Dependence of elastic and strength characteristics of high-modulus composites on schemes of reinforcement

The elastic and strength characteristics of high-modulus composites with 12 different reinforcement schemes have been studied thoroughly. The effect of reinforcement schemes on change in elastic and strength characteristics of composites has been evaluated. A calculation of the elastic characteristics of high-modulus composites has been performed from the properties of the reinforcement and binder, and a comparison of the results with experimental data is given. Diagrams of deformation upon extension of the composites studied are given.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1019–1027, November–December, 1974.     

Deformative characteristics of plastics reinforced with high-modulus anisotropic fibers

The independent elastic constants of plastics unidirectionally reinforced with transversely isotropic fibers have been determined. It has been assumed that the distribution of reinforcement in a transverse section of the plastic is regularly rectangular or hexagonal. To determine the transverse elastic modulus and the shear modulus in the plane of reinforcement, a constancy-of-plane-sections hypothesis was used. Values of deformative characteristics determined by the assumed calculational dependences have been compared with the experimental ones for plastics reinforced with graphite fibers.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 631–639, July–August, 1972.     

Carrying capacity of thick-walled glass-reinforced plastic rings operating under pressure

Experimental data are presented on the carrying capacity and deformability of thick-walled rings made of unidirectional and two-way glass-reinforced plastic subjected to external and internal pressure. A limitation on the carrying capacity of the rings with increase in relative thickness is noted; an explanation of this effect is offered.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1130–1132, November–December, 1971.     

Testing the strength of anisotropic rings

A study was made of the distribution of stresses in an anistropic ring under compression or tension with rigid cams, taking into account the final dimensions of the zone of contact.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 1, pp. 175–177, January–February, 1974.     

Realization of the mechanical properties of fibers in high-modulus polymer composites

The effect of scatter in the strength and deformation properties of the high-modulus fibers, the degree of twist, and the presence of pores in the polymeric matrix on the degree of realization of the potential possibilities of these fibers in composite materials is briefly considered.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1123–1125, November–December, 1972.     

Winding fiber composites with additional pressure

Possibilities of compacting reinforced plastics by applying additional pressure have been established in which application of additional pressure is rational. The effect of this technological device on the magnitude of the initial stresses which arise in the wound construction in the relative thickness range k=1.01–1.15 has been studied.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 793–796, September–October, 1972.     

Radial reinforcement of thick-walled rings of composite materials

The possibility of improving the resistance to internal pressure of thick-walled rings with circumferential reinforcement by introducing radial or axial reinforcement has been investigated in the first approximation. Axial reinforcement is considered in relation to the use of combined (unidirectional + fabric) materials. On the basis of hypotheses concerning the homogeneity and linear-elastic behavior of the material and simple fracture criteria numerical estimates are obtained for the relative efficiency of the reinforcement scheme, the optimal material structure, and the corresponding ranges of relative thickness of the rings. The qualitative conclusions are compared with experiments on rings of combined material.     

Structural stresses in composites reinforced with a system of anisotropic fibers

The effect of the anisotropy of the mechanical and thermophysical characteristics of the reinforcement on the temperature stresses in unidirectional composites has been investigated. The stresses near fibers forming a regular structure in the transverse plane are estimated as a function of the thermoelastic properties of the components and the structure parameters.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 728–731, July–August, 1974.     

Effect of viscosity of a thermoplastic prepreg and matrix upon winding of rings

The problem of compression of a unidirectional layer and shear of a polymer interlayer during winding of rings is considered. The equations determining the dependence of the layer thickness and stresses on the parameters entering into the power flow law for a prepreg and polymer matrix and on the basic parameters of the winding process—the initial tension of the prepreg, its placement rate, and the radius of a mandrel—are derived. The ring thickness measurements obtained at various temperatures and initial tension forces of plies confirm the adequacy of the model offered. It is found that the viscous properties of the prepreg and matrix upon winding affect the relative change in the layer thickness to a greater extent than the stresses in these layers. With increase in temperature and tension force upon winding, the effect of viscous deformations of the prepreg and matrix increases. A decrease in viscosity and an increase in the tension force of the tape lead to a higher strength of the ring in tension and interlaminar shear; however, the growing percolation of the polymer melt leads to a greater inhomogeneity of the structure of the composite in the ring and to a lower reinforcing effect of the factors mentioned. Presented at the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000). Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 419–428, 2000.     

Properties of fiberglass-plastics reinforced with high-modulus fibers

The question of reinforcement of unidirectional fiberglass-plastic with boron or carbon fibers is considered. Static fatigue curves for the Poisson coefficient and the elastic modulus as functions of the volume content of the glass and the high-modulus fibers have been constructed. The theoretical dependences are compared with the experimental data.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Moscow. Translated from Mekhabika Polimerov, No. 1, pp. 68–74, January–February, 1972.