Reinforcement is done in composite materials in various ways. One of these ways is the reinforcement with addition of particles and flakes into matrix of composite materials. In here, we will take a look at the general characteristics of particle and flake reinforced composite materials.
Actually, the strengthening mechanism changes with the used particle size in composite materials. Sizes of particles changes around both microspic and macroscopic basis. With the increasing size of particle inside composite, the mechanism of reinforcement for matrix material changes.
If the small particle sizes are used in particle reinforced composite materials, the main strengthening mechanism is not load carrying by reinforcement phase. The main mechanism is that the small or microscopic particles act as prohibitors of dislocation motions in matrix phase of composite materials. These dislocations leads to the failure of material, if they prevented by an action, material can be strengthened. In common, the proportions of microscopic particles inside matrix materials is around 15% or low.
But if the particle size increased into macroscopic sizes, the proportion of particle reinforcement phase also increases. It increases up to 25% or more with the increased size of reinforcement particles. Also the mechanism of reinforcement changes into that load carrying by reinforcement particles in which load is transmitted by matrix phase, just like in fiber reinforced composites. This is the main difference of small particle reinforcement phase and big particle reinforcement phase in composites.
Flakes are also very important type of reinforcement in composite materials. The difference of flakes in terms of shape, compared with particles, flakes are in the form of two dimensional platelets. The sizes of platelets changes from 0.01 to 1 milimeters and the thicknesses of these flakes changes between 0.001 to 0.005 milimeters.
The materials of particle and flake reinforcements can be metals and ceramics. The distribution of reinforcement particles inside matrix phase is generally random, but obtained mechanical and physical properties are generally isotropic.
Sizes of small particles or microscopic particles can be around 1 micrometers.
The most important and known application of particle reinforced composites is the Tungsten Carbide(WC). This is a type of cemented carbide that tungsten carbide is held in cobalt binder. In here, cobalt binder is matrix phase and tungsten carbide particles are particle reinforcements.
Important application of flake reinforcement in composites; flake shaped mica and talc are used in various polymers as reinforcement. Polymers are used as matrix materials. This application of flakes, add stiffness and strength to plastic materials and plastic molding compounds.
These are the general characteristics of particle and flake reinforcement in composite materials.
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