Carrying capacity of rings formed by winding composites with high-modulus anisotropic fiber reinforcement

The characteristics of composites associated with the essential anisotropy of the reinforcing fibers are studied. The effect of distortion and pretensioning of the reinforcement on the axisymmetricity of the strain field, the moduli of elasticity, and the strength in the direction of the fibers under external and internal pressure are investigated with allowance for the high compliance of the material in the transverse direction. Numerical estimates are obtained for the moduli of elasticity E and E_r, expansion coefficient and _r, and initial temperature stresses _r ⁰ and ⁰ for a model material. The dependence of the bursting pressure on the thickness of the rings is described and strength criteria are formulated. In all the problems considered it is necessary to make allowance for the high compliance of the composites in the transverse direction.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 673–683, July–August, 1973.     

On the theoretical strength limit of the layered elastic and viscoelastic composites in compression

The theoretical strength limit in compression (TSLC) of composite material with two alternating isotropic homogeneous elastic and viscoelastic layers is studied. The investigation is made within the piecewise-homogeneous body model with the use of the Three-Dimensional Linearized Theory of Stability for elastic and viscoelastic materials. It is assumed that there is an initial imperfection in the local curving form of the reinforcing layers along the direction which is inclined to the layers. As the criterion for determination of the TSLC, the case is taken for which the aforementioned imperfections start to increase indefinitely. The numerical results for the TSLC are presented and discussed. According to these numerical results, in particular, the direction (or the surface) along which the fracture in compression takes place, is determined.     

Structural characteristics of materials reinforced with high-modulus fibers

Research on the mechanics of boron and carbon-reinforced plastics is briefly reviewed. The design and testing characteristics of these materials associated with the high degree of anisotropy of their elastic properties, as compared with those of glass-reinforced plastics, are discussed. Problems relating to testing at an angle to the direction of the reinforcement, the effect of misorientation and distortion of the fibers, and the consequences of the low shear strength are considered. Experimental confirmation has been obtained by testing unidirectional (1 : 0), orthogonally reinforced (1 : 1 and 2 : 1), and tridirectional (1 : 1 : 1 in the 0°, +60°, and –60° directions) boron and carbon-reinforced plastics.DeceasedInstitute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 676–685, July–August, 1971.     

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.     

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.     

Effect of structural and processing parameters of the reinforcement on the strength of unidirectional metalfiber composites under different types of loading

Conclusion The above studies show that the strength of unidirectional FCP's in uniaxial and biaxial tension is largely determined by the strength of the bond between the fibers and matrix and the internal geometry of the reinforcement. This dependence is particularly significant when the FCP product is loaded across as well as along the fibers. Impulsive loading as a method of making FCP's makes it possible to broadly vary the strength of the fiber-matrix interfaces. The unidirectional FCP's and tubular products of FCP's obtained by this method have a high strength under different types of loading, and this strength can be predicted by calculation.Presented at the Sixth All-Union Conference on the Mechanics of Polymer and Composite Materials (Riga, November, 1986).Translated from Mekhanika Kompozitnykh Materiaiov, No. 6, pp. 1033–1038, November–December, 1986.     

Long-term strength of reinforced composites

Conclusion A criterion of long-term strength was proposed for composite materials. The criterion can be used to calculate time to failure for arbitrary loading programs. It was shown that the criterion provides for good agreement with the experimental data not only in the cases of instantaneous and long-term static loadings, but also for fatigue loading in tension, in compression, and in mixed regimes with different asymmetry coefficients.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 16–22, January–February, 1989.     

Shear strength of composites based on whiskerized fibers

The elastic and strength characteristics of unidirectional carbon plastics have been studied, based on carbon fibers, whiskerized with fiber crystals of silicon nitride prepared from the gaseous phase and titanium dioxide from an aerosol. The advantages of these composites and glass textolites based on satin-type fabrics whiskerized with fiber crystals of aluminum nitride and titanium dioxide over the usual carbon and glass plastics are demonstrated.All-Union Scientific-Research Institute of Aviation Materials. Institute of Polymers Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 492–501, May–June, 1973.