(a) What is the distinction between matrix and dispersed phases in a composite material? (b) Contrast the mechanical characteristics of matrix and dispersed phases for fiberreinforced composites.

Matrix phase refers to the continuous phase in a composite material that binds the dispersed phase together. This phase is often a polymer, metal, or ceramic material. The primary function of the matrix is to provide mechanical support to the dispersed phase and protect it from the external environment. Additionally, the matrix phase is responsible for transferring any applied stress or load to the dispersed phase, which ultimately dictates the composite material's behavior. The dispersed phase, on the other hand, refers to the secondary phase that is embedded within the matrix. This phase is usually in the form of fibers, particles, or plates. The purpose of the dispersed phase is to provide improved specific properties (strength, stiffness, thermal, electrical, or magnetic) that are significantly superior to those of the matrix phase.

Matrix Phase: The mechanical properties of the matrix are generally lower than those of the dispersed phase. For instance, the matrix has a lower modulus of elasticity, strength, stiffness, and thermal conductivity. The matrix phase's primary role in a fiber-reinforced composite is to transfer load between fibers, provide ductility, and prevent crack propagation. In addition, the matrix deforms more easily than the dispersed phase, hence providing toughness and ability to absorb energy. Dispersed Phase: In fiber-reinforced composites, the dispersed phase is typically stronger, stiffer, and more resistant to crack growth compared to the matrix phase. The mechanical properties of the dispersed phase, such as tensile strength and elastic modulus, are considerably higher than those of the matrix phase. This results in a significant improvement in the mechanical properties of the composite material. The dispersed phase bears the major portion of the applied loads, and adding more fibers (increasing volume fraction) to the composite generally increases the material's strength and stiffness. However, the material may become more brittle with a higher fiber volume fraction. In summary, the matrix phase provides ductility, toughness, and support to the dispersed phase in fiber-reinforced composites, whereas the dispersed phase (fibers) enhances the material's strength, stiffness, and resistance to crack growth. By carefully adjusting the properties and proportions of these two phases, a wide range of composite materials can be designed and tailored to meet specific engineering requirements.