Design and Analysis of Composite Structures Figure 1.6 Airbus A-320(Photo courtesy Brian Bartlett;see Plate 6 for the colour figure) consumption and cruising speeds missed their targets by a small amount.Structurally however, the Starship I proved that all-composite aircraft could be designed and fabricated to meet the stringent FAA requirements.In addition,invaluable experience was gained in analysis and testing of large composite structures and new low-cost structurally robust concepts were developed for joints and sandwich structure in general. With fuel prices rising,composites with their reduced weight became a very attractive alternative to metal structure.Applications in the large civilian transport category started in the early 1980s with the Boeing 737 horizontal stabilizer which was a sandwich construction,and continued with larger-scale application on the Airbus A-320(Figure 1.6).The horizontal and vertical stabilizers as well as the control surfaces of the A-320 are made of composite materials. The next significant application of composites on primary aircraft structure came in the 1990s with the Boeing 777 (Figure 1.7)where,in addition to the empennage and control surfaces,the main floor beams are also made out of composites. Despite the use of innovative manufacturing technologies which started with early robotics applications on the A320 and continued with significant automation(tape layup)on the 777,the Figure 1.7 Boeing 777(Photo courtesy Brian Bartlett;see Plate 7 for the colour figure)
consumption and cruising speeds missed their targets by a small amount. Structurally however, the Starship I proved that all-composite aircraft could be designed and fabricated to meet the stringent FAA requirements. In addition, invaluable experience was gained in analysis and testing of large composite structures and new low-cost structurally robust concepts were developed for joints and sandwich structure in general. With fuel prices rising, composites with their reduced weight became a very attractive alternative to metal structure. Applications in the large civilian transport category started in the early 1980s with the Boeing 737 horizontal stabilizer which was a sandwich construction, and continued with larger-scale application on the Airbus A-320 (Figure 1.6). The horizontal and vertical stabilizers as well as the control surfaces of the A-320 are made of composite materials. The next significant application of composites on primary aircraft structure came in the 1990s with the Boeing 777 (Figure 1.7) where, in addition to the empennage and control surfaces, the main floor beams are also made out of composites. Despite the use of innovative manufacturing technologies which started with early robotics applications on the A320 and continued with significant automation (tape layup) on the 777, the Figure 1.6 Airbus A-320 (Photo courtesy Brian Bartlett; see Plate 6 for the colour figure) Figure 1.7 Boeing 777 (Photo courtesy Brian Bartlett; see Plate 7 for the colour figure) 4 Design and Analysis of Composite Structures
Applications of Advanced Composites in Aircraft Structures QANTAS Figure 1.8 Airbus A-380(Photo courtesy Bjoern Schmitt-World of Aviation.de;see Plate 8 for the colour figure) cost of composite structures was not attractive enough to lead to an even larger-scale(e.g.entire fuselage and/or wing structure)application of composites at that time.The Airbus A-380 (Figure 1.8)in the new millennium,was the next major application with glass/aluminum (glare)composites on the upper portion of the fuselage and glass and graphite composites in the center wing-box,floor beams,and aft pressure bulkhead. Already in the 1990s,the demand for more efficient aircraft with lower operation and maintenance costs made it clear that more usage of composites was necessary for significant reductions in weight in order to gain in fuel efficiency.In addition,improved fatigue lives and improved corrosion resistance compared with aluminum suggested that more composites on aircraft were necessary.This,despite the fact that the cost of composites was still not competitive with aluminum and the stringent certification requirements would lead to increased certification cost. Boeing was the first to commit to a composite fuselage and wing with the 787(Figure 1.9) launched in the first decade of the new millennium.Such extended use of composites,about 50%of the structure (combined with other advanced technologies)would give the efficiency improvement (increased range,reduced operation and maintenance costs)needed by the airline operators. Figure 1.9 Boeing 787 Dreamliner(Courtesy of Agnes Blom;see Plate 9 for the colour figure)
cost of composite structures was not attractive enough to lead to an even larger-scale (e.g. entire fuselage and/or wing structure) application of composites at that time. The Airbus A-380 (Figure 1.8) in the new millennium, was the next major application with glass/aluminum (glare) composites on the upper portion of the fuselage and glass and graphite composites in the center wing-box, floor beams, and aft pressure bulkhead. Already in the 1990s, the demand for more efficient aircraft with lower operation and maintenance costs made it clear that more usage of composites was necessary for significant reductions in weight in order to gain in fuel efficiency. In addition, improved fatigue lives and improved corrosion resistance compared with aluminum suggested that more composites on aircraft were necessary. This, despite the fact that the cost of composites was still not competitive with aluminum and the stringent certification requirements would lead to increased certification cost. Boeing was the first to commit to a composite fuselage and wing with the 787 (Figure 1.9) launched in the first decade of the new millennium. Such extended use of composites, about 50% of the structure (combined with other advanced technologies) would give the efficiency improvement (increased range, reduced operation and maintenance costs) needed by the airline operators. Figure 1.8 Airbus A-380 (Photo courtesy Bjoern Schmitt – World of Aviation.de; see Plate 8 for the colour figure) Figure 1.9 Boeing 787 Dreamliner (Courtesy of Agnes Blom; see Plate 9 for the colour figure) Applications of Advanced Composites in Aircraft Structures 5
6 Design and Analysis of Composite Structures 70 Percent of Struct Weight 60 50 B-787■ 40 ◆F-35 30 -2 Rafale AV-8B A380 20 Gripen◆ 2 19 10 A30B-T7 B-787 ◆Military F.14F.15 F.16B757 310 W0-80■A300 1970 1975 1980 1985 1990 19952000 2005 2010 2015 Year starting service Figure 1.10 Applications of composites in military and civilian aircraft structures The large number of orders(most successful launch in history)for the Boeing 787 led Airbus to start development of a competing design in the market segment covered by the 787 and the 777.This is the Airbus A-350,with all-composite fuselage and wings. Another way to see the implementation of composites in aircraft structure over time is by examining the amount of composites (by weight)used in various aircraft models as a function of time.This is shown in Figure 1.10 for some civilian and military aircraft.It should be borne in mind that the numbers shown in Figure 1.10 are approximate as they had to be inferred from open literature data and interpretation of different company announcements [1-8]. Both military and civilian aircraft applications show the same basic trends.A slow start (corresponding to the period where the behavior of composite structures is still not well understood and limited low risk applications are selected)is followed by rapid growth as experience is gained reliable analysis and design tools are developed and verified by testing, and the need for reduced weight becomes more pressing.After the rapid growth period,the applicability levels off as:(a)it becomes harder to find parts of the structure that are amenable to use of composites;(b)the cost of further composite implementation becomes prohibitive;and (c)managerial decisions and other external factors (lack of funding,changes in research emphasis,investments already made in other technologies)favor alternatives.As might be expected,composite implementation in military aircraft leads the way.The fact that in recent years civilian applications seem to have overtaken military applications does not reflect true trends as much as lack of data on the military side(e.g several military programs such as the B-2 have very large composite applications,but the actual numbers are hard to find). It is still unclear how well the composite primary structures in the most recent programs such as the Boeing 787 and the Airbus A-350 will perform and whether they will meet the design targets.In addition,several areas such as performance of composites after impact,fatigue,and damage tolerance are still the subjects of ongoing research.As our understanding in these areas improves,the development cost,which currently requires a large amount of testing to answer
The large number of orders (most successful launch in history) for the Boeing 787 led Airbus to start development of a competing design in the market segment covered by the 787 and the 777. This is the Airbus A-350, with all-composite fuselage and wings. Another way to see the implementation of composites in aircraft structure over time is by examining the amount of composites (by weight) used in various aircraft models as a function of time. This is shown in Figure 1.10 for some civilian and military aircraft. It should be borne in mind that the numbers shown in Figure 1.10 are approximate as they had to be inferred from open literature data and interpretation of different company announcements [1–8]. Both military and civilian aircraft applications show the same basic trends. A slow start (corresponding to the period where the behavior of composite structures is still not well understood and limited low risk applications are selected) is followed by rapid growth as experience is gained reliable analysis and design tools are developed and verified by testing, and the need for reduced weight becomes more pressing. After the rapid growth period, the applicability levels off as: (a) it becomes harder to find parts of the structure that are amenable to use of composites; (b) the cost of further composite implementation becomes prohibitive; and (c) managerial decisions and other external factors (lack of funding, changes in research emphasis, investments already made in other technologies) favor alternatives. As might be expected, composite implementation in military aircraft leads the way. The fact that in recent years civilian applications seem to have overtaken military applications does not reflect true trends as much as lack of data on the military side (e.g several military programs such as the B-2 have very large composite applications, but the actual numbers are hard to find). It is still unclear how well the composite primary structures in the most recent programs such as the Boeing 787 and the Airbus A-350 will perform and whether they will meet the design targets. In addition, several areas such as performance of composites after impact, fatigue, and damage tolerance are still the subjects of ongoing research. As our understanding in these areas improves, the development cost, which currently requires a large amount of testing to answer 0 10 20 30 40 50 60 70 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Year starting service Percent of Struct Weight Military F-14 F-15 F-16 Commercial F-18 AV-8B Gripen Rafale F-22 F-35 B-727 B-757 MD-80 B-767 A-300 A-310 A-320 A-330 B-777 B-787 A-380 A-350 Figure 1.10 Applications of composites in military and civilian aircraft structures 6 Design and Analysis of Composite Structures
Applications of Advanced Composites in Aircraft Structures 7 questions where analysis is prohibitively expensive and/or not as accurate as needed to reduce the amount of testing,will drop significantly.In addition,further improvements in robotics technology and integration of parts into larger co-cured structures are expected to make the fabrication cost of composites more competitive compared with metal airplanes. References 1.Jane's All the World's Aircraft 2000-2001,P.Jackson (ed.),Jane's Information Group,June 2000. 2.NetComposites News,14 December 2000. 3.Aerospace America,May 2001,pp 45-47. 4.Aerospace America,September 2005. 5.www.compositesworld.com/hpc/issues/2005/May/865. 6.www.boeing.com/news/feature/concept/background.html. 7.www.4spe.org/pub/pe/articles/2005/august/08_toensmeier.pdf. 8.Watson,J.C.and Ostrodka,D.L..AV-8B Forward Fuselage Development,Proc.5th Conf.on Fibrous Composites in Structural Design,New Orleans,LA,January 1981
questions where analysis is prohibitively expensive and/or not as accurate as needed to reduce the amount of testing, will drop significantly. In addition, further improvements in robotics technology and integration of parts into larger co-cured structures are expected to make the fabrication cost of composites more competitive compared with metal airplanes. References 1. Jane’s All the World’s Aircraft 2000–2001, P. Jackson (ed.), Jane’s Information Group, June 2000. 2. NetComposites News, 14 December 2000. 3. Aerospace America, May 2001, pp 45–47. 4. Aerospace America, September 2005. 5. www.compositesworld.com/hpc/issues/2005/May/865. 6. www.boeing.com/news/feature/concept/background.html. 7. www.4spe.org/pub/pe/articles/2005/august/08_toensmeier.pdf. 8. Watson, J.C. and Ostrodka, D.L., AV-8B Forward Fuselage Development, Proc. 5th Conf. on Fibrous Composites in Structural Design, New Orleans, LA, January 1981. Applications of Advanced Composites in Aircraft Structures 7
