Finite element and experimental analysis of dented aircraft panels

Abstract

Aircraft fuselage panels are susceptible to low velocity impact damage in the form of "dents" from a variety of in-service sources, such as cargo and service trucks, dropped tools during servicing, walking on "no-step areas" and baggage handling mishaps. These dents result in a redistribution of load in the structure due to the change in shape and associated residual stresses. Although the load carrying characteristics of the undamaged structure are well understood a knowledge gap exists regarding the effects of dents on the ultimate compressive strength of the fuselage panel. It was this knowledge gap that the author sought to explore in investigating the compressive strength reduction characteristics of fuselage panels due to local denting. The effects of dent depth, diameter, shape and location were investigated in an experimental and numerical work programme. In addition the efficacy of current repair methods was studied and current modelling methods assessed. The results display the inherent ability of the stiffened fuselage panel to maintain stability through load redistribution away from the damaged area. Numerical and experimental results are shown to be in close agreement showing the compressive strength of a panel with a dent of 10mm depth on a stringer to be 91% of the undamaged compressive strength. Parametric studies established the worst case location for a dent and the effects of increasing dent depth. The current repair procedure of dent dress back was shown to recover 80% of the load reduction due to the unrepaired dent.