き裂長さ依存性を考慮したCF/PEEK積層板の疲労層間はく離伝ぱの下限界測定

概要

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Model I delamination fatigue crack growth behavior was investigated with unidirectional laminates made from ICI APC-2 (AS 4/PEEK). Tests were carried out by using double cantilever beam specimens. Fatigue tests under the constant maximum energy release rate indicated that the crack growth rate decreases with increasing crack length from the initial defect. Hence, the conventional load-shedding method gives higher threshold values corresponding to the increment of crack length. The most conservative growth law and the threshold value were obtained by using the growth rate at the zero increment of the crack length from the starter film. Here, the existence of the growth threshold was shown by nonpropagating cracks. Since this method requires a computer controlled test system and a number of specimens, another simplified method was proposed. This newly developed method is the iteration of several load-shedding tests. In this method, the threshold value converged after only several tests. This threshold value agreed well with that obtained by the tests under the constant maximum energy release rate. Moreover, the threshold value for this method was lower than that determined by the delamination growth onset method.
1995-03-25