Effects of R-ratio on the off-axis fatigue behavior of unidirectional hybrid GFRP/Al laminates at room temperature
✍ Scribed by M. Kawai; K. Kato
- Publisher
- Elsevier Science
- Year
- 2006
- Tongue
- English
- Weight
- 556 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0142-1123
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✦ Synopsis
Effects of stress ratio on the off-axis fatigue behavior of the unidirectional fiber-metal hybrid GFRP/Al laminate (GLARE-2) at room temperature are studied. Constant amplitude fatigue tests at three kinds of stress ratios R = 0.4, 0.1 and À0.2 are performed on coupon specimens with different fiber orientations h = 0°, 5°, 10°, 15°, 20°, 30°, 45°, 60°and 90°in the GFRP layers. It is observed that the fatigue life of GLARE-2 is extended by the increase in stress ratio for every fiber orientation. A linear relationship of the Goodman type can approximately be fitted to the constant fatigue life data for GLARE-2, regardless of the fiber orientations. The fatigue fracture of GLARE-2 is characterized by the fatigue failure of the GFRP layers for h = 0-15°, while it is brought about by the fatigue failure of the aluminum-alloy layers for h = 30-90°. For each of the two groups, a master S-N relationship can be identified by means of a modified fatigue strength ratio. A fatigue damage mechanics model that considers the effect of stress ratio is developed using a modified theoretical fatigue strength ratio based on the Tsai-Hill static failure criterion. It is demonstrated that the fatigue model can successfully be used for description of the off-axis fatigue behavior of GLARE-2 over a range of stress ratios.