Effect of processing technology on the structure and properties of polypropylene

The methods of macro- and microstructural analysis are used to investigate the relation between the injection molding parameters, on the one hand, and the structure and physico-mechanical properties of the molded polypropylene block, on the other. It is shown that the structure takes the form of layers of different thickness and shape. Certain properties of molded products are determined not only by the spherulitic structure but also by the nature of the macrostructure of the polymer in the block.Voronezh Technological Institute. Translated from Mekhanika Polimerov, No. 2, pp. 200–204, March–April, 1971.     

Effect of hydrostatic pressure on the tensile strength of polymer materials

The effect of hydrostatic pressure on the tensile strength of amorphous, crystalline, and thermosetting polymers has been investigated. The maximum hydrostatic pressure was 2000 kgf/cm². The surfaces of some specimens were protected from the ambient medium (oil). The tests showed that hydrostatic pressure improves the strength or high-elastic limit and Young's modulus of all the materials investigated. In the case of brittle materials, the increase in strength is greater if the surface is protected, whereupon the plasticity is also improved. Hydrostatic pressure produces important changes in the deformation behavior of crystalline polymers.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1043–1047, 1967     

Effect of tensile stresses on the strength of heat-treated glass fibers

Possibilities of controlling the internal stresses developing during production of glass reinforced plastics were investigated. A favorable effect can be obtained by prestressing the glass fiber reinforcement during molding. Prestressing during heat treatment was found to increase the strength of the fibers. The strengthening is due to a reduction in stress concentration around microcracks as a result of forced elastic and plastic deformation.Mekhanika polimerov, Vol. 1, No. 1, pp. 89–92, 1965     

Molecular orientation and the tensile strength of polystyrene

The tensile strengths of uniaxially oriented polystyrene films with molecular orientation determined by IR spectroscopy are compared. Two different orientation methods involving different time and temperature regimes are employed. It is found that the tensile strength is a unique function of the degree of orientation of the molecular segments of the polystyrene carbon chain irrespective of the means used to orient the specimens and increases linearly with increase in the degree of molecular orientation of the polymer. The experimental dependence is in satisfactory agreement with the results of a theoretical analysis.A. F. Ioffe Physico Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 612–615, July–August, 1969.     

Prediction of changes in the strength of filled thermoplastics upon aging in an oxidizing atmosphere

Problems related to analyzing specimens with damaged surface layers have been examined using polyamide, trioxane—dioxolane copolymer, and polycarbonate as source materials. A model was developed for the brittle fracture of block specimens with damaged surface layers, which provides an estimate of the restraints to plastic deformation in these layers. Three segments are seen in the strength—time curves featuring 1) increasing strength, 2) decreased strength with brittle fracture, and 3) constant low strength. The strength of filled specimens of a specific period permits us to evaluate the effect of the filler on the fracture resistance of the matrix. A method was proposed for predicting the strength of filled samples using the matrix aging data.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 3, pp. 375–380, May–June, 1993.     

Effect of processing conditions on the supramolecular structure and strength properties of polycaprolactam

The formation of supramolecular structures in block polycaprolactam is considered. It is shown that technological factors have a considerable effect on the nature of the supramolecular structure. Two of these factors are the temperature gradient of the polymer melt and the nature of its motion in the cylinder of the injection molding machine up to the moment of injection into the mold. It is shown that the nonuniformity of deformation and the considerable number of defects associated with large supraspherulitic formations lead to a deterioration in the strength and deformation properties of polymers.Mekhanika Polimerov, Vol. 2, No. 5, pp. 659–663, 1966     

Effect of certain structural and technological parameters on the tensile strength and deformation of unidirectionally reinforced plastics

A model of the deformation and failure of unidirectionally reinforced plastics in short-time static tension with allowance for the effect of the properties of the components, the adhesion interaction between them, and the structure of the material is proposed as a basis for the selection and development of nondestructive methods of testing glass-reinforced plastic articles. It is shown that the proposed model is in qualitative agreement with the experimental data.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1042–1048, November–December, 1973.     

Structural changes and defect development in epoxy adhesive compounds during thermal aging

The structural characteristics of epoxy adhesive compounds and the development of surface defects during thermal aging have been investigated. Profilograms of the fracture surfaces of bonded joints have been obtained and certain causes of the increased dispersion of the bond strength characteristics explored.Mekhanika Polimerov, Vol. 4, No. 2, pp. 293–295, 1968     

Effect of temperature on changes of tensile stress at constant elongation in certain human soft tissues

The nature and magnitude of the temperature-induced changes in the initial tensile stress at constant elongation have been investigated in relation to the human artery and vein walls, tendons, and muscle tissue. It has been established that for a cylindrical segment and a specimen of artery wall heated from 10 to 45°C the stress increases, whereas for the vein wall, the tendon, and the muscle tissue it decreases. This behavior of the artery and vein walls is attributed to their different biochemical composition. The difference in the stress-temperature dependence associated with age has been studied. The stresses in the walls of the human femoral artery and great saphenous vein have been determined during autopsy.     

Experimental estimation of the transverse tensile strength of carbon-reinforced plastics

The transverse tensile strength of carbon-reinforced plastics is estimated on the basis of the results of bending tests on open rings and segments. It is shown that structural discontinuities due to technological factors sharply reduce the transverse tensile strength of carbon-reinforced plastics. The radial stresses have an important influence on the strength of segments tested in three-point bending.     

On the effective viscosity of a dilute emulsion of gas bubbles

The problem of the motion of a rigid spherical body in a homogeneous emulsion of gas bubbles is considered in the Stokes approximation, using the self-consistent field method. An expression is obtained for the correction factor in the Stokes formula for the drag of the body in the first approximation with respect to the volume concentration of the dispersed phase. An analytical relation between the correction factor and the ratio of the sizes of the bubbles and the body is found. It is shown that, in the limit when this ratio tends to zero, the correction factor obtained is identical to Taylor's result for the effective viscosity of an emulsion of gas bubbles. In the case of non-point bubbles, the coefficient on the volume concentration in the expression for the effective viscosity of the emulsion can be considerably different from Taylor's result. A similar conclusion was also obtained in the case of the problem of the motion of a spherical bubble of arbitrary size in an emulsion of gas bubbles.     

A method of testing the transverse tensile strength of wound articles

A theoretical and experimental justification is provided for a method of determining the transverse tensile strength of composites on the basis of bending tests on a segment of a circular ring. Test data obtained by different methods are compared.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 759–761, July–August, 1973.     

Anisotropy of the low-cycle tensile fatigue strength and deformability of a glass-reinforced plastic

Experimental results on the anisotropy of the strength and deformability of a 1:1 SVAM oriented glass-reinforced plastic in low-cycle tension in the directions =0, 15, 30, and 45° are discussed. The loading frequency was 1–1.5 cycles/minute. A three-dimensional fatigue strength diagram is constructed in _max - - log N coordinates. It is shown that in the direction =0° the fracture strain depends on stress, whereas at 0° the glass-reinforced plastic fails at almost the same maximum strain, the value of which depends on , but is invariant with respect to _max. It is established that the rate of development of the strain extrema on the linear part of the (N) graph and the stress _max are related by a power-law dependence, whose parameters are determined by the anisotropy of the mechanical properties of the composite.Institute of Mechanics, Academy of Sciences of the Armenian SSR, Erevan. Translated from Mekhanika Polimerov, No. 3, pp. 425–429, May–June, 1976.     

Effect of thermal aging on the adhesive strength of joints of double-chain polymers with fibers and on the properties of unidirectional CFRPs based on them

The paper presents a study on the effect of thermal aging on the adhesive strength of joints of some double-chain polymers and fibers. It is shown that the initial shear strength of joints of a steel wire with double-chain polymers based on bisaminonitrile (R = −CH₂−) is significantly higher than that in the case of polymers based on the “A-B” monomer. The type of thermal stabilizer affects the strength of the fiber/matrix interface only slightly. Prolonged heating (up to 100 hours) of the joints at 350 °C does not reduce the strength of joints based on the “A-B” monomer, while that of joints based on bisaminonitrile decreases by 20-30%. The thermal stability of carbon-fiber-reinforced plastics appeared to be higher, which was likely due to the effect of scale factor. The strength of a test specimen batch decreased only upon exposure to 400 °C for more than 100 hours.     

Effect of structural and processing parameters of the reinforcement on the strength of unidirectional metalfiber composites under different types of loading

Conclusion The above studies show that the strength of unidirectional FCP's in uniaxial and biaxial tension is largely determined by the strength of the bond between the fibers and matrix and the internal geometry of the reinforcement. This dependence is particularly significant when the FCP product is loaded across as well as along the fibers. Impulsive loading as a method of making FCP's makes it possible to broadly vary the strength of the fiber-matrix interfaces. The unidirectional FCP's and tubular products of FCP's obtained by this method have a high strength under different types of loading, and this strength can be predicted by calculation.Presented at the Sixth All-Union Conference on the Mechanics of Polymer and Composite Materials (Riga, November, 1986).Translated from Mekhanika Kompozitnykh Materiaiov, No. 6, pp. 1033–1038, November–December, 1986.