Hair Breakage 290 Table 11. Weibull parameters describing the formation of differently sized breakage Fragment Size Characteristic Lifetime Shape Factor ≤ 2 mm 252,000 1.80 2 mm – 1 cm 1,940,000 1.13 1 cm – 3 cm 34,000,000 0.76 ≥ 3 cm 627,000,000 0.53 The findings from this experiment show notable systematic trends. Longer fiber fragments are modeled by a low shape parameter, indicating that the highest incidence of formation occurs early in the combing process. Conversely, short fragment formation is described by a higher shape factor, illustrating increased formation with additional grooming cycles. In short, the smallest fiber fragments are generated in a “wear-out” mechanism, while the longer fragments form by a “premature failure” mechanism. Moreover, fragment sizes in between these extremes show intermediate behaviors. It appears that the original hypothesis will be realized upon extending the test out to a higher number of cycles however the complete reverse is obtained earlier in the experiment. An explanation for this occurrence may involve the combined effects of fatigue theory and simple hair entanglement. The premature failure mechanism (i.e. a shape parameter less than unity) by which the longer fragments occur results from the relatively rapid failure of pre-existing defects, without appreciable generation and propagation of new ones. Earlier in the grooming process, there is also a higher likelihood of tangling that may produce localized high stress conditions and exacerbate breakage. With time these tangles are “brushed out,” the hair fibers become better aligned and fatigue theory applies. Of course, the above explanation also highlights the major drawback of this method, in that consumers do not brush their hair thousands of times without some intermittent treatment/ manipulation process. Therefore conditions are still somewhat