In order to build fatigue lifetime diagram, a laminated C/Ccomposite 0/60/-60. was loaded with a sinusoidal cyclic loading ata frequency of I Hz. The difficulty of this study was in thedetermination of the fatigue limit, because of the large scatteringobserved in the number of cycles to failure when the same maximumstress level was applied to the specimens. To solve this problem, anew concept called the master-curve was defined. This concept isbased on an analysis of the primary tensile curve, largely scatteredfrom one specimen to another, which directly controls the accuracy ofthe determination of the cyclic fatigue limit. Some tensileparameters such as the elastic modulus, the failure stress and thenon-linear strain to failure were chosen for constructing themaster-curve. This concept was then applied at the first cycle ofcyclic fatigue tests to determine the real lifetime diagram.
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