This paper deals with a determination of the fracture toughness requirement to obtain leak-before-break performance for a 155–175 ksi strength level high-pressure gas cylinder. Analytical LEFM methods along with Irwin’s KIc-Kc equation related by the parameter βIc were used to predict the fracture toughness requirement for the plane-stress fracture state problem. Experimental work was conducted on flawed cylinders to quantify the fracture toughness requirement for leak-before-break performance. The results indicated that the analytically predicted toughness requirement is 4 to 25 percent higher than that established experimentally. The results also indicated that the minimum specified KIc(J) value of 85 ksi $in.$ (93.5 MPa$m$) for the gas cylinder is sufficiently higher than the analytically and experimentally established toughness values to provide the desired leak-before-break performance.

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