A nondestructive method of testing the mechanical strength anisotropy of cellulose compositions

A nondestructive method of testing the mechanical tensile strength anisotropy of cellulose compositions from the coefficients of reflection of polarized shf waves is described. Equations for finding the reflection coefficient from the measured value of the SWR of the shf wave are presented. It is shown that there is a close linear correlation between the mechanical strength anisotropy and the anisotropy of the shfwave reflection coefficient.     

Experimental evaluation of the strength anisotropy of a unidirectionally reinforced organic fiber-reinforced plastic

Conclusions The strength of a unidirectional organic fiber-reinforced plastic has been experimentally determined in various special cases of plane stress. An analysis of the data obtained shows that it is possible to describe the strength of the material in plane stress by means of a second-order surface equation containing linear and quadratic terms. The dependence of the strength in tension and compression on the angle between the directions of loading and reinforcement has been predicted and experimentally confirmed using the values found for the components of the strength surface tensors. The results of the study can be used to estimate the strength of multilayer organic fiber-reinforced plastics in cases where a unidirectionally reinforced layer can be taken as the basic structural element of the material.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 799–803, September–October, 1979.     

Problems in the prediction of the long-term strength of polymer materials. A review

Conclusions As in the case of the selection of the simplified equations used in the theory of nonlinear viscoelasticity, variants of the equations of the temperature-time dependence of the strength of polymer materials are constructed on the basis of some similarity condition of the experimental lifetime curves. Principles according to which it would be possible to make a prior assignment of a material to some class on the basis of similarity criteria only using, for example, information on chemical composition and structure without testing for long-term strength are lacking. The equations presented in this review may be used for predicting the lifetime only when the nature of the resistance to long-term destruction over time in a given temperature range exactly corresponds to the assumptions inherent in some equation. Thus, the selection of the boundaries of the temperature ranges, in which we may assume uniformity for the deformation and destruction mechanisms leading in the final analysis to identical types of destruction, becomes most significant. Hence, the parametrical methods have a series of advantages since they do not place rigid limitations on the nature of the long-term strength curves at a given temperature.The temperature-time analogy method is the most favored method for predicting long-term strength since this method, without negating other approaches, is their generalization. The use of this method is most promising for cases of a complex stressed state and complex stress pathways. In this case, the temperature -time shift function is most conveniently introduced into the surface strength functionals.Translated from Mekhanika Kompozitnykh Materialov, No. 4, pp. 694–704, July–August, 1979.     

Experimental investigation of the anisotropy of strength of bolted joints of laminated composites upon variation of geometric and design parameters

Conclusion In the present work we investigated the anisotropy of the characteristics of tensile (buckling) strength and elasticity of plates made of KMU-4L in a bolted joint in a wide range of parameters of the material (stacking, number of layers), geometric parameters of the joint, parameters of the fastening element and of design parameters. An analysis of the results showed that the strength of the bolted joint under static loading can be increased for thin plates with h = 1–2 mm by local reinforcement of the zone of the hole by layers with = ±45 °, and also by increasing the moment of preliminary tightening; for plates with h = 3–4 mm the only feasible measure is increasing the moment of preliminary tightening to 20–40 Nm. All the results of the experiment were graphically generalized in the form of surfaces of maximal stress; this made it possible to predict the load bearing capacity of a joint for intermediate values of the parameters by calculating the safety factors.Translated from Mekhanika Kompozitnykh Materialov, No. 2, pp. 268–272, March–April, 1990.     

Increasing the optical anisotropy of polyethylene spherulites

The authors show that in some cases chemical modification leads to an increase in the optical anisotropy of polyethylene spherulites; this phenomenon can be used to obtain additional information on the structure and growth of the spherulites.Institute of the Mechanics of Metal-Polymer Systems, Academy of Sciences of the Belorussian SSR, Gomel'. Translated from Mekhanika Polimerov, No. 2, pp. 343–344, March–April, 1974.     

Forced viscosity anisotropy of polymers

For two-dimensional flow the viscosity of an anisotropic medium is determined by two quantities. In relation to polymer melts, one of these corresponds to the viscosity for tension in the direction of orientation and the other to viscosity for shear in planes parallel to the orientation. By solving the problem of the flow of such a medium in a plane convergent channel and making optical-polarization measurements we were able to observe and quantitatively describe this phenomenon.Mekhanika Polimerov, Vol. 1, No. 5, pp. 13–18, 1965     

Investigation of the anisotropy of the properties of glass-reinforced plastic shells

The load-carrying capacity and deformation of cylindrical and conical glass-reinforced plastic (ÉDT-10 resin) shells loaded in axial compression have been investigated experimentally in relation to the orientation of the fabric reinforcement. The results of the tests are compared with the relations of the theory of elasticity of an orthotropic body.Zhukovskii Central Aerohydrodynamics Institute, Moscow Region; Scientific Research Institute of Production Technology and Organization, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 814–818, September–October, 1969.     

Method of the anisotropy potential in the linear mechanics of polymers

The potential of the displacements due to the anisotropy of the physical properties of a material (the anisotropy potential) is used in order to reduce the solution of the linear statistical boundary problem of elasticity theory and that of the linear creep of homogeneous anisotropic bodies to two simpler problems: one involving an anisotropic medium, and the other involving an equation analogous to the Poisson equation.S. M. Kirov Ural Polytechnic Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 1, pp. 24–31, January–February, 1972.     

The anisotropy of compact bone material

From the measurements of the main elements of the microstructure of compact bone material, it is concluded that the theoretical model of a transtropic material can be applied to bone tissue. This conclusion is confirmed by the experimental data obtained on compression. The correlation connection between the ultimate strength of compact bone material and the elasticity modulus has been found. It is shown that the anisotropy of the compact material is satisfactorily described by the tensor formula.Scientific-Research Institute of Medical Radiology, Academy of Medical Sciences of the USSR, Obninsk. S. M. Kirov Leningrad Order of Lenin Wood Technology Academy. Translated from Mekhanika Polimerov, No. 4, pp. 711–716, July–August, 1972.