Predicting the porosity of glass-reinforced plastics from their thermal conductivity

The effect of porosity, reinforcement ratio and specific weight on the thermal conductivity of a series of glass-reinforced plastics has been investigated. It is shown that, if the thickness, the weight characteristic (weight per square meter), and the number of layers of reinforcing fabric are known and the thermal conductivities of the components are constant, then the porosity of the glass-reinforced plastic can be predicted from its thermal conductivity. Data on the relation between the specific weight and the thermal conductivity of the glass-reinforced plastics investigated are presented.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 522–525, May–June 1971.     

Correlation between the strength and thermal conductivity of glass-reinforced plastics

The effect of changes in the component ratio and porosity of glass-reinforced plastics on their strength and thermal conductivity is considered. A correlation is shown to exist between the bending strength and thermal conductivity of a glass laminate.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 749–751, July–August, 1969.     

Predicting certain structural characteristics and physicomechanical properties of glass-reinforced plastics from their thermal activity

A procedure and apparatus for determining the thermal activity of glass-reinforced plastics with one-sided access have been developed. A correlation is established between the interlaminar shear modulus and interlaminar shear strength and the thermal activity of a glass laminate. The effect of structural inhomogeneities and bonding flaws on the thermal activity of a glass-reinforced plastic is investigated and it is shown that the location of an inhomogeneity within the article can be determined.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 128–132, January–February, 1976.     

Ultrasonic method of determining the resin content and porosity of glass-reinforced plastics

The possibility of using the pulsed ultrasonic testing method for checking the resin content and porosity of unidirectional glass-reinforced plastics is considered in relation to the case of broad independent variation of the parameters.Mekhanika Polimerov, Vol. 4, No. 3, pp. 547–554, 1968     

Calculation of the moduli of elasticity and tensile strength of oriented glass-reinforced plastics on the basis of a nondestructive determination of their composition and structural parameters

The theoretical basis of the nondestructive determination of the modulus of elasticity and tensile strength of oriented glass-reinforced plastics in the direction of the principal axes of anisotropy from the resin content and porosity of the finished product is examined. The results of an experimental verification are presented.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 332–341, March–April, 1969.     

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.     

Mechanical characteristics of oriented glass-reinforced plastics in shear

The mechanical characteristics of oriented glass-reinforced plastics stressed in shear are considered. Various methods of determining them are compared. The dispersion of the shear strength is characterized and the possibility of glass-reinforced plastics elements failing as a result of low interlaminar shear strength is discussed.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1008–1013, November–December, 1969.     

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.     

Mechanical characteristics of radiation-cured glass-reinforced plastics

Data are presented on the mechanical characteristics of oligoester maleates copolymerized with styrene and the corresponding glass-reinforced plastics crosslinked by the thermochemical and radiation methods. It is established that the radiation-cured glass-reinforced plastics have improved strength and stiffness as compared with similar specimens obtained by thermochemical curing.Institute of Mechanics, Institute of High Molecular Compounds, Institute of Physical Chemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 4, pp. 704–710, July–August, 1969.     

Relationship between strength characteristics of unidirectional glass-reinforced plastics and their composition

The article discusses the effect of the amount of binder present and the porosity of the glass reinforced plastic on the usable strength of the glass fibers, the tensile strength, and the elasticity module in stretching. It is shown that a relationship exists over the whole range tested between the volume ratio of the components (binder and glass fiber), certain strength characteristics, and porosity. A method is suggested for the comparison of glass-reinforced plastics according to their usable fiber strength which can be used for the selection of the best binder, the glass material, the glass composition, glass fibers, the lubricant, the technological scheme, etc.Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 477–480, May–June, 1970.     

Possibilities of a nondestructive one-parameter method of checking the strength of anisotropic glass-reinforced plastics in uniaxial compression

A nondestructive method of checking the strength of glass-reinforced plastics (GRP) in finished products is proposed. This method is based on the correlation, investigated by the authors, between the modulus of elasticity and the compressive strength determined by a standard method. Various orientations in the plane of reinforcement of glass-reinforced plastics with different ratios of the orthogonally arranged fibers are investigated. It is proposed to determine the modulus of elasticity from the propagation velocity of an ultrasonic pulse measured under conditions of one-sided access to the surface of the product."Ritm" Research-Production Association, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 909–919, September–October, 1974.     

Relation between the interlaminar shear modulus and thermal conductivity of oriented glass-reinforced plastics

The relation between the interlaminar shear modulus G of oriented glass-reinforced plastics and their thermal conductivity in a direction orthogonal to the plane of reinforcement is investigated. It is shown that G can be predicted from the measured values of and the bending deformations from and the propagation velocity of ultrasound.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Makhanika Polimerov, No. 6, pp. 985–989, November–December, 1970.     

Estimation of the stability of the strength of glass-reinforced plastics in conical shells

On the basis of a statistical analysis of the test data it is shown that there is a difference between the mechanical characteristics (in tension and compression) of laminated glass-reinforced plastics obtained under laboratory and industrial conditions by impregnation under pressure in a closed mold. The stability of the strength properties of the glass-reinforced plastic in various conical shells, produced in large batches, is considered. Certain experimental relations between the material properties and the total number of shells produced are also established.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 102–108, January–February, 1970.     

Resistance of wound glass-reinforced plastics to failure by unwinding

The debonding of wound glass-reinforced plastics is examined from the statistical standpoint. The statistical stress intensity distribution function characterizing the fracture toughness is obtained. The effect of defect size on the critical nominal stresses is discussed.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 5, pp. 881–885, September–October, 1969.     

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.     

Mechanical properties of glass fabric-reinforced plastics in tension and compression normal to the plane of reinforcement

The behavior of glass-reinforced plastic based on ASTT (b)S₂-O fabric and NPS-609-21M resin in tension and compression normal to the plane of reinforcement has been investigated and the mechanical characteristics determined. Recommended values are given for the size and shape of the test pieces, and a method of determining the tensile and compressive characteristics of glass-reinforced plastics is proposed.Leningrad. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 803–809, September–October, 1968.     

A rheological model of polymers and glass-reinforced plastics

Network polymers and the corresponding glass-reinforced plastics are investigated for a homogeneous uniaxial state of stress and constant temperature. A physical law relating the high-elastic strain and the stress in explicit form with once-determined structural constants is obtained for the damped (bounded) creep regime. The theoretical solutions are compared with the experimental data for a glass-reinforced plastic based on unsaturated polyester resin and glass mat reinforcement.Institute of Engineering Mechanics, Bulgarian Academy of Sciences, Sofia. Translated from Mekhanika Polimerov, No. 5, pp. 851–857, September–October, 1971.     

Prediction of the thermal conductivity of oriented fiberglass plastics

An analytical equation has been derived for calculating the thermal conductivity of fiberglass plastic pipes in the axial direction. The pipes, which represent items with the most general type of reinforcement, were manufactured by uninterrupted slanting and longitudinal-transverse winding. Equations for calculating the thermal conductivity of oriented fiberglass plastics with other types of reinforcement featuring various angles to the direction and plane of reinforcement are particular cases of the derived equation. The results of an experimental check for this equation for calculating the thermal conductivity of epoxy fiberglass plastics are presented.Translated from Mekhanika Kompozitnikh Materialov, Vol. 29, No. 3, pp. 381–386, May–June, 1993.     

Theory of shrinkage stresses in oriented glass-reinforced plastics

The problem of shrinkage stress distribution in glass-reinforced plastics is examined on the basis of an improved model under certain assumptions concerning the nature of the curing process. Cylindrical tubes of epoxy glass-reinforced plastic are investigated under stepped temperature conditions.Mekhanika Polimerov, Vol. 1, No. 6, pp. 61–68, 1965     

Experimental testing of the applicability of a fourth degree polynomial in describing surfaces of equicritical planar stress distributions in glass-reinforced plastics

The possibility of using a fourth degree polynomial for calculating the anisotropy of glass-reinforced plastics in the planar stress state is evaluated experimentally. The experiments were carried out on industrial specimens of glass-reinforced plastic tubes loaded with an internal pressure, and subjected to an axial tensile force and a torque. Surfaces of equicritical planar stress distribution were constructed for the material of the glass-reinforced plastic tubes. The experimental and theoretical values of the breaking stresses were compared statistically. Most of the experimental values of the breaking stresses were found to lie within the confidence intervals of their theoretical values.S. M. Kirov Timber Technology Academy, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 284–294, March–April, 1970.