Composite materials - future materials. Composite materials with a metal die. Classification of composite materials, страница 3

The basic deficiency of composite materials about one and bivariate sheathing is low resistance to interlaminar shear and cross-section abruption. It are deprived materials with volume sheathing.

2.2 Dispersibly-strengthened composite materials

Unlike filamentary composite materials in the dispersibly-strengthened composite materials the die is a basic element which is carrying load, and disperse particles slow down movement in it of dislocations. High strength is reached at the size of particles of 10-500 nanometers at average distance between them of 100-500 nanometers and their equal distribution in a die. Strength and hot-resistance depending on the volume contents of hardening phases do not submit to the additivity law. The optimum contents of the second phase for various metals unequally, but usually does not exceed 5-10 about. %.

Use as hardening phases of stable high-melting joints (oxides of thorium, a hafnium, a yttrium, difficult joints of oxides and rare-earth metals), not dissolved in matrix metal, allows to save high strength of a material to 0,9-0,95 Т. In this connection such materials apply as heat resisting is more often. The Dispersibly-strengthened composite materials can be received on the basis of the majority of metals applied in the technician and alloys.

Most widely use alloys on the basis of aluminium - САП (спеченный an aluminium dust). САП consists of aluminium and disperse чешуек AlO. Particles AlO effectively slow down movement of dislocations and by that raise strength of an alloy. Contents AlO in САП fluctuates from 6-9 % (САП-1) and to 13-18 % (САП-3). With increase in contents AlO raises from 300 for САП-1 to 400 МПа for САП-3, and the elongation accordingly decreases with 8 to 3 %. Tightness of these materials is equal to tightness of aluminium, they do not yield to it on a corrosion stability and even the titan and noncorrosive steels can substitute at operation in the range of temperatures 250-500 °С. On long strength they exceed deformable aluminium alloys. Long strength for alloys САП-1 and САП-2 at 500 °С makes 45-55 МПа.

The big perspectives at the nickel dispersibly-hardened materials. Alloys on the basis of nickel with 2-3 have the highest hot-resistance about. % of a two-oxide of thorium or a hafnium two-oxide. A die of these alloys usually? - Firm solute Ni + 20 % Cr, Ni + 15 % Mo, Ni + 20 % Cr and Mo. Wide application alloys ВДУ-1 (have received the nickel hardened by dioxide of thorium), ВДУ-2 (the nickel hardened by dioxide of a hafnium) and ВД-3 (die Ni of +20 % Cr hardened окисью of thorium). These alloys possess high hot-resistance. At temperature 1200 °С alloy ВДУ-1 has 75 МПа and 65 МПа, alloy ВД-3 - 65 МПа. The Dispersibly-hardened composite materials, just as filamentary, stands to разупрочнению with rise in temperature and duration of self-control at the given temperature.

2.3 Karbovoloknity

Карбоволокниты (углепласты) represent the compositions consisting from polymeric connecting (die) and Uprochniteli  in the form of carbon filaments (карбоволокон).

High bond energy С-С of carbon filaments allows them to save strength at very high temperatures (in neutral and regenerative environments to 2200 °С), and also at low temperatures. From oxidising of a surface of a filament protect sheetings (pyrolitic). Unlike glass fibres карбоволокна are badly moistened connecting (low surface energy), therefore them expos pickling treatment. Under the contents карбоксильной groups degree of activation of carbon filaments is thus augmented by their surfaces. Interlaminar strength at shear углепластиков is augmented in 1,6-2,5 times. It is applied вискеризация threadlike chips TiO, AlN and SiN that gives increase in interlaminar ruggedness in 2 times and strengths in 2,8 times. Spatially reinforced structures are applied.

As the connecting synthetic polymers (polymeric карбоволокниты) serve; the synthetic polymers exposed pyrolysis (коксованные карбоволокниты); pyrolitic carbon (пироуглеродные карбоволокниты).