Effect of fiber orientation on the structure of shock waves in carbon fiber-epoxy composites

Using an analytical relation between the Hugoniot (anisotropic and isotropic) states and other thermodynamic (anisotropic and isotropic) states at high pressures, the effect of fiber orientation on the structure of shock waves in carbon fiber-epoxy composites of various symmetry is investigated. A correct nonlinear model of propagation of shock waves in anisotropic materials is proposed, which employs the conception of total generalized pressure and the pressure corresponding to the thermodynamic response, i.e., to the equation of state. The equation generalizes the nonlinear Hugoniot equation to anisotropic materials and is reduced to the classical variant in the case of isotropy. Invoking the relations of nonlinear anisotropic solids and the generalized decomposition of stress tensor, the double structure of shock waves, consisting of nonlinear anisotropic and isotropic elastic parts, is examined. The numerical calculations of Hugoniot levels of stress agree well with experimental data for a carbon fiber-epoxy composite selected.     

Structural changes in a cotton fiber under load

Mechanical tests and x-ray studies have shown that a shift of the meridional reflection towards smaller angles signifies the stretching of the crystallite lattice in the meridional direction. The shift has been used to determine the modulus of elasticity of the crystal lattice of cotton. The microdeformation (of the crystal lattice) and the macrodeformation (extension of the specimen as a whole) are compared. The modulus of elasticity of the crystal lattice is an order greater than that of the fiber itself.V. I. Lenin Tadzhik State University, Dushanbe. Translated from Mekhanika Polimerov, No. 4, pp. 594–598, July–August, 1973.     

Effect of neutron irradiation on the lifetime of polycaprolactam

On the basis of a study of the temperature-time dependence of polycaprolactam irradiated with thermal neutrons, it has been shown that strength and lifetime and the parameters which determine lifetime vary as functions of the radiation dose.     

Influence of fiber structure modification on the mechanical properties of flax fiber-epoxy composites

The mechanical characteristics of flax fibers were optimized by using the NaOH treatment process to improve the properties of composite materials. Shrinkage of the fibers during this treatment had a significant effect on the structure and, as a result, on the mechanical properties of the fibers and the composites based on them. Due to the higher mechanical strength and stiffness of flax fibers after NaOH treatment under isometric conditions, the strength and stiffness of composites in general increase. Further, NaOH treatment leads to a rougher surface morphology, as shown, e.g., for jute fibers, compared with the surface of untreated fibers without improved fiber/matrix adhesion.     

Effect of uv irradiation on the mobility of the molecular chains in polyethylene

Conclusions 1. A decrease in the mobility of molecular chains in polyethylene after UV irradiation was discovered by the spin probe method. This decrease is proportional to the time of irradiation.2. A discontinuity lacking in unirradiated polyethylene was found on the curve for the logarithm of the rotational correlation time of the spin probe in polyethylene as a function of the inverse temperature. It was shown that the nature of the discontinuity is related to a "thawing out" of the rotational motion of the chains in the crystalline phase.Institute of the Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel. Translated from Mekhanika Polimerov, No. 4, pp. 603–608, July–August, 1976.     

Effect of multiple extension on the thermal degradation of triacetate fiber

The effect of multiple extension on the vacuum thermal degradation of triacetate fiber, in the starting state and treated with hot air or saturated steam, has been experimentally investigated.Lithuanian Scientific-Research Institute of the Textile Industry, Kaunas. Translated from Mekhanika Polimerov, No. 6, pp. 1114–1116, November–December, 1971.     

Effect of UV radiation and vacuum on the strength and failure of polymer films

The effect of UV radiation and vacuum on the strength and failure of polytetrafluorethylene (PTFE) films has been studied. After irradiation samples were extended in air. It was found that the strength and plasticity of the films is diminished by irradiation in vacuum or in air.Mekhanika Polimerov, Vol. 2, No. 3, pp. 359–364, 1966     

Effect of annealing temperature on the mechanical properties of polyethylene terephthalate fiber

The mechanical properties of polyethylene terephthalate fibers stretched at 45 and 110° C have been investigated in relation to annealing temperature. It is shown that for fibers with the maximum degree of stretch the annealing temperature has no effect on mechanical strength. Reduction in the stretch of the fibers leads to an increase in strength upon annealing, and this may be associated with densification of the amorphous zones due to the formation of a large number of intermolecular bonds between the links of the polymer chains.Mekhanika Polimerov, Vol. 3, No. 3, pp. 503–506, 1967     

Effect of electron irradiation on the mechanical and thermal properties of some polymer materials

The effect of electron irradiation on the mechanical properties (deformability) of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide (PI), and Fenilon (Fe) films, as well as the thermal properties (heat conductivity and capacity) of PTFE is studied experimentally. The thickness of the films was 40–50 m. Mechanical tests showed that polyimide films were more resistant to radiation than the other films. The investigation of the changes in the thermal properties of PTFE due to electron irradiation revealed that the phase transitions observed at temperatures of 293 and 303 K in unirradiated PTFE were shifted to lower temperature regions.Abai Alma-Ata State University, Kazakhstan. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 683–689, 1998.     

Effect of proton-electron irradiation on the strength of a glass-reinforced plastic and its components

The action of protons and electrons on the properties of glass strands under vacuum conditions has been experimentally investigated. The experimental procedure is described. The effects of irradiation, strain rate, and reduced temperature and pressure on the properties of glass reinforcement and glass-reinforced plastics are estimated.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev; Physicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 4, pp. 755–760, July–August, 1970.     

Effect of structure on the mechanical properties of block copolymers

Experimental data are given on the transitions in three block types in styrene-butadiene copolymers; these transitions were obtained by the dynamic-mechanical method on a torsional pendulum in the –180° to +170° temperature range. Based on these data, kinetic aspects have been advanced on the nature of the transitions based on the formation and decomposition of supramolecular structures of varying type and dimensions.Voronezh Technological Institute. Translated from Mekhanika Polimerov, No. 5, pp. 774–779, September–October, 1972.     

Effect of small additives of oligomer on the viscoelastic properties of carbon fiber plastics

The viscoelastic properties of carbon fiber composites whose phenol-formaldehyde matrix is modified by thermodynamically incompatible isocyanate derivatives have been investigated. Data are given on fiber wetting (Table 11), internal stress (Table 2), viscoelastic properties (Fig. 1), and tensile strength (Fig. 2). The modified composites are strengthened by the addition of 0.5–4% oligomer additive. This process involves the formation of a two-phase structure, in which the additive phase microparticles act as a polymer filler. Due to selective interactions, the intermediate layer formed at the fiber-binder interface leads to changes in the viscoelastic properties and tensile strength of the matrix and improved maintenance characteristics for the material as a whole.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 4, pp. 440–445, July–August, 1993.     

Effect of fiber tension on the unwinding resistance of hardening layers of glass-reinforced plastic

The shear fracture toughness characteristics of glass-reinforced plastics used for strengthening metal pressure vessels have been determined by testing metal-GRP rings. The shear fracture toughness characteristics are statistically estimated for a unidirectional GRP as a function of the winding tension.K. É. Tsiolkovskii Moscow Aviation Engineering Institute. Translated from Mekhanika Polimerov, No. 5, pp. 935–938, September–October, 1975.     

On the fiber structure of symmetry invariance sets of solutions to quasilinear equations

Known results about the unique continuation of solutions of anisotropic linear and weakly nonlinear differential equations and the extension of the invariance property of these solutions are applied to prove theorems about the fiberwise quasianalyticity and the fiber structure of sets of symmetry invariance of solutions to quasilinear equations.