New orthogrid stiffened panel concept

December 2015

In 2013, Fokker Aerostructures developed a radically new stiffened skin panel concept with welded frames. The concept features frames that are welded to an orthogrid stiffening structure, thus eliminating a large number of costly mechanical fasteners. The concept is made possible by butt joining of stiffeners; stiffener plates are butt jointed to a skin laminate by melting them together. The cost of a thermoplastic butt joint is lower than that of conventional panel-to-stiffener joints due to the use of simple, flat stiffener preforms that are co-melted to the skin.

In 2014 and 2015, this panel concept has been further developed and optimized within the TAPAS2 project. Besides cost, weight is reduced also because stiffeners can now be designed with layups that are independent of the layup of the skin. The material used for stiffeners and skin is a carbon fiber/PEKK unidirectional tape. A radius filler is used in injection molded carbon/PEKK compound.

Fokker Aerostructures develops the panel concept and has manufactured a large number of test panels. Trade studies, carried out in 2014 and 2015, show a significant cost and weight reduction potential as compared to traditional metals and composite stiffened shell concepts.TenCate Advanced Composites supplies the carbon/PEKK UD tape material used and partner Airborne develops stringer preforms. The NLR will test 1.8 x 0.8 metre test panels in compression and shear in 2016.