The Fracture Diagram: A New Design Tool for Stiffened Panels

A detailed explanation is presented for the use of fracture diagrams in the design of stiffened panels. Based upon some recent work on the development of fracture diagrams for a large sheet containing a crack midway between two parallel, riveted stiffeners, this paper emphasizes a methodology for employing fracture diagrams to estimate maximum loads, critical flaw sizes, and fatigue life for stiffened panels. In addition, the fracture diagram approach enables failure predictions to be made ranging from linear elastic rapid crack propagation to net section failure at the ultimate strength level of the material. The fracture diagrams are dimensionless and can be used for any material where meaningful yield strength and fracture toughness properties are available. References are provided for background and theoretical development of the fracture diagram approach.