Notched Fatigue Life Prediction for Short Carbon Fiber Reinforced Polyamide Stampable Sheet Composite

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  • カーボン短繊維を用いたスタンプ成形複合材料の切欠き疲労寿命とその予測

Abstract

Notched fatigue behavior of a stampable short fiber reinforced polyamide composite material was investigated. In addition, development of an engineering prediction methodology was attempted. From the static tests performed, it was found that the notch sensitivity of the composite can accurately be predicted by the notch sensitivity model for both in tension and compression. It was found that the notched S-N relationships obtained from the notched fatigue tests agree with the S-N relationships associated with the condition under which the static notch sensitivity remains the same value during fatigue loading at any stress ratio. The fatigue life of the press-molded short fiber reinforced polyamide composite can adequately be predicted for any stress ratio as well as for any relative notch size using the integrated notched fatigue model that consists of the notch sensitivity model to evaluate the notched strength, the anisomorphic constant fatigue life diagram to evaluate the S-N curve for unnotched configuration and the improved notched S-N curve model. It was found that crack propagation in the press-molded short fiber reinforced polyamide composite can be described by means of the Foreman’s law. The use of the Foreman’s law allows evaluating the crack initiation life, and the predicted value are shown to be in good agreement with the experimental results, regardless of the stress ratio of fatigue loading.

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