Experimental verification of PEKK stiffened panel under compression

Abstract

Abstract The paper presents the experimental strain and stress analysis of a thermoplastic composite stiffened panel subjected to compression load. The panel has five stringers with a non-symmetric design. Two panels are investigated. The experimental analysis deals with the pristine panel without any flaws and the panel with an artificial crack at the middle stringer interface with the skin. Panels were made from a thermoplastic polyetherketoneketone (PEKK) carbon composite. The buckling and mechanical analysis is based on digital image correlation, strain gauge measurements, and linear variable differential (LVDT) transducers. The crack subcritical extension was defined and analysed. The results show that crack propagation starts coupled with sudden buckling mode transition. The crack growth behaviour is influenced by the buckling shape, which consists of two main modes (with three and four half-waves) in the longitudinal direction in each skin bay.