For a fiber-reinforced composite, the efficiency of reinforcement η is dependent on fiber length l according to where x represents the length of the fiber at each end that does not contribute to the load transfer. what length is required for a 0.62 efficiency of reinforcement, assuming that x is 0.61 mm?

l = 3.21 mm

Explanation:

The efficiency of a fiber-reinforced is the following:

Where:

η: is the efficiency

l: is the fiber length

x: is the length of the fiber at each end that doesn't contribute to the load transfer

So the length required for a 0.62 efficiency of reinforcement is:

I hope it helps you!  

real, smaller and upside-down.   so the answer should be b.