1. In all useful fiber-reinforced composites, the elastic moduli of the fibers are higher than those of the matrix. Explain why.
2. Consider the matrix of elastic constants for a composite consisting of an elastically soft matrix reinforced by a 90-degree cross-ply of stiff fibers. The general form of the matrix of elastic constants is
Young’s modulus for the composite when loaded parallel to one of the sets of fibers is 100 GPa,so s11 = 10 × 10−12 Pa−1. Of the values listed, which is most likely for s12? for s66?
