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Composite mould tool based on 3D printing

Periodic Reporting for period 1 - COMBO3D (Composite mould tool based on 3D printing)

Reporting period: 2019-04-01 to 2020-03-31

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 the consortium has finished the concept phase for the full scale flaperon and begun the testing and manufacturing work.
Per description of action the concept phase (WP2) consisted of:
• Temperature control definition for the tool, allowing for faster heating and cooling.
• Material selection of feasible PAEK compounds suitable to the mould, capable to withstand the process conditions during use, but also processable in large scale additive manufacturing in a cold environment, herein the consortium also decided on formulations regarding the fiber content of the compound to achieve thermal expansion of the mould similar to an aluminum backing structure containing the handling elements.
• Optimization of fluid flow geometry and effect on temperature distribution based on the defined heating/cooling system and the distribution, shape and size of channels and heating elements in the tool. Work on this is continuing with simulation and optimization with dissemination activities planned for late 2020.
Additionally, in this phase the consortium worked on:
• Core and sealing concepts for the full scale mould, to account for the 6 cores needed in the final demonstrator which need to be sealed against the mould.
• First investigations into mechanical behavior at high temperatures of thermoplastics
• The consortium decided on adding another small-scale demonstrator in the project containing already the critical design elements such as cores and critical radii to allow for lessons learned to be integrated into the full-scale demonstrator to reduce the technical risk.

After this work on the testing and manufacture work package (WP3) has begun.
• Process quality development and simulation includes the identification and optimization of relevant process parameters for the materials selected. A total of 14 Materials is investigated with potentially more compounds with a higher fiber content to be produced if the results are promising. First parts include 6kg compact blocks with integrated test cooling channels and parts with 1m in length. Both manufactured with an extruder on a robot in a cold environment. This has not been reported in literature so far.
• Design of tools for coupon tests is close to finalization with final adjustments being made. The consortium decided on using inserts where connections are needed, for example to connect the pressurized cooling fluid hose.
• Production of test tools for the manufacture of test specimens is set to begin as soon as the design is finished. A reference test specimen has been produced in autoclave by the topic manager and a second reference will be made in a conventional metal RTM mould by TUM. Thereby the coupons made with the manufactured plastic RTM mould can be compared to both the state-of-the-art process used in the topic managers current production, as well as the state of the art for the new RTM process.

Communication & Dissemination activities have been planned and agreed on and dissemination set to begin in the second half of the project
The first print trials using PAEK in a cold environment show great promise and are already some of the biggest reported structures. Additionally, the mechanical performance of printed coupon tests made from unreinforced plastic shows almost isotropic behavior including the usually critical interlaminar direction. Both the process development and the material development go beyond the state-of-the-art.
The planned result for the second half of the project include the manufacture of the three moulds – coupon, small-scale and full-scale – and the derivation of design guidelines. Also results of the coupon tests comparing the material properties of autoclave cured prepreg, metal tool RTM and plastic tool RTM are expected within the next months.
Towards the end of the project results on the actual cycle time improvement, mould robustness and repair strategies for damaged tool surfaces are expected. Together with a preliminary business case prepared in WP4 this will give the foundation for successful exploitation of the project results not just in research but also commercially in industry.
Test print with cooling channel in PAEK with 10% carbon fiber content
Print head used for test tool
Top view of cooling channel design in coupon plate tool