It is desired to produce an aligned carbon fiber-epoxy matrix composite having a longitudinal tensile strength of 750 MPa. Calculate the volume fraction of fibers necessary using the following data: the average fiber diameter and length are 1.2 ´ 10-2 mm and 1 mm, respectively; the fiber fracture strength is 5000 MPa; the fiber-matrix bond strength is 25 MPa; the matrix stress at fiber failure is 10 MPa.