Statistical Distribution of Fatigue Life of Injection Molded Short Carbon Fiber Reinforced Polyamide Composites

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Other Title
  • 射出成形 CF/PA の疲労強度のバラツキと変動疲労寿命予測


The statistics distribution of fatigue life of a short carbon fiber-reinforced polyamide-6 composite and its stress ratio dependence are examined. A procedure for predicting S-N relationships for different constant values of probability of failure P, i.e. P-S-N curves, is proposed. Fatigue tests are performed at different stress ratios R = 0.1, 10 and R = χ = σUTSUCS, respectively. To identify the statistical nature of fatigue life, lognormal and Weibull distributions are fitted to the fatigue data obtained. The plot of fatigue data on a probability paper and the goodness-of-fit tests using the modified Kolmogorov–Smirnov suggest that both lognormal and Weibull distributions are acceptable as the distributions for the static strength data as well as fatigue life data. The P-S-N curves at different stress ratios for different probabilities of failure (10%, 50% and 90%) are constructed not only using the experimental data but also a theory developed in this study, and they are compared to each other to evaluate the accuracy of the theory.



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