celc 12 2012 - cayley

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New generation of materials for the Aerospace industry:

Green Aircraft Interiors

Pedro P. Martín Leuven, 04.12.2012

Engineering, Operations & Technology | Boeing Research & Technology

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Industrialization of the manufacturing process and technologies for the fabrication of novel environmentally friendly aircraft interiors based on natural fibers and alternative matrices.

Aircraft interiors: Strict requirements, mainly related to fire performance, weight, and mechanical properties.

Industrialization: Assemble the novel green panels in just a one-step at high production rate (1 panel each 15 minutes) using automatised technologies.

Main benefits:

Replacement of hazardous materials (e. g. phenolic resins, glass fibers). Replacement of non-renewable resources. Weight reduction (less fuel consumption/CO2 emissions).

Versatile technology, exploitable in other specialized sectors such as transport: Interiors

for trains, busses, ships, etc.

CAYLEY Objective


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The CAYLEY Consortium


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Partner Roles


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Safety related requirements, regulated by international organisms such as

the FAA (Federal Aviation Administration) and the EASA (European Aviation

Safety Agency).

For interior applications (decorative panels without structural purpose), the

strictest requirements are related with the fire resistance of materials.

The fire performance is evaluated and validated through four tests according

to the FAR 25, Section 25.853 Appendix F:

• Flammability

• Heat release rate test (OSU)

• Smoke density

• Smoke toxicity

Fire resistance is the most challenging issue to overcome when working

with natural fibers.

Requirements I


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Design parameters of the specific part fulfilling the client specifications,

aircraft model, etc. Not available for public dissemination:

• Mechanical properties (skin-core adhesion, flexural strength, impact

resistance)

• Acoustical properties (transmission loss)

• Resistance to cabin environment (vibration, humidity, fluid susceptibility,

etc)

• Weight

Weight is a key factor for aircraft manufacturers due to the contribution to

the final efficiency of the aircrafts. Novel solutions with reduced weight are

always welcomed.

Natural fibers are interesting due to their reduced weight compared with

glass fibers. Additional advantages are reduced vibrations, increased

acoustic behavior and reduced cost.

Requirements II


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Skins: Fire proof alternative matrix (biopolymer, thermoplastic, inorganic thermoset

matrix). Natural fibers treated with non-halogenated flame retardants.

Core: recyclable materials

Fire resistant (FAA certified) thermoplastic recyclable foam.

Adhesive: Matrix itself.

Decorative film:

Conventional decorative film FAA certified.

Green Aircraft Interiors - Structure

Skins:

Natural fiber-based

composites

Core: recyclable foam

Decorative film


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Compliance with technical requirements for aircraft interior panels

All fire requirements according to FAA&EASA

Standards.

Weight & thickness requirements for sidewall

panels.

Most of the mechanical requirements for

sidewall panels.

BR&T-E Approach to Green Aircraft Interiors

Solution developed through several previous projects, based on Inorganic

thermoset resin, natural fibers (flax), and thermoplastic foam core.

Panels handmade by vacuum bag at lab scale for characterization, directly from

raw materials


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CAYLEY objective: Development of pre-pregs based on inorganic resins and natural fibers,

allowing a 1 step manufacturing process compatible with industrial processes in a relative short period.

• Proof of the pre-preg concept

• Reduction of Curing time of the inorganic resin pre-pregs

• Increase of the pre-preg shelf-life (if possible)

Scale up of fabric impregnation for pre-preg production at industrial

scale.

BR&T-E Approach to Green Aircraft Interiors


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Natural fiber fabrics used as base of the pre-pregs. The fabrics are fire protected with non halogenated flame retardants.

Pre-pregs prepared from natural fiber fabrics by impregnation with the inorganic resin and stored at -18 oC

Characterization of the pre-pregs after different storage periods:

• Qualitative pre-preg tack evaluation • Manufacturing of panels • Determination of fire and mechanical properties • Comparison with panels made from fresh resin to determine the

pre-preg shelf-life

Pre-pregs stored for more than 30 days could be used to produce panels without losing properties

Proof of the pre-preg concept


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Particular composition of inorganic resin: more than 1.5h of curing under vacuum conditions at moderate temperature (< 100 oC) Conventional manufacturing methods require curing times between 10-15 min

Testing of higher temperatures for curing: The increase in the curing

temperature reduces the curing time, but considerably decreases the the quality of the surface and reduces the mechanical performance.

The incorporation of additives improves the quality of the surface, but the mechanical performance do not recover the initial values yet.

Testing B-stage process: currently on-going. No major achievements yet.

Reduction of Curing time of the pre-pregs


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The polymerization process of the inorganic resin is very sensitive to the temperature. The standard storage temperature is -18 oC. The approach explored so far is to lower the storage temperature. Storing the pre-pregs at -30 oC considerably extends their shelf-life, but these are not standard storage conditions for composite producers.

Increase of the pre-preg shelf-life

The goal is to extend the shelf life at standard conditions (or room temperature if possible). Further research on-going


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Testing of the pre-preg production method in a conventional pre-preg setup for continuous production of epoxy and natural fiber pre-pregs (LINEO facilities, Meulebeke – Belgium)

Production of pre-pregs at two stages:

First stage: Fire protection treatment of natural fibers. Completed • Linen fabrics produced continuously with the required characteristics of fire

resistance previously obtained by manual processing. • Homogeneous distribution of the flame retardant along the fabric

Second stage: Impregnation with the inorganic resin. On-going • Testing of continuous impregnation in the immersion bath • Testing of the reproducibility of the impregnation ratio along the fabric • Testing of the properties of produced pre-pregs.

Scale up of fabric impregnation for pre-preg production at industrial scale


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Objective: Demonstrate the suitability of the green sandwich panels developed to built real 3D shaped parts such as sidewall for aircraft interiors.

Demonstration of the technology: production of 3D shaped panels

• Manufacturing by vacuum bag using a 1:1 scale sidewall tool

• Identification of issues related to manufacture of real applications

• In-flight test of the developed technology.


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Panels reproducing the 3D shape of real panels, with similar weight and excellent fire behaviour

Demonstration of the technology: production of 3D shaped panels

Manufacturing issues identified:

• Very short pre-preg life out of the freezer (pot-life)

• Very long manufacturing cycle: 2h vs 15 min of current panels


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• It is possible to introduce natural fiber-based composites in highly specialized

sectors such as the Aircraft industry.

• The solutions based natural fiber composites for the Aircraft industry are

subject to strict requirements mainly related to safety (fire resistance),

mechanical performance and weight.

• The Cayley consortium is working to industrialize solutions for the Aircraft

industry (exploitable by other transport industries) based on natural fiber

systems, using biopolymers, thermoplastics and inorganic thermosets as

matrices.

• The industrialization of those solutions will require manufacturing methods and

rates similar to the used for the current solutions based on conventional glass

fiber composites.

Conclusions


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• The natural fiber and inorganic matrix pre-preg concept has been proved at lab

scale, obtaining pre-pregs with a shelf-life longer than 30 days.

• The continuous production of pre-pregs at industrial scale is under

development, with very promising results achieved so far.

• The curing time cycle, the shelf life and the pot life of the pre-pregs must be

optimized.

• The pre-pregs developed allows the fabrication of panels reproducing the 3D

shape of real sidewalls, with similar weight and excellent fire behaviour.

Conclusions

Thank you for your attention!

More info on the CAYLEY consortium at

www.cayley.eu


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This project is co-funded by the European Union within the CIP Eco-Innovation initiative of the Competitiveness and Innovation Framework Programme, CIP.

The CAYLEY Project

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celc 12 2012 - cayley

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