For a fiber-reinforced composite, the efficiency of

(a) For a fiber-reinforced composite, the efficiency of reinforcement ? 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. Make a plot of ? versus l to l = 40 mm (1.6 in.) assuming that x = 0.75 mm (0.03 in.).
(b) What length is required for a 0.80 efficiency of reinforcement?