Design, numerical and experimental characterization of the composite rib for a regional aircraft

The work is part of the Clean Sky 2 - AIRGREEN2 (AG2) project which aims at designing, analysing, manufacturing and ground-testing a full scale composite Outer Wing Box (OWB) demonstrator for a regional aircraft. The OWB has been designed in order to withstand stiffness, strength and stability requirements under critical loading conditions taken from the flight envelope. In particular, a minimum weight design has been obtained with an optimization based on genetic algorithms that explored several thickness distributions and stacking sequences. As important step of the project, a composite rib has been designed, manufactured and tested in order to validate the related technologies. The rib, object of this work, corresponds to a middle section rib of the Outer Wing Box (OWB). Static and nonlinear finite element analyses have been performed in order to verify that the proposed rib test geometry would fail at a machine load less than the current maximum available testing load machine. Moreover, buckling analysis has completed the FE analyses as required by the design specifications. The composite rib was manufactured by hand-layup and by using the Liquid Resin Infusion (LRI) method, an Out Of Autoclave method (OoA), in which Dry Non Crimp Carbon Fabrics are impregnated by epoxy resin (high temperature cure) under the application of vacuum only. The impregnated Carbon fabric material was then cured in a standard oven. CATIA software was used for both the tool and part design. Respective material allowables have been obtained by testing standard coupons manufactured by the same base materials (dry carbon fabrics and resin) and manufacturing method (LRI). Standard hand layup procedures were followed during the layup process of the fabrics. Appropriate auxiliary materials capable to withstand the respective LRI infusion and curing process specifications were used. The rib has been tested up to failure under an in-plane shear loading condition. The scope of the test was to validate the manufacturing process, as well as the design and FEM analysis in terms of allowables and final failure of the component.