Simultaneous design of a stiffened fuselage panel and number of structural tests "Code 98243"

Abstract

Reliability-based sizing optimization of a stiffened fuselage panel together with the numbers of coupon and element tests is performed for minimum lifecycle cost. The probability of passing certification test is used as the measure of reliability. Certification test evaluates the capability of the panel to sustain a two bay skin crack with broken central stiffener under ultimate load. Uncertainty in the fracture toughness prediction, variability due to the finite number of coupon tests, and uncertainties in geometry and loading conditions are studied. The effects of structural element tests on reliability are evaluated through Bayesian updating of the fracture toughness distribution. It is found that the number of coupon tests is only marginally sensitive to the weight penalty parameter, while the number of element tests is strongly dependent on it. If the weight penalty parameter increases, each pound of structural weight becomes more valuable, the designer tend to increase the additional knockdown factors to save weight and the number of element tests increases to compensate for the increased knockdown factor. © 2013 by Erdem Acar.