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Direct filament wound rotor carbon resin sleeves by bulk curing and layer-by-layer Electron beam polymerisation

Final Report Summary - E-SLEEVE (Direct filament wound rotor carbon resin sleeves by bulk curing and layer-by-layer Electron beam polymerisation)

Executive Summary:
The E-SLEEVE project has dealt with the design, set-up and demonstration of two distinct processes for the filament winding of carbon composite retaining sleeves, to be realized directly integrated onto the electric rotor of high speed motocompressors for air conditioning systems used in aircraft applications: the first process uses cyanate ester resin and subsequent bulk curing, the second one uses an epoxy resin specifically formulated for high temperature and for direct layer-by-layer curing to be performed via low energy Electron Beam, simultaneously to the filament winding process itself. Both processes need to provide the necessary radial pressure to ensure safe retainment of the rotor magnets at high revolution speed. Next Technology Tecnotessile has deployed internal and external specific expertise and equipment, and reached stable conditions in manufacturing sleeves on mandrels and rotors via the new filament finding process improved to reach high winding tension, and developed and tested new E-beam curable resins with high Tg. Further industrial up-scaling scenarios with cost analyses have been produced for full exploitation of results in both processes.

Project Context and Objectives:
The E-SLEEVE Topic Manager had already worked on composite sleeves for rotors in air conditioning system for aircraft applications. This study resulted in the development of a carbon sleeve produced on a separate mandrel and subsequently transferred and shrunk on the rotor. This technology requires small tolerances on the sleeve inner diameter and expensive shrink tooling. The aims of the Topic were:
1- to develop an equivalent sleeve by direct winding such that the filament undergoes enough tensile stress to provide, at the required final thickness, the necessary radial preload on the magnets;
2- to find the best resin/fibre combination that could withstand operational temperature and humidity conditions.
3- to produce sleeves wound on rotors capable to withstand testing on a real turbomachine.

To reach the objectives, an intermediate step had been foreseen, in which sleeves are wound on a stainless steel mandrel representative of the rotor, whereby strain gauges provide measurement of the deformation induced by the sleeve and therefore of the retaining radial pressure.

Two project Scopes had been required:

- Scope 1 dedicated to wet direct winding of T800 or equivalent roving in combination with Cyanate-Ester resin, to be consolidated in autoclave.
- Scope 2 aimed at finding a new alternative resin/ winding/curing combination capable of withstanding 220°C in normal operation, and at fully characterizing it in terms of Tg and of Interlaminar Shear Stress (ILSS) measured after thermal ageing (up to 250°C) and humidity/temperature cycles).

A minimum of eighteen sleeves had to be produced, of which:
- 9 via Scope 1 process (5 on mandrel and 4 on rotors)
- 9 via Scope 2 process (5 on mandrel and 4 on rotors)

A cost analysis had been requested in order to compare direct winding for both Stages with the shrunk sleeve indirect method.

Project Results:
The following results have been reached:

- improvements to the design of the rotor and the sleeve (for both Scopes)

- Significant improvements to the filament winding unit have been designed, manufactured and widely tested to allow high tension winding and impregnation, including a reliable resin temperature control system and a design algorithm for accurate roving placement and a numerical simulator predicting radial pressure (for both Scopes).

- At least two new formulations for epoxy resin with high Tg (> 250°C) suitable for E-beam curing have been created and tested (Scope2).

- A new method has been designed and implemented to solve the interaction between magnets and the curing electrons (Scope2).

Potential Impact:
Environmental benefits

The indirect shrinking method requires extremely low temperatures with related equipment and energy costs. Direct winding methods for both Scopes allow for a more targeted and calibrated use of energy, since curing is carried out on either the single sleeve or at a layer-by-layer scale.

The work program has resulted in the full definition and validation of two distinct processes for the manufacturing, directly on the rotor, of retaining sleeves for high-speed permanent magnet machines.

This solution will bring benefits in terms of performance of the sleeve for the full life expectancy, as well as benefits in terms of costs for logistics and for manufacturing, with respect to the technology actually used by the Topic Manager (carbon sleeve shrunk on the rotor).

These successful results allow NTT, after the project end, to:
- produce one or more pre-series, in order to define the process and its costs more accurately; extend production at industrial level;
- transfer knowledge and technology expertise about the new process (equipment, materials, methods, controls) to the Topic Manager assisting them in the creation of a suitable production facility;
- transfer the technology to a manufacturing enterprise identified by the Topic Manager, with constant support during all phases, thus optimising time and resources for the qualification of new manufacturing process of the retaining sleeve directly on the rotor sub-assembly;
- collaborate with Topic Manager to the identification a possible supplier of the technology and product made in the course of the project, with transfer of necessary technology in the hands of the latter.
- evaluate further applications to the new technologies achieved, in areas not competing with the Topic Manager.

List of Websites:

Coordinator: ing. Marco Barbieri
Next Technology Tecnotessile s.r.l.