Creep prediction of a layered fiberglass plastic

The results of short-term creep tests of a layered glass fiber/polyester resin plastic in tension at angles of 90, 70, and 45° to the direction of the principal fiber orientation are presented. The applicability of the principle of time-temperature analogy for the prediction of long-term creep of the composite and its structural components is revealed. The possibility of evaluating the viscoelastic properties of the composite from the properties of structural components is shown.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 3, pp. 295–306, May–June, 1998.     

Vibrocreep of polymeric materials

The recovery of rigid porous polyurethane after preliminary static and vibrational creep has been experimentally investigated. The effect of a small additional vibrational load on the recovery process is discussed. The results of describing the recovery with the aid of an expression in the form of a Volterra multiple-integral series and a relation of the Leaderman-Rozovskii type are examined.For Communication 6 see [17].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 818–824, September–October, 1970.     

Viscoelastic characteristics of the interaction between structures and soils

The shear coefficients of a body relative to the soil and the shear creep and relaxation kernels are determined from the data of creep and relaxation tests.Urazbaev Institute of Mechanics and Earthquake Resistance of Structures, Academy of Sciences of the SSR, Tashkent. Translated from Mekhanika Polimerov, No. 2, pp. 207–211, March–April, 1973.     

Forward and reverse creep of a physically nonlinear polymer material

From tension and torsion experiments under constant load, the authors determine the parameters of a material with physically nonlinear creep. They examine the applicability of these parameters to represent the deformation properties of materials under other loading systems. They give a method of drawing the reverse creep curve (in integral form) with parameters different from those of active creep.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 786–795, September–October, 1973.     

Problems of the theory of deformation of polymeric materials under complex loading

Research on problems of the theory of deformation of polymeric materials under complex loading based on a synthesis of creep theories and the local strains theory is reviewed.Presented at the 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.M. V. Lomonosov Moscow State University. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 434–443, May–June, 1972.     

Investigation of the integral creep equations (cubic nonlinearity) for different loading paths

Expressions for the creep strain obtained in accordance with the Leaderman-Rozovskii theory and in the form of a multiple-integral Volterra series are compared for different loading paths. The influence functions are assumed to be symmetrical. The strain intensity-time curves are calculated for a complex loading path for which the stress intensity is constant. It is found that these curves are nonmonotonic for both linear and nonlinear creep.Read at Fourth Symposium on Rheology, Moscow, May 27–30, 1969.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 35–42, January–February, 1970.     

Effect of aging creep of polyestermalein resin/mineral filler composites

Long-term (More than 20 years) creep under compression of two polymer concretes, polyestermalein resin/mineral filler composites, was studied. The concretes differ with diabase filler size (d=5–10 mm and d=10–20 mm). It was shown that nonlinearity of viscoelastic properties of concrete increases as the size of filler particle decreases. Aging of the polymer concretes reduces their viscoelastic compliance and shortens the time interval necessary to reach equilibrium conditions under stable loading state.Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Institute of Theoretical and Applied Mechanics of the AS CR, Prague 9, Prosecká 74, Czech Republic. Central Laboratory of Physical-Chemical Mechanics of the BAS, Sofia 1113 Acad. Bontchev Street, IV km, Bl. 1. Published in Mekhanika Kompozitnykh Materialov, Vol. 32, No. 2, pp. 190–194, March–April, 1995.     

Static and vibrational creep of a fabric-reinforced plastic in shear in the plane of the reinforcement

The results of a comparative experimental investigation of the short-term static and vibrational creep of a fabric-reinforced plastic in shear in the plane of the reinforcement are presented. The experimental procedure is described in detail. It is shown that on the investigated ranges of temperature, stress, and amplitude-frequency parameters the effect of an additional vibrational load on the creep process is unimportant.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 605–610, July–August, 1971.     

Time — Moisture superposition

The results of creep tests on PN-3 polyester resin are given for various values of the temperature and moisture content of the material. It is shown that moisture content and time, like temperature and time, have an interchangeable effect on creep; i.e., in addition to a time-temperature (T-t) there is also a time-moisture (w-t) analogy. The (w-t) analogy can be used to predict the long-time creep from accelerated test data.Institute of Polymer Mechanics, Academy of Sciences of the Latian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 780–786, September–October, 1972.     

Influence of physical aging on creep of rubber

The effect of physical aging on the creep response of chloropren rubber filled with carbon black was studied. The method of reduced variables and analytical method of determination of influence of physical aging on the creep compliance in short creep time test are proposed.Glówny Instytut Górnictwa, Pl. Gwarków 1, 40–166 Katowice, Poland. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 112–118, January–February, 1997.     

Creep of polyester resin PN-3 under moisture-absorption conditions

A procedure is described for testing samples for creep in a climatic chamber of the Feutron 3001 type. Results of an experimental study of forward and back creep of polyester resin PN-3 under simultaneous moistening of samples in an air medium with elevated humidity are discussed. It is shown that the rate of the creep process depends greatly on the humidity state of the material.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 579–584, July–August, 1972.     

Prediction of the creep of polyester resin in the presence of randomly acting temperature and humidity factors

The possibility of using the theory of random processes to predict the temperature and moisture creep of polymeric materials in the presence of randomly acting temperature and humidity factors is considered. A procedure for estimating the long-term deformation under such conditions is described with reference to the uniaxial creep of PN-3 polyester resin using time—temperature and time—moisture superposition. The possible correlation of the ambient temperature and humidity is taken into account. The results of a computer calculation show that the theoretical and experimental data are in satisfactory agreement.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 219–226, March–April, 1973.     

Thermocreep of polyethylene in the cyclic temperature regime

The shear creep and recovery of low-density polyethylene has been investigated in the constant and cyclic temperature regimes. It is shown that in the cyclic regime the relaxation processes are accelerated and the nonisothermal creep strains become progressively greater than the isothermal strains at the maximum temperature of the cycle. In recovery the relaxation spectra are shifted along the time scale relative to the creep spectra, the shifts for simple shear and uniaxial tension being nonidentical.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 227–235, March–April, 1969.     

Prediction of the deformation and fracture of polymeric materials

Research on the development of express methods of estimating the long-term deformation of polymeric materials based on the use of the time-temperature, time-stress, time-vibration, and time-moisture analogies (superposition) is briefly reviewed. Questions of the multiparameter prediction of the creep of plastics with parallel and serial application of the various analogies are considered. A program of further research is outlined. The possibility of predicting the fracture processes of polymeric composites and estimating the comparative strength of the products obtained from them on the basis of the acoustic emission and thermal radiation effects is demonstrated.Presented at the 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 498–514, May–June, 1972.     

Characteristic features of the deformation process on creep and secondary creep of polymers under conditions of monaxial tensioning. Part I

Experiments carried out in the field of linear and nonlinear creep of a filled polyethylene and Teflon resin, including two complete cycles of creep and deformation recovery at monaxial tensioning, show that the bulk deformations (t) change nonmonotonically, and relationships computed by summation of terms containing a function of time cannot be used to approximate the deformation.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 399–405, May–June, 1974.     

Influence of temperature and humidity on the creep of polymeric materials. 4. Prediction on the basis of field test results

Conclusions Comparison was made of the results of prolonged (from 2 to 6 years) control experiments of tubular specimens of PN-3 for creep during tension, torsion, and simultaneous tension and torsion under various temperature-humidity conditions with calculation based on data of short-term (up to 5 h) experiments, in which the creep process was accelerated by increase in temperature and humidity of the material. Calculation of the prolonged creep deformations expected was done from the relationships of viscoelastic properties of a linearly changing solid, generalized for the case of influence of temperature and humidity under the assumption that the volume changes only elastically. On the basis of this generalization, adherence to the temperature-humidity-time analogy is assumed to be experimentally confirmed. Satisfactory agreement of results of prediction and prolonged control experiments is established.For communication 3 see [3].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 982–987, November–December, 1976.     

Creep and damage accumulation in orthotropic composites under cyclic loading

Experimental results and theoretical prediction of the response of glassfiber-reinforced polyester under quasi-static, static (creep), and cyclic (fatigue) loading are presented. The nonlinear strain component at static loading and the strain amplitude rate at cyclic off-axis loading of an orthotropic composite are shown to follow the associated flow rule with a single-parameter quadratic potential function. The influence of fatigue damage on deformation is considerable due to the reduction in the elastic modulus of the composite and is apparently negligible with respect to its effect on the parameters of the creep kernel.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 447–460, July–August, 1998.     

Effect of aging on creep of SVAM glass-reinforced plastic in tension with allowance for the orientation of the fibers

The author presents the results of an experimental study of the effect of aging under room conditions on the creep deformation of SVAM glass-reinforced plastic. It is established that with prolongation of the aging period up to two years the resistance of the material to creep deformation increases. The effect of aging is investigated in relation to anisotropy.Mekhanika Polimerov, Vol. 1, No. 6, pp. 20–29, 1965     

Influence of vibration on creep in glass-fiber-reinforced plastic in a complex state of stress

The author describes the method and results of tests on tubular specimens of glass-fiber-reinforced plastic for creep under simultaneous torsion (shear in the plane of reinforcement), compression, and vibration in the longitudinal direction. He finds that vibratory creep is not manifested if the amplitudes of the alternating component of the stress are up to 0.1 times the limit of short-term strength and the frequency is 20 kHz.Institute of Mechanics of Polymers, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 358–360, March–April, 1974.     

Effect of temperature and moisture on the creep of polymeric materials 1. One-dimensional extension under stationary temperature-moisture conditions

Creep tests have been carried out on PN-3 polyester resin for one-dimensional tension in the linear region of the stress-strain relation at various fixed values of the temperature and moisture content of the material. The temperature and moisture dependence of the instantaneous elasticity and creep characteristics of the material have been determined. It is shown that time-temperature-moisture superposition can apply in creep under various fixed temperature-moisture conditions.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 393–399, May–June, 1975.