Time-temperature superposition applied to the relaxation properties of a glass-reinforced plastic and its matrix

The relaxation behavior in compression of an unsaturated polyester resin and the corresponding glass-reinforced plastic has been investigated. The time-temperature superposition principle is shown to be applicable to the cross-linked polyester resin and the glass-reinforced plastic. The temperature dependences of the shift functionsa _T of the resin and the glass-reinforced plastic are found to satisfy an Arrhenius equation with the constant equal to 21–25 kcal/mole.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 360–363, March–April, 1972.     

Strength of orthogonally reinforced plastics in uniaxial tension

Failure conditions are proposed for an orthogonally reinforced plastic in uniaxial tension at an arbitrary angle to the directions of reinforcement. The failure conditions are formulated for the case when the strength of the bond between the resin and the reinforcement is greater than the strength of the resin. The strength of the resin, which is in a volume state of stress, is determined by an energy criterion.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 629–633, July–August, 1973.     

Effect of water on the adhesion of epoxy resin to steel

The change in the adhesion of epoxy resin to steel in the presence of water has been investigated. It is shown that under these conditions the adhesion is reduced. The reduction is reversible above and irreversible below the glass transition temperature of the resin.Ural Scientific-Research Chemical Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 4, pp. 733–736, July–August, 1971.     

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.     

Resistance of composite flywheel rim to radial tensile stresses from centrifugal forces based on results of pure bending of a rim segment

A method is proposed for evaluating the resistance of a flywheel rim to radial stresses in free rotation. The method is based on loading a rim segment in pure bending and calculating the limiting moment and the corresponding limiting angular velocity. Applicability of the method is substantiated theoretically by investigating the similarity of the radial stress diagrams in rotation and pure bending. The method is verified experimentally for the strained state of a rim segment in pure bending.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 4, pp. 521–526, July–August, 1993.     

Analysis of the tensile deformation of glass-reinforced plastics

The deformation of an orthotropic glass-reinforced plastic is considered with allowance for the failure of the resin in the transverse layers.Ordzhonikidze Moscow Aviation Institute. Translated from Mekhanika Polimerov, No. 1, pp. 144–147, January–February, 1970.     

Stresses in various resins cured on glass films

By using Sanzharovskii's method for determining the stresses in lacquer coatings and employing as a model a layer of resin deposited on a glass film, it is possible to simulate the processes that take place in glass-reinforced plastics and determine the stresses that develop in different resins cured under various conditions. The method proposed makes it possible to estimate the effect on the stresses of the shrinkage of the resin, its elasticity, and the difference in the coefficients of thermal expansion of the resin and the glass. Such an investigation is desirable before selecting the composition of the resin, additional organic or mineral fillers and elasticizers, and the optimal curing regime for glass-reinforced plastics.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 481–486, May–June, 1969.     

Friction and rheological properties of resin-impregnated glass tape

The dependence of the dynamic coefficient of friction of resin-impregnated glass tape on the sliding speed over the mandrel surface and the viscosity of the resin is derived. The formulas obtained are confirmed by the results of experiments which indicate a linear dependence of the coefficient of friction on the sliding speed of the tape over a metal mandrel. Graphically, this dependence is expressed by straight lines with a common origin and a slope that increases with the viscosity of the resin. The coefficient of friction of glass tape sliding over a prewound layer at low speeds also has a linear dependence. At high speeds the dependence takes the form of a damped curve.Translated from Mekhanika Polimoerov, No. 1, pp. 166–170, January–February, 1976.     

Effect of fillers on the structure and properties of cured resins

It is shown for the first time that the increased strength of filled plastics is associated with an increase of the internal pressure in the resin determined by the nature of the filler surface and the curing conditions.For communication 1, see [1].Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 54–58, January–February, 1970.     

Strain distribution in composites

The strains in specimens of epoxy-furan resin and rubber simulating the structure of a composite material have been experimentally investigated by the network method. The strains in the components are distributed in accordance with an almost normal Iaw.Gomel's State University. Translated from Mekhanika Polimerov, No. 4, pp. 731–734, July–August, 1974.     

On the limiting Pitman efficiency of some rank tests of independence

The limiting (as the significance level approaches 0) Pitman efficiency of a new “regression-based” rank test of independence to Kendall's tau and Spearman's rho is derived. The result is based on a version of [17], Ann. Statist.4 1003–1011) on coincidence of the limiting Pitman efficiency and the local (as the alternative approaches the hypothesis) approximate Bahadur efficiency. [7], Trans. Amer. Math. Soc.87, 173–186) result is applied to verify the main assumption of Wieand's paper. This approach is shown to be useful in some other situations, also.     

Investigation of the adhesion strength of carbamide resins

The adhesion of carbamide resin to clean or treated fiber glass surfaces has been determined. The effect of this adhesion on the strength of glass-reinforced plastics is examined.Moscow Mendeleev Chemical Engineering Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1119–1121, November–December, 1968.     

Methods of exploiting natural internal stresses to strengthen composites

A method of strengthening nonuniformly reinforced composites is proposed. A rational scheme for coordinating the external stress field, the resistance field, and the internal stress field is examined in relation to the case when the internal stresses are caused by shrinkage of the resin.Ural Kirov Polytechnic Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 5, pp. 870–875, September–October, 1970.     

Effect of the nature of the filler surface on the properties of phenol-formaldehyde molding powders

The physicomechanical properties and microstructure of phenolic molding powders containing fillers with different surface energies have been investigated. It has been found that an increase in filler surface energy leads to an increase in the density of the resin around the filler particles and hence to an improvement in the physicomechanical properties of the molding powder. A parallel investigation of a molding powder containing a lubricant shows that adsorption of the lubricant on the filler surface reduces the density of the resin, which is accompanied by a deterioration in the properties of the material.Scientific-Research Institute of Precision Engineering Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 677–681, July–August, 1968.     

Effect of temperature — Time factors on the yield point of crystalline polymers in the flat stressed state (high-density polyethylene)

Conclusions 1. Experiments have been performed on biaxial stretching of HDPE over a wide range in ratios of the principal stress components, strain rates, and temperature. The character of change in the limiting characteristics of HDPE are different in different temperature regions.2. The limiting resistance of HDPE in the flat stressed state for T=const and v_i=const is described satisfactorily by the Malmeister and Gol'denblat-Kopnov criteria.3. Prediction of the limiting resistance of HDPE should be carried out within limited temperature ranges, in which similarity of strain diagrams, a similar character of structural changes in the material (accumulation of damage), and identical character of change in its limiting characteristics are observed.Okhtinsk "Plastpolimer" Scientific and Production Union, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 247–254, March–April, 1977,     

Express determination of polymer composite porosity

Results are given for an experimental and theoretical study of a rapid method for determining the porosity of polymer composites by measuring the limiting moisture content in the material. The limiting moisture content was calculated using Fick 's equation solved for a plane parallel plate. The necessary parameters required for solving Fick 's equation were determined experimentally in the initial stage of the kinetic curve for water absorption. The porosity calculation was carried out using constants of a control material previously determined for pilot samples. This method is sufficiently accurate for engineering purposes and does not require special equipment.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 824–827. November–December, 1995.     

Effect of porosity and component ratio on the thermal conductivity of glass-reinforced plastics

The dependence of the thermal conductivity of glass-reinforced plastics on porosity and component ratio is investigated. The possibility of determining the porosity, specific weight, and resin content of glass-reinforced plastics from their thermal conductivity is confirmed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 487–491, May–June, 1969.     

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     

Some special features of the structural changes of epoxy resins under the action of magnetic fields

Conclusions 1. The action of a magnetic field leads to a change in the structure of an epoxy resin both at the molecular and at the supramolecular levels.2. A homogeneous magnetic field acting on the hardening process of an epoxy resin, due to the presence of the orientating moment, is able to produce ordered formations.3. A nonhomogeneous magnetic field results in a distribution of anisotropic morphological formations along the field gradient, promoting a change in the physicomechanical properties of the material.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 583–587, July–August, 1978.     

Estimating a Distribution Function for Censored Time Series Data

Consider a long term study, where a series of dependent and possibly censored failure times is observed. Suppose that the failure times have a common marginal distribution function, but they exhibit a mode of time series structure such as α-mixing. The inference on the marginal distribution function is of interest to us. The main results of this article show that, under some regularity conditions, the Kaplan–Meier estimator enjoys uniform consistency with rates, and a stochastic process generated by the Kaplan–Meier estimator converges weakly to a certain Gaussian process with a specified covariance structure. Finally, an estimator of the limiting variance of the Kaplan–Meier estimator is proposed and its consistency is established.