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Composite mould tool based on 3D printing

Periodic Reporting for period 2 - COMBO3D (Composite mould tool based on 3D printing)

Reporting period: 2020-04-01 to 2021-09-30

COMBO3D proposes to additively manufacture a short fibre reinforced thermoplastic tool with integrated active temperature control, to shorten the cure cycle time and so to focus on the objectives addressing the limitations and implementing the improvements of the state of the art project. By using a robot guided large scale short fibre reinforced plastics extrusion additive manufacturing process the tool can be produced as a single part, directly integrating the temperature control, shortening the lead-time and enabling simple and fast restoration of the tool surface to compensate for the expected lower lifespan. Using a robot-guided process also allows to print the final demonstrator tool in one piece in curved layers (real 3D printing). To ensure tool stability during the curing cycle, short carbon fibre reinforced semi-crystalline high performance thermoplastic PAEK will be used. Commercially available PAEK have a form stability of over 250°C in unreinforced grades and CF filled grades are available with heat deflection temperatures of 315°C and more.
By introducing heating elements in the tool, it can conduct heat to the parts lower surface, in combination with the autoclave or oven, heating it up from both sides. These heating elements can be electrical or fluid channels connected to an external temperature control. Electric heating elements provide higher heat up rates but fluid heating allows to change from heating to cooling mode and hence to also cool the tool. Thereby it is possible to also achieve faster cool down. COMBO3D therefore proposes to use both heating elements in the tool.
The whole development of the printed tool is supported by simulation. The design of the tool will be optimized by implementing the heating and cooling system in a thermal simulation. The manufacturing process simulation supports the printing process by generating knowledge about the temperature distribution during printing and correlating it with path planning.

The objectives derive from the call:
1. The concept shall decrease the current lead time for metallic mould tools for composite part production.
2. The concept shall achieve a shorter cycle time, considering different methods of heating/curing the composite part, in a production method to be defined at the project start.
3. The concept shall be designed for automation to assure effective production with rates of up to 200 parts per month for approximatly 10 years.
4. The concept may have a lower life span compared to production, but shall not have a sigificant impact on recurrent costs or production rate due to replacement or restoration.
5. Coupon level test samples produced with the concept tool shall be defect free and meet the laminate quality and geometric requirements equal to today’s aeronautic prepreg quality.
6. The tool concept shall be verified first on a small scale and then be produced as a full scale final tool, which is to be used in the production of the WP A-3.1 demonstrator.
In project COMBO3D three moulds were printed.
First a flat mould was manufactured and used to produce composite test plates on which coupon level tests were performed to validate the composite performance is at the same level as produced with traditional tooling.
Second a single curved small scale tool was printed that included the most critical design elements. These included a injection concept through hollow cores to fill the part from the inside out. The design had to consider the additive manufacturing process with miniumum feature size, maximum overhangs etc. Internal fluid chanels were designed conformal to the curved cavity. This tool was used to validate the 3D printing process, the key design aspects and the injection concept.
Finally a full scale mould for a flaperon designed by the TM Saab was manufactured. To the knowledge of the consortium, at 3,1m total length and 430kg the upper mould shell is the largest and heaviest PAEK print produced worldwide to this date.
This work was done on a new material formulation with modified crystallization kinetics with high potential for commercialization for large scale additive manufacturing. Additionally simulations o the tool wer undertaken to model the heat transfer from the internal cooling channels into the anisotropic mould material.
Project results were disseminated in:
Three SAMPE Europe Conference Papers:
https://mediatum.ub.tum.de/node?id=1593642&change_language=en
https://mediatum.ub.tum.de/node?id=1593634&change_language=en
(Third article added to repository soon, title: Feuchtgruber, M.; Consul, P.; Colin, D.; Zaremba, S.: CONFORMAL TEMPERING CHANNELS IN A 3D PRINTED CORE FOR RTM TOOLING. SAMPE EUROPE Conference and Exhibition 2021, 2021)

One Journal paper:
https://onlinelibrary.wiley.com/doi/full/10.1002/pi.6168
A technical article on composites world: https://www.compositesworld.com/articles/3d-printing-cfrp-molds-for-rtm-flaperon-exoskeletons-and-more-
And a article in the project repository journal: https://doi.org/10.54050/PRJ1117715

Two more scientific journal papers are planned.
The project progresses beyond the state of the art in 3D printing by enabling large scale additive manufacturing with semi-crystalline high performance polymers. This type of material enables new applications requiring higher thermal, tribological and chemical resistance and offer longer lifespans than the more common amorphous thermoplastics for additive tooling.
Using tooling to develop the process the project contributes to the implementation of additive manufacturing in aerospace, potentially saving material and energy through higher efficiency and thereby strengthening the competitiveness.
By taking advantage of AM the project is able to produce tooling with internal channels for fluid temperature control and injection lines, enabling more robust filling processes in composite production.
Upper Mould half after printing Cavity side
Upper Mould half after printing back side
Overview Cores and lower shell
Detailed view cavity with openings for inserts
Detail view backing with extruder
Side view finished mould