Short, but aligned, Al2O3 fibers with a diameter of 20 m are introduced into a 6, 6-nylon

Question:

Short, but aligned, Al2O3 fibers with a diameter of 20 µm are introduced into a 6, 6-nylon matrix. The strength of the bond between the fibers and the matrix is estimated to be 1000 psi. Calculate the critical fiber length and compare with the case when 1 µm alumina whiskers are used instead of the coarser fibers. What is the minimum aspect ratio in each case?