Concept and Objectives:

Main aim of the project is the development of a complete, integrated process chain for the cost effective serial production of various aerospace CFRP stiffener profiles. The production is foreseen in the two steps: Preform manufacturing and infiltration / curing. The project will focus on complex profile geometries with variable cross sections, single or multiple curvature and integrated load introduction areas. Braiding will be useful for the net shaped preforming of more massive straight and curved profiles like frames and floor beams, as well as for drive shafts, rods and other pipe-like structures. The technology offers a high potential for the cost effective production of net shaped fibre preforms with respect to optimized load paths and light weight design. For the production of stringers, especially for those with double curvature, the so called Fibre Patch Placement FPP should be used to manufacture tailored non crimped multidirectional tapes. FPP works with spread and bindered rovings, which can be laid up in any desired angle and in uni- or multilayer configuration, according to the needs of the stringer design. The infiltration of the preforms is planned with RTM technology or with the so called Stacked Curing technique, an open mould infiltration technique which allows the simultaneous curing of up to 20 profiles in one shot in a tool with comparably low complexity.

IMAC-PRO Results in brief:

Aircraft composites’ produced cheaper

EU-funded scientists developed cost-effective manufacturing technology for widely used composite aircraft structures. Reducing the cost of production will have significant impact on the competitiveness of the EU aerospace industry.

Carbon fibre-reinforced plastics (CFRPs) are increasingly employed in the production of aircraft structures. CFRPs have high strength-to-weight ratio resulting in high mechanical performance with reduced fuel consumption and emissions. Current long-range aircraft have utilised CFRP structures produced primarily with costly state-of-the-art manufacturing processes.

The EU-funded project ‘Industrialization of manufacturing technologies for composite profiles for aerospace applications’ (IMAC-PRO) developed cost-effective CFRP stiffener production chains. Their focus was on two types of aircraft structures: the stringers (longitudinal stiffening elements) of the fuselage, and frames and beams.

Three different technologies were developed for stringer pre-forming. A discontinuous hot pressing (HP) process was employed to form non-crimped fabric material. Scientists also developed a fibre patch pre-forming (FPP) production route for an integrated pre-form tape made from single patches cut from unidirectional (UD) glass tapes to be formed into a T-stringer. Finally, they developed a pre-form for curved stringers consisting of stringers made from tubular braided sleeves. Pultrusion and infusion technologies were investigated for curing of stringers. Although HP technology is quite mature, FPP has more potential for high-volume production due to faster production speeds.

Two heavy profiles, a JF-frame and a C-beam, were selected for development of pre-forming appropriate for frame and beam manufacture. UD braiding technology for the manufacture of textile-based composites is the preferred pre-forming technique to avoid the limitations of prepreg (pre-impregnated fibres for which a matrix is already present). UD-braided pre-forms are produced from dry carbon fibre. The pre-forms are then resin-infused, cured and finished. New curing tools were produced for each profile using novel technology enabling a very short infusion time before closing the mould for wetting and curing. The UD technology was shown to be highly effective at producing complex curved pre-forms cost-effectively with minimal scrap.

Frames, stringers and floor beams are important light-weight structures with high stiffness and strength that are largely responsible for the aerodynamic shape of an aircraft. Optimised design and cost-effective manufacturing of such components as demonstrated within the IMAC-PRO project will have major impact on the competitiveness of the EU aerospace industry.

Public Documents

Periodic Report Summary
Periodic Report Summary 2
Final Report Summary
Periodic Report