Looking at the case study provided under the Companion Material section, what is the main problem that is addressed in this case study?

1. Ef > Em and 5. lf < lcritical

Explanation:

The critical length of fiber is given by

where d is fiber diameter, is ultimate strength of fiber, and is fiber matrix bond strength.

When fiber length increases above critical length, the reinforcement becomes more effective since maximum fiber load is achieved by most part of the fiber hence

In matrix composite, matrix phase remains intact when fiber phase fails since the fracture strain in matrix is more than in fiber hence

Moreover, strain is inversely proportional to elastic modulus hence

meaning  or