Enhanced Mould for Thermoplastic Fuselage in and out of Autoclave Consolidation

Project Information

EMOTION

Grant agreement ID: 864474

DOI

10.3030/864474

Project closed

EC signature date 28 August 2019

Start date 1 September 2019

End date 28 February 2022

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 1 938 831,75

EU contribution

€ 1 419 057,22

Coordinated by

TECHNISCHE UNIVERSITAET MUENCHEN
Germany

Periodic Reporting for period 2 - EMOTION (Enhanced Mould for Thermoplastic Fuselage in and out of Autoclave Consolidation)

Reporting period: 2021-03-01 to 2022-02-28

Summary of the context and overall objectives of the project

EMOTION – Enhanced Mould for Thermoplastic Fuselage in and out of Autoclave Consolidation
The project provides a tool that enables the production of high volume half-shells from thermoplastic fibre composite. The tool is used in the CS2 joint project STUNNING, contributing to the Multi-Functional Fuselage Demonstrator.
Composite structures are used for latest airliner generation. Further improvement for the airframe lightweight structure shall be achieved by using thermoplastic based composite materials. While the use of carbon fibres as strong and stiff material remains the same, the matrix materials shall be changed to thermoplastics. This change is also motivated by potential improved end-of-life properties, e.g. meaning improved recyclability.
Lightweight structures are essential for the environmental friendly operation of airliners and in general mobility providers. Less weight, means more passenger or freight can be transported at same CO2 footprint. New propulsion technologies will not replace this need for lightweight structures. Instead, electrification and hydrogen technology in the area of propulsion require further improvements in lightweight construction to compensate for lower energy storage densities.
Composite structures are stacked from several thin plies which need to be consolidated to a solid and strong material. Consolidation means that a pressure of up to 10 bars and temperature up to 400°C is applied to the stacked material. Doing that, a shape-defining tool is required which resists the temperature and pressure applied by an autoclave.
The EMOTION consortium is researching durability and process suitability with the aim of achieving the best interaction between mold and component. During component manufacturing, the composite material is positioned at room temperature but need to be heated up to 400°C for consolidation later. The tool material (typically metal) as well as the composite material will expand and shrink during that operation. The difference in thermal behaviour causes the challenges. In the worst case the manufactured composite structure is affected by wrinkles. Wrinkles in the fibre architecture reduces the strength of a composite material.
Carbon composite materials itself creates due to their energy intensive production a relative high CO2 footprint. By using thermoplastic matrix materials, processing temperatures rise and therefore energy efficient processing technologies are requested to provide an overall benefit in terms of ecological footprint.
The project is therefore split into a near term and midterm technology approach. Processing in an AC is state of the art and can provide superior consolidation qualities. Processing out of an AC (ooA) is an objective for energy reduction, making thermoplastic composites even more competitive and providing a reduced ecological footprint.
The EMOTION project has shown at the end, that both approaches are based on same technological keys: 1) Use of special alloys for the mould skin addressing the CTE differences between tool and component 2) Multi material tool design capable to handle inhomogeneous thermal expansions. Both set up the base for an induction heated tooling system which can replace the AC operation.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The initial design phase was dominated by the search for the most suitable tool material. The challenge lies in low thermal expansion in the temperature above 340°C, where the thermoplastic matrix is liquid. A special Ni alloy offers the best properties here. However, this alloy is not or very rarely used for larger components.
TUM activities were the tool-component interactions and the support of the material selection process. Processing trials on flat panels considered different alloys, surface qualities, bagging and heating strategies.
The tool design at the project partner ALPEX focused on a multi-material design with a relatively thin tool shell supported by a standard steel base structure. Technical risks such as welding of the Ni alloy, spot welding of different steels to attach tension rods to the skin and process-safe (vibration-free) milling had to be secured by trials.
The tool was built mostly during the first project period by the EMOTION consortium and could be finalized in the second period in which it was used by the joint project STUNNING. The benefits of the multi alloy design with optimized tool properties could be proven.
In the 2nd phase, the integration of an induction heating system at the tool skin backside was a major development task at Ostseestaal. The basic tool design remains identical and is capable to compensate differences in elongation while processing. Demonstrations were performed with a small square meter large tool. The homogeneity of the heating is of high relevance to achieve the quality standards required for aerospace applications. Two aspects had to be considered: 1) Temperature distribution at the tool surface, which is a result of tool and induction system design. 2) Temperature gradients inside the composite material while processing, which is a result of the single sided heating and insulation on top of the component. The overall power is more than high enough for the application as ooA consolidation tool. However, a temperature gradient beyond application industry expectations remained and requests further development to higher TRL.
Results summary:
Development and successful demonstration of new tool design capable to consolidate thermoplastic composites at high temperature and quality.
Next tool generation for ooA operation was demonstrated by the use of an induction heating system. The learnings of tool-component interaction and induced effects on composite materials were presented at TUMs PhD seminar and will be integrated to the lecture Aerospace Materials Science and Processes at TUM. The industry partners ALPEX and Ostseestaal have demonstrated their innovation and design capabilities with the EMOTION project and extended their expertise for thermoplastic composite manufacturing tools.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

A special Ni alloy is being used for the first time for tooling to consolidate fibre composites. The good results of the laboratory tests were confirmed on a full-scale basis. Large shell components made of thermoplastic fibre composite material can also be produced from unidirectional individual layers in the highest quality. This step allows further optimisation of aircraft structures, weight savings and improvement of eco-efficiency.
The use of costly special alloys requires a new tool design in which the base structure can still be made of low-cost steel. While the tool base is allowed to expand during heating, the tool surface must be kept geometrically within tight tolerances. Stiffness on the one hand and flexibility between components that expand differently must be taken into account in the tool design and are the key to manufacturing high quality fibre composite components.
EMOTION extends the knowledge and capability to design and manufacture tools capable for high temperature thermoplastic composites usable in highest challenging aerospace applications.
For future energy efficient production the tool integrated single sided heating was integrated. While the mechanical tool design already provides the capability for this approach, the effects on the composite material side requires further research activities to assure the safety levels of aerospace applications.

Geometry measurement by laser tracker of the full scale EMOTION tool after first assembly