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Materials, Process and CAE Tools Developments for Pre-impregnated Carbon Binder Yarn Preform Composites

Final Report Summary - PRECARBI (Materials, Process and CAE Tools Developments for Pre-impregnated Carbon Binder Yarn Preform Composites)

The PRECARBI project aimed to develop new materials (carbon fibres and liquid resins) as well as supporting technologies, already proved on a laboratory scale, that bring together prepreg and liquid composite moulding (LCM) technologies to combine the advantages of each. Essentially pre-impregnated carbon fibres with a polymer binder formulation were developed for LCM and tow placement processes. Activation (e.g. heat, microwave, and ultrasound) allows binder yarns to be (repeatedly) shaped prior to resin infusion. The binder yarns enhance mechanical properties, due to their formulation and ability to eliminate fibre waviness; also, they have indefinite shelf life, improve preform handling / trimming and drape ability.

The combination of superior performance and cost-effective manufacture is expected to ensure composites growth in future aircrafts leading to improved performance, greater payloads and fuel/emissions reductions.

Below are some of the most important innovations and results of the project.
-Automated fibre placement of dry fibre/binder yarns. This concerns preform manufacturing for complex component geometry.
-Manufacture of highly integrated RTM fittings. This concerns manufacturing of fittings for horizontal tail plane application.
-Design of complex RTM tooling. This helped with manufacturing of complex RTM parts. It is expected to yield cost saving due to new lean design and associated reduced manufacturing efforts.
-A modelling methodology for the mechanical and damage behaviour was developed based on use of PAM-CRASH. The methodology can be implemented as a separate material model within PAM-CRASH. This addresses a potential market need that will become relevant once the use of preforms with binder expands and the potential damage of them during handling, storage and transportation becomes an issue.
-A method for the multi-objective optimisation of draping was developed and implemented. The method can be implemented as a routine of existing optimisation packages. Application of the methodology will lead to novel process designs for draping than can use fully the design flexibility offered by composite materials.
-A methodology for the automated identification of damage parameters and their stochastic properties using Markov chain Monte Carlo was developed and implemented. The technique developed can be implemented as a software routine in a stochastic simulation package. This development addresses the long-term need for robust estimation of stochastic properties of composite materials; this will become more relevant as the use of composite materials expands with their variability becoming a frontline issue.

New PAM-QUIKFORM software functionalities can be reported as results:
- possibility to use a curve to define the draping direction with a constant ply angle;
- possibility to drape the part with a defined order;
- possibility to export the flat pattern curve in IGES format;
- validation of new genetic algorithm for fibre optimisation.

PAM-RTM software functionalities can be reported as:
-new infusion material data collected for binder yarn composites;
- validation simulation of three demonstrator parts.

New PAM-CRASH/Visual composites software functionalities can be reported:
- new data on material characterisation - preform analysis;
- validated simulation of preform impact.

The exploitation will require the active participation of the industrial partners - Airbus Spain, Airbus Germany, Eurocopter and FACC. It is anticipated that these partners will continue to apply the new binder yarn technologies and simulation methods to their future industrial parts. ESI Group and the industrial partners will initiate discussions on the software application following the end of the project. The results can be useful for advanced composites industry, especially aeronautics. However, it is felt that the materials and methods developed in PRECARBI can be applied to other manufacturing industries and especially the automotive sector.

Toughened resin systems for high-end applications were developed. In the frame of the PRECARBI meeting one-component resin systems were developed since this is the state-of-the-art for the aerospace industry nowadays. It seems that there is a big interest to move towards two-component systems that show advantages of room temperature transportation and storage. Therefore, it should be considered to use the formulating routes developed in PRECARBI for two-component toughened systems.

Binder yarn seems to be an innovative product which may overcome drawbacks of current carbon fibre reinforcements. Therefore, technical and economic potentials are promising. Potential obstacles which might prove to be barriers to commercialisation: all carbon fibre products need a material qualification from fixed production technology. The current demand of binder yarn is limited to development projects and thus the production yield of a pilot plant is suitable. Any bigger, commercial production site will produce more material than needed today. This being said, binder yarns for material qualification are currently only available from a pilot plant which will probably not meet future demand. Therefore, re-qualifications of industrial plants are likely.

Draping simulation and optimisation tools were developed. It is possible to have a reduction of lead time ('first-time-right') and enhancement of part performance through reduced maximum shear angles and respect of design constraints.

Knowledge was gained to manufacture, in a commercial manor NCF materials from binder impregnated carbon using stitch media, having identified processing parameters required to produce material acceptable to meet aerospace specifications. Also, knowledge gained to manufacture, in a commercial manor woven materials from binder-impregnated carbon, having identified processing parameters required to produce material acceptable to meet appropriate aerospace specifications. Using this knowledge, it is possible to get material qualified on an aerospace part utilising its preforming capabilities to reduce costs; materials could be exploited in other markets, such as automotive, marine or industrial applications.

During the project it became apparent that the binder yarn incorporated into a woven 3D shape greatly helped the performing, hence infusion process. 3D woven structures are in their infancy as a perform solution with a lot of further work required to understand the intricacies of the structures and their failure modes , the fibre needs to be fully commercialised and production ready, for this technology there are no competing binder systems. This could potentially reduce impact on the environment by helping cut waste (material, transport, power) in the manufacture of the components.

During the project with TTE work was done looking at the possibility of high-volume performing, using vacuum pressure moulding, could be developed to be done by stamping presses. Taking layers of binder fabrics and laminating through a laminating machine, cutting then pressing. The method would lend itself to high volume automotive, industrial components, possibly interior aircraft components.

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