Hair Breakage 262 resulted in an approximate 30% decrease in the break stress by conventional stress-strain testing. Figure 7 shows fatigue results in the form of an S-N plot for both virgin and relaxed Afro hair at 60% relative humidity. Results again show a sizable shift in the position of the S-N plot and indicate differences in cycles-to-fail approaching two orders of magnitude. Thus, Table 2 shows average cycles-to-fail for the three hair types discussed above upon repeated application of a 0.010 g/μm2 stress (i.e. approximately half the break stress of virgin Caucasian hair at 60% RH) and convincingly illustrates why different habits and practices are necessary for Afro hair. Table 2. Average number of cycles-to-fail for different hair types after repeated application of a 0.010 g/μm2 stress at 60% RH Hair type Average cycles-to-fail Virgin Caucasian hair ~ 37,000 Virgin Afro hair ~ 5,500 Relaxed Afro hair ~ 160 Figure 7. S-N Curves for virgin (dark gray data points) and relaxed (light gray data points) Afro hair at 60% RH