テラヘルツ透過測定による熱可塑性樹脂の分子配向と疲労破壊メカニズムの相関に関する一考察

抄録

To predict the fatigue life of CFRTP with high accuracy, it is necessary to ascertain the fatigue failure mechanism of the base material, that is, thermoplastic resin. The failure behavior of thermoplastic resin is greatly affected by polymer orientation, which distributes at random owing to manufacturing process with heating. In this study, the polymer orientation of specimens was identified by THz transmission measurement for the investigation of the correlation between its randomness and fatigue failure mode. As a result, the specimens with small randomness in polymer orientation along the loading axis did not yield fatigue fracture, and significant elongation was observed. The specimens with large randomness yielded fatigue fracture without significant elongation. In the latter case, the local plastic strain range caused by cyclic loading seems higher at the position where the polymer orientation is perpendicular to the loading axis. Fatigue damage seems to accumulate at the perpendicular orientation position so as to yield fatigue fracture. Based on the tentative theory, we conclude that the plastic strain range in the perpendicular direction to fiber orientation seems to align with the polymer orientation and governs the fatigue life of carbon fiber reinforced thermoplastic specimen.