What is the ultimate longitudinal strength of a polyurethane/carbon fiber composite with a 25% fiber loading? The modulus of PUR is 30MPa with a strain-to-break of 500%. The modulus of the carbon fiber is 800GPa and the ultimate strength is 3.5GPa. In this case, the matrix is very rubbery and the fiber will break first. As a result, you are provided the following information about the matrix: strength at 0.1% strain 0.5MPa strength at 0.5% strain 1MPa strength at 1% strain 10MPa