Resistance to interlayer shear of plastics on a carbon filament base

Conclusions 1. An equation has been derived for the strength during interlayer shear along reinforcing fibers of a composite material of unidirectional texture which allows calculation of this index as a function of composition of the material and state of the interphase boundary. Experimental confirmation of this equation has shown that the effectiveness of surface treatment of the reinforcing filler can be estimated by its use.2. It has been shown that the strength during interlayer shear of an epoxy-phenol plastic can be increased by a factor of more than 3, and during bending by a factor of 1.3, as the result of treatment of high-modulus carbon fibers in nitric acid.3. A correlation has been established between changes in electrical resistivity of the carbon fiber and the molecular component of adhesion to it of consolidated epoxy-phenol binder.Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 445–451, May–June, 1977.     

Some properties of the polypropylene - aluminum system

The effect of composition on the properties (bulk resistivity, hardness, compressive deformation, density, and microstructure) of polypropylene-aluminum specimens has been investigated. The changes are not additively related with the composition. An explanation of the observations is proposed.Riga Lenin Komsomol Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 323–326, March–April, 1971.     

Averaging of electrical properties of anisotropic fiber-metal composites

The electrical properties of fiber-metal composites with anisotropic components were averaged within the framework of a regular structure model. The corresponding current problem was reduced to a system of two integral equations with elliptical kernels. The effective electrical conductivity tensor of such materials was defined as several functionals based on integral equation solutions for the boundary problem. The calculation results are given.Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 2, pp. 263–268, March–April, 1997.     

Regulation of the mechanical properties of thermoplastic carbon fiber-reinforced plastics by changing their production conditions and surface treatment of the fibers

The effect of technological parameters of processing and surface treatment of carbon fibers on the mechanical properties of carbon fiber-reinforced plastics (CFRPs) was investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane was used as the polymer matrix, and medium-modulus hydrated cellulose Ural LO-24 carbon fibers served as the reinforcing filler. The polymer matrix was mixed with the carbon fibers by the method of combined extrusion. The dependence of the mechanical properties of CFRPs on the technological parameters of screw-disk extrusion was studied. It was found that the properties of the composites were greatly affected by the size of the working disk gap, the disk rotation rate, and the temperature in the zone of normal stresses. The surface of the carbon fibers was activated with atmospheric oxygen in the temperature range of 450–600°C, with mass loss of the fibers no greater than 3–4%. A 30–40% increase in the mechanical properties of the CFRPs was achieved. A decrease in the melt index of the 1,3,5-trioxane copolymer with 1,3-dioxolane reinforced with oxidized carbon fibers was observed, which should be taken into account in processing the composites into products. Introduction of carbon fibers in the 1,3,5-trioxane copolymer with 1,3-dioxolane allows us to increase the wear resistance and decrease the friction coefficient, which makes it possibile to use these materials in the friction units of machines and mechanisms, such as plain bearings, gears, and flange packings.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 673–682, September–October, 1998.     

Averaging the electrical properties of fiber-reinforced metal composites with hollow fibers

We consider the problem of determining the effective electrical conductivity tensor of a metal composite with ideal (biperiodic) packing of the fibers. We assume that the transverse cross sections of the fiber are concentric circular rings and have identical electrical conductivity. We look for a solution in the form of a series in Weierstrassian elliptic functions with subsequent averaging of the electrical properties of the structure.Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 3, pp. 377–383, May–June, 1997.     

Shear strength of composites based on whiskerized fibers

The elastic and strength characteristics of unidirectional carbon plastics have been studied, based on carbon fibers, whiskerized with fiber crystals of silicon nitride prepared from the gaseous phase and titanium dioxide from an aerosol. The advantages of these composites and glass textolites based on satin-type fabrics whiskerized with fiber crystals of aluminum nitride and titanium dioxide over the usual carbon and glass plastics are demonstrated.All-Union Scientific-Research Institute of Aviation Materials. Institute of Polymers Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 492–501, May–June, 1973.     

Thermal dependence of electric conductivity in thermoplastic composites

Thermal dependence of the electric conductivity of thermoplastic composites based on both amorphous (hiPS) and crystallized (PP) polymers is investigated in this study. Two types of carbon black fillers with different values of BET surface area were used as charge conductors. Composites based on crystallized polymer matrices indicate the sharp growth of electric resistivity just before the melting range. This maximum is followed by substantial decrease of resistance at T > T_melt. With the decrease of carbon black concentration both relative growth of resistance at the T T_melt and further dropping resistance at T > T_melt increase. Composites filled with particles of higher surface area are characterized by less pronounced matrix influence on thermal dependence of electric conductivity than composites filled with particles of lower surface area; this can be caused by more pronounced matrix/filler interaction in the first case. The range of temperatures at which the resistance increase occurs does not depend on the type of carbon filler and its concentration. Composites with amorphous matrices are characterized by distinct increase of resistance above glass transition. Thermal treatment of the sample significantly affects the initial values and intensity of the temperature dependence of the resistance.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. 526–532, July–August, 1995.     

Influence of physical aging on creep of rubber

The effect of physical aging on the creep response of chloropren rubber filled with carbon black was studied. The method of reduced variables and analytical method of determination of influence of physical aging on the creep compliance in short creep time test are proposed.Glówny Instytut Górnictwa, Pl. Gwarków 1, 40–166 Katowice, Poland. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 112–118, January–February, 1997.     

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.     

Effect of thermal treatment temperature on the structure and properties of carbon fibers

Conclusions 1. It has been shown that the presence of a maximum in the dependence of strength on Young's modulus for carbon fibers made from PAN fiber may be explained by an effect of the process of temperature stress accumulation which takes place under the conditions of isometric heating. The start of this process, which causes a rearrangement of the internal structure of the high-modulus fiber, coincides with the start of the anomalous rise in fiber density.2. The interconnection between surface and internal defects and the elastic-strength properties of carbon fibers made in the temperature treatment range 600–3000°C has been studied.3. Original data on the elastic-strength properties of borided carbon fibers have been obtained; the structure of these is marked by a high degree of perfection. It has been shown that in boriding, which facilitates graphitization of the carbon, the process of regular reduction in fiber strength which is reached in the precrystallization stage is somewhat retarded.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1036–1042, November–December, 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.     

Investigation of the structure of carbon fibers by means of the scanning electron microscope

The structure of carbon fibers based on hydrated cellulose and polyacrylonitrile after heat treatment between 800 and 3000°C and of carbonized fibers based on polyacrylonitrile, submitted to oxidation in air, was investigated. It was established that significant changes in the surface structure occur after heat treatment at 2600°C and above. Structural changes in the carbonized fibers after various degrees of oxidation were demonstrated. Additional data were obtained on the change in the surface structure and the formation of a porous structure in carbon materials during oxidation under certain conditions.Translated from Mekhanika Polimerov, No. 5, pp. 925–926, September–October, 1972.     

Electron diffraction investigation of the fracture surfaces of filled mixtures of SKS-85 butadiene-styrene copolymer

As the result of an electron microscope study of replicas from the fracture surface during the disintegration of samples of mixtures of SKS-85 butadiene-styrene copolymer with 20 vol.% DG-100 carbon black and chalk, in the temperature range from +60 to –60°C, it is shown that, in the region of vitrification of the copolymer and of the loss of the reinforcing effect of the carbon black, there is a sharp change in the character of the fracture micro-surface, and the particles of carbon black become the sites of additional fracture. In the region of the temperature transition of the copolymer, connected with the mobility of the phenyl groups in the same way as in the vitrification region, there is a sharp decrease in the number of particles of carbon black at the fracture surface, while the fracture surface of a mixture with chalk passes selectively along the contact boundary of a polymer with larger particles. The microstructure of the Wallner lines on the surface of a mixture with carbon black, at Tst, is made up of traces of secondary fracture, arising around the particles of carbon black.Moscow Institute of Technology for the Meat and Dairy Industry. M. V. Lomonosov Institute for the Technology of Fine Chemicals, Moscow. É. L. Ter-Gazaryan State Scientific-Research and Design Institute, Kirovakan. Translated from Mekhanika Polimerov, No. 3, pp. 437–444, May–June, 1970.     

Some properties of filled polyvinyl chloride

The effect of TiO₂, SiO₂, and carbon fillers on rigid, partly plasticized PVC has been investigated. Interaction in the polymer-filler system improves certain important properties — hardness, stiffness, wear resistance, etc., — the effect of the fillers being highly specific.M. V. Lomonosov Odessa Technological Institute. Translated from Mekhanika Polimerov, No. 1, pp 124–126, January–February, 1970.     

Effect of temperature on the mechanical characteristics of carbon plastics reinforced with metal mesh

The behavior of carbon plastics based on FN resin and FN plus rubber and reinforced with metal mesh is investigated over a broad range of temperatures in tension, compression, and pure bending. The presence of a rubbery component considerably reduces the strength of the plastic while improving its deformation properties.Dnepropetrovsk State University. Translated from Mekhanika Polimerov, No. 2, pp. 358–361, March–April, 1971.     

Effect of surface treatment of carbon fibers on the strength properties of carbon fiber plastics

Conclusions The strength characteristics of composites based on carbon fibers having a coating of silicon carbide are in direct dependence on the coating thickness and on the porosity, which makes it possible to assume the possibility of increasing the degree of realization of the strength characteristics of fibers having a coating in a composite by increasing the degree of impregnation of the carbon cord with the binder. The latter finds confirmation also in the fact that at a small coating thickness on the carbon fiber (of the order of 5 nm) the porosity of the composite obtained is equal to the porosity of the material based on the carbon fiber without coating. Moreover, as is evident from Fig. 3c, the casing of silicon carbide does not form a continuous coatting over the whole perimeter of the cord. The presence of these prerequisites, and also the high resistance of carbon fibers having a silicon carbide coating to oxidation [9], open up wide prospects for creating new composite materials based on them.Translated from Mekhanika Kompozitnykh Materialov, No. 4, pp. 603–606, July–August, 1979.     

Reduced strength of polymethyl methacrylate saturated with carbon dioxide at high pressure

The effect of external pressure on the amount of carbon dioxide sorbed by specimens of polymethyl methacrylate and on the strength of the specimens after removal of the pressure during the initial period of desorption has been experimentally investigated. The experiments were conducted at 20°C, the pressure varied from 20 to 56 bar.S. M. Kirov Ural Polytechnic Institute, Sverlovsk. Translated from Mekhanika Polimerov, No. 2, pp. 243–246, March–April, 1971.     

Dynamic compressive strength of epoxy composites

The strength of laminated and unidirectionally reinforced composite materials was investigated in conditions of dynamic uniaxial compression with a strain rate of 50–1000 sec^–1 using the split Hopkinson pressure bar method. It was shown that in conditions of dynamic compression, glass/epoxy, aramid/epoxy, and carbon/epoxy composites exhibit elastic-brittle behavior with anisotropy of the strength and elastic properties. The effect of the strain rate on the strength characteristics of fiberglass-reinforced plastics was demonstrated.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 776–782, November–December, 1995.Presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October, 1995).     

Averaging the electrical properties of fiber-reinforced metal composites

Using the regular structure model, we average the electrical properties of unidirectional fiber-reinforced metal composites and propose procedures for determination of the effective electrical conductivity tensor of these materials. For the general case of packing of fibers of arbitrary cross section, the problem is reduced to calculation of some functionals determined in solutions of the integral equation of the corresponding boundary current problem for the structure. In the special case of symmetric packing of fibers of circular cross section, the solution is written in the form of series in elliptic functions.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 533–539, July–August, 1995.     

Influence of technological processing parameters on the properties of carbon filled thermoplastics

The effect of processing parameters of injection molding on the mechanical and tribotechnical properties of carbon plastics based on polyacetals is investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane is used as the polymer matrix. Hydrated cellulose Ural LO-24 carbon fibers are used as the reinforcing filler. The effect of molding temperature, pressing time, and temperature of the casting mould on the properties of carbon plastics is investigated. It has been found that for improving the mechanical properties of carbon plastics it is necessary to raise the molding temperature up to 200–210°C. Prolongation of the technological cycle leads to thermal degradation of the polymer in the cylinder of a casting machine. The mould temperature only slightly affects the composite strength properties, but lower temperatures create better conditions for polymer crystallization. As a result of our investigations, the optimal processing parameters of the above carbon plastics are determined.Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 385–392, 1999.