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Flexible RTM tool with automated distortion correction

Periodic Reporting for period 2 - FLEX (Flexible RTM tool with automated distortion correction)

Reporting period: 2019-09-01 to 2021-08-31

The FLEX proposal answers to the scope of JTI-CS2-2017-CfP07-AIR-01-33 call on the topic “Flexible RTM tool concept for composites with spring back adjustments capabilities”. The main aim of the project was to design an RTM tooling system that will feature decreased lead times and increased productivity. The primary goal was to develop a novel distortion compensation capability based on actively changing the mould shape.
The distortion compensation process is driven by accurate modelling of the spring back effects thanks to the simulation of the phenomenon by analytical surrogate models. The project also investigated key manufacturing points for automation to increase productivity improvements to the preform/fibre placement, the resin injection process and mould cleaning. Work was also conducted to incorporate an advanced monitoring system to offer improved quality assurance . The technology demostrator for this work was a mould for a 1-metre span, full chord flaperon that will feature all complexities of a real production piece. The final tool, for a 3-metre span part, was built using the same design principles according to the specification of the Topic Manager (SAAB), verified for compliance and functionality and delivered to its premises.
Overall, FLEX aimed to advance its technologies from TRL3 to TRL5 and potentially reach TRL6. Within the project, the integrated system (tooling and technologies) was developed and validated in a relevant environment, thereby ensuring that TRL5 was achieved upon its completion. The Call required that tooling be delivered to the Topic Manager premises, so that TR6 can be achieved post-project within the Airframe ITD. As of October 2021, the first full-scale part had been successfully produced from the FLEX tooling.
Post-project development will take place across Europe with the inclusion of exploitation partners who can help take the product closer to market. The scientific knowledge developed within FLEX will continue to be disseminated to the public, scientific communities, and end-users through established links fostered by large beneficiary partners within the consortium.
The following aspects were addressed during the second reporting period (RP2) from Month 13 to Month 30:

Design of a novel RTM tool with distortion compensation capabilities.
Tooling design and manufacture has been completed for both the FLEX Tools; the Small Tool (1m span demonstrator) and the Large Tool (3m span full-size part tool). These were delivered to TWI and Saab, respectively, to enable the manufacturing trials described under the project to be undertaken. The Small Tool was then used to manufacture part demonstrator to validate the thermal control system and the as-moulded part distortion, to assess the tool capacity for adjustment
Reduce the lead time to compensate for part distortion and spring back.
The surrogate model and thermal control of the part were developed and successfully demonstrated the capability of the model to predict the part distortion as a result of the part curing and to identify the resulting adjustments necessary to produce a part on nominal shape as intended
Induce compensated mould shape through a set of external actuators that impose the correct shape based on a closed loop feedback control system.
The FLEX Small Tool was cycled through the full ±2mm range of the actuators for adjusting the tool shape during the tool validation process at LRT. The feedback system was designed and implemented but not fully tested due to the challenges relating to COVID and Brexit that affected the final trial phase significantly
Efficient thermal management of the tooling operation.
The thermal management system was implemented by ETS, using the heater elements embedded within the tool by LRT. Integration of the chosen heater elements within the tool material was challenging, however it provided an opportunity to demonstrate the on-line quality control through the thermal management system, in conjunction with the cure monitoring, to validate the part had the correct final properties. Work continued on the development of the fibre alignment monitoring system (WP3.2) and this demonstrated a potential system for assessing fibre angle deviations during layup through camera monitoring and control software, developed by BU. The injection strategies necessary to manufacture the parts, in the individual tools were developed and implemented through close collaboration between LRT, TWI and BU, with the high part quality from each first article produced demonstrating a successful infusion.
A methodology for an overall design and evaluation of the production cell.
The FLEX Large Tool was successfully integrated into the Topic Manager facilities to enable the manufacture of demonstrator parts. The Small Tool was delivered to TWI and formed part of a representative proof-of-concept manufacturing process. The demonstration of all the automated steps identified in the deliverable were not fully realised in a single location.
The project outputs have been disseminated via two separate conference proceedings, a peer-reviewed journal article is in preparation and the learning on tool design has already contributed to the SEER project, where the advances through self-heated benzoxaine resin tooling is being used to provide smart, self heated tooling. LRT are, in particular, keen to provide this tooling technology to commercial clients as the impacts of COVID ease on the aerospace manufacturing sector.
The main objective of the project is to address a common drawback in the manufacture of large and complex composite parts, the distortions (e.g. deformation, spring-back effect) that cause deviations from its desired geometry. The current strategy to achieve a desired pre-defined geometry in a composite part is iterative. It consists in measuring the deviations from said geometry and incrementally optimising the tool geometry. The FLEX partners have collaborated to demonstrate that it is possible to make high quality digital models based on simple materials characterization tests and knowledge of the cure cycle, to predict the distortion of the part as a result of the thermal stresses during curing. In conjunction with tooling that allows for shape-compensation, this enables a manufacturing process that minimises the distortion of the final part through intelligent adjustment of the tool based upon knowledge of the fibre angles and the part cure parameters.
The FLEX project has completed a demonstration of the self-heated, composite RTM tooling with the smart control systems for the production of parts at the scale and complexity of the flaperon chosen by the Topic Manager. LRT and ETS will use these successful demonstrations of their technology to win new business within the worldwide aerospace supply chain, as the industry recovers from the challenges of COVID, because these systems pave the way towards a streamlined and greener production process for composite parts for the aerospace industry and beyond, thereby driving the use and implementation of lighter composite parts, generating a greener and fuel-efficient fleet.
Full Scale part produced from FLEX tooling delivered to Topic Manager facilities
Small tool (mould used to manufacture the flaperon)
Small Tool demonstrator part with person for scale
FLEX Small Tool including actuation system (bottom) prepared for part manufacture
Spring back effect compensation strategy on small tool
First part manufactured from FLEX Small Tool