Elasticity and strength of polyurethane foams with cylindrical cavities

The strength and elasticity of layers of polyurethane foam with cylindrical cavities have been investigated on the interval of variation of the specific weight of the foam from ₀ = 0.2 to ₀ = 0.7 gf/cm³. A correlation has been established between the proportionality limit in compression along the channel axes and the modulus of elasticity of a cylindrical tube of foam with a radially restrained outer surface taken as a model of a layer with cylindrical cavities. The experimental results are compared with the theory of elastic compression of tubes with free and restrained ends.Translated from Mekhanika Polimerov, No. 5, pp. 813–819, September–October, 1971.     

Some properties of rigid polyurethane foam obtained from oligoglycerooxalate

The dependence of the modulus of elasticity and compressive strength on the apparent density has been found for polyurethane foam based on oligoglycerooxalate.Institute of Wood Chemistry, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, p. 739, July–August, 1973.     

Properties of fiberglass-plastics reinforced with high-modulus fibers

The question of reinforcement of unidirectional fiberglass-plastic with boron or carbon fibers is considered. Static fatigue curves for the Poisson coefficient and the elastic modulus as functions of the volume content of the glass and the high-modulus fibers have been constructed. The theoretical dependences are compared with the experimental data.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Moscow. Translated from Mekhabika Polimerov, No. 1, pp. 68–74, January–February, 1972.     

Model analysis of the cellular structure of plastic foams of the polyurethane type

A mathematical analysis of the mechanical properties of foam materials at the cellular structure level is given on the basis of a proposed 14-faced model of the cell of an opencelled plastic foam of the polyurethane type. The results obtained are shown to be in good agreement with the experimental data even without the introduction of arbitrary constants.Vladimir Scientific Research Institute of Synthetic Resins. Translated from Mekhanika Polimerov, No. 5, pp. 859–865, September–October, 1970.     

Morphological characteristics of carbon fibers

Scanning electron microscopy has been used to study the surface, before and after thermochemical treatment, and the fracture sites of PAN carbon fibers heat-treated at 2100°C. The fractographs are analyzed in an attempt to estimate the effect of various defects on the strength of PAN carbon fibers.All-Union Scientific-Research and Design-Technological Institute of Electro-Carbon Products, Moscow Region. Translated from Mekhanika Polimerov, No. 1, pp. 158–160, January–February, 1976.     

Mechanical properties of carbon fibers coated with refractory carbides

The internal friction method has been used to investigate the protective function of barrier coatings of silicon and zirconium carbide. The effect of the thickness of the coating on the mechanical characteristics of carbon fibers and their oxidation resistance is examined. The optimal coating thickness is established. A surface hardening effect of the coatings has been detected.Voronezh Polytechnic Institute, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 536–538, May–June, 1976.     

Interfacial strength of joints between fibers and dispersedly filled epoxy matrices

The concentration dependences of adhesive strength are investigated for fiber/dispersedly filled epoxy matrix systems. The measurements were carried out using an improved model of adhesiometer under normal conditions at a constant rate of loading. It is shown that the adhesive strength as a function of filler concentration has a maximum, which is more or less pronounced. The location of the maximum depends on the nature of filler and particle geometry. The increase in the adhesive strength at the maximum reaches 20–30% in comparison with that for the unfilled epoxy matrix. Since the interfacial strength between steel wire and all the mineral powders investigated is zero, the growth in the adhesive strength upon introduction of a finely divided filler in polymer binders is rather un expected. The possible reasons for the phenomenon observed are discussed. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 3–14, January–February, 2007.     

Properties of fillers and reinforcing fibers

Fillers have always played an important role in the plastics industry. Filled polymers form a specific class of composites, which are tending to replace many traditional materials. Various kinds of organic fillers are used. The experimental study of such nonconventional organic and inorganic fillers obtained from agricultural waste is presented to modify the properties of thermoplastics, such as pVC, HDPE, LDPE, and ABS. The properties obtained by using these fillers alone and in combinations show very interesting results, which are tabulated. The use of organic fillers should help lower the cost of many plastic products required in the building and agricultural industries.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Maharashtra Institute of Technology, Pune, India. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 651–663, September–October, 1998.     

Effect of the crosslink density of elastic polyurethane fibers on their mechanical properties

The effect of the nature of the bonds and the degree of crosslinking on the properties of elastic polyurethane fibers has been investigated in relation to various fiber treatments. The fiber properties are mainly determined by the chemical bonds, the proportion of which should be not less than 40%.Leningrad Branch, All-Union Scientific-Research Institute of Artificial Fibers. Kaunas Artificial Fiber Plant. Translated from Mekhanika Polimerov, No. 3, pp. 515–516, May–June, 1976.     

Quantitative evaluation of the brittleness of carbon fibers

A simple method is proposed for the rapid determination of the brittleness of fibers. Measurement data are given for glass and carbon fibers. It is shown that the conditions of heat processing for carbon fibers may fundamentally alter their brittleness.A. F. Ioffe Physical-Engineering Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 950–952, September–October, 1973.     

Estimation of the optimal distribution of the fibers in carbon/carbon composite

Carbon/carbon (C/C) composites are widely represented in the industry and are utilized for extreme thermal and mechanical loading. Optimization of the fibers distribution allows by still high stiffness to provide reducing of the weight of the components that has crucial importance in aircraft and aerospace industry. A microstructure optimization problem for estimation of the microstructure with minimal compliance is formulated. The design variables of the posed problem are the local fibers distribution and porosity. The volume fractions of the fibers and pores in the whole microstructure are fixed. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)