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Cheaper, Lighter, Safer Composite Materials for Aircraft Interiors

Periodic Reporting for period 2 - IntAir (Cheaper, Lighter, Safer Composite Materials for Aircraft Interiors)

Okres sprawozdawczy: 2017-11-01 do 2018-10-31

What is the problem/issue being addressed?

The aim of the IntAir project was to refine the materials and upscale the manufacturing process for a new generation of aircraft interior composite materials that are cheaper, lighter and safer than the toxic, carcinogenic materials that are currently used.
Composite materials are well-established for aircraft interior sidewalls, galleys, lockers and seating. To meet the strict fire and weight requirements for aircraft interiors, the current solution is to use a fire resistant composite made of phenolic (phenol formaldehyde) resin with carbon or glass fibre reinforcement. However, there are three major problems with phenolics:

- Cost: phenolic parts have relatively long moulding times and their poor surface finish necessitates additional hours of manual finishing.
- Weight: the poor surface finish of phenolics means that secondary filler is needed, adding to the component weight.
- Safety: phenolics emit toxic and carcinogenic materials during processing.

Why is it important for society?

Most composite aircraft components are manufactured from prepreg, an intermediate material in which the resin is pre-impregnated into a reinforcement fabric, for subsequent moulding into parts.
The solution explored by the project was to replace the existing phenolic resin in the prepreg with a 100% bio-based polyfurfuryl alcohol (PFA) resin. PFA resin has been demonstrated to provide the following societal advantages:

- Improved sustainability: phenolic resins are derived from non-sustainable fossil-fuel based resources. The PFA resin utilised within the project is 100% derived from waste agricultural biomass.
- Improved passenger safety: in many fire tests, PFA-based composites have been demonstrated to outperform the incumbent phenolics.
- Improved worker health & safety: reduced exposure to toxic emissions when manufacturing aircraft parts from the new PFA resin system. The PFA resin uses water as a solvent. It does not require the use of volatile organic compound (VOC) solvents.

What are the overall objectives?

The overall objective of the project was to enable significant improvements in aircraft interior part cost, component weight and worker safety compared to phenolic composites by addressing the following three issues associated with the introduction of PFA-based prepregs:

- Refinement: whilst the mechanical and fire performance of PFA prepregs at the start of the project met the required performance levels, customers were looking for further refinement of the prepreg formulation to allow faster, easier processing.
- Repeatability: the pre-project method of impregnating the reinforcement with PFA resin did not provide the required high levels of accuracy and consistency in the material’s properties.
- Scale: prior to the project, the PFA prepreg development had been undertaken on small-scale and prototype equipment that did not provide the manufacturing tolerances, robustness or scale needed for secure supply.

Therefore, the specific objectives of this project were to address these three issues - to enhance the formulation, optimise the impregnation and upscale the production process of the PFA prepregs, thereby enabling the replacement of phenolic composite materials in aircraft interiors.

Final period – Conclusion of the action

By the end of the final period, the key results can be summarised as follows:

- Refined formulations of the PFA prepreg, which have been validated through the production and testing of two demonstrator parts - a train seat component and a helicopter roof panel.
- The development and implementation of an up-scaled production process that is capable of manufacturing the PFA prepregs with the required quality and production volumes to support post-project exploitation.
- The preparation of a robust business plan to support the post-project commercialisation of the PFA prepregs.
From the outset, the programme of work was underpinned by a commercialisation plan in order to provide a strong market and customer focus for the research and development activity. This plan encompassed a broad range of aspects including market intelligence, the supply chain, sales and marketing strategies and distribution/logistics. It had a significant ongoing input into the development of both the PFA prepreg materials and their method of manufacturing.

Based on the findings of the commercialisation plan, a range of PFA resin formulations was tested and refined with a view to meeting customers’ requirements for processability (tack [stickiness] of the material, resin flow, working life) and process cycle times (prepreg line speed, part cure time). By the end of the project, a preferred resin formulation had been identified and has now been standardised within Composites Evolution’s own internal New Product Development procedure.

Investigations also took place into the most-effective means of bringing together the PFA resins with the carbon and glass reinforcement fabrics. Different methods of applying the resins were explored, as was the interface between the resin and the reinforcement, to achieve the required impregnation (resin weight %), final product performance (e.g. interlaminar shear strength), surface finish and process consistency.

Having optimised the resin formulation and its method of impregnation, the next step was to implement a modified up-scaled process for producing PFA prepregs of the required specification, quality and volumes. Each aspect of the production process was examined and refined. This included improved approaches to material handling, control of resin content, resin impregnation strategy, in-line quality control and product presentation/packaging.

Finally, in order to demonstrate and validate the performance of the improved PFA prepregs, two demonstrator parts were manufactured by Bercella - a train seat component and a helicopter roof. These parts were extensively evaluated by Element in terms of their mechanical and fire performance. For the vast majority of the application requirements, the refined, up-scaled prepregs were found to perform exceptionally well. Furthermore, a robust prepreg costing model developed by Composites Evolution has demonstrated that the PFA prepregs are cost-competitive with phenolics.
The results achieved are all in line with the expected impacts of the project. Specifically, the material that has been developed has been demonstrated to provide a viable alternative to the state of the art phenolics that are currently employed in aircraft interiors. The new materials are also highly relevant to a number of other markets and applications that have stringent fire requirements, including rail, maritime, offshore and construction.

With this single substitution, existing phenolic users will improve their economic (cheaper processing), environmental (lighter parts, bio-sourced material) and social (safer working practices) performance as part of a truly sustainable business improvement.
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