My colleague Ming Zhou has contributed the following post:
At the recent COMAC Composite Forum in Shanghai, we heard a good deal about the Commercial Aircraft Corporation of China’s use of composites in the C919, the company’s first product, a single-aisle plane designed to compete with the A320 and B737 later in the decade.
According to a presentation by Dr. Zhou, deputy chief designer for COMAC responsible for structures, composite usage on the C919 is around 20 percent. This is significantly higher than the composite percentage on other airliners in this category, like the A320 and B737; however, it is much lower than that of new wide-body programs from Boeing and Airbus, specifically the B787 and A350XWB, which are essentially full-composite airframes. The higher level of composite usage should make the C919 competitive against the newly launched, re-engined A320Neo and B737MAX programs, with aircraft due for delivery in 2016 and 2017, respectively. First flight and delivery of the C919 – which has a payload and dimensions very similar to those of the A320, with a base capacity of 168 seats – are scheduled for 2014 and 2016, respectively.
Several speakers at the event emphasized the design challenges that engineers experience with composite structures. In a presentation on durability assessment of composite structures, Dr. Yang, deputy director of the COMAC Composite Structure Manufacturing Center emphasized the difference in fatigue behavior between metal and composite airframes and noted that composite structures are designed to operate in a stress range below infinite life. Therefore, damage in the material, sustained during operation, is the most dominant factor for durability assessment.
My own presentation focused on advanced simulation and design optimization for composites. First, I addressed advanced FEA simulation for damage assessment caused by various impact events (bird, debris, hail, ditching etc.). The second portion focused on the challenges that come with increased design freedom, where material (laminate properties) design becomes an integrated part of structural design. This additional design freedom brings unmatched design potential, since the laminate material properties can be tailored almost continuously throughout the structure. However, it also brings new challenges for design engineers. It is a very different process from – and much more complex than – engineering a structure for a pre-defined material. Details of my presentation can be found in the Altair HyperWorks Resource Library.
Altair has developed a comprehensive optimization process in OptiStruct that leads the design from concept to plybook details. This technology has been quickly adopted by Airbus, Boeing and Bombardier in new airliner programs. Recently, COMAC rapidly expanded optimization applications on the C919 program with help from engineers of Altair China. Discussions during the event also have led to the possibility of COMAC starting a pilot project with Altair China to apply OptiStruct composite optimization technology.