Advanced Technologies Supplement: Composites Fly Lighter, Stronger
Tape laying and fiber placement systems automate composite structure production and reduce costs
By Jim Lorincz
The challenge in the commercial aircraft business today is turning orders into deliveries and doing it with the most fuel-efficient airplanes possible.
Orders for new airplanes in 2005 for Boeing Inc. (Chicago) and Airbus SAS (Toulouse, France), the two industry giants, were at record levels that will challenge the capacity of the global supply chain for the next decade. Combined aircraft orders for both companies in 2005 were records with a total of 2057 net new orders. Backlogs at Airbus alone swelled to 2177 airplanes valued at $220.3 billion.
The global supply chain for aircraft parts and structures is likely to be stretched tighter as industry observers expect existing programs to take 5–10 years to work their way through to delivery. Both companies have set ambitious delivery targets for 2006: 400 for Airbus and 395 for Boeing.
In 2005, both companies introduced their next-generation aircraft. Boeing’s 787 Dreamliner is slated for 2008 delivery. Airbus’ A380 super jumbo is in test and will be delivered later this year. The A350 wide-body airliner was launched with delivery set for 2010. Each model accelerates the percentage and weight of composites that will be used in structural components.
Boeing’s 787 Dreamliner, for example, will feature composites in its major structures, including wings, fuselage, and empennage, all fabricated of composites. Outside suppliers are expected to play an increasingly important role as the supply chain stretches its capacity to produce composite structures for the airliners.
Boeing retained its lead in wide-body airliner orders. Of the total of 1002 airplane orders in 2005, there were 235 orders for its 787 Dreamliner, bringing the total to date to 350. The Boeing 787 will be fabricated with 50% of its weight in composites. A major step forward was the building of the first composite fuselage section in 2005.
Airbus launched its A350 wide-body airliner in 2005. The A350 will introduce an all-composite wing, as well as feature an airframe fabricated with 60% composite materials such as carbon-fiber reinforced-plastic (CFRP) and aluminum-lithium alloys. The A350 will also have a composite rear fuselage and tail cone, each being built for the first time in one “skin.” Use of composites in the A350 will reportedly save 17,600 lb (7983 kg) compared with use of conventional materials.
The Airbus A380 features greater use of composites if only because of its sheer size. The overall dimensions of the A380 are 73- m long, 24.1-m high, and 7.1-m diam fuselage. The A380’s wingspan is 79.8 m with a wing area of 845 m2. That compares with the overall length of the A350 of 58.8 m, height of 17.4 m, and fuselage diam of 5.6 m. Wingspan is 61.1 m and wing area is 362 m2.
Automated tape layers feature long X-axis travels that can be extended to handle the largest aircraft structural components.
As more composite components are utilized on future commercial aircraft, automated tape laying will reportedly be considered for the larger, lower complexity components, such as Airbus A380 stabilizer skin panels.
The key to meeting production schedules is matching manufacturing capabilities of the global supply chain with the requirements of aircraft designers. Their goal is to produce larger, lighter, more fuel-efficient airplanes and composites are fast becoming the advanced material of choice.
Advanced composite material technology is not new to the aerospace industry. Carbon-fiber composite materials first made their mark in the manufacture of missiles and military aircraft. The reasons are not difficult to appreciate. Carbon-fiber composite materials are attractive because of their superior strength-to-weight ratio and resistance to corrosion and fatigue.
The high-strength reinforcement fibers can be oriented in specific directions in the resin prepreg to deliver maximum strength only in the direction that is needed. The benefit to large composite structures such as spacecraft and missiles, and now aircraft wings and body skins, was obvious. Initially, the composite components were produced manually making them costly, at the time a less-important consideration for defense and space purposes.
According to Ron Hennies, product manager, Cincinnati Machine (Hebron, KY), tape layer sales, which peaked in 1988 with the US defense buildup, rebounded in late 1993 with the introduction of composite stabilizer skin panels on commercial aircraft. Fast forward to the present with soaring cost of aviation fuel and the intense competition between Airbus and Boeing, and the stage was set for a new round of orders for the technology and systems that can automate the production of fuel-saving composite structures.
At the heart of advanced composite technology are two basic systems: automated tape layers (ATL) and fiber placement systems. Today, there are more than 50 tape- laying machines and fiber placement systems known to be operating in the world, typically representing capital investment of between $2–$6 million each.
Boeing Commercial Airplanes has ordered two Cincinnati Machine (Hebron, KY) Version 5 High Contour Tape Layers (HCTL), as well as having two existing Contour Taper Layers retrofitted at its Composites Manufacturing Center in Frederickson, WA.
Both the new tape layers and retrofitted machines will be used to produce composite components for the Boeing 777, now in its twelfth year of production, as well as for Boeing’s 787 Dreamliner airplanes. This brings the total number of Cincinnati Machine ATLs being utilized for 777 and 787 production to eight.
The global supply chain continues to ramp up to meet expanded demand for composites. Two Cincinnati Machine HCTLs with 150-mm and 300-mm tape capability owned by Alenia Aeronautica SpA (Italy) were qualified by Boeing for the production of structural components for the 787 Dreamliner. The two HCTLs were the first tape layers outside of Boeing and the first of Cincinnati Machine’s new generation of contour tape-laying machines to be qualified for the production of structural components for the 787 Dreamliner. Cincinnati Machine will also deliver a version 5 HCTL to Korean Airlines for use on the 787 program. This brings the total number of new Cincinnati Machine ATLs ordered for the 787 program to seven.
In addition to supporting Boeing aircraft programs, Cincinnati Machine also supplies tape-laying machines and fiber placement systems to Airbus to support a variety of commercial and military programs including the new A380 and A400M.
Another supplier for the Airbus A380 program, MTorres Group (Navarre, Spain) is supplying its Torreslayup 11-axis CNC tape layer machines to Airbus manufacturing operations in Germany and Spain. In addition to the 11-axis gantry CNC tape layer, MTorres Group designs and manufactures special machine tools and assembly jigs to machine and assemble aerospace components. The company’s product line covers the whole production process.
In 2005, Spirit AeroSystems Inc. (Wichita, KS) produced the first developmental barrel section, Section 41, for the 787 Dreamliner at its Wichita, KS, plant. The forward section of the 787, which measures 19' (5.8 m) in diam and 24' (7.3-m) long, is made with advanced composite materials. The forward section will be produced complete with flight deck and systems installations and shipped from Wichita in 2007.
MTorres fiber placement equipment used in manufacturing the 787's section 41 utilizes SINUMERIK 840D CNC control from Siemens Energy & Automation Inc. (Elk Grove Village, IL).
Spirit, the former commercial aircraft manufacturing division of Boeing, has signed an agreement with BAE Systems to acquire the Aerostructures business unit of BAE Systems, which has operations in the UK and produces structural components, chiefly wings for Airbus, Boeing, and Raytheon.
Ultrasonic knife oscillates at 20,000 Hz to produce clean cutting as shown in this composite test laminate piece at Cincinnati Machine.
Cost was a barrier to the widespread use of composites when production was done manually. The development of CNC-controlled automated taper layers and fiber-placement systems has created two classes of machines that can meet the demand for volume production of complex contoured components and large composite structures.
ATLs are designed to lay up composite tape in either flat or contour configurations. Flat tape-laying machines (FTLM) can be configured either as “fixed bed” machines or as “open-bay gantry” machines that are basically the same configuration as a contour layer. Contour tape-laying machines (CTLM) are normally an open-bay gantry configuration.
Gantry-type ATL systems are constructed with X-axis ways in incremental lengths. “Machines can be configured with longer way systems to allow use of multiple gantries on a common set of ways and permits not only lay up of long wing skin panels but also lamination on different tools simultaneously,” explains Cincinnati Machine’s Hennies. “Another advantage of these ‘super tape layers’ is the capability of loading and unloading tools on one end of the machine while lay-up operations continue on the other end.”
The most commonly used tape layer consists of a gantry structure (parallel rails), a cross-feed bar that moves on precision-ground ways, a ram bar that raises and lowers the material delivery head, and the material delivery head that is attached to the lower end of the ram bar. Tooling is rolled under the gantry structure, fixtured, and the machine delivery head is then registered to the lay-up surface.
Delivery heads for FTLM and CTLM machines are similar in configuration with the primary exception being the addition of an A axis to the CTLM head for laying on contoured surfaces. Today, for maximum productivity, both FTLM and CTLM systems typically use material in 150-mm or 300-mm widths.
Large composite structures can be handled by Cincinnati Machine’s contour tape-laying machines, which have typical travels of 9.1 × 6.1 × 1.2 m (X, Y, Z axes). The X- axis travel can be extended to accommodate the largest airplane structures like wings by adding incremental rail sections.
An option that is becoming increasingly popular is the addition of an ultrasonic knife to trim composites structures on the tape layer rather than refixturing and registering the component at a trimming station further down the line. “The ultrasonic knife vibrates at 20,000 Hz, reciprocating just like a jig saw, to produce a good cut in laminates to 15-mm thick,” explains Jim Hecht, Cincinnati Machine manager of composites processing. “Customers are beginning to see that trimming the laid-up blanket on the tape layer is really more productive, saving refixturing and registering the part on a cutting machine further down the line. Not only is accuracy improved, but customers can lay up a wider blanket and cut it to produce more parts.”
ATLs are credited with 70–85% reductions in manhours and are able to lay up material at the rate of 4000 lb (1816 kg) per 40 hr on flat applications. CTLM lay-up rates are somewhat lower depending on the contour of the component.
High-contour components can be more efficiently handled with fiber placement systems that combine the advantages of tape laying with filament winding. With seven axes of motion, fiber placement systems are particularly suited to highly contoured structures such as cowls, ducts, fuselage sections, pressure tanks, nozzle cones, tapered casings, fan blades, spars, and “C” channels.
Cincinnati Machine’s VIPER 1200 CNC fiber placement system and off-line composite programming were used to produce a one-piece carbon-fiber fuselage developed by a consortium of European firms under the $13.2 million Full-Barrel Composite Fuselage (FUBACOMP) project. (See “Fiber Placement System Produce One-Piece Fuselage,” Manufacturing Engineering, February 2006, p. 36.) The one-piece business-jet fuselage, measuring 4.5-m long by 2 m at its widest point was manufactured using pre-impregnated carbon fiber slit tape and honeycomb core.
The single-piece fuselage would replace the need for many individual components and thousands of fasteners that are used in a typical business-jet structure. Other benefits include producing high-contour variable wall thickness and cut-out sections to near-net configuration, significantly reducing scrap. Less material is wasted in the initial lay up and post-process machining, and material removal operations are reduced. Scrap savings in the range of 65% are achieved.
The largest of Cincinnati Machine’s three models, the VIPER 6000 machine automatically controls as many as 32 individual strands or tows of material that can come in eighth-inch (3.2 mm), quarter-inch (6.3 mm), and half-inch widths (12.7 mm). Each tow can be independently dispensed, clamped, cut, and restarted during fiber placement. Gaps and overlaps are minimized.
The latest versions of automated lamination systems require sophisticated software and controls. Creating the CNC machine program requires specialized software and programming techniques to assure that material lay-up follows the desired path across the contour of the tool. Individual courses of material are programmed to meet component design criteria including gap, end placement, and ply orientation. Input to the programming software includes tool surface definition, ply boundaries, ply orientation, and machine processing parameters.
Using this information, programming software also has the capability to generate computer simulations of the manufacturing process. Simulating the manufacturing process provides data on lay-up rates and scrap factors.
Cincinnati Machine’s CM100 open-architecture, PC-based control can handle 32 coordinated axes and supports eight split axes, giving programmers the power to process even highly complex part geometries. Cincinnati Machine’s current tape layers feature a fifth-generation delivery head that is optimized for high-volume and high-contour tape laying. The head is able to accommodate smaller bend radii without bridging and can lay more pounds of tape per hour compared with the previous generation.
This article was first published in the March 2006 edition of Manufacturing Engineering magazine.