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A comprehensive collection of news and information about composites.

Posted by: Jeff Sloan

31. August 2015

This new video from Boeing gives a sense of the length and flexibility designed into the composite wings on the 777X.

When Boeing decided to redesign the 777 as the 777X, it opted to apply composites in the wings only, which might have come as a modest disappointment to the composites industry. But use of composites in the wings is not trivial. In fact, Boeing will be creating the longest — and possibly most flexible — composite wings on a commercial aircraft. 

Boeing is building on lessons learned with the 787, the wings of which are notoriously flexible, as shown in this famous image from 787 static testing in 2010:

 

The 787's wingspan, however, is 197 ft/60m. Wingspan on the 777X will be 235.5 ft/71.8m. Boeing will use this length, and the latest design and materials, to create wings on the 777X that will be even more flexible, allowing it to glide more bird-like. Check out the above video for a short review of the theory and technology behind the flexible wing design.

Posted by: Heather Caliendo

26. August 2015

As CW reported earlier, the wings for the first Airbus A350-1000 have begun the process of assembly in Broughton, North Wales. This news is pretty significant to the composites industry as the company says the A350 XWB wing is the largest single part made from carbon fiber composite material in use in civil aviation today.

But let’s not forget about the Boeing 777X, which the Airbus A350 is in direct competition with. For the purpose of this blog article, let’s take a close look at the wings for each aircraft. So here’s what we know about the Airbus A350-1000. The A350-1000 wing has the same span of the A350-900 (105 feet) that is already in service, but 90% of the parts have been modified and the trailing edge has been extended to resize the wing for the additional payload and range. They are designed and developed at Airbus’ facility in Filton, near Bristol, where a number of other systems are designed and tested including fuel systems and landing gear.

Airbus touts that the high-performance wings of the A350 XWB make the aircraft faster, more efficient and quieter. The wing design includes several streamlined features. Among these are droop-nose leading edge devices and new adaptive dropped-hinge flaps, which increase the jetliner’s efficiency at low speeds.

To improve efficiency at higher speeds, the A350 XWB can deflect its wing flaps differentially, optimizing the wing profile and providing better load control.

The Boeing 777X wing will be big— the composite wingspan of the 777X measures 71.7m/235.4 ft, 6.95m/22.8 ft longer than the span of today's 777-300ER. The 777X features folding wingtips, which sound very interesting as Boeing says the that the 777X’s folding racked wingtip and optimized span will deliver greater efficiency, ‘significant’ fuel savings and complete airport gate compatibility (a biggie). Construction has started on the Boeing 777X at Boeing's Everett, WA, site with the manufacture of the carbon fiber composite wings to start in 2016.

These wing structures will include skins and spars fabricated via automated tape laying (ATL), which will be cured in one of the facility's three 37m autoclaves. Parts will be assembled into wings in the adjacent aircraft assembly plant.

Airbus is estimated to fly out of the gates first with initial delivery of the A350-1000 scheduled for 2017 whereas the first delivery of the Boeing 777X is targeted for 2020.

While both wings represent an advance for the composites sector, the real winner of the battle of wings will be determined based on how well the competing aircrafts perform – especially when it comes to sales and profits. 

Posted by: Ginger Gardiner

26. August 2015

Cevotec's Fiber Patch Placement (FPP) process uses scale-like carbon fiber patches.

As promised from my blog in July, here is a more in-depth update on Cevotec’s development of the Fiber Patch Placement (FPP) process. FPP was originally developed by Airbus Group (previously EADS Innovation Works, Ottobrunn, Germany) and has been further developed by Cevotec (Garching near München, Germany), a spin-off from TU München (Munich, Germany).

FPP is an automated process that builds complex part preforms by placing unidirectional CF patches along calculated load paths, achieving very efficient structures like those seen in nature. SOURCE: Cevotec.

FPP takes unidirectional carbon fiber (CF) patches (e.g. 20-mm wide by 60-mm long by 0.1-mm thick) and precisely places them along calculated load paths to create highly optimized preforms. The automated process is able to build very complex structures quickly. For example, working with a leading medical device OEM, Cevotec is using FPP to build a one-piece CF orthosis preform in 30 minutes that previously required more than 40 separate pieces of prepreg and 1.5 hours of hand lay-up. Cevotec is currently using HTS45, IMS65 or UTS50 carbon fiber from Toho Tenax Co., Ltd. (Tokyo, Japan) and T300 and T700 fibers from Toray (Tokyo, Japan) in tapes from 15-40 mm width and 60-180 g/m² areal weight with Spunfab thermoplastic web applied as binder. The preforms are subsequently molded using standard vacuum infusion or resin transfer molding (RTM) processes. Cevotec has worked with Airbus to advance the FPP automated robotic hardware, software and process chain to speed up the patch-based laminate generation and also to make it more stable and flexible.

Cevotec preforms and samples made using FPP.  SOURCE: Cevotec.

Faster, more flexible production
Co-founder Thorsten Groene describes Cevotec’s work to ready FPP for broad commercial application. “We have improved the robotic arms to optimize their movement and cooperation. We are also using faster pick and place units with nominal 160 picks/min, which will speed up the placement process.” According to Groene, a new FPP line, operational in March 2016, will be capable of longer patches as well as using wider and thicker tapes. “Thickness influences both the process speed and the mechanical properties of the preform,” he notes. Higher performance parts will use thinner tapes, while the challenge for industrial and recreational product preforms will be balancing thickness vs. properties. The new production line will also build bigger parts due to a wider placement window (2500-mm x 1500-mm x 500-mm). “We have a larger 6-axis robot to hold heavy and large preform tools,” says Groene. While the initial production line could produce preforms at speeds of up to 500 grams/h, the new FPP line will expand greatly to 2000 grams/h of dryfiber mass throughput.

Of course, with new hardware improvements, the software must be updated accordingly. “We can now combine longer and thicker patches with small and thin patches,” says Groene. The new line will also enable thick-walled parts and improve the ability to form more convex and concave surface structures. “We have developed machine control adaptations that enable this greatly improved production flexibility while avoiding bridging effects during placement.” Cevotec’s team has also completed a software suite that enables virtual product development, seamless from product conception to part production. “We have full orientation control of every patch placed,” says Groene, “and can vary thickness locally by numerical optimization analysis. No material is placed where not needed.” He says that compared to stacking and draping fabric or even using automated layup technologies, FPP’s patch-based approach is a completely new category. “This approach is best able to utilize the opportunities provided by anisotropic materials,” he asserts. “But it requires sophisticated software in order to construct what is ideally possible.”

So what is possible? Groene says FPP can produce highly optimized preforms with 150% increased stiffness and up to 50% less scrap vs. continuous fabric preforms. For example, Cevotec has produced a CF snowboard reinforcement which achieves separately optimized bending and torsional properties as well as precise longitudinal loads with a zero material scrap during manufacturing. “The layer of continuous fibers the manufacturer was previously using does not provide the properties needed exactly and adds weight.” FPP reduced that weight by two-thirds and simplified the layup and fabrication process while increasing the value of the product and the price the manufacturer can command.

FPP can also be used to provide local reinforcement for fastener holes, increasing bearing strength of bolts by 25%. SOURCE: Cevotec.

Build-ups for bolt holes
FPP can also be used to reinforce holes for mechanical fasteners. “The objective is to build structures that are as thin and light as possible," says Groene. "However, drilling holes into structure requires handling the resulting shearing stresses and providing sufficient bearing strength for the fasteners.” Ideally, the best solution would be to reinforce locally vs. having to build a thicker overall structure. However, local  reinforcement is not typically efficient in conventional high-volume production. Groene says FPP is well-suited for high-volume production and enables patch-based layups with a radial orientation of fibers in every direction, vs. just a few orientations with conventional layups. The FPP reinforcements are inherently scarfed so that the center portion is thicker and the edges are thinner. Groene says this provides effective load transfer into the surrounding laminate, increasing the bearing strength of bolts by 25% compared to conventional layups for the same part. With FPP, it is easy to produce complex shapes needed to reinforce local areas and apply the heated FPP reinforcements onto existing layups. This technology is also well-suited for producing repair patches, which Groene says is definitely within Cevotec’s focus for the future.

Turnkey solutions
Groene points out that Cevotec’s capability extends beyond just designing and producing FPP patches and parts. “We are offering a one-stop shop, providing manufacturing companies with a turnkey solution that includes software, hardware and pre-production assistance.” He gives the automotive industry as an example. “We are based in Munich with great automakers on our doorstep. We are in touch with these companies, and see very interesting applications for FPP in high-end car models. However, we also see that other manufacturers may take a less capital-intensive approach which would fit well with FPP.” In other words, FPP could help achieve some of the tailoring and improved performance in a way that demands less in-house complexity for the manufacturer. “We are also offering a new carbon fiber look which is already interesting to companies using carbon fiber but which want new aesthetics.”

FPP offers a new aesthetic for CF parts. SOURCE: Cevotec.

Discontinuous fiber is the new black
“We are breaking the paradigm that carbon fiber has to be continuous,” says Groene. Testing of a tensile open-hole specimen with conventional (LEFT, below) and FPP-based lay-up (see RIGHT, below) showed a 120% increase in mass-specific max. strength with FPP. Cevotec has verified this through tests on various geometries with curved load paths, confirming increase of specific stiffness and strength as high as 150%.

FPP allows following a curved load path, such as around bolt holes, for a 120-150% increase in specific strength. SOURCE: Cevotec.

Groene concedes that discontinous fiber laminates in conventional tensile-based specimens do have a 20-25% knockdown in strength vs. continuous fiber, “but if the load path is curved we can follow it and gain massive performance, more than compensating for this knockdown." He notes that with conventional laminates, a 15% deviation in the angle of the fiber vs. the load can produce an 85% drop in strength. "We also do not put fiber where it’s not used," he adds, "so the weight is much more optimized.” Groene explains that with the part geometry and loads defined, Cevotec can perform finite element analysis (FEA) calculations to identify how the load path will run through the part. “We then use this information to orient our fibers along these paths.”

Groene acknowledges that Cevotec has a long road ahead in gaining widespread commercial applications. However, the company has received a lot of interest so far and has developed a plan that targets “low-hanging fruit” first, via medical and sporting goods applications, while developing partnerships for longer-range, larger applications. “We are still seeking customers and partners to develop parts as well as investors,” says Groene, “but we are confident in FPP’s future and the opportunity for lower cost and greater efficiency that it offers for manufacturing with composites.”

Posted by: Sara Black

19. August 2015

New composite products for aircraft interiors are coming, including flax/epoxy prepreg, a natural fiber product.

Aircraft OEMs are striving to make their products more fuel-efficient, with improved engines and ever-increasing use of composite materials, including in interiors. Composites have long had a role in cabin finishes, because of their high strength to weight ratio and thus contribution to higher aircraft fuel efficiency. As we have reported in CW in the past (e.g., Chris Red’s market outlook article here: http://www.compositesworld.com/articles/composites-in-aircraft-interiors-2012-2022), interior composite components can include seats, floor boards, bulkheads and cabin dividers, lavatories, galleys, wall and ceiling panels and stowage bins. While obviously not as structural as aircraft airframes, nevertheless composite materials for interiors must have strength and meet very stringent flame, smoke and toxicity (FST), heat release, burn rate/flame spread, crash safety and other performance mandates published in the US Federal Aviation Administration’s Federal Aviation Regulations (FAR), Part 25. Equivalent European regulations have been formulated by the European Aviation Safety Agency (EASA). A wide variety of interiors materials, including epoxy, phenolic and high-performance thermoplastic resins, cores, reinforcements, adhesives, potting compounds, decorative films, veils and much more, are available from many suppliers. And it’s a multi-billion dollar industry, as airlines seek to differentiate interior looks and amenities in new aircraft, and as older craft get refurbished.

With that said, well-established, qualified materials remain at the forefront, so truly new products are somewhat rare. But, a few new products have popped up recently, along with news from two European consortia exploring new material approaches. First, BASF (Ludwigschafen, Germany) has introduced an expanded polypropylene foam trademarked Neopolen P reFLAM, which was tested in an institution certified by the aviation industry, in accordance with the specification CS25.853. It is a second-generation version of the company’s expanded polypropylene foam Neopolen. The material owes its enhanced level of fire safety to its special flame-retardant additives, and offers a further improvement in thermal insulation properties while meeting the requirements of European REACH and those of the ROHS Directive and its amendments. The material is approved for molding densities from 36g/l to 75g/l in accordance with applicable requirements. The certification allows Neopolen P reFLAM to be used in numerous applications with the highest fire safety requirements, particularly in the aviation sector.

"The level of interest in new, lightweight and at the same time flame-retardant materials is very high, particularly in the aviation industry", says Carsten Junghans, the key account manager, BASF’s Specialty Particle Foams Europe. He points out the foam’s high thermal insulation characteristic and almost unlimited scope for forming. "Neopolen P reFLAM now provides manufacturers with a foam material which combines these requirements and enables a wide variety of different applications."

Although first introduced last year at the Aircraft Interiors show, SABIC’s (Riyadh, Saudi Arabia) new offerings include two new LEXAN clear sheet products. The thermoplastic polycarbonate LEXAN XHR2000 sheet, with 80% light transmission, has the highest level of light transmission available in an OSU-compliant sheet material and meets typical industry flame, smoke, toxicity (FST) requirements (FAR25.853, BSS7239, ABD0031). (A note: OSU refers to Ohio State University’s accepted rate of heat release test, which measures heat evolution energy during burning, reported as peak heat release in kilowatts per square meter, and total heat release in kilowatts per minute per square meter; the FAA’s regulatory peak/total requirement number is 65/65.)  According to SABIC, its patent pending LEXAN LIGHT F6L300 sheet, the lightest thermoplastic sheet option available today, provides long-awaited solutions to airlines’ quest for differentiated cabin interior designs while also helping to take out significant weight, resulting in more a fuel efficient aircraft. For instance, cabin dividers can be made with the clear LEXAN XHR2000 sheet and LEXAN LIGHT material has been used to create aircraft sidewalls.

Award-winning LSG Sky Chefs and Norduyn1 in-flight trolleys, certified as the lightest in the world, incorporate SABIC’s ULTEM thermoplastic polyetherimide (PEI) resin in the extrusion profiles and door latch, while ultra-tough NORYL modified polyphenylene (PPE) thermoplastic resin replaces metal in the frame and other components. The ability to custom-color ULTEM resin allows Norduyn and LSG Sky Chefs to offer trolleys in the relevant airlines’ brand colors. A new passenger service unit (PSU) engineered and supplied by PECO Manufacturing (Clackamas, OR, US) for the new Boeing 737 uses LEXAN and ULTEM resins. PECO used an integrated structural design which consolidated parts in order to reduce the footprint of the PSU. The use of ULTEM 9085 resin enabled thinner walls, resulting in a 30% smaller unit with considerable weight savings for the airline.

Now, sustainability and “green” interiors are entering the conversation. A European project called “Cayley,” which concluded about two years ago, brought together Boeing Research and Technology Europe (Madrid, Spain), Invent GmbH (Braunschweig, Germany), Aimplas  (Valencia, Spain) and Lineo (St.-Martin du Tilleul, France) and was aimed at industrializing environmentally-friendly interior panels made with renewable polymers or recyclable thermoplastic sheets and natural fibers, namely flax. Lineo's linen uni tape, called FlaxTape, and FlaxPreg linen/epoxy prepregs intended for transport interiors (cars, trains and aircraft interiors), reportedly are 35% lighter than carbon fiber/epoxy prepreg tapes. Lineo also offers a sandwich product, called Simbaa, as an alternative to traditional sandwich constructions.

A spinoff of flax grower parent LSM, Lineo is reportedly gearing up for large volume production. Francois Vanfleteren, company CEO, told European Plastics News at the conclusion of the Cayley project that Lineo's UD tape production line for the project makes tape that is 40cm wide, but when scaled up for series production 1m wide tape will be possible. PSA Peugeot Citroën is reportedly already starting to incorporate the material into its automotive platforms.

Pedro Martin, material scientist in the materials and fuel cells department at Boeing Research & Technology Europe, has given presentations about Cayley, and reported that Boeing is working with the partners on the flax sandwich panel made with epoxy, which can be used for cabin sidewalls, while other partners are investigating PP and PLA. "Fire resistance is the most challenging issue to overcome when working with natural fibers," Martin has told European Plastics News. During the project research, flax fabrics were treated with halogen-free flame retardants and used to produce a full-scale sidewall panel for a 737 interior in a vacuum bag process. At laboratory scale, the biocomposite achieved compliance with FAA and EASA fire resistance requirements. Curing time for the thermoset resin is reportedly too long, and shelf life for the prepreg needs to be increased. The project had a target to produce panels in an automated one-step process at a rate of one panel every 15 minutes.  

CW contacted Lineo, and got some additional information from Lineo’s R&D engineer Bruno Dellier. “Our FlaxPreg product meets the FAA’s FAR 25.853a self-extinguishing characteristics,” he notes. A video showing FlaxPreg’s fire resistance is available on the company’s Web site: http://www.lineo.eu/#!applications/vstc2=property-no3. Dellier goes on to tell CW that while Boeing and Airbus have shown interest in using the material, for the moment “the qualification process has not yet started.” When asked about the price of FlaxPreg compared to a glass/epoxy unidirection prepreg, he says that the price is similar.

A second natural fiber for aircraft consortium dubbed “DesAIR “Design of Environment Friendly Structures for Aircraft” was an R&D consortium project that brought together 4 Portuguese organizations – Almadesign (AD), Amorim Cork Composites (ACC), Instituto De Ciência e Inovação em Engenharia Mecânica e Engenharia Industrial (INEGI) and Universidade da Beira Interior (UBI) – with the intent of developing new high performance composite solutions for aircraft interiors, integrating natural materials, including cork,and developing specific manufacturing processes. This research appears to be inactive at the moment but interesting from the standpoint that major groups, including aircraft OEM Embraer, were involved.

Will natural fiber products perform well enough be be adopted in interiors, in the future? Given the substantial weight savings over traditional reinforcements, their on-par cost, renewable nature and life cycle benefits, they look like serious contenders. Indeed, Lineo had a stand at this year’s Paris Air Show, and was mentioned in Aviation Week magazine as an innovative company to watch. We’ll keep our eyes and ears open. 

Posted by: Ginger Gardiner

5. August 2015

High-speed machining has become a necessary function for carbon fiber reinforced plastic (CFRP) parts production. The video below shows the type of detailed, high-speed machining now common in the manufacture of CFRP parts for the aerospace industry.

Video of CFRP ring frame machining completed at Leading Edge Aerospace using an Anderson America large-format 5-axis CNC router.  SOURCE: Anderson America.
 

“High-speed 5-axis CNC routers not only move the head at a high rate, but also the tool at high RPM, which is key for machining carbon fiber parts,” says David Steranko, VP of sales for Anderson America (Pineville, NC, US). “These machines have the ability to pay back the capital expense rapidly as well,” he notes. For example, in the past, fabricators bought large-format metal machining centers costing $4-5 million. “CNC routers were viewed as not precise enough,” says Steranko, “but advances over the past decade have enabled the precision and even higher speed, without the cost.” He notes these large-part capable, high-speed 5-axis CNC routers cost $500,000 to $900,000.

Steranko says the shape, thickness and size of parts being demanded today typically won’t fit standard 5-axis CNC routers. “The challenge for us is to have bigger, faster machines but maintain high precision.” He says this has indeed been mastered, as can be seen in the video, and these machines can also machine multiple parts at the same time. “One customer is using twin tables so that the machine runs 24 hrs/day, 7 days/week,” says Steranko. “This is two to three times the performance of old machining centers.”

For those not as involved in the machining end of composites operations, here is a primer from our sister magazine, Modern Machine Shop:

Five-Axis Machining Centers do not just move in the linear axes X, Y and Z. Instead, these machines also move in two rotary axes, often identified as A and B. The rotary axes tilt the tool with respect to the part. Physically, it can be either the tool that tilts or the part that tilts. Different machines accomplish the rotary motion in different ways. Some machines move the rotary axes only to position the tool or work outside of the cut. This is referred to as 3+2 machining. Moving the tool in this way dramatically increases the machining center’s access to features at different angles or on different faces of the part. A machine capable of 3+2 machining often can reach all of the machined features of the part in a single setup. True five-axis machining refers to the ability to not just position the tool along the rotary axes, but also to feed the tool through the cut using these axes. Interpolated combinations of A-axis, B-axis and linear axis motions can allow the tool to smoothly follow a contoured surface. This type of machining has long been important in the aerospace industry, where machined parts follow the aerodynamic forms of aircraft.

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