Particulate Reinforced Materials

As regards mechanical behaviour, the particulate reinforced material is nearly an isotropic material while a fibre reinforced composite is nowhere near to isotropicity. Fibre reinforcement provides high directional strength in comparison to the matrix material but costs much more than particulate reinforcement. If the requirement upon material is tribological in the sense of wear and seizure resistance the costlier fibre reinforcement does not contain as high resistance as the cheaper particulate reinforcement. From particulate to whisker and to fibres present enhancing cost. Besides cost, the particulate reinforced materials are less expensive to synthesise and machine. They might be processed through casting or sintering with equal ease based upon the application. The secondary machining of particulate composites is convenient & cheaper.

Other properties in which particulate composites exceed the matrix material considerably are temperature and oxidation resistances, better electrical conductivity (in case of metal matrix) , good damping capacity, and controlled thermal expansion coefficient.The particles that might be utilized to reinforce plastic matrix include chopped glass firbes, metal powder, saw dust, fly ash and natural minerals. Natural mineral particulates might also be used in softer metallic matrix such like aluninium alloys. Natural minerals could be granite and sillimanite or other similar materials.

A very common instance of large size composite is concrete.The cement is matrix while sand and gravel are reinforcement.Particles have variety of geometry however those which are equiaxed or have simialr dimension in all of directions and are small in size provide effective reinforcement. Even distribution of particles throughout the body of matrix is further helpful to attain better composite. The modulus of elasticity of particulate composite is function of modulii of elasticity of materials of particle and matrix & their volume functions. Eqs. (4) and (5) which describe modulus of elasticity of fibre reinforcement composite respectively under isostrain and isostress conditions are the upper and lower bounds of modulus of elasticity of particle composite.