A Study on Composite Materials

Composite Materials: The word “composite” in composite materials signifies that two or more materials are combined on a microscopic scale to form a useful material. The advantage of composite is that they usually show the best qualities of their constituents and often some qualities that neither constituent possesses. The properties that can be improved by forming a composite material include: Strength, Stiffness, Corrosion resistance, Wear resistance, Attractiveness, Weight, Fatigue life, Temperature-development behaviour, Thermal insulation, Thermal conductivity, Acoustical insulation. Naturally, not all of the above properties are improved at the same time.

Classification and Characteristics of CompositeMaterials: There are three commonly accepted typesof composite materials:

1.Fibrous composites which consist of fibres in a matrix.

2.Laminated composites which consist of layers of various materials.

3. Particulate composites which are composed of particles in a matrix.

Fibrous Composites: Long fibers in various forms are much stiffer and stronger than the same material but in different form, for example, ordinary plate glass fractures at stress only a few thousand pounds per square inch, yet glass fibers have strength of 400,000 to 700,000 psi in commercially available forms and about 1000,000 psi in laboratory prepared forms.

Laminated composites:Laminated composites consist of layers of at least two different materials thatare bonded together. Lamination is used to combine the best aspects of theconstituent layers in order to achieve a more useful material. The propertiesthat can be emphasized by lamination are strength, stiffness, low weight,corrosion resistance, wear resistance, beauty or attractiveness, thermalinsulation, acoustical insulation etc.

Particulate Composites: Particulatecomposites consist of particle of one or more materials suspended in a matrixof another material. The particles can be either metallic or non metallic ascan the matrix. Non metallic in metallic composites, also known as metal matrixcomposites, are now being used recently.

Based upon type of matrix phase, metal matrixcomposites could be categorised into:

1.Aluminium MatrixComposites(AMC).

2.Magnesium Matrix Composites.

3.Titanium Matrix Composites.

4.Copper Matrix Composites.

5. Cobalt Matrix Composite.

Out of these, Aluminium based metal matrix composites are being used now a days. This preference is mainly due to their outstanding physical and mechanical properties, which include low density, exceptional resistance to wear and corrosion, a high strength-to-weight ratio, elevated hardness, excellent formability, resistance to thermal shocks, a high modulus, impressive fracture strength and fatigue resistance.

Conclusion: Present industrial developments are associated with materials having advantageous physical and mechanical characteristics that can achieve technological needs. Aluminium and its composites are best suited materials as have better properties than unreinforced materials. Beneficial properties with reduced prices have enlarged their applications. Al MMCs are used in defence, aerospace, automotive, aviation, thermal management areas in engine pistons, cylinders barrel, connection rods, elements of vehicles braking systems because of their unique properties of high hardness, high strength, high stiffness, high wear, abrasion and corrosion resistance.

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