High Rate Production of laminar Wing Covers-With modular "Shoe Box" tooling

Abstract

The “Shoe Box” Approach

Efficient wing structures are essential to ensures competitiveness of future aircraft concepts and composite materials provide a wide range of technological options that can be utilized to optimise the wing for its application scenario. The developed “Shoe Box” upper wing cover structure is fully integrated and based on toughened prepreg for the skin and the backing structure.

In case of the skin laminate a robot based multi head ATL (Automatic Tape Laying) concept has been chosen because it allows to increase the lay-up rate without exceeding a critical lay-up speed and limits the investment costs because flexible standard robots and rail systems can be used.

To realize the stringer/rib cap backing structure box like tooling modules are wrapped with prepreg fabric and combined in a way that stringers and rib caps are formed. To provide the required consolidation pressure for the prepreg a material mix of aluminum and Invar is used where the thermal expansion of the aluminum compresses the prepreg stack. To provide maximum geometrical precision each tooling module is mechanically linked to an Invar base plate. Since it is a known problem that heating and cooling of massive tooling constructions is critical for the cycle time hollow tooling modules where applied. To further increase heat-up and cool down rates the air flow of the autoclave was lead through the tooling modules.

Finally Skin lay-up and backing structure lay-up together with their dedicated tools are combined. The resulting tooling set-up is an partly elastic closed autoclave mould without vacuum bags.

High precision GOM ATOS measuring equipment has been used to prove the excellent geometrical accuracy.