Determine the volume fraction of fibers required to obtain a longitudinal tensile strength of 812 mpa in a unidirectional carbon fiber reinforced composite. you are given that the tensile strength of the carbon fibers are 1240 mpa and that the stress in the matrix at fiber failure will be 300 mpa. answer format x. xx unit: unitless (fraction, example: 50 vol% fiber would be entered as 0.50)