In this study, the intrinsic static/dynamic fracture toughness of Al 7175-T74 is evaluated from the apparent static/dynamic fracture toughness of a notched specimen. A critical average stress fracture model is suggested to establish the relationship for predicting the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relationship between the notch root radius and the effective distance calculated by finite element analysis. The effective distance is the major characteristic describing stress distributions ahead of the notch tip. Therefore, the effective distance can be used to evaluate the behavior of structures containing notches. In this study, effective distance is applied to estimate the failure criterion for the combustion chamber with a notch. It is concluded that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective distance can be used to evaluate the failure criterion of structures with notches.