Reinforcement in the composite particles is large, no longer serve to block the movement of disloca

Composite materials foam wrap have been designed to replace a growing proportion, ferrous and nonferrous traditional materials, which are characterized by shortcomings foam wrap on the performance, processes for obtaining and processing, gauges, mass, geometric complexity, usage areas and costs.
The major advantage, composites consists essentially of the modulation properties foam wrap and obtain in this way a wide variety of materials, the use of which may extend to almost all fields of technical activity.
In practice, composite materials consist of a matrix (plastic, ceramic or metal) and reinforcements (reinforcing filler), which are arranged in matrix in different proportions and orientations. The reinforcement gives the composite material a high strength and is the primary element of the load, and the matrix has the role of binder between the reinforcing elements and the load transfer medium exterior to them.
Ø Low power consumption and less expensive installations in obtaining relative to metals;
Chemical resistance and resistance to high temperatures (Kevlar fibers, Teflon hyfil to 500 C, and the ceramic fibers SiC, Si 3 N 4 and Al 2 O 3 at 1400 C and 2000 C).
A more general foam wrap composite materials, posed in a synthetic way, is based on the concurrent use of two criteria, namely: geometric peculiarities of complementary material foam wrap and how its orientation matrix (Figure 1).
A) fiber reinforced composite materials
In the figure above are shown differ ite orientation modes of these fibers within the matrix. The composite material thus obtained with very good strength, foam wrap stiffness and strength ratio - density. Mechanical behavior of such a composite depends on:
If the composite particles of very small size (100 ... 2500) and blocks the movement of dislocations. Thus, although small amounts of material are required disperse, the effect of the hardening is very high.
The dispersed phase is usually a hard stable oxide (Al 2 O 3, ThO 2, ZrO 2, BeO, etc.). She must have a certain size, shape, quantity and distribution to obtain the best properties for the composite material. At the same time the particles must be of low solubility dispersed in the matrix material and not chemical reactions occur between the particles and the matrix.
Reinforcement in the composite particles is large, no longer serve to block the movement of dislocations. Depending on the ratio between the amount of particles and the binder are obtained unusual combinations of properties.
Carbide can be regarded as such composite materials, tungsten carbide is embedded in a mass of cobalt, cutting tools combined with the advantages of data resulting hardness and resistance to cutting temperature increase of CW and good impact resistance data cobalt.
Particulate abrasive stones foam wrap made of silicon carbide (SiC), boron nitride, or diamond embedded foam wrap in a matrix of glass or polymers, may also be considered as particulate reinforced composite materials.
Another example foam wrap is the material used for electrical contacts which consists of tungsten particles embedded in a silver matrix. foam wrap In this mode is desired combination of properties, namely good electrical conductivity (due to silver) and high wear resistance (due to tungsten particles).
Are obtained foam wrap by applying to the surface of the base material, a layer of another material. foam wrap Applying this layer of another material with properties different from those of the base material is made most often by casting, welding or lamination.
The main advantage of these materials is economic and qualitative because by using them saves significant amounts of expensive materials or poor, improving at the same time, product quality and increasing the duration of operation in terms of performance high.
In addition, the bicomponent composite materials, described above, is used, and three-component composite ("sandwich"). For example, in order to prevent diffusion of carbon from a steel to another, can be interposed by plating a layer of nickel, which does not allow the diffusion of carbon through it.
All material "sandwich" is shown in the figure below. It is made up of two thin plates of metal (e.g., aluminum, titanium or steel), between which is a honeycomb structure, the harder material (duralumin or titanium alloy) resulting foam wrap in a composite material highly resistant and rigid.