Tag Archives: dry material automation

Mitsubishi Regional Jet (MRJ), new aircraft program with dry composites for the empennage using A-VaRTM technology

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Recently we assisted to the roll out first flight of the test aircraft for the Mitsubishi Regional Jet (MRJ) programme. The empennage of the MRJ is produced by a RTM process using dry fabrics .

MRJ_1 MRJ_2MRJ first flight

We have found many informations published on the issue and we want to share with you some of the most interesting aspects we have read refering to the use of dry fabrics to manufacture the composite part in this project.

The company is developing a highly competitve aircraft. On the one hand, they are offering interesting operating costs with a good efficiency, in a big measure, thanks to light weight materials. On the other hand, they are working on a price competitive airplane, through improved production costs.

Cost reduction strategies:

  • Precision on parts production for easing assembly.
  • Lean manufacturing concepts like moving assembly lines: the product moves through the factory from one manufacturing process to the next.
  • Circular body cross section for simplified tool design.
  • Oven cured composite parts.

The composite empennage (horizontal and vertical stabilizers and fuselage interface) has been fabricated using an improved Liquid Moulding process called A-VaRTM. This process was developed jointly with Toray.

A-VaRTM molding technology is an advanced version of VaRTM. Vacuum Asisted Resin Transfer Moulding is a low cost composite manufacturing technique where, differing from prepreg laminated composites, the resin is infused into dry fabric, formed on a mold near product shape under vacuum pressure and cured in an oven.

A-VaRTM is a new version of it, suitable for aeronautic parts and with very good mechanical properties, by means of:

  • Adoption of a fiber-reinforced base material with high quality and strength (dry Non Crimp Woven). Carbor fiber bundles form the primary structural element. Very fine glass fibers are used as auxiliary warp fiber to facilitate flow during resin infusion and to tie warp and auxiliary and fibers toghether.
  • Application of thermoplastic particles designed to toughen the composite materials. They are used as a tackifier to consolidate the preform and also permit the use of a lower-viscosity and less expensive epoxy thermoset resin.
  • Optimization of the forming process to obtain a high volume fraction of fiber (Vf = volume of fiber/volume of object × 100, targeted value 55 to 60%). MHI uses a proprietary diffusion or flow media to control the resin infusion flow and rate, as well as to bleed off excess resin. This maximizes fiber volume in the finished composite part; for aircraft primary structure.
  • Oven cure occurs in two steps: first, cure under vacuum and then postcure in an oven at 350°F/180°C VaRTM

    Conventional process vs VaRTM

With the A-VaRTM process mechanichal properties similar to prepreg have been achieved.

Mechanical propertiesMechanical properties

The new process improves costs in all the aspects. Cost associated to materials are lower , the composite manufacturing using oven heating to cure is cheaper, we see cost improvements even in assembly and quality assurance. Although aluminium is still more cost competitive, A-VaRTM gets very close to it, as the component in composite has only 1.2 times the cost of the aluminium part.

CostCost comparison

The VaRTM uses dry fabric that is not impregnated with resin so the material is easier to fit around a three dimensional geometry.

WrinklesNo wrinkles using dry woven fabrics

The composite manufacturing cycle times have also been dramatically reduced on the stringers. They are cobonded with the precured skin panel, using a film adhesive, and the assembled component is subsequently postcured in an oven more than 19.7-ft/6m long.

Vertical stabilizer
Therefore Liquid Moulding with dry (engineered) fabrics proves succesful for the composite manufacturing of exigent aeronautic parts at lower overall costs.
You will find more information in the following articles : FightGlobal; CompositesWorld; MHI(1); MHI(2) ; ICCM

-Advanced dry composite materials offer new opportunities in the aerospace industry

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The number of flights expected for the next 2 decades shows a an annual growth rate of 4.7%, but needs to satisfy very tight constrains on fuel consumption (with fuel consumption being about 30% of the operating cost). It is required to strongly reduce fuel consumption of the future aircrafts manufactured.


ScreenHunter_1350Growth perspective for annual flights from AIRBUS market forecast

One of the approaches required to do so is the introduction of advanced materials to reduce their weight, and composite materials in particular. Major manufacturers have increased the content of composite materials from 5% (A300) to 52% (A350XWB) for AIRBUS or to 46% for the CSeries (Bombardier), including wings, fuselage, and other structural parts etc.

Traditionally, structural components in aerospace have used carbon fiber pre-impregnated with epoxy resins (pre-pregs) that require to be cured in an Autoclave. Although the properties of the pre-pregs are outstanding, the cost associated to the maintenance, shelf life and autoclave processing of these pre-pregs represents a high percentage of the total cost of the part.

In order to reduce these costs, a strong effort has been performed to develop dry composite materials with suitable material properties, and reduced manufacturing costs due to higher deposition rates, no costs of refrigeration, and longer shelf life.  Due to this effort, the use of dry composite materials emerges as a new material feasible for the manufacture of structural components.

The CSeries Aircrafts, from Bombardier Aerospace represents a breakthrough in the use of composite materials, since some of their structural components, such us the wings are being manufactured using dry composite materials. Bombardier expects to reduce 20% the fuel consumption, and have 25% less maintenance costs. The CSeries aircraft is expected to make the first flight shortly. In particular, the manufacturing process is based on pick and place of dry composite material cut on a 2D table and positioned in the mould.

Bombardier

Bombardier is not the only one aircraft manufacturer that uses dry composites in the design of the new aircraft to reduce costs and increase productivities: A400M from AIRBUS cargo door (also a structural component) is also manufactured using dry composite materials. Furthermore, their manufacturing method uses alternatives to autoclave, by means of the VAP (vacuum-assisted process) demonstrating that dry composite materials can achieve mechanical properties required to be used in structural components. The manufacture of these components also takes benefit of the combined infusion of the different parts (skin and stringers), avoiding about 3000 metallic rivets.

0507HPC_IM_A400M_Step_3The investigation and development on dry composites, offers a critical opportunity to push forward the presence of composite materials in the aeronautic field by reducing costs, and maintaining the mechanical properties of pre-preg materials.

Airbus and Bombardier are setting up the first steps regarding the use of dry composites in the aeronautic sector. This sets the path to the industrial development of processing technologies of the fabrication of the materials and the components, and moving from manual manufacturing for short series to high production for larger series, as has happened with glass fiber or pre-preg carbon fiber materials.

There are still strong challenges remaining to take full advantage of this disruptive material that require a strong synergy between all the agents responsible of the introduction, design and development of components manufactured from dry composite materials: companies, Research Centers, academics and experts.