PSI - Issue 80

Seiji Mitsubayashi et al. / Procedia Structural Integrity 80 (2026) 431–442 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 7. Relationship between tooth bending strength and the chopped carbon fiber content. Figure 8 compares the tooth bending strengths under conditions No. 2, No. 3, and No. 4 in Table 2, all of which were prepared with a chopped fiber content of 0.2 wt%. The addition of a single layer of carbon fiber cloth (condition No. 3) resulted in an approximately 69% increase in the tooth bending strength compared to the unreinforced condition (condition No. 2), suggesting that aligning fibers along the direction of maximum principal stress at the tooth root effectively enhanced strength. Furthermore, the strength under condition No. 4 increased by approximately 7.8% compared to condition No. 3. These results indicate that increasing the number of reinforcing cloth layers contributes to the enhancement of CFRP gear strength.

Fig. 8. Tooth bending strength of CFRP gears with 0, 1, and 2 layers of cloth along the tooth surface. Fig. 9 shows a comparison of the tooth bending strengths under conditions No. 3 and No. 5 in Table 2. Condition No. 3 corresponded to the gear molded under a pressure of 4.2 kPa during curing, while condition No. 5 was molded without applying pressure. The gear molded without pressure exhibited a tooth bending strength approximately 20.4% lower than that of the gear molded under pressure. This decrease in strength is likely due to insufficient resin impregnation into the reinforcing cloth caused by the absence of pressure inside the mold during curing.