Tag Archives: dry fabric

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

-AeroComposit chooses innovative solutions to build MS-21 composite wings

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MS-21´s wing spars, wing skins and six section panels will be manufactured by resin infusion and oven curing

Resin infusion is being applied in the newest commercial aviation programmes. One of them is the Irkut´s Corporation´s (Russia) MS-21 aircraft, which could be rolled out in 2015 (prototype). The post offers some details about the MS-21 aircraft, as well as about the innovative resin infusion technology they are applying in order to push the Russian companies at the the forefront of the worldwide aircraft industry.

Although Irkut will only produce 40 aircrafts/year (compared to approximately 500 each for Airbus and Boeing), the new MS-21 could compete with worldwide market leaders in the single-aisle commercial jet market.

Irkut MS-21 aircraft

Irkut´s MS-21 aircraft

To succeed in this highly competitive market, Irkut´s aircraft will have to offer a good performance and a greater fuel efficiency than its competitors. MS-21 will have a lower empty weight, a better aerodynamics and more efficient engines. The company is confident that if the MS-21 can use composites in a way that reduces weight and manufacturing costs in that 45 percent with a a target price of 35 Million US$.

To this end, in terms of technology, the company has decided to go one step ahead ,since the very beginning of the programme definition, being at the cutting edge of the aircraft industry, using Out of Autoclave methods for structural parts manufacturing.

Infusion and oven curing have been chosen for the MS-21’s large integrally stiffened primary structures including the wing spars, wing skins and six section panels

Infusion and oven curing have been chosen for the MS-21’s large integrally stiffened primary structures including the wing spars, wing skins and six section panels for the centre wing-box. These will be manufactured and assembled at the AeroComposit (also subsidiary of UAC) plant in Ulyanovsk. These process have been chosen due to its potential to reduce costs (avoiding the costly autoclave curing and reducing resin and dry material costs), and its opportunity to create integral constructions.

MS-21 resin infused wing

MS-21 resin infused wing (Diamond Aircraft´s photo)

AeroComposit has worked with a variety of experts worldwide to develop the design, materials and the process to achieve the requisite precision and quality. In terms of raw material, Hexcel and Cytec have been selected to provide dry carbon fiber and compatible liquid epoxy infusion resin. Hexcel´s OoA HiTape (up to 30mm thick) and it´s HexFlow infusion resin have been already tested to be used for the wing manufacturing.  The company affirms that 58 to 60% fiber volume content can be achieved with these  materials. An equivalent system from Cytec is also being used in the project.

The wing is based on the new carbon-infusion technology that allows building big components, like tail units or wings, with high stability at low weight.

Regarding the infusion process, FACC and Diamond Aircraft will be responsible for optimizing the wing and wing-box manufacturing process. Diamond Aircraft has developed the resin infusion process for the wing manufacturing. The wing is based on the new carbon-infusion technology that allows building big components, like tail units or wings, with high stability at low weight. The resin is cured at an aerospace standard of 180°C/356°F with a service temperature of -60°C to 160°C (-76°F to 320°F) while the production cycle can vary from 5 to 30 hours. The manufactured wing meets the requirements of the aircraft industry with a porosity of 0,3%. Diamond Aircraft claims that this achievement does not depend on the type of construction, but instead on the ability to maintain strict control of the process parameters. According to the company, the prototype wing is a a great achievement, that will have a mayor impact on the design of future airlines.

You can find more information in these CompositesWorld, Diamond Aircraft and Russia Beyond the State of the Art articles.

-Advancements in dry reinforcements for aerospace infusion process

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While in some previous posts we focused on talking about different automated processes for dry material deposition (ADMP, Pick-and-place and DAFP), this post deals with information about dry reinforcements aimed at aerospace infusion process and automation.

  • Why dry reinforcements?

Dry reinforcements offer significant advantages versus prepreg materials that have been traditionally used in the aerospace sector. They present several benefits, thanks to their low prices, their long shelf life, reduction in inventory costs, potential to increase parts integration and  potential to avoid the costly autoclave curing process.

The growth of the resin infusion process in the aerospace industry (as  can bee seen in the image above and our -Aerospace Looking to Dry Fiber/Infused Composites post) is increasing the need to adapt dry materials to the aerospace and new technologies requirements.

Infused Aerospace parts

Infused Aerospace parts  in Boeing 787, A380, A400, Bombardier C-Series and IRKUT MS-21

  • What is driving innovation in dry reinforcements?

Although there is still much to do in the area, material suppliers offer more and more products oriented to automated dry material deposition processes. Focusing our attention on dry reinforcements, the main research and developments in the area are aimed at:

Binders which are compatible with the resin to be infused and ease the manageability of the fiber during the material deposition.

Thin layers of thermoplastic veils to facilitate the flow of resin infusion and provide the final part with a greater toughness.

Dry carbon fibers that provide the strength and stiffness in a unique or multiple directions (unidirectional or multiaxial reinforcements). Different forms of dry carbon fabrics can be used to this end. NCF (Non crimp fabrics) are the most used fabrics nowadays, whereas the woven fabrics have also improved their properties in order to ensure the achievement of the required qualities.

The combination of the dry reinforcements with the proper resin is essential in order to manufacture a good quality part. Great developments are being carried out in this area.

  • Unidirectional tapes or Non Crimp Fabrics: Different choices for automation.

Unidirectional tapes up to 1″ offer high flexibility in terms of the geometries they can achieve. Automated process, such as the Dry Automated Fiber Placement (DAFP), use these tapes to produce preforms that will be infused during further stages. The productivity they can reach is low so far.

Wider Non Crimp Fabrics (NCF) can be used with the automated process such as ADMP and Pick-and-Place. The improvements in these materials and related automated deposition technologies could revolutionize the composites sector because of the great production rates they can accomplish.

You can have an overview of these different automated process in our post Making a Preform – How Can I Count the Ways?

  • What are the most common dry material forms used by the latest aerospace programmes?

It is known that the Saertex group supplies high-performance multiaxial and unidirectional NCFs for the manufacturing of the Bombardier´s C-Series and Learjet 85´s major primary structures.

Meanwhile, AeroComposit has qualified Hexcel´s OoA Hi-Tape material to produce Irkut Ms-21´s wings and wingboxes, whereas Spirit AeroSystems has also used the same material to form a skin of an engine nacelle outer fan cowl. Aircraft structures made with HiTape are reported to demonstrate mechanical properties as high as those found in parts  made with the latest generation primary structure prepregs.

Hexcel´s OoA HiTape

Hexcel´s OoA dry HiTape

Finally, it is worth mentioning that Cytec offers a material with equivalent properties, being applied also in the Irkut  MS-21. Both tapes (Hexcel´s and Cytec´s) will be used to manufacture the aircraft structures automatically within a DAFP machine.

-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.