In fiber-reinforced composites, significant reinforcement is achieved only if which condition is satisfied?

• A. The matrix must be very brittle
• B. The fibers must be longer than the matrix can support
• C. The matrix-fiber bond must be strong
• D. The matrix must transfer all load without fibers

Answer: (C)

Load transfer between the fibers and the surrounding matrix is what gives a fiber-reinforced composite its extra strength and stiffness. For the fibers to carry significant load, the interface between fiber and matrix must be able to transmit shear stresses effectively. A strong matrix–fiber bond ensures the applied load is shared with the stiff, high-strength fibers rather than causing them to slip or debond from the matrix. If the bond is weak, the fibers can pull out or slide, so the reinforcement contribution is greatly reduced and the composite behaves more like the matrix. Other factors like fiber length and orientation matter, but without a strong interfacial bond, substantial reinforcement cannot be achieved.