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. 9. Tooth bending strength of CFRP gears with and without press molding. Figure 10 shows the effect of the fiber length mixed into the epoxy resin on the tooth root bending strength of CFRP gears. The bar chart in Figure 10 represents the results for gears fabricated under conditions No. 2, No. 3, No. 6, and No. 7 as listed in Table 2. Condition No. 2 corresponds to a gear with 0.2 wt% chopped carbon fibers added. Condition No. 3 involves the same chopped fiber addition with the tooth surface reinforced by a single carbon fiber cloth. Condition No. 6 is a gear with 0.2 wt% carbon milled fibers added, and Condition No. 7 adds cloth reinforcement to this configuration. A comparison of the tooth root bending strength between conditions No. 2 and No. 6 shows that the gear with milled fiber reinforcement exhibited an average increase of approximately 12.2% over the chopped fiber gear. Moreover, the data showed less variation under condition No. 6. Similarly, under conditions No. 3 and No. 7, where cloth reinforcement was applied, the gear containing milled fibers demonstrated a 7.7% higher bending strength than that with chopped fibers. This improvement is attributed to the shorter fiber length of the milled fibers, which is considered to have enabled a more uniform dispersion within the epoxy resin matrix compared to chopped fibers.

Fig. 10. Tooth bending strength of CFRP gears reinforced with epoxy resin containing milled fibers or chopped fibers.