Effects of fillers on the impact damage and compressive residual properties of single hat-stiffened composite panels

Abstract

Hat-stiffened composite panels have been widely used in the primary structures of airplanes, such as fuselage sections and wing boxes. Impact damage in the structures can significantly reduce the residual load capacities and inserting fillers into the deltoid regions between the stiffener and skin could be a method of enhancing the damage tolerance of the hat-stiffened composite skin. In this study, impact and compression after impact (CAI) tests have been conducted on the single hat-stiffened composite skin specimens, and the effects of the fillers on the buckle load, failure load and impact damage tolerance are analyzed through comparing the compressive test results of the specimens with/without fillers and with/without impact damage. The usage of the fillers increases not only the buckle load and final failure load of the single hat-stiffened composite skins, but also the impact damage tolerance largely. Furthermore, finite element models are developed for the simulations of the post-buckling and failure process, and the influential mechanisms of the impact damage and fillers are revealed through analyzing the post-buckling failure process. This work provides a study about the influences of the usage of fillers on the mechanical properties of the single hat-stiffened composite skin and it can be a method for initial design of large multi-stringer composite panels.