Residual strength analyses of stiffened and unstiffened panels––Part II: wide panels

This paper highlights the results from fracture analyses conducted on the FAA/NASA wide panels (with and without stiffeners) using structural analysis of general shells code and the critical crack-tip-opening angle (CTOA) fracture criterion. The critical CTOA and plane-strain core height values, calibrated from a fit to the experimental load-against-crack-extension results from a series of unstiffened panels (76–1016 mm wide) tests with anti-buckling guides (Part I of this paper), were used in the analyses of wide stiffened and unstiffened panels. As discussed in Part I of this paper, high constraint around the crack front like plane strain has been accounted for by using the “plane-strain core” option in all analyses. By accounting for high constraint around crack front, it was possible for the critical CTOA fracture criterion to predict wide panel failures from small laboratory tests. As followed in Part I of this paper, rivet flexibility and stiffener failures in the analyses of wide panels were based on methods and criteria like that currently used in the industry. Analyses were able to predict stable crack growth and residual strength of both stiffened and unstiffened panels with various amounts of multiple-site damage within ±10% of the test results. Finally, it has been demonstrated that, it is possible to predict the residual strength of wide stiffened and unstiffened panels with critical CTOA calibrated from small laboratory coupons.