corresponding states (relative to the glass transition temperature) and to the dependence of the shear modulus of solutions of polar polymers on the nature of the solvent and temperature. It is shown that there is a universal relaxation spectrum in the flow zone for solutions of different polydisperse polymers after normalization with the shear modulus and the natural relaxation time determined as the ratio of the viscosity to the shear modulus.A. M. Gor'kii Ural State University, Sverdlovsk, A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 729–736, July–August, 1973.     

Self-heating and failure of plastics under cyclic loading

It has been shown that plastics heated by cyclic deformation have two characteristic temperatures—a critical temperature T_hc, at which the most heavily stressed part of the test piece is intensely heated, and a temperature T_h, at which the test piece fails. The values T_hc and T_h are determined not only by the physicomechanical properties of the material, but also by the state of stress and strain, by the scale factor, and by the heat transfer conditions. It has likewise been shown that the form of the fatigue fracture surface of plastics is determined by the type of deformation and the temperature T_h.Mekhanika Polimerov, Vol. 3, No. 3, pp. 483–492, 1967     

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.     

Application of Rosenbrock-type methods to a finite element formulation based on large strain viscoelasticity

The present paper is focused on the solution of differential–algebraic equation systems (DAE), which arise in large viscoelastic deformations within the quasi–static finite element context. For this purpose linearly implicit methods of Rosenbrock–type are used, which avoid completely the solution of non–linear equations. This article investigates a possible treatment of the new global approach with respect to expense and achievable accuracy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fatigue strength and structure changes of polyethylene-oxide films under static and cyclic loading

Conclusions The behavior of the PEO films under long-term loadings show certain special features reflected mainly in the unusual form of the fatigue curve and the presence of three types of creep curves. The most significant factors affecting the fatigue characteristics of the PEO films are the molecular mass and the degree of crystallinity — when these factors increase the fatigue resistance also usually increases. To evaluate suitability of PEO films for service it is promising to use the cyclic bending test. This loading mode characteristic of practice makes it possible to carry out tests at low strain levels and cumulate considerable damage. Examination by the x ray diffraction method showed that in cyclically bent PEO films not only the amorphous but also crystalline structures are damaged.Translated from Mekhanika Kompozitnykh Materialov, Vol. 3, No. 3, pp. 404–412, May–June, 1994.     

Comparison of the temperature-time dependences of polymer strength under static and cyclic loading

A comparison of the temperature-time dependences of the strength of highly oriented fibers under static and cyclic loading shows that in the region of high temperatures and low loading frequencies the static and cyclic specimen lives always coincide. The discrepancy between the static and cyclic lives observed in the region of low temperatures and higher loading frequencies is related with differences in the structural changes in the different loading regimes. These changes are relaxational in nature.The experimental data were reported at the 14th and 16th All-Union Conferences on High-Molecular Compounds (1964 and 1966).A. F. Ioffe Physicotechnical Institute, Leningrad. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 648–655, July–August, 1968.     

Effect of foam stability on pore coherence and mechanical properties of rubber latex based materials

The effect of a foaming agent, gelling agent, porous and nonporous fillers (silica gel and chalk) on the ability of latex foam to resist rupture of pore walls, the coherence of the pore volume, and the mechanical properties of foam rubber are investigated. It is demonstrated that the average size of the pores and the through junctions between pores can be increased by up to 1.5 times, their ratio by up to 1.5 times, and pore coherence by up to two times by varying compositional factors.Translated from Mekhanika Kompozitnykh Materialov. Vol. 31, No. 6, pp. 828–833, November–December. 1995.     

Comparison of the reliefs of fracture surfaces in PMMA under static and cyclic loading

Investigations of the relief of fracture surfaces in PMMA with the help of optical and interference microscopes have shown that there are no qualitative differences in the appearance of the fracture surfaces obtained under static and cyclic loading conditions. Quantitative studies have established that the size of the specular zone increases linearly with increase in the logarithm of the lifetime at a given test temperature. Other conditions being equal, in cyclic tests the specular zone is larger than in static tests. The results obtained are considered to be further confirmation of the validity of the theory that under any loading conditions fracture is based on the same thermo-fluctuation mechanism.Mekhanika Polimerov, Vol. 2, No. 1, pp. 52–59, 1966     

Regularity of Skorohod integral processes based on integrands in a finite Wiener chaos

Summary Letf be a square integrable kernel on them-dimensional unit cube,U the Skorohod integral process in them ^th Wiener chaos associated with it. Isoperimetric inequalities for functions on Wiener space yield the exponential integrability of the increments ofU. To this result we apply the majorizing measure technique to show thatU possesses a continuous version and give an upper bound of its modulus of continuity.     

The ultimate state of polymeric materials and laminated and fibrous composites under asymmetric high-cycle loading

The prediction of the high-cycle fatigue strength of polymeric and composite materials in asymmetric loading is considered. The problem is solved on the basis of a nonlinear model of ultimate state allowing us to describe all typical forms of the diagrams of ultimate stresses. The material constants of the model are determined from the results of fatigue tests in symmetric reversed cycling, in a single fatigue test with the minimum stress equal to zero, and in a short-term strength test. The fatigue strength characteristics of some polymers, glass-fiber laminates, glass-fiber-reinforced plastics, organic-fiber-reinforced plastics, and wood laminates in asymmetric tension-compression, bending, and torsion have been calculated and approved experimentally. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 1, pp. 87–102, January–February, 2008.     

Effect of the starting structure of a polymer on the time dependence of its strength under cyclic loading

The stress dependence of the logarithm of the cyclic life for different modifications of the same polymer is represented by a fan of straight lines that converge upon extrapolation to zero stress at a single point log A_cy, which differs from the analogous extrapolation point log A_st. The possible causes of this effect are discussed.Ioffe Physico-Technical Institute, AS USSR, Leningrad. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1008–1013, November–December, 1968.     

Prediction of creep of polymeric materials during random processes of change in loading and temperature-humidity conditions of surrounding media

Conclusions 1. On the basis of the exponentialsmoothing method, a method is suggested for estimating the probability characteristics (statistical moments) of nonstationary random processes of change in temperature conditions of the surrounding medium.2. The possibility is shown of the application of the methods of theory of nonstationary random processes to the prediction of creep of polymeric materials which belong to the class of thermal—moisture rheologically simple solids during nonstationary random change in temperature and humidity of the material. The proposed method of prediction has been experimentally confirmed for the example of prolonged (27,000 h) creep of PN-3 polyester resin during simple shear under the climatic conditions of Riga.For Communication 1 see [1].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 616–621, July–August, 1976.