TESTING AND ANALYIS OF ANISOGRID PREPREG ELEMENT SPECIMEN UNDER UNIAXIAL TENSION AND COMPRESSION

Kurzfassung

This paper reports on test results and analysis of Anisogrid Prepreg knot and rib specimen under uniaxial tension and compression. Due to the special knot design of the Anisogrid Prepreg structure concept, this investigation aims to characterize stiffness and strength properties for these two kinds of specimen. Integral Anisogrid structures contain intersecting, integral manufactured ribs with different directions (circumferential, axial, and/or helical) 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, element-sized specimens of this Anisogrid Prepreg structure concept has been analysed and tested. This design concept consists of undisturbed and disturbed Prepreg layers with 60% fibre volume ratio, which are placed in an alternating pattern in the structure. Disturbed layers are cut in the point of intersecting rib directions. Due to the special stacking of the ribs with rectangular cross-section and very narrow ply widths, a wide reference testing program is used additionally. This means that in the testing program laminate specimens with typical stacking, rib test specimens cut out of a thick plate and manually laid rib and knot specimens have been produced, tested and compared to analytical strength calculations. As result, an answer is given which stiffness and strength properties in tension and compression can be expected for this Anisogrid Prepreg structure concept.