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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SHERLOC QSP (Quilted Stratum Processes (QSP) for low cost and eco thermoplastic manufacturing of complex composite parts)

Teaser

Summary

The SHERLOC QSP aims at designing and manufacturing a batch of composite panels incorporating thermoplastic composite window frames made following an innovative manufacturing process, called QSPÂ® that allows lighter mass with cheaper cost and shorter manufacturing cycle time of parts than existing processes.
1 Choice of material and characterization
The thermoplastic composite material selected to manufacture the window frame is PEEK This material was selected because it is meets the thermal requirements and it is already used in other sub-projects in SHERLOC project.
More than 100 coupons of both thermoplastic and thermoset materials were manufactured and tested at room temperature and in hot and wet conditions. The characterization bore a specific focus on determining interlaminar and delamination behaviour, which was particularly considered particularly useful for a QSP design which uses discontinuous patches of composite.
2 Design
The design of the window frame was driven by the optimization of shape in order to reduce the mass of the part, acting on the outer geometry and local thickness of the part.
The window frame features a flange on its outer edge, which limits the out-of-plane deformation of the fuselage skin. The thicknesses and orientations are variable depending on the areas of the part to optimize the use of carbon fibres. The design results in a part composed of an assembly of 8 patches, each consisting of 2 or 3 plies of carbon fabric. The use of patches also reduces the rate of material scrap.
Numerical simulations of the forming process were performed prior to design finalization, as a way to guarantee that the preform was formable without significant redesign of the patching plan.

Work performed

3 Manufacturing
The used process, named QSPÂ® (QUILTED STRATUM PROCESS), relies on the assembly of a multi-layered TP preform, which is melted in two successive ovens and then formed in a closed mould.
For the window frame, the preform is composed of 8 patches as described above. This assembly is entirely robotized, which allows for a very short manufacturing cycle time, i.e. less than 5 minutes.
Thanks to robotization, the precision of preform assembly and positioning in the mould allowed for net-shape manufacturing of the parts (meaning that no machining finish of the edges is required).
With the QSPÂ® process and multi-patch perform, the waste rate has been divided by 2 compared to the conventional thermo-stamping process, i. e. with a single layered preform.
4 Control and quality part
Several Non-Destructive Testing (NDT) methods were tested on the window frame to select and qualify the most relevant. Both window frames and bonded assemblies were then inspected.
The methodology followed the ensuing steps:
Selection of the reference samples including artificial and natural defects and representative of the final parts
Qualification of Ultrasonic Phased Array and Infrared Thermography methods to inspect the window frames
Selection of the most relevant method according to defects sensitivity, ease of implementation, respect of requirements (among other criteria).
Design and manufacturing of a robotised NDT equipment to inspect the structural integrity of the window frames and of the bonding between the C/epoxy skins and the window frame.
Robotised Non-Destructive Testing of the window frames and of its bonding with the fuselage.
In parallel with NDT techniques, destructive tests were carried out to compare with the NDT inspection results. Finally, the quality of the parts from the second manufacturing campaign is satisfactory with measured porosity rates below 0.5%.

Final results

1 Cost assessment

The cost assessment of the production of the window frame considered the main costing items: cost of material purchase, non-recurring costs of investing in the thermostamping technology (including general capacity and product specific tooling) and amortization of said tooling, recurring manufacturing costs and production overhead costs.
The cost assessment did not account for commercial margins and NDT inspection of finished part.
CETIM has had contact with a manufacturer of composite aircraft window frames who procured valuable information on current thermoset designs. At the time of writing of this document, window frame parts in serial production are made using the RTM process (injecting dry fibre preforms with liquid resin in a closed mould), which is a process causing little raw material waste.
As a consequence, any thermoplastic window frame design will need to focus on limiting material waste to be competitive against its thermoset counterpart

2 Industrial transfer and intellectual property

Concerning the net-shape manufacturing process without edge overmoulding developed for the SHERLOC project, Cetim filed two French patent applications.

3 Dissemination

The Sherloc QSP project has been presented or mentioned in 7 oral presentation during international events:
SFIP, June 2018 (Nantes, France)
ITHEC, Oct. 2018 (Bremen, Germany)
NAFEMS, Nov 2018 (Paris, France)
JEC World, March 2019 (France, Paris)
Thai Subcontracting Promotion Association
Salon International de lâ€™AÃ©ronautique (SIAE), June 2019 (France, Bourget)
SAMPE, Sept 2019 (France, Paris))

Demonstrators was exhibited at 2 international trade fairs:
Salon International de lâ€™AÃ©ronautique (SIAE), June 2019 (France, Bourget)
JEC World, March 2019 (France, Paris)