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Volume 7 № 4 Композиты и наноструктуры

2015__________________________________________ COMPOSITES and NANOSTRUCTURES

Mileiko S.T.

SYNERGY IN COMPOSITES............................................................................................................................................ 191

A well-known definition of composite as «a heterogeneous mixture of two or more homogeneous phases which have been bonded together» (Oxford dictionary) does not stress at an important property of the composite aroused as a result of appropriate mixing phases in composites. Moreover, an overwhelming growth of applications in the last decades of just one family of the composites - a family of carbon fibre reinforced plastics - makes people to focus on just one example of synergy in composites that is fracture toughness of the FRP, which are inherently strong due to the fibre. A purpose of the present paper is to draw attention to a number of the synergy effects arising in both ductile-metal matrix composites and brittle-matrix composites. In particular, it is shown that fibre/matrix interactions in a composite can affect essentially properties of the components. The composite microstructure and fabrication technology of composite elements can be optimized provided the effects mentioned are taken into account. Reinforcing refractory-metal matrix with a fibre of an appropriate chemical composition can yield a decrease by orders of the magnitudes in oxidation rate of the matrix. An interaction of brittle components in brittle-fibre/brittle-matrix composites determines damage tolerance of the composites (p. 191-206; fig. 14).

R.A. Andrievski

NANOMATERIALS IN EXTREME ENVIRONMENTS..................................................... 207

The present review briefly examines results of the latest research of nanomaterials behavior under extreme conditions, especially in the case of combined effects of stress corrosion cracking, joint effect of temperature and irradiation, etc. Particular attention is paid to the characterization of nanostructures able to maintain their properties under extreme conditions. Twinned and gradient structures seem to be particularly promising for usage under extreme conditions. Lesser known problems are noted (p. 207-215; fig. 6).

A.R.Bunsell, A.Thionnet

FAILURE PROCESSES GOVERNING LONG TERM RELIABILITY

OF CARBON FIBRE COMPOSITE STRUCTURES................................................................................................................................................... 216

Advanced composites are now used in many critical civil applications for which long term reliability is an absolute necessity. Testing based on more traditional metal structures has been shown to be inappropriate and there is a pressing need to develop new tests based on an understanding of damage processes in composite structures. Multi-scale modelling which takes into account the characteristics of the fibres, matrix and fibre/matrix interfaces is now well developed. It allows the kinetics of fibre failure during monotonic loading and sustained loading of composites to be explored and identifies the critical damage levels leading to failure for these loading conditions. This information allows safety factors based on the intrinsic properties of the composites to be determined and quantified (p. 145-150; fig. 5).

Suresh Kuma, Rajesh Chandra, Anil Kumar, N. Eswara Prasad and L.M. Manocha

C/SIC COMPOSITES FOR PROPULSION APPLICATION................................... 225

Carbon fiber reinforced silicon carbide (C-SiC) composites are ideal materials for thrust vectoring control of missiles due to their high specific strength, erosion resistance and high temperature capability. Jet-vanes based thrust vectoring control is required in the initial phase of the launch where aerodynamic forces are insufficient to get required maneuverability. The environment experienced by the jet-vanes is very severe with typical gases temperature around 2500K at about 3-4 Mach; the exhaust gases contain hard tiny particles of alumina and results in severe erosion ofjet-vanes. An indigenized technology based on liquid-silicon-infiltration method is developed for C-SiC composite jet-vanes. The jet-vanes have been tested and repeatedly performed successfully in solid propellant rocket motor. This paper describes the research efforts put for developing the technology and fabrication of the Jet-Vanes (p. 225-230; fig. 4).

I.V.Ignatova, S.B.Sapozhnikov

SURFACE TREATMENT OF ARAMID FABRICS TO THE CONTROL IMPACT ENERGY

ABSORPTION IN LAYERED COMPOSITES ..................................................................... 231

An experimental study of an effect of aramid fabric surface treatment by polymer compositions with nanodiamonds or carbon nanotubes on impact energy dissipation were presented. Dry friction between yarns of fabric is an effective way to absorb kinetic energy of a bullet. In the first part of the paper, the results of quasi-static yarn pull-out test of aramid plain woven fabric is presented. In the second part, the ballistic tests conducted to determine an effect of the surface treatment on the depth of indentations in a special plasticine. For example, surface treatment of fabrics with addition ofjust 5 wt. % increases the frictional interaction between yarns by 4 times and reduces the deflection of multilayer textile package under a local impact by about 20%. It is also shown that the viscous fluid, which is working effectively under quasi-static yarn pull-out test, loses its effectiveness under local impact (p. 231-240; fig. 6).

S.A.Firstov, V.F.Gorban, N.A.Krapivka, E.P.Pechkovsky, M.V.Karpets, A.V.Sameljuk, V.N. Tkach

FORMATION OF PHASE COMPOSITION AND MECHANICAL PROPERTIES OF CAST

MULTICOMPONENT EQUIATOMIC ALLOYS WITH m-PHAS...................................... 258

Seven cast multicomponent (5-7 elements, among which Cr, Mo, W, Mn, Fe, Co, Ni) equiatomic three-phase alloys are studied. They contain intermetallic polycomponent m- phases that include m-forming elements Mo, W, Fe, Co) together with BCC- and FCC-substitutional solid solutions. Tungsten is present in all alloys.

Formation of the phase compositions of the alloys was studied taking into account individual characteristics of the chemical elements and their electronic concentration Csd. At melt crystallization at a temperature higher than 2000 °C, BCC-substitutional solid solution crystallizes on the basis of tungsten (~60 ат. %) and molybdenum (~30 ат. %) is crystallized first as dendrites. At temperatures between 1400 and 1500 °C a polycomponent m-phase, which includes all elements, is formed; the contents of elements being close to equiatomic. It has also a dendrite shape, contacts all primary dendrites BCC-phase. Then at temperatures 1270-1360 °C, FCC-substitutional solid solutions crystallizes on the basis of FCC- metals (their total content is ~70 at. %). It locates mainly between dendrites and crystals of m-phase in composition of eutectic in which the m- phase is second component. The maximum quantity of m- and BCC-phases in an alloy is about 50 mass. %, FCC-phase is about 65 mass. %. When electronic concentration increases from Csd = 7.40 up to Csd = 8.00 el/at the quantity of m-phase decreases from 50 to ~10 mass. % in the interval of Csd between 7.60 and 8.00 el/at, the quantity of FCC and BCC-phases is going up just slightly.

An optimum combination, high-temperature strength and ductility of alloys is achieved at a quantitative ratio of m-, BCC- and FCC-phases equal to 40-45-15 mass. %. The elastic modulus of alloys at room temperature measured by indentation is between 130 and 190 GPa (p. 241-258; fig.7).