The world’s two largest aerospace manufacturers, once again, shared center stage as commercial aircraft stayed in the composites spotlight. Airbus (Toulouse, France) and The Boeing Co. (Chicago, IL, US) expected to be increasingly heavy users of carbon fiber composites, for primary and secondary airframe structures, and foresaw the increasing use of a mixture of glass and carbon-reinforced thermosets and thermoplastics in a growing and diverse suite of interior applications.
Both of the majors predicted futures replete with upward trends. Airbus anticipated in its Global Market Forecast for 2015-2034 “Flying By Numbers” that air traffic will grow by 4.6% annually and, therefore, increase in value to nearly US$4.9 trillion, up from its 2014 estimate of US$4.6 trillion. Total commercial aircraft deliveries by 2034 will number 32,585 (that’s up from the 31,358 predicted in 2014) — 31,781 of them for passenger service and the remainder, 804, freighters. Over the next 20 years, passenger aircraft deliveries will break down as follows: 22,927 single-aisle, 8,108 twin-aisle, and 1,550 in the “jumbo” class, all up from 2014 estimates. Airbus says passenger traffic continued to outperform the world’s gross domestic product (GDP) in terms of growth in 2015 by 5.8%, and that both traffic and GDP will go up, powered by emerging economies, which will grow on average by 4-6% per year in the 2015-2034 timeframe. The world’s “middle class” will increase from 33% of the total population in 2014 to 55% in 2034, so Airbus predicts air traffic will double by 2029 and that 74% of the population in emerging economies will take at least one commercial plane fight per year by 2034. Further, the Asia Pacific region will account for 34% of all air traffic. Significantly, Airbus also predicts a 33% decline in fuel consumption per revenue passenger kilometers (RPKs), a testimony, in part, to anticipated increased use of composites on aircraft.
For its part, Boeing, in its Current Market Outlook 2015-2034, as it did in 2014, paints an even more optimistic picture: Growth in passenger traffic (in RPKs) will exceed 4.9% and air cargo traffic will increase by 4.7%. The air traffic market will be valued at US$5.6 trillion, and 38,050 commercial aircraft will be required to meet demand in the next 20 years. About 40% of those will be delivered to passenger airlines in the Asia Pacific region. European and North American airlines will buy 20% of the new aircraft and another 20% will go to airlines in the Middle East, Latin America, the Commonwealth of Independent States (CIS) and Africa.
Single-aisle aircraft will continue to dominate the commercial aircraft market. About 26,730 new ones will be needed over the next 20 years, says Boeing, driven by demand from low-cost carriers and the need to replace aging models. The twin-aisle fleet will require 8,830 new planes. Regionally, demand for aircraft among Asia Pacific carriers, according to Boeing, will be double that from any other region — 14,300. European carriers will order 7,310, North American carriers, 7,890, Middle Eastern airlines will demand 3,020, the CIS will claim 1,150 and African carriers will need 1,170.
In the short term, the indicators for composites use trended up as well. As 2015 began, Airbus had just reported (Dec. 22, 2014) delivery of the first A350 XWB to Qatar Airways. At the end of November 2014, the A350 XWB had attracted 778 orders from 41 customers, worldwide, and, like The Boeing Co. (Chicago, IL, US) and its 787 Dreamliner program, Airbus was seeking ways to ramp its A350 production rates up into line with its delivery schedules.
As 2015 closed out, Boeing readied its new Composite Wing Center in Everett, WA, US) for opening, signaling the ramp up to production for its vaunted Boeing 777X program, the redesigned version of its popular mid-size commercial jet, which will convert its wing structures from legacy metals to composites. The massive facility will have 120,774m2 of workspace, roughly the size of 25 American football fields, for manufacture of the plane’s composites-intensive wings. Completion is expected in May 2016, and its likely that the Center will be busy — so far, the 777X program has attracted 300 orders and commitments.
In the longer term, however, the composites trend line’s trajectory is less certain. One reason is that the 777X program is the last major aerospace program into which the composites industry can expand its products and services in the near term. Observers say new opportunities for composites use of this size and scope in the commercial aircraft industry are unlikely until the 2030s — the most likely timeframe for wholesale re-imaginings of the two workhorses of the large narrow-body fleets — Boeing’s 737 and the Airbus (Toulouse, France) A320. Add to that the fact that questions have been raised, in some circles, about the practicality of composites for narrowbody primary fuselage structures, which might limit composites to wing and empennage. For 10-15 years to come, then, applications of composites in new aircraft are likely to occur in (relatively) smaller programs — rotorcraft, business jets and a commuter aircraft or two. Although Bombardier (Montrèal, QC, Canada) put its Learjet 85 program on indefinite hold as 2015 began, those aircraft should include Bombardier’s CSeries aircraft, for which it has more than 240 firm orders. Its CS100 is expected to enter service in early 2016.
Outside the commercial airlines realm, Lockheed Martin’s composites-intensive F-35 Lightining II is powering up for full production at a worldwide array of suppliers. Textron AirLand’s (Wichita, KS, US) light strike/ISR jet, the Scorpion, designed by a group of longtime aircraft engineers outside the defense industry infrastructure, went from drawing board to prototype in 24 months and could be providing ground support and reconnaissance to several militaries in short order. But here again, these programs are notable, in part, for the fact that no other major manned military aircraft programs are on the horizon. Unmanned aerial vehicles (UAVs), of course, have been much in the composites news over the past decade, but 2015 was notable for the lack of new military UAV program announcements. Unmanned aircraft programs, like their manned cousins, are stabled, ongoing concerns. UAV growth is now predominantly civil, and that growth is still hindered by restrictions in many locales on their use in civil airspace.
Another newcomer, a business jet, is the Flaris. a single-engine, composites-intensive light jet, built by Metal-Masters’ (Podgorzyn, Poland), which is close to first flight, and certification activities have begun. Composite Helicopters International (Auckland, New Zealand) anticipates certification for its all-composite airframed KC630 helicopter in late 2017, followed by the KC640 and KC650 (equipped with larger turbines) in 2018. A full design review in line with the Federal Aviation Admin.’s FAR Part 27 certification requirements will run concurrently.
In the business jet sector, one example is XTI Aircraft Co.’s (Englewood, CO, US) entry is unusual not only for its concept — the 6-seat TriFan 600 is powered by two engines that will drive three large, multi-functional ducted fans — but also for the equity crowdfunding approach XTI is taking to help raise capital for its venture, in addition to more traditional venture capital and private equity funding. XTI aims to “transform flight” with what the company calls the first commercial vertical takeoff airplane. Essentially a hybrid plane/helicopter, its fans will enable vertical takeoff and landing (VTOL) and hover, but according to XTI, the fans transition seamlessly after liftoff in seconds to wing-borne forward flight.
All that to say this: 2016 might represent the beginning of an aircraft composites plateau, where composites industry developmental expansion in the aerospace realm is measured less by programs and unit numbers and more by technology impact and effectiveness.
One possibility in that vein could be multi-functional composites — laminates that not only provide lightweight, load-bearing structures, but also perform additional functions. One pioneer in this area is start-up MultiFun (Varthur, Bengaluru, India), which has designed an aircraft wing that integrates piezocomposites and battery (energy-storage) composites to harvest vibrational energy, convert it to electrical energy and store that energy for use in local subsystems, eliminating the need for external batteries and cabling. MultiFun combined the piezocomposite and the battery composite into a single, hybrid material. Combining two different fibers in a single laminate with the same epoxy matrix, the hybrid is able not only to harvest vibrational energy but also to store it as electricity and then release it later for use. Although this and similar multi-functional composite efforts are fledgling at best, and some distance yet from commercialization, its an idea whose time has definitely come: The 20th International Conference on Composite Materials (July 19-24, 2015, Copenhagen, Denmark), which featured more than 100 presentations on multifunctional composites (see “Aerocomposites: The move to multifunctionality” under “Editor’s Picks”).
A continuing hallmark of the plateau period will be intense work in incremental adoption of composites to increase aircraft fuel efficiency via lightweighting. Chris Red, president of Composites Forecast and Consulting LLC (Mesa, AZ, US), estimates that a mere 0.45 kg of weight savings reduces annual fuel expenses (at $3/gal) by US$175 to US$432 per year for passenger jets, dependent on aircraft size and annual flight hours. Some of that will be earned by increased use of composites in passenger cabins. The composite interiors market is fairly mature — glass and carbon fiber composites, thermoset and thermoplastic, have been used to reduce the weight of interior components for more than three decades. But Red claims there is “still plenty of room for improving weight, durability, aesthetics and functionality.” Composites currently represent only 20-25% of total interior weight, but could increase to 30-40% in 10 years. Emerging interiors applications, says Red, could drive annual production volumes up an additional 60% by 2023.
Attacking weight from another direction, Sigma Precision Components (Hinckley, UK) introduced in 2015 composite replacements for metal piping used as jet engine drainage, scavenge, sensor and vent lines. The company has developed a commercial-scale process for producing post-formable braided carbon fiber/PEEK that offer 50% weight savings vs. metallic pipes while hitting competitive cost targets. According to Sigma, more than one-third of the dressing pipes (150) on a typical jet engine could be replace with its SigmaLite pipe product (read more in “Re-dressing aeroengines with composite pipes” under “Editor’s Picks”). Results are significant: A 150-pipe composite assembly can cut weight by 10 kg per engine, with weight savings cascading to a 50-kg reduction per twin-jet aircraft. Further, the pipe has sustained 275.8 bar pressures, temperatures to 235°C and passed vibration, damage tolerance and fire tests.
Another key driver for carbon composites continues to be the need to increase jet engine bypass ratio (BPR), that is the amount of air the fan moves past the engine, compared to the air it introduces into the engine combustion chamber. BPRs have increased from 5:1 in the 1970s to 10:1 today and could climb to 50:1 or by 2050 via advanced concepts. This increase in ratio results in better fuel efficiency, but also increases the size and weight of the air-delivering turbofan. That’s where composites come in. The trend in aeroengine blades is toward not only larger fan diameters but also lower blade counts. GE Aviation’s (Cincinnati, OH, US) next-generation GE9X engine, for example, will feature fewer and thinner composite fan blades than any GE widebody engine in service. To do this, GE is designing a new composite fan blade, using next-generation carbon fiber composite material. The GE9X will have just 16 fan blades on its 3,404-mm diameter front fan.
Although the average fuel burn per aircraft seat-km today, compared to 1980, has been reduced by 27% for widebody aircraft and 35% for narrowbody models, more ambitious reductions have been called for by the Advisory Council for Aviation Research in Europe (ACARE) in Flightpath 2050 — a 75% reduction in CO2 per passenger-km, a 90% reduction in nitrous oxide (NOx) emissions and a 65% reduction in noise by the year 2050 vs. performance levels recorded in 2000.
The dire need for such reductions has stimulated replacement of aeroengine metals with ceramic-matrix composites (CMCs). Although they’re considerably more expensive — reportedly hundreds to thousands of dollars per kilogram — they are roughly one-third the weight and twice the strength of the nickel alloys currently used in jet engines, and they offer a 100-200°C improvement in high-temperature capability. GE Aviation, for example, expects a tenfold increase in the use of CMCs in its engines over the next decade, in part because, unlike metals in the hot zone, CMCs don’t need to be air-cooled, freeing up flow to boost the engine’s propulsion and efficiency. But CMCs also are expected to see use in places now frequented by carbon composites, such as fan blades.
And although CMCs were first targeted to static applications, the real revolution, say proponents, will come when CMCs are used to reduce weight and promote cooling in rotating parts. In February 2015, GE successfully tested CMC rotating parts in an F-14 military jet engine. Similar to the fan disk reduction enabled by CFRP fan blades, these CMC LP turbine blades allow smaller, lighter metal turbine disks and bearings, and other parts can be downsized as well, multiplying weight savings by as much as a factor of three. (Read more about composites’ ability to help meet ACARE environmental requirements in “Aeroengine composites, Part 1: The CMC invasion” and “Aeroengine composites, Part 2: CFRPs expand” under “Editor’s Picks.”)
In the realm of space exploration, the private space race continued to promise the growth of composites in vehicles for unmanned and manned missions. After Space Exploration Technologies Corp.’s (SpaceX, Hawthorne, Calif.) Dragon unmanned space vehicle successfully docked at the International Space Station (ISS) in 2014, delivering 400 kg of supplies to the orbiting laboratory and returning 759 kg of cargo, to Earth splashdown (the first of — 12 contracted resupply missions (through 2016) under NASA’s Commercial Resupply Services contract, worth US$1.6 billion) attention turned to manned space craft: After months of speculation in 2014, NASA selected The Boeing Co. (Houston, Texas) and SpaceX to develop spacecraft to transport U.S. crews to and from the ISS. Boeing was the big winner, awarded $4.2 billion to develop its CST-100 spacecraft. SpaceX was awarded a smaller amount, $2.6 billion, to develop its Crew Dragon spacecraft. Sierra Nevada Corp. (SNC, Sparks, Nev.) and its Space Shuttle-like crew ship, the Dream Chaser, was eliminated. On May 6, 2015, SpaceX successfuly demonstrated its Crew Dragon spacecraft abort system, proving the spacecraft’s ability to carry astronauts to safety in the unlikely event of a life-threatening situation on the launch pad and was a milestone in its efforts to launch crewed flights as early as 2017. NASA already is preparing the International Space Station (ISS) for commercial crew spacecraft and the larger station crews that will be enabled by the Crew Dragon and Boeing’s CST-100. NASA plans to use the new generation of privately developed and operated spacecraft to carry as many as four astronauts each mission. (See a video of the recent controlled-burn touch down of a Spacex first-stage launch vehicle as it returned to Earth — the finale of the first-ever launch vehicle vertical takeover and vertical landing — by clicking on “SpaceX successfully recovers Falcon 9 rocket first stage” under “Editor’s Picks.”)
Although NASA rejected its crew vehicle bid, Sierra Nevada Corp. (SNC) Space Systems (Louisville, CO, US) continued on with the development of its Dream Chaser spacecraft, updating two developmental spacecraft, and making significant progress on the build of its first orbital vehicle, manufactured by Lockheed Martin with a unitized cabin assembly that features three-dimensional woven joints, to integrate internal frames with external carbon skins in a single co-bond operation, meaning nearly all fasteners on this critical cabin assembly are eliminated.
“Upon completion, the Dream Chaser orbital vehicle will be the most advanced composite structure ever built,” claims Mark Sirangelo, corporate VP of SNC’s Space Systems. “We look forward to Dream Chaser becoming the world leader in this area and to its first orbital flight.”
Meanwhile, a 2016 rollout is expected at Scaled Composites (Mojave, CA, US) for the massive Stratolaunch six-engine air launch system, with a 118.5m wingspan, designed to carry a rocket-powered orbital vehicle with payload, weighing up to 6,136 kg, to a launch altitude of around 10,800m, where the vehicle is released for self-propelled flight into low Earth orbit. Funded by billionaire Paul Allen in collaboration with Scaled Composites’ founder Burt Rutan, the launch vehicle it will carry is in progress at Vulcan Aerospace Corp. (Seattle, WA, US).
Finally, Virgin Galactic (Las Cruces, N.M.) says it is back on track, with plans for its next spaceship and expects to show off a new version of its SpaceShipTwo (SS2) early in 2016 and recommence testing. The company’s space tourism aspirations — and private space-travel development in general — suffered a sobering blow in late October 2014: The original SpaceShipTwo space plane disintegrated during a test flight, killing one of its pilots and seriously injuring another, when its feathering system transitioned from a locked to an unlocked position and deployed prematurely. The U.S. National Transportation Safety Board (NTSB) ultimately determined that the accident was the result of pilot error.