TESTING AND ANALYIS OF POST-BUCKLING BEHAVIOUR OF ANISOGRID PREPREG PANEL UNDER COMPRESSION

Kurzfassung

This paper reports on buckling test results and analysis of an Anisogrid Prepreg Panel under uniaxial compression. Due to the special design of the Anisogrid Prepreg Structure Concept with load bearing skin this investigation aims to characterize the wide post-buckling behaviour. Grid structures consist of intersecting, integral manufactured ribs with different directions (helical, circumferential and/or axial) and optionally a load bearing skin. The classical manufacturing method for aerospace grid structures is wet-filament winding. For airframes, an Anisogrid Prepreg Structure Concept has been developed considering high quality assurance demands and the need of a State of Art manufacturing process (Advanced Fibre Placement). In this investigation, a flat panel of this Anisogrid Prepreg Structure Concept has been manufactured, analysed and tested. The intersecting ribs are manufactured of Prepreg layers with 60% fibre volume ratio and special interface layers for a better connection of the grid structure to the skin. In the point of intersecting rib directions (the rib knots) an alternating pattern of cut and uncut layers is used. The interface layers are placed into the rib laminate building rib feet as connection to the skin. In numerical post-buckling analysis, anisogrid panels with triangular skin bays show a different buckling behaviour than orthogonal stiffened panels. It differs in terms of missing change of buckling modes in the skin until global buckling failure and in consequence keeping more constant panel stiffness. As result of the investigation, the post-buckling behaviour of the tested panel will be compared with the numerically observed behaviour and the functionality of the interface layers will be evaluated during post-buckling state.