CompositesWorld
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49 CompositesWorld.com NEWS N E W S N S N E W S E N W S W SHM Update CW senior editor Ginger Gardiner has an engineering/materials background and has more than 20 years of experience in the composites industry. ginger@compositesworld.com Airbus has developed what it terms an "SHM Toolbox" of at least 14 pre-developed technologies for generic applications. "We then work with developers and operators to mature these tools for specifc applications on an aircraft," says Bockenheimer. "Not all of the technologies are ready to be implemented," Speckmann concedes, "but some should reach technology readi- ness within the next 5 years." He cautions that for a technology to be used in commercial service, the technology readiness level (TRL) "is for a specifc SHM tool coupled with a specifc aircraft application." When an SHM technology is applied to a diferent component or vice versa, the TRL must be reassessed. He also warns that companies will say their technology has reached TRL 7 — indicating it has fown on an aircraft — without having yet completed all of the testing required for TRL 4, TRL 5 and TRL 6. Speckmann reports that there are fve to seven diferent tech- nologies in Airbus' SHM Toolbox that apply to composites, and it should be possible to move them from TRL 3 to TRL 6 within 2-5 years, depending on the type of application. "Tis will go faster if you have the money to do a lot of tests concurrently," he suggests, adding that time for testing also will decrease with computer modelling and simulation — like that now used to improve and automate NDT. Trough the envisaged SHM V&V; Center, Airbus MP&T; will defne the maturation required for a given SHM technology and application. Ten, TESTIA will work with the V&V; Center, subcon- tracted in a way, to present SHM maturation and testing require- ments to the technology companies, system integrators and OEM, organize the testing program and then help to perform these tests. Today, TESTIA is providing NDT services and training NDT personnel for a wide range of OEMs, airline operators and parts manufacturers. "SHM will automate NDT on the aircraft," notes Speckmann, "so we will be installing the systems when the SHM solution has been accepted by the individual Airbus aircraft programs." Established in 2013 to support SHM implementation, TESTIA also will develop installation procedures and train installation personnel. Finally, smart structures Te ultimate benefts of SHM are anticipated when sensors can be incorporated during manufacture to achieve the long-envisioned smart structures (see Fig. 3, p. 48). "Our SMART Layer materials were developed to be co-cured into a composite structure," says Acellent's Kumar. She notes that Acellent's SHM system is now capable of performing all four of the necessary functions required for oversight of composite structures: 1) Damage detection (is there damage?) 2) Localization (where is the damage?) 3) Quantifcation (how much damage?) 4) Characterization (what type of damage? — delamination, honeycomb damage, fber breakage, etc.) At SMS, much of its early SHM development work also was in composites. As an alternative to embedding sensor pads, SMS learned the composite itself can be molded or laser-machined to form the sensor galleries and then covered with a thin Tefon manifold. Chilcott recalls, "We did a lot of testing to make sure integration of the CVM sensors did not afect the composites' properties. Te results were so positive, it generated a great deal of interest in our technology." Also capable of reading strain, CVM sensors reportedly can detect a 0.00254 mm crack. "Tey are easily integrated into a CFRP stringer or door and detect when there is a disbond or delamination." Airbus also is developing small-diameter (50-125 μm) fber- optic sensors that can be embedded into CFRP structures during manufacture. Tey reportedly can measure temperature and stress felds during cure, residual stress build-up during assembly, and in the fnal structures, they can monitor impact damage and structural loads, helping to further weight-optimize designs. Bockenheimer cites SHM as a key to achieving the best aircraft operability and revolutionary structural design, but acknowledges much work remains. "Many subsequent tests are required to prove durability," he says. "We want to defne new tests which combine chemical, temperature and mechanical loadings, for example, to reduce cost and time." Speckmann notes the formation of an OEM group within the SHM-AISC at its most recent meeting in April, which will initially include Boeing, Airbus, Sikorsky (Stratford, CT, US), Bombardier and Embraer (São José dos Campos, Brazil). It will begin iden- tifying ways to work cooperatively on maturation of systems for commercial aircraft. "We are already doing this independently," says Speckmann, "but there is too much work to be done yet for it to be duplicated." Te ultimate goal, he says, "is to speed up maturation of SHM technology worldwide, so that all OEMs and operators can start to take advantage of its benefts." Read this article online | short.compositesworld.com/SHMupdate Read CW's previous coverage of this subject online in "Structural Health Monitoring: Composites get smart" | short.compositesworld.com/SHMsmart Read about design and fabrication of CVM and SMART Layer systems in CW's online sidebar, "Designing SHM systems" | short.compositesworld.com/SHMdesign