Many of our modern technologies require materials with unusual combinations of properties that cannot be met effectively by using conventional materials such as metals, plastics and ceramics.Hence we use combinations of certain materials called Composite Materials to fulfill the requirement.
Composite Materials are those materials that are produced by combining 2 or more dissimilar materials into a new material in order to obtain desirable material properties. Composite materials are generally application specific and they are utilized for their individual properties which may be far better suited to that specific application than conventional materials.
Most Composite materials consist of a material that acts as a matrix and a second material acting as a reinforcement. As the name suggests, the reinforcement is used to support or reinforce the material, while the matrix acts as a binder or a base.The matrix protects the reinforcement from damage due to abrasion and chemical action with the environment.
Composite Materials can be classified into 3 broad categories according to their construction and structure.
1.Particle Reinforced Composites : In this type of composite, the reinforcement is in the form of particles. The matrix and reinforcement share the load almost equally in this type. These are manufactured cheaply and find wide use in the industry. Examples of Particle Reinforced Composites are Concrete (M-Cement,R-Sand & Gravel), Vulcanized rubber(M-Rubber, R- Carbon Black), Cemented carbide tools (M-Cobalt/Nickel R-Tungsten Carbide/Titanium Carbide).
2.Fiber Reinforced Composites : These are the most important form of composites. The Fiber Reinforced Composites contain the reinforcement in the form of numerous tiny fibers. The fiber reinforced composites usually have high strength and stiffness along with a very low weight. This brought about by the concentration,arrangement and orientation of the various fiber materials with each other and with the reinforcement. The Fiber reinforced composites are manufactured by applying layers of the fibers and impregnating them with the matrix in the form of thick resins.The layers of matrix are stacked on top of each other until the desired product thickness is reached. A very good and well known example of Fiber-Reinforced Composites is FRP which stands for Fiber Glass Reinforced Plastic. In this composite material, the Reinforcement is in the form of fine fibers of glass contained within a Plastic matrix.This material has a very high Strength to weight ratio and is chemically inert to a variety of corrosive environments. FRP is used in many objects such as surfboards,helmets,wind turbine blades and bowling balls. Other principle fiber reinforcements include carbon and aramid fibers, and matrix materials include polyesters, vinyl esters and epoxy resins.
3.Structural Composites : Structural Composites are composite materials made up of multiple homogenous materials that are physically stacked on top of the other.The properties of such composites depend on the properties of the constituent materials as well as the geometrical design of the components. Based on the basic structure, there are two main types of structural composites- Laminations and Sandwich panels
A laminate or Laminar Composite Material is made from multiple 2-dimensional sheets or panels that are stacked together one on top of the other. A laminar layer can be made up of fabrics like paper,cotton or woven glass or organic materials like wood. A common Example of Laminar Composites is Plywood which is made up of multiple layers of wood joined together with adhesives.
A Sandwich Panel Composite is made up of two strong outer sheets which are separated by a relatively less dense material having lower stiffness and low strength. The outer faces bear most of the loading on the face and any transverse bending stresses. The core resists deformation perpendicular to the face plane and separates the faces. Faces can be made up of Aluminium, FRP, Titanium, Steel or Plywood. Cores can be made from polymers,rubber,inorganic cements or wood and into specific intricate shapes such as a honeycomb structure to enhance its load bearing capability. Sandwich Composites are used in many applications such as Roofs and walls of Buildings,in Aircraft Wings,Fuselage and Tail skins.
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