Seismoacoustic prediction of the fracture processes in glass-reinforced plastics

A technique and equipment for investigating the seismoacoustic emission associated with the fracture of a loaded glass-reinforced plastic are described. It is shown that the emission is present from the beginning of loading and increases regularly up to failure. Glass strands consisting of 100 plain elementary fibers of varying diameter and resin-impregnated strands have been investigated in tension and specimens of glass-reinforced plastic and unreinforced epoxy resin in tension and bending. Experimental data on short-time, static and repeat loading are presented for the glass-reinforced plastic. It is shown how the integral pulse distribution and the pulse amplitude frequency function depend on the applied load level.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 421–429, May–June, 1971.     

Effect of building structure on the distribution of random bending strength of multilaminate reinforced plastics

A probabilistic structural model has been constructed for predicting the bending strength distribution in multilaminate reinforced plastics. The number and random strength/elastic properties of the layers or repeating structural elements are parameters of the structure. The random properties of the repeating structural elements are characterized by the scheme and geometry of the unidirectional layers. Two failure conditions have been analyzed: multistep failure caused by successive failure of separate layers and failure caused by the failure of the weakest component. The effect of the number of layers and the instability of the strength and elastic properties on the basic statistical properties of the bending strength was analyzed numerically for typical structures and for both failure conditions. The quantitative significance of the size effect determined by the thickness of the plastic was investigated. The main theoretical results were checked experimentally for unidirectional reinforced carbon plastic under uniaxial bending. The experimental distribution agrees well with the predicted distribution.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 3, pp. 336–344, May–June, 1993.     

Effect of stress ratio on the fatigue strength of organic plastics

Conclusions Experimental fatigue curves of a unidirectional organic plastic are obtained for a number of asymmetry factors and diagrams of the limiting cycle stresses are constructed for a load in the direction of the fibers and across the fibers, and for in-plane shear of a layer. The simplest methods of approximating the calculated diagrams are tested. It is shown that the method of layer-by-layer analysis of fatigue failure makes it possible to construct limiting-stress diagrams for a laminar oblique-ply composite with an accuracy acceptable for engineering calculations, proceeding from the same analysis as for an individual layer.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 421–429, May–June, 1991.     

Deformation and failure of angle-plied organic fiber-reinforced plastics in the 3D stress state

Tubular specimens of organic fiber-reinforced plastic (OFRP) are tested in tension under a high hydrostatic pressure of up to 300 MPa. The specimens are made by winding at an angle of ±60° to the generatrix. The experimental equipment and technique are described. The tests show the insignificant effect of hydrostatic pressure on the elastic properties and the failure mode of the OFRP. The hydrostatic pressure considerably affects the strength properties of the OFRP. The material strength increases almost twofold under a pressure of 300 MPa. The failure strains of the material increase significantly as well.N. E. Bauman Moscow Higher Technical School, Moscow, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 5, pp. 592–602, September–October, 1997.     

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.     

Bending of a cantilevered glass-reinforced plastic cylindrical shell weakened by a circular opening

The stress concentration is investigated in the neighborhood of a circular opening in a cantilevered glass-reinforced plastic cylindrical shell with a concentrated load at the free end. The problem is solved by the Bubnov method using a Ural-2 computer. The theoretical results have been checked experimentally on glass-reinforced plastic shells.All-Union Correspondence Polytechnic Institute, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 152–157, January–February, 1970.     

Preparation of fiberglass plastics by the method of curing under vacuum

A method of preparing fiberglass plastic articles using vacuum treatment in the curing process is considered. It has been established that the strength and deformation properties of fiberglass plastics so made improve greatly as the degree of vacuum is increased.Voroshilovgrad Engineering Institute. Translated from Mekhanika Polimerov No. 6, pp. 1128–1130, November–December, 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.     

Behavior of antifrictional self-lubricating plastics at elevated temperatures in the friction process

Conclusions 1. The process of friction of antifrictional self-lubricating plastics based on F-1 polyarylate and various fillers has been studied. It has been shown that a distinctive feature of this process is the formation of a film of the same composition as that of the antifrictional plastic on the steel surface.2. It has been shown that during the process of friction of antifrictional self-lubricating plastics both structural changes in the mobybdenum disulfide and also tribochemical transformations of molybdenum disulfide and copper, plus reaction of these with the counterbody material, take place in the surface films.3. It has been found that the nature of the tribochemical transformations depends on the chemical composition of the antifrictional self-lubricating plastic and affects the temperature limits of the friction zones.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 649–657, July–August, 1976.     

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.     

Behavior of glass-reinforced plastic cylindrical shells subjected to an external pressure pulse

The transient process of deformation of a cylindrical glass-reinforced plastic shell loaded with an axisymmetric external pressure pulse has been experimentally investigated. It is shown that as the amplitude of the load is monotonically increased (duration fixed), the axisymmetric motion of the shell is characterized first by linear and then nonlinear flexural oscillations.Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 327–330, March–April, 1972.     

Inelastic deformation and fracture of disordered fiber-reinforced composites

Conclusions Simulation of the process of nonlinear deformation and failure in the structure of a unidirectional epoxy glass plastic under transverse loading has indicated that equilibrium regions of failure receiving only hydrostatic compressive loading may form. The development of this region explains the high (up to 40%) nonlinearity of deformation diagrams under transverse biaxial compressive loading. The regions of nonlinear deformation of the epoxy matrix affect less markedly the nonlinearity of the macroscopic s* diagrams. This fact and also the formation and avalanchelike propagation of regions of complete failure explain the linear form of many diagrams corresponding to tensile and shear loading in the transverse plane. The relations of the nonlinear theory of elasticity make it possible to describe with sufficient accuracy the entire set of the calculated diagrams.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 5, pp. 621–628, September–October, 1993.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 5, pp. 621–628, September–October, 1993.     

Fiber distribution in oriented glass-reinforced plastics

The distribution of the fibers in the structure of a glass-reinforced plastic has been experimentally investigated. Data have been obtained on the distribution of interfiber distances, fiber diameters, and the angles between the lines of centers. Experimental histograms and distribution curves are constructed.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 282–287, March–April, 1969.     

Thermal deformation of unidirectional hybrid composites. 2

Conclusions A variant of the solution of the problem of the thermorheologically complex temperature strain of a hybrid composite containing viscoelastic thermorheologically simple components with differing functions for temperature-time reduction in addition to elastic components, is proposed. An experimental study is conducted on unidirectional specimens of organic- and glass-fiber-reinforced plastic, organic- and carbon-fiber-reinforced plastic, and carbon- and glass-fiber-reinforced plastic at a constant rate of temperature change in the 20–150 °C range. Satisfactory correspondence is obtained between predicted and experimental data.For previous communication, see [1].Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 969–979, November–December, 1989.     

Creep of unidirectional glass-reinforced plastics based on new types of fibers

Theoretical and experimental compressive creep relations for a unidirectional glass-reinforced plastic based on hollow fibers are presented. The agreement between the theoretical and experimental data is shown to be satisfactory. The effect of fiber capillarity on the creep process is unimportant.All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Fiber Glass, Moscow; Institute of Mechanics of Machines and Polymeric Materials, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Mekhanika Polimerov, No. 4, pp. 747–750, July–August, 1971.     

Elastic and strength characteristics of a glass-reinforced plastic in compression

The elastic constant and strength characteristics in compression have been experimentally determined for a cold-cured glass-reinforced plastic in the direction of all three principal axes of anisotropy. It is shown that the elastic constants obtained satisfy the constraints imposed on orthotropic materials by the thermodynamic relations.Translated from Mekhanika Polimerov, No. 5, pp. 866–869, September–October, 1970.     

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.     

Relation between the strength of polyethylene-steel adhesion bonds and the thickness of the ultrathin layer of polymer remaining on the surface of the metal

On the basis of the principle of ellipsometry and, moreover, the method of pyrolitic decomposition of the polymer with subsequent chromatographic analysis of the products of pyrolysis, a procedure has been developed for experimentally determining the thickness of the ultrathin layer of polymer that remains on the metal after failure of a polyethylene-steel adhesion bond. The nature of the relationship between the thickness of the residual polymer layer (200–800 Å) and the strength of the adhesion bond is established. It is concluded that the cohesion strength and the deformation at failure of the layer of adhesive next to the more rigid and stronger boundary layer have a decisive influence on the strength of the adhesion bond.Riga Polytechnic Institute. Translated from Mekhanika Polimerov, No. 3, pp. 420–424, May–June, 1976.     

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.     

Calculation of the residual stresses and strains in wound reinforced-plastic products

A method is proposed for determining the residual stresses and strains in wound glass-reinforced plastic products. The fabrication process is divided into five stages: winding, heating polymerization, cooling, and removal from the mandrel. The initial stresses that develop during winding and the subsequent stress increment associated with heating are taken into account. Polymerization is treated as a process during which the mechanical and thermophysical properties of the material change. Chemical shrinkage of the resin and its filtration through the fiberglass are disregarded. Equations are derived for the residual radial and peripheral stresses in the finished product, for the residual change in inside diameter, and for the temperature at which the product is released from the mandrel during the cooling process. The experimental data relating to two types of wound products are discussed. The results of a computation of the residual stresses and the residual changes in inside diameter are compared with the experimental data.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 134–139, January–February, 1969.