Material-Adapted Design of Textile-Reinforced Composite Structures with Optimized Vibro-Acoustic and Damping Properties Including Shear Effects

Advanced analytical models have been developed at the ILK, which offer a possibility of calculating the vibro-acoustic and damping behavior of textile-reinforced composite shells and plates with account of shear effects. The simulation models elaborated have been verified on selected examples, and the analytical results were fully corroborated by accompanying numerical calculations for typical lay-ups.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 3, pp. 289–302, May–June, 2005.     

Newtonian viscosity of polymer solutions over a wide range of compositions as a function of certain parameters determining it

Using solutions of various polymers in a large number of solvents as an example, the possibility of constructing a generalized characteristic for their viscosity, which is invariant relative to the molecular weight of the polymer and the nature of the solvent, is indicated. It is shown that the parameters characterizing the properties of individual macromolecular chains are the dimensions of the coils [], and the rheological effectiveness of interaction of the segments K_M retain their importance and quantities determining the viscous properties of the polymer solution over the whole range of compositions. A connection is established between the datum parameter K_M and the thermodynamic properties of dilute solutions of polymers, the flexibility of the polymer chain, and the energy of its intermolecular interaction.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. 6, pp. 1110–1117, November–December, 1972.     

Temperature-time dependence of the adhesion strength for polymer — Polymer systems

The temperature — time dependence of the adhesion strength has been studied for polymer systems differing in the thermodynamic compatibility of the substrate and adhesive and in the rate of polymerization of the latter. The fracture-activation energies of these systems have been calculated. It is shown that the temperature — time dependence of the adhesion strength varies depending on whether chemical intermolecular forces are responsible for the strength of the joint.Perm Scientific-Research Institute of Polymer Materials. A. M. Gor'kii Ural State University. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 665–671, July–August, 1968.     

Lower critical solution temperature and hydrophobic hydration in aqueous polymer solutions

Phase diagrams of aqueous solutions of poly(N-vinyl caprolactam) (PVCL), N-vinyl caprolactam copolymer with vinylamine (3.8 mol%) (CP(VCL-VA)), and poly(N-vinyl propylacetamide) (PVPA) were shown to be binodal curves with lower critical solution temperatures (LCST) in the range 304–313.5 K and critical concentrations in the range of 0.02–0.08 polymer weight fraction. Aqueous solutions of N-vinyl caprolactam copolymer with N-vinyl pyrrolidone (80 mol%) (CP(VCL-VP)) remained homogeneous in the entire region of the liquid state of water. The enthalpy of mixing with water of PVPA and CP(VCL-VP) was negative and the curve was concave over the entire range of composition at 298 and 308 K. The excessive heat capacity and partial heat capacity at infinite dilution of PVPA were positive, proving the hydrophobic character of hydration of this polymer. In contrast, these parameters were negative for CP(VCL-VP), revealing hydrophilic hydration. Hydrophilic hydration was predominant in solutions which were homogeneous over a wide temperature range, whereas hydrophobic hydration predominated in solution of polymers with LCST.     

Effect of the molecular weight of polystyrene on the viscosity of concentrated solutions

The viscosity of solutions of polystyrene of various molecular weights (from 1.04 · 10² to 3.8 · 10⁵) in a poor solvent (decalin) and a good solvent (ethylbenzene) has been measured at temperatures from 15 to 70°C over a broad range of shear stresses from 10² to 10⁶ dyne/cm². The nature of the solvent has a considerable influence on the critical molecular weight and the absolute value of the viscosities of the solutions over the entire range of molecular weights and on the form of the flow curves of decalin solutions of polystyrene as a function of temperature. The heat of activation of viscous flow increases with increase in molecular weight and shear stress on the interval 20–80°C. The results obtained are explained in terms of the effect of the molecular weight of the polymer, the nature of the solvent, stress and temperature on structure formation in the solution and on the orientation of the macromolecules and structures in the flow process.Ural Gor'kii State University, Sverdlovsk. Translated from Mekhanika Polimerov, No. 5, pp. 920–926, September–October, 1970.