高強度GFRP積層板の層間はく離疲労き裂進展におよぼす混合モード比の影響

概要

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The effect of mode mixty on 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 mixed mode bending specimens at a stress ratio of R=0.1. In UD and C laminates, the crack propagation rate da/dN decreased as mixed mode ratio G_/G_<T max> decreased when compared at the same total maximum energy release rate G_<T max>(=G_+G_<II max>). At a constant crack propagation rate under mixed mode loading, the driving force is expressed in terms of a linear combination of the pure mode I G_ and the pure mode II G_<II max>. The G_<T max> in C laminates approached the G_<T max> in UD laminates as G_/G_<T max> increased at the same crack propagation rate. In UD and C laminates, fiber bridging took place at G_/G_<T max>=0.70 and the crack propagation rate was expressed by a power function of the maximum value, G_<T tip max>, of the energy release rate at the crack tip. Fractographic observation UD and C laminates showed that the crack propagation path was on the surface of fibers at G_/G_<T max>≦0.41 and some resin facture was observed at G_/G_<T max>=0.70.
2004-12-25