In Large Particle particle reinforced composites, the matrix transfers some applied stress to the particles.

• A. The matrix transfers some of the applied stress to the particles
• B. The matrix absorbs all the stress with no transfer
• C. Particles transfer stress to the matrix
• D. There is no interaction between matrix and particles

Answer: (A)

When a particulate-reinforced composite is loaded, the load is shared between the matrix and the particles through the matrix–particle interface. The matrix initially carries the applied stress, but because the particles are stiffer and bonded to the matrix, shear stresses develop at the interface and a portion of the external load is transmitted into the particles. This load transfer enhances the overall stiffness and strength of the composite.

The effectiveness of this transfer depends on how well the particles are bonded to the matrix and on the particle size and distribution. With large particles, there is still a mechanism for stress to move from the matrix to the particles, just not as efficiently as with very fine or fiber reinforcements, but the transfer is definitely nonzero and real. If there were no transfer at all, the particles wouldn’t contribute to reinforcement, and the composite wouldn’t gain stiffness.

Thus the statement that the matrix transfers some of the applied stress to the particles captures the essential load-sharing behavior that underpins particulate-reinforced composites.