Effect of scale and temperature factors on the compressive and shear strengths of plastics

Results are given of investigations of certain strength characteristics of a number of thermosetting plastics in relation to the scale of specimens reduced to 1/5 the standard size, i. e., the effect of the scale factor on the mechanical characteristics of plastics in compression and shear. In addition, results of a study of the dependence of the mechanical characteristics of plastics on the degree of heating in the temperature range from 20 to 200°C, i. e., the effect of the temperature factor on these characteristics, are also given.Mekhanika Polimerov, Vol. 1, No. 4, pp. 92–99, 1965     

Investigation of the elastic properties of friction plastics with ultrasound

Using data on the rate of propagation of longitudinal vibrations and the dynamic Young's modulus, we studied two-component friction plastics over the temperature range 20–150°C by an ultrasonic pulse method at a frequency of 1 Mc. The changes in acoustic characteristics were investigated in relation to the degree of vulcanization, plasticization and polarity of rubber at 20°C.Mekhanika Polimerov, Vol. 1, No. 2, pp. 152–158, 1965     

Tensile strength of acrylic plastics (PPM) in the presence of a temperature gradient over the thickness of the material

Experimental values of the strength and deformation are presented for SO-95, SO-120, and SO-140 acrylic plastics (polymethyl methacrylate: plasticized, unplasticized, and copolymer) stressed in unaxial tension at v=10 mm/min, stationary temperature gradients of from 2.5 to 17.5 deg/mm over the thickness of the material, and a constant cold-face temperature of 25°C. The deformation properties under these conditions are described: in the presence of a temperature gradient the ultimate strains are higher than for a uniform temperature field at a temperature equal to the cold-face temperature, and the elongation at break falls as the hot-face temperature rises. The tensile strength of plastics with a temperature drop over the cross section can be approximately calculated from the mechanical characteristics obtained for a uniform temperature field.Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 963–969, November–December, 1969.     

Structural characteristics of materials reinforced with high-modulus fibers

Research on the mechanics of boron and carbon-reinforced plastics is briefly reviewed. The design and testing characteristics of these materials associated with the high degree of anisotropy of their elastic properties, as compared with those of glass-reinforced plastics, are discussed. Problems relating to testing at an angle to the direction of the reinforcement, the effect of misorientation and distortion of the fibers, and the consequences of the low shear strength are considered. Experimental confirmation has been obtained by testing unidirectional (1 : 0), orthogonally reinforced (1 : 1 and 2 : 1), and tridirectional (1 : 1 : 1 in the 0°, +60°, and –60° directions) boron and carbon-reinforced plastics.DeceasedInstitute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 676–685, July–August, 1971.     

A study of the physicomechanical properties of carbon fibers at high temperatures

Conclusions 1. Carbon fibers, similar to graphite materials, are heat-resistant and do not Iose their short-term tensile strength in the temperature range studied — 20 to 2000°C.2. Young's modulus of carbon fibers hardly changes in the temperature range 20 to 1200°C, but a significant decrease is observed upon a further increase in temperature.Translated from Mekhanika Polimerov, No. 4, pp. 626–630, July–August, 1977.     

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.     

Determination of adhesive strength in a thermoplastic-resin-thin-fiber system

Conclusion A method was developed for determining adhesive strength in thermoplastic-material—thin-fiber systems formed from a melt. Values of _o were determined for joints between PSF and PC On the one hand and high-modulus organic fibers on the other hand. We studied the dependence of the bond strength on the temperature at which the contact is formed, the area of the contact, and the condition of the surface. The adhesion of PC and PSF to organic polyamide fibers is good enough to make it unnecessary to develop adhesives or specially modify the fiber surfaces for the production of organic-fiber-reinforced plastics. The low shear strength of laminated plastics based on thermoplastic resins is evidently due to the small area of actual contact, which is in turn a consequence of the poor wetting and impregnation of the fiber filler by the melt.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 9–12, January–February, 1990.     

Glass-reinforced plastics based on matrices combining thermoplastics and thermosetting plastics

The conditions of fabrication and the physicomechanical properties of glass-reinforced plastics based on polysulfone combined in different ratios with epoxy resin and Rolivsan were investigated. It was found that realization of the strength of the fibers in glass-reinforced plastics based on three types of binders and mixtures of them at room temperature is approximately the same. The lower strength of glass-reinforced plastics based on polysulfone is determined by the lower concentration of fibers. Modification of thermosetting plastics with polysulfone significantly increases (by 5–8 times) the specific energy of delamination of the glass-reinforced plastics G_1c, which should be manifested by an increase in their crack resistance and other operating characteristics. Modification of ED-20 with polysulfone and polysulfone with Rolivsan significantly increases the glass transition temperature of the polymer and affects the character of the temperature curves of the strength of the glass-reinforced plastics.Institute of Chemical Physics, Russian Academy of Sciences, Moscow. D. I. Mendeleev Russian Chemical Technological University, Moscow. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 111–117, January–February, 1996.     

On the causes of strength differences in molded plastics filled with mineral powder fillers

It has been established by investigating the effect of common mineral powder fillers on the rate and depth of resin cure that such additions may have an inhibiting or catalytic influence on the hardening process, depending on their nature and method of preparation. The fillers which catalyze the hardening process increase the strength and heat resistance of the cured plastics. When introduced in small amounts into resins used as binders for unsized glass fibers, these fillers equalize the rate and depth of cure in the resin layers, thus increasing the strength and heat stability of glass-reinforced plastics.Mekhanika Polimerov, Vol. 1, No. 5, pp. 58–65, 1965     

Temperature dependence of the mechanical properties of polymers of different chemical structure in the temperature range from 4.2 to 300°K

Conclusions 1. The temperature dependences obtained for the ultimate alongation, tensile strength, and elastic modulus of various polymers showed that the relationship between the mechanical properties and chemical structure of macromolecules found in our earlier work at 4.2°K is retained at 78°K and, possibly, up to 90°K.2. It was shown that the passage of the tensile strength through a maximum upon warming from 4.2°K results from a corresponding increase in deformability, which is accompanied by a decrease in the elastic modulus and deviation of the polymer bodies from Hooke's law progressively with increasing temperature.3. It was shown that the amorphization of crystallizing polymers, for example, by quenching, gives a marked change in the deformability, tensile strength, and elasticity of the polymer body over the entire range from 300 down to 4.2°K.4. Study of the mechanical properties of polymers at 78°K in a helium medium and liquid nitrogen showed a marked effect of contact of the polymer with liquid nitrogen on these properties. This effect is different for polymers of varying chemical structure as well as for the same polymer in different physical states.Report presented at the Third All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1976.L. Ya. Karpov Scientific-Research Institute of Physical Chemistry, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 387–391, May–June, 1977.     

Influence of structure on the mechanical properties of block copolymers

The relationship between the breaking strength and the temperature has been studied for butadiene/styrene block copolymers of the three-block configuration styrene-butadiene-styrene. The studies were carried out over the temperature range –20 to 60° at crosshead speeds of 5, 50, 250, 500, and 1000 mm/min. An analysis was carried out on the values of the parameter U in the equation linking the breaking strength with the temperature.For Communication 2 see [3].Voronezh Technological Institute. Translated from Mekhanika Polimerov, No. 3, pp. 392–398, May–June, 1974.     

Effect of elevated temperatures on the strength of cured resins and resin-based materials

An analysis of the relationship between the relative changes of compressive strength and weight loss for glass laminates has shown that at elevated temperatures (to 600° C) the changes in strength are primarily caused by processes of mechanical destruction of the resin phase. The process of thermo-oxidative degradation of the resin in the laminate is described by the same stages as were detected in studying cured resins.Moscow Aviation-Engineering Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 832–838, September–October, 1968.     

Effect of boundary-layer processes on the strength of glass-reinforced plastics

It is shown experimentally that the strength of glass-reinforced plastics is determined by the properties of the resin close to the fibers; these depend on the structure and chemical composition of the fiber surface. A study is made of the effect of modification of the glass fiber on curing conditions in the layer next to the fiber for a number of resins (K9 silicone resin, ED-6 epoxy resin, polyacrylate-911, and furfural PF resin).Mekhanika polimerov, Vol. 1, No. 1, pp. 26–35, 1965     

Impact strength of high-density polyethylene with various molecular weight distributions

The Charpy impact strength of high-density polyethylene specimens prepared under low pressure with average molecular weight from 60·10³ to 1.5·10⁶ and differing substantially in molecular weight distributions has been studied at room temperature and at –190°C. It is shown that, both at room temperature and at temperature considerably below the glass-formation temperature, the impact strength of polyethylene in the range of molecular weights mentioned is determined mainly by the content of fractions with molecular weights about 10⁵ and more and does not depend on the width of the molecular weight distribution."Plastpolimer" Scientific-Research Association, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 919–921, September–October, 1973.     

Deformation and strength properties of carbon-reinforced plastics in compression

The deformation and strength properties of unidirectionally reinforced carbon plastics have been experimentally investigated for uniaxial compression in the longitudinal and transverse directions and at 45° to the direction of reinforcement in both short-time and long-time tests. On the basis of the deformation properties of the components an attempt is made to describe the creep curve of the plastic in all three loading directions. The Mohr theory is used to predict the compressive strengths in the direction of reinforcement and at right angles to the reinforcement.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 29–35, January–February, 1973.     

Statistical analysis of the results of humidity-temperature tests of glass reinforced plastics (GRP)

The effect of moisture and temperature factors on the strength of glass-reinforced plastics (GRP) is examined. In view of the considerable dispersion of the experimental data, a statistical method is used for analyzing the test results. The tensile strength distribution law for KAST-V glass laminate under various humidity and temperature conditions is analyzed.Mekhanika Polimerov, Vol. 1, No. 5, pp. 135–141, 1965     

Polymer fractography and fracture kinetics

The fractographic method makes it possible to determine the test temperature and time at which anomalies appear in the temperature-time dependence of the strength of polymethyl methacrylate and polycaprolactam by finding the conditions of disappearance of specular zones from the fracture surfaces of these polymers. For PMMA these values are –40°C and 10^–2 sec, for PCL –120°C and 10^–7 sec, respectively.For communication 1 see [2].Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 232–237, March–April, 1971.     

Effect of combined extrusion parameters on mechanical properties of basalt fiber-reinforced plastics based on polypropylene

Basalt fibers are efficient reinforcing fillers for polypropylene because they increase both the mechanical and the tribotechnical properties of composites. Basalt fibers can compete with traditional fillers (glass and asbestos fibers) of polypropylene with respect to technological, economic, and toxic properties. The effect of technological parameters of producing polypropylene-based basalt fiber-reinforced plastics (BFRPs) by combined extrusion on their mechanical properties has been investigated. The extrusion temperature was found to be the main parameter determining the mechanical properties of the BFRPs. With temperature growth from 180 to 240°C, the residual length of the basalt fibers in the composite, as well as the adhesive strength of the polymer-fiber system, increased, while the composite defectiveness decreased. The tensile strength and elastic modulus increased from 35 to 42 MPa and 3.2 to 4.2 GPa, respectively. At the same time, the growth in composite solidity led to its higher brittleness. Thus, a higher temperature of extrusion allows us to produce materials which can be subjected to tensile and bending loads, while the materials produced at a lower temperature of extrusion are impact stable. The effect of the gap size between the extruder body and moving disks on the mechanical properties of the BFRPs is less significant than that of temperature. An increase of the gap size from 2 to 8 mm improves the impregnation quality of the fibers, but the extruder productivity diminishes. The possibility of controling the properties of reinforced polypropylene by varying the technological parameters of combined extrusion is shown. The polypropylene-based BFRPs produced by the proposed method surpass the properties of glass and asbestos fiber-reinforced plastics.Submitted to the 10th International Conference on Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 6, pp. 845–850, November–December, 1997.     

Effect of temperature on the mechanical properties of boron fibers

The effect of exposure to temperatures on the interval 20–600°C for up to 1000 h on the physicomechanical properties of boron fibers at room temperature has been investigated. Prolonged exposure to temperatures up to 200°C does not have much effect on the mechanical characteristics of the fibers, whereas heating for one hour at 300–350°C increases the strength of the fibers by 10–12%.All-Union Scientific Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 329–332, March–April, 1971.     

Creep and long-time strength of tubular specimens of asbopolyethylene

Results are presented of an experimental investigation into the mechanical properties of asbopolyethylene obtained by adding 25 parts by weight of asbestos to pure low-density polyethylene to improve strength and stiffness characteristics. Test data on the creep and static strength of tubular specimens of asbopolyethylene at room temperature in uniaxial tension are given. The long-time strength of asbopolyethylene was determined at 20°, 50°, 80° and 100° C. To estimate the effect of adding asbestos to the polyethylene the mechanical characteristics of pure polyethylene and asbopolyethylene are compared.Mekhanika Polimerov, Vol. 1, No. 5, pp. 51–57, 1965