Fatigue Life Prediction of Center Cracked CentrAl Stiffened Panel Subject to Spectrum Loading

Abstract

Fiber Metal Laminates (FML), such as GLARE and CentrAL, offer improved structural performance as compared to that obtained from monolithic materials. FML are expected to enhance durability and damage tolerance (D&DT), and fatigue life of aircraft structures. Weight reduction is another anticipated benefit from FML. A building block verification strategy involving testing and analytical simulation of FML structures was conducted to demonstrate the FML technology. Notched and un-notched coupons made from CentrAL material subjected to static and fatigue loadings were tested and analyzed using multi-scale progressive failure analysis (MS-PFA). Analytical predictions were validated with tests. The results from analyses were in very good agreement with those obtained from tests. The D&DT approach predicted conditions that would produce damage initiation and propagation, fracture initiation and propagation and final failure. It also calculated the residual strength of the FML structure. The MS-PFA approach was also applied to simulate crack growth behavior for a five-stringer stiffened panel designed for a lower wing section subjected to fatigue spectrum loadings. The prediction results matched test within 10%.