高強度GFRPのモードIII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 III crack growth tests were carried out by edge crack torsion specimens under cyclic and monotonic loadings 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). The test results of mode III crack growth were compared with those of mode I and II. The fracture toughness, G_<IIIR>, was nearly constant during the crack extension of about 2mm for UD and C laminates. The fracture toughness value for UD laminates was much lower than that of C laminates. The fracture toughness increased in the order of mode I, III, and II. Fatigue crack growth tests were carried out at the stress ratios of R=0.1, -0.5, and -1. In the low growth rate region, the crack growth behavior was controlled by the range of the energy release rate, ⊿G_<III>, in UD and C laminates. The threshold value of the range, ⊿G_<IIIth>, was independent of the stress ratio in UD laminate, while, in C laminates, the value of ⊿G_<IIIth> at the negative stress ratio was about 1.6 times larger than at positive stress ratio. In the high growth rate region of UD and C laminates, the crack growth behavior was controlled by the maximum value of the energy release rate, G_<IIImax>, as in the case of mode II.
2006-05-25