高強度GFRPのモードII層間はく離疲労き裂進展におよぼす応力比の影響

概要

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The mode II fatigue crack growth behavior from delamination was investigated with UD laminates (made of unidirectional laminates) and C laminates (made of unidirectional laminates and cloth laminates) of high strength glass fiber reinforced plastics (GFRP). Fatigue crack growth tests were carried out by end notched flexure speciments at the stress ratios R=0.3, 0.1, -0.5, and -1. In UD laminates, the theshold of energy release rate range, ⊿G_<11th>, of fatigue crack growth was independent of the stress ratio. In C laminates, the ⊿_<11th>value at negative stress ratios was about four times of that at positive stress ratios. In C laminates, a fatigue crack propagated along the interface of the unidirectional laminate at positive stress ratios, while along the interface of the cloth laminate at negative stress ratios. When the stress ratio was negative, the fracture surface of C laminates was rough because of the resin rich area of fabric crossing, and this roughness shielded the crack tip, restricting the shearing deformation near the crack tip. Thus the crack growth resistance of C laminates at negative stress ratios in much larger than that at positive stress ratios.
2004-04-25