Definition

Composite materials are macroscopic combinations of two or more distinct materials having a discrete and recognizable interface separating them

Characteristics of Composite Materials

• Composite materials are macroscopic combinations of two or more distinct materials having a discrete and recognizable interface separating them
• Thus composites are heterogeneous materials, and many are naturally occurring; the most common is wood.
• One constituent is called the reinforcing phase and the one in which it is embedded is called the matrix.
• The reinforcing phase material may be in the form of fibers, particles, or flakes.

• The matrix phase materials are generally continuous.

  Examples of composite systems include concrete reinforced with steel and epoxy reinforced with graphite fibers, etc.

• Composites can be very strong and stiff, yet very light in weight, ratios of strength-to-weight and stiffness-to-weight are several times greater than steel or aluminum

Role of Matrix

• to give shape to the composite part

• to keep the fibers in place

• to transfer stresses to the fibers

• to protect the reinforcement from the environment, such as chemicals & moisture

• to protect the surface of the fibers from mechanical degradation

• to act as shielding from damage due to handling

Role of Reinforcement

• The strength to the composite material is imparted mainly by reinforcement

• They serve additional purpose of heat resistance on conduction, resistance to corrosion and provide rigidity

• A reinforcement that embellishes the matrix must be stronger & stiffer than matrix & capable of changing failure mechanism of composites

• Also their contribution to other properties such as the co-efficient of thermal expansion , conductivity etc is remarkable