Tag Archives: Aerospace

Bombardier Learjet 85- OoA prepreg and infusion process

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Bombardier Learjet 85- OoA prepreg and infusion process

At the end of the year we have thought it would be interesting to review one of the most interesting discussions we have had in our activity on linkedin. It was at the Composites Group. The news that Bombardier was using dry fiber and Resin Transfer infusion on the Learjet 85 wing box started an enriching discussion about the technical difficulties and possibilities of resin infusion processes and out of autoclave curing.

Learjet-85-mockupLearjet 85

Bombardier Learjet – composite

“Bombardier unveils OoA composites process for Learjet. Wingskins and spars for the plane are manufactured in Belfast using an in-autoclave resin transfer infusion (RTI) process. The fuselage and autoclave are manufactured in Querétaro, Mexico, via an out-of-autoclave (OOA) prepreg process.”

“ It makes use of composites not only to reduce airframe weight and increase fuel economy, but also to significantly reduce the part count because composites have enabled Learjet to produce large, integrated structures.”- Composites World

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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

Raw material suppliers outlook a good future for dry composite materials

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Key structural composite components are being manufactured with dry preforms and resin infusion, replacing in many cases the use of prepreg materials for parts manufacturing. In this sense, raw material suppliers play a key role when developing the newest materials to meet the aerospace sector strict quality requirements. What are their thoughts regarding the use of infusion process for the aerospace industry?
We have had a short interview with some experts in the area. Henri Girardy, from Hexcel and Sven Blank, from Saertex have shared their overview about this subject with us.
Thank you Henry and Sven!

Saertex HExcel

1. What are the primary benefits that Infusion offers in aerospace applications, compared with long established prepreg and autoclave curing processes commonly used today? What applications appear to be most promising?

Sven Blank (SB): Multiple layers/orientations in a single fabric can facilitate higher deposition rates resulting in savings of both time and money. Moreover, the use of NCF can eliminate some, if not all debulking processes. In addition, most infusion materials can be stored at ambient temperatures and have extended shelf life (1-2 years) when compared to prepregs. This way, the material handling is simpler and there is no need to chart out time or storage temperature and it is not required to wait until materials come to ambient temperature.
There is no risk of foreign materials to be present in laminates due to use of release paper, etc.

Henry Girardy (HG): Key benefits are cost and production rates. Cost savings have been demonstrated in part design, function integration, less assembly time, and potentially fewer finishing operations.

2. Automation such as AFP has played an important role increasing quality, increasing rate and reducing cost of parts made with prepreg. Are there opportunities to do the same with Infusion processes?

SB: Parts with complicated geometries, thick parts or parts with large surface areas are requiring higher deposition rates. Therefore automated dry fabric deposition technology could be a good option to enhance increasing rate and quality. On the other hand, narrow dry tapes could be used as localized reinforcement of NCF lay ups.

GH: We strongly think that automation of the dry preform is a key success of factor for aerospace structures made by OOA technologies. OEMs and Tier 1s are looking forward for eliminating the costly autoclave curing process.Moreover, as we see it, one of the main reasons why dry materials do not fully meet the mechanical performance requirements for primary structure, is the lack of automation in lay-up process. Therefore, there is a need to automate the process.

3. It is a commonly held perception that infused materials do not provide as good mechanical properties as prepreg/autoclave materials.
a. If true, this means that an Infused part will have a weight penalty?.
b. If false, what can be done to improve the understanding of these materials?

SB: Infused materials could also provide good mechanical properties, but there is some work to be done to improve the understanding of the materials. Such as…
-Educating customers regarding the advantages of NCF and infusion.
-Expand marketing of  infusion materials into aerospace applications
-Publish/present data from controlled experiments comparing infused and prepreg laminates.

GH: The new materials, such as our HiTape® fabric, enables really good properties in vacuum infused parts. Parts up to 30mm thick with a 58 to 60% fibre volume content can be achieved. Infused materials will play a key an important role for next generation aircraft, due to the fact that apart from weight, costs will also drive the material and technology choice.

-Sampe Europe 2014: from aerospace OoA to automotive thermoplastics

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The title of the 35th International Technical Conference & Forum organized by SAMPE was “Low cost Composite Processing, from Aerospace OOA to Automotive Thermoplastic”. As the title indicates the main issues were the way to decrease the manufacturing cost in aerospace composites and the relation between thermoplastics and composites in automotive.

As it is known, it is very important to avoid the autoclave in order to reduce the composites manufacturing

  • reducing tooling cost for component development and low-rate production runs
  • adding capability for manufacturing of very large highly integrated composite components
  • reducing capital costs for autoclave and associated facilities
  • and removing autoclave bottleneck for production

Different methods for avoiding the autoclave were discussed along the conference, the experts presented different projects related to this subject, focused on the use of NCFs and resin infusion methods (summarized below).

Taking into account the unique challenge of increasing the presence of composites in new single aisle aircraft, current works are targeting at developing robust, fully automated processes for the realization of large scale structures. New functionalities are being added to existing materials, like e.g. enhancing conductivity for the improvement of lightning strike behavior.

On the other hand, thermoplastic materials are being optimized and, last but not least, new multi-functional composite materials are under development to broaden the range of composite applications. In addition, huge efforts are being undertaken to enable structural bonding for composite repair.

With respect to the automotive application, the use of carbon fiber reinforced thermoplastic was considered the next challenge. The laser assisted and induction processes in welding and heating with thermoplastics were the most important topics of discussion.

Related to the main subject of the DRY COMPOSITES blog, some projects have been outlined from the conference:

  • In terms of OoA manufacturing technologies by means of NCF and RTM, Airbus Military presented its BAHIA project, focused on alternative fan cowl doors configuration and manufacturing.  Within the project framework a new fan cowl door is designed and a RTM technology is used in order to manufacture the structure, by eliminating 2 autoclave curing cycles and joining grid and skin through a unique bonding line. This way, Airbus Military intends to obtain a more competitive and reliable product.

       Co-authors: Javier Gomez Vega, Maria Antonia River Orellana, Luis Rubio García

Airbus 340-642 fan colw door

Airbus 340-642 fan cowl door

  • Researches from Irish Centre for Composite Research, MSSI and University of Limerick presented a design of experiments study assisted in optimising the LRI manufacturing process (liquid resin infusion). According to them, LRI processes is challenging due to the difficulty in achieving full fibre wet-out, target fibre volume fraction and acceptable void content etc. In this study, flat composite panels were manufactured using aerospace grade Benzoxazine resins systems (one of which is targeted at high temperature applications) and aerospace grade carbon fibre NCF (non-crimp fabric with and without powder binder).

      Co-authors: Anthony Comer, Dipa Ray, Winifred Obange, Gearoid Lancy, Inga Rosca, Walter    Stanley

Double-omega stiffened skin manufactured by VIM using Benzoxazine B.

Double-omega stiffened skin manufactured by VIM using Benzoxazine B.

  • Other EADS, Eurocopter and University of Stuttgart researchers did also present a study, aimed at the fundamental material behavior of such unidirectional-braided structures, which are converted from carbon-fibers and thin thermoplastic auxiliary-yarns directly to the part geometry as UD-plies. The promising results emphasize the feasibility of using UD-braiding for structures with high stiffness as well improved damage resistance.

Co-authors: C. Metzner a, A. Gessler a, C. Weimer a, U. Beier b, P. Middendorf

UD-braiding – the machine, process and textile

UD-braiding – the machine, process and textile

 

-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.

-Resin Infusion techniques in the aerospace industry

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Many methods have been developed to perform the resin infusion in the aerospace industry, once the dry preforms are created manually or automatically. These processes are identified by different names and acronyms, which can lead to some confusion. Here is a description of some of the more widely known infusion methods.

SCRIMP (Seemann Composites Resin Infusion Molding Process) is one of the earliest patented infusion methods. It is used for many marine and Wind blade applications, but was also licensed by some aerospace firms. It relies upon the use of a flow or “distribution media” with high permeability between the layup and vacuum bag to rapidly and evenly distribute resin laterally across the part.

SCRIMP Schematic

SCRIMP Schematic (link)

VARTM (Vacuum Assisted Resin Transfer Molding) is the name of the process used by Lockheed Martin that is similar to SCRIMP, but does not use a flow media. The entire fuselage of the AGM 159 JASSM missile is made using VARTM.

JASSM made with VARTM

JASSM made with VARTM (link)

CAPRI (Controlled Atmospheric Pressure Resin Infusion) was patented by Boeing and is said to reduce thickness variation and result in fiber volumes and mechanical properties equivalent to prepreg/autoclave materials. First it uses vacuum debulking cycles on the dry preform to reduce compressed thickness prior to infusion. During infusion, the resin supply is held at partial vacuum, which assists in degassing the bulk resin but also reduces the pressure differential driving resin into the preform.

CAPRI Schematic

CAPRI Schematic (link)

VAP (Vacuum Assisted Process) was patented by EADS and used in parts like the A380 Aft Pressure Bulkhead and the massive A400 Cargo Door. VAP features a gas permeable membrane placed over the infused layup, which helps to evacuate trapped air and volatiles in the infused layup prior to cure. By letting gases through the membrane (but not the resin) VAP is said to achieve lower voids and higher, more controlled fiber volume for better laminate quality.

VAP membrane

VAP membrane (link)

RTI (Resin Transfer Infusion) is a Bombardier patented process used to produce the wing skins of its CSeries aircraft. Infusion of resin into the preform is performed with vacuum pressure only. However, the mold is located in an unpressurized  autoclave during the infusion step. After the preform is fully infused, the autoclave is pressurized and heated to perform cure. This makes it easier to achieve high laminate quality because positive cure pressure (>14 psi) helps prevent void formation from entrapped air and volatiles. It has the drawback that a suitable size autoclave is still requited. All other methods cited above are true Out of Autoclave processes.

C-Series wing made with RTI

C-Series wing made with RTI (link)

There are also other acronyms for similar processes, which can create a kind of “alphabet soup” confusion about infusion.

The important thing to remember is that many different users have had success making a wide range of parts (some very large and critical) using infusion processes.

-Aerospace Looking to Dry Fiber/Infused Composites

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Most aerospace composite structures are produced today using prepreg and autoclave cure. Recently an increasing number and type of large and critical structures are being manufactured in a very different way – using Preforms assembled from dry fabrics and tapes and then infusing the epoxy resin into the Preform followed by cure. If the infusion is performed in a matched closed mold under high pressure, the process is called RTM. For many larger parts, infusion is performed using vacuum pressure only with single surface tools. This process has many different names reflecting slight differences in the infusion process including VARTM, CAPRI, VAP, RTI, RFI, BRI, SCRIMP and several others.

A wide range of aerospace parts are fully qualified and in production today made from dry fiber and vacuum infusion – a few examples are shown below. Some of these assemblies, such as flight control surfaces (flaps and ailerons) and fuselage frames are considered secondary or redundant components. Others such as the Aft Pressure Bulkheads of the A380 and 787 are primary structure – failure of these critical components would likely lead to loss of the aircraft. The A400 Cargo Door operates in an even more challenging environment – this flat and large door sees full cabin pressurization, and experiences significant bending  and tension loads during flight.

That these highly critical parts are made using these materials and processes speaks to the high degree of confidence that the aircraft OEM’s and regulatory authorities have in the reliability, performance and safety of the dry fiber/infusion approach.

787 Dry fiber/infused parts include (left to right) ailerons and flaps, fuselage frames and the aft pressure bulkhead (APB) of the fuselage

787 Dry fiber/infused parts include (left to right) ailerons and flaps, fuselage frames
and the aft pressure bulkhead (APB) of the fuselage

A380 Aft Pressure Bulkhead (APB) and A400 pressurized Cargo Door

A380 Aft Pressure Bulkhead (APB) and A400 pressurized Cargo Door

Arguably the most advanced use of dry fibers and infusion is in the wings of next generation airliners such as the Bombardier CSeries and Irkut MS21 aircraft shown below. These aircraft, serving 120 to 200 passengers, are the newest in commercial aviation and have leveraged the latest advances in composite materials, processes and production methods available today. The CSeries has passed ground structural tests and is expected to make its first flight mid 2013, with the MC21 to follow about a year later.

The Bombardier CSeries wing (left) and Irkut MS21 wing (right) both are made from dry fiber preforms and resin infusion

The Bombardier CSeries wing (left) and Irkut MS21 wing (right) both are made from dry fiber preforms and resin infusion

How about your company – is this technology being considered and for what applications? What are the benefits, tradeoffs, concerns and issues associated with the use of these processes? Let us know what you think.

-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. 


-We go dry

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Dry Composites is an initiative by Danobat Composites to share the latest advancements in automation using dry composite material. This online community aims to connect companies, research centers, academics and experts interested in the use of dry composite material to develop structural parts in aerospace.

What do we mean by Dry Composites? There are two distinct methods of making composite structures. The first involves impregnating the fibres in a dedicated off-line machine to make a pre-impregnated material, called pre-preg. This is then transported to a factory that makes structures where it is laid up by machines or manually.

The second, more direct route is to take dry fibres, usually in some textile format and after assembly into a pre-form, infuse them with liquid resin. The infusion process is known by a number of trade names and acronyms such as RTM, VARTM etc.

The pre-preg route involves an extra process and hence cost, but it does result in structures with good consistent properties. Recently, the performance of structures made by infusing Dry Preforms has improved and is now claimed by some, to match that of more conventional pre-preg materials. Working with dry fibers, fabrics and textiles enables thicker layers to be used, saving time and labour costs, plus aiding in the creation of more complex, one-piece structures.

However whereas the pre-preg manufacturing industry is well served by automation with dedicated machine tools, the lay-up of dry fabrics has not received the same attention. Danobat Composites has pioneered the development of Automatic Tape Laying using woven and NCF fabrics. This has improved laminate quality, repeatability and reduced the cost of composite structures by significantly cutting manufacturing labour and material costs. Moreover, it is worth mentioning that the use of dry materials can give rise to out of autoclave curing processes acquiring required properties in primary structural aerospace parts.

Today, manufacturers face the challenge of doing more with less, the aerospace industry needs to adapt quickly to new material and process developments to remain competitive. In doing so, the ultimate goal of a disruptive automation technology is to introduce new processes that may deliver better high efficiencies and control at less cost. This requires broad support from an ecosystem of R&D, manufacturing, engineering teams and material developers.

Dry Composites is an open space for those interested in learning more about how automation using dry composite material can be applied to the aerospace industry. From sharing industry news, information, data and technical solutions about dry composite solutions to interviews and perspectives from expert sources. Our target audience includes decision makers, R&D engineers, global suppliers of advanced materials, software and automation companies.

If you are interested in learning more about advancements in the use of dry material in the aerospace industry, follow us on Twitter @drycomposites and join the LinkedIn Group Dry Composites.

Stay tuned for more!