For a polymer-matrix fiber-reinforced composite: (a) List three functions of the matrix phase. (b) Compare the desired mechanical characterisics of matrix and fiber phases. (c) Cite two reasons why there must be a strong bond between fiber and matrix at their interface.

Question (a): List three functions of the matrix phase in a polymer-matrix fiber-reinforced composite. Answer: The three main functions of the matrix phase are: 1. Transfer of load: Distributing the load uniformly among fibers to prevent concentrated loads that could cause failure. 2. Protection of fibers: Encasing the fibers to protect them from environmental damage and wear, such as corrosion and abrasion. 3. Maintaining fiber alignment: Holding fibers in their intended orientation and spacing to maintain an organized structure, contributing to the composite's overall strength and stiffness. Question (b): Compare the desired mechanical characteristics of matrix and fiber phases in a polymer-matrix fiber-reinforced composite. Answer: The main differences are: 1. Fiber phase: Provides high strength and stiffness, with a high tensile strength and modulus of elasticity for withstanding significant loads without breaking or deforming. 2. Matrix phase: Provides ductility, toughness, and load transfer, with good flexibility and adhesion properties to accommodate fiber movements and ensure a strong bond. Question (c): Cite two reasons why there must be a strong bond between fiber and matrix at their interface in a polymer-matrix fiber-reinforced composite. Answer: A strong bond is crucial for two main reasons: 1. Load transfer: Ensuring efficient load transfer from the matrix to the fibers, maximizing the use of fibers' high strength and stiffness for better overall mechanical properties. 2. Stress distribution: Ensuring uniform stress distribution around the fibers to prevent localized stress concentrations, which could lead to premature failure through debonding, matrix cracking, or fiber breakage.