Numerical Treatment of Damage Propagation in Axially Compressed Composite Airframe Panels

In the design phase of stringer-stiffened composite airframe panels, it is a key issue to exploit material reserves as far as possible to create lighter and safer aircraft. A recent approach is to apply postbuckling design — standard for metallic panels — also to composite parts. This work focusses on the development of a simulation procedure which accurately predicts the postbuckling response of composite panels while accounting for damage propagation. For this purpose we employ a robust shell element formulation which allows for arbitrary stacking sequences as well as a variable location of the reference plane. A ply discount model is incorporated to account for intralaminar damage growth. The cohesive zone approach is implemented in a so-called interface element to predict interlaminar damage growth, respective skin–stringer separation. The numerical model is validated via a numerical example with experimental evidence.