Question

In a fiber-reinforced composite, the primary role of the matrix is to

• A. Carry the major load
• B. Transfer stress to the fibers and protect them
• C. Increase the density
• D. Decrease the thermal conductivity

Hint:

In a composite material, remember this division of duties: the fibers provide the structural muscle to carry the load, while the matrix acts as the glue that bonds them together, transfers stress between them, and protects them from damage.

Answer 1

The Correct Option is B

Concept: A fiber-reinforced composite material is engineered by embedding high-strength, high-stiffness structural fibers (such as glass, carbon, or aramid) inside a continuous binding phase known as the matrix (such as polymer, metal, or ceramic resins). Each component phase serves a specific mechanical purpose to optimize performance.

Step 1: Functional roles of Fibers vs. Matrix.
Let us break down the mechanical distribution of duties inside a composite:
• The Fibers (Reinforcement Phase): These are thin, strong filaments designed to carry the major mechanical loads applied to the component. They provide high tensile strength and stiffness along their alignment axes.
• The Matrix (Continuous Phase): The matrix is generally softer and more ductile than the fibers. It performs several critical functions:
• Stress Transfer: The matrix grips the embedded fiber walls via interfacial bonding forces. When an external macroscopic load is applied, the matrix deforms elastically/plastically and transfers the stress directly to the high-strength fibers, ensuring they carry the load.
• Fiber Protection: The matrix encapsulates the delicate fiber filaments, serving as a physical barrier that protects them from environmental corrosion, moisture, chemical attack, and surface abrasion. Surface scratches can dramatically lower the strength of brittle fibers.
• Fiber Alignment: It holds the thousands of individual fiber strands firmly in their designated spatial configurations and orientations, preventing them from buckling under compressive loads.

Step 2: Evaluating the options.

• Carry the major load: This is the primary function of the *fibers*, not the matrix.
• Transfer stress to the fibers and protect them: This accurately describes the mechanical purpose of the matrix phase, matching option (B).