CompositesWorld
Issue link: https://cw.epubxp.com/i/630867
FEBRUARY 2016 2 CompositesWorld OOA vacuum-bag-only process makes carbon fiber structures a reality for a unique personal jet. VBO prepregs: The Vision SF50 » Cirrus Aircraft's (Duluth, MN, US) Vision SF50, when it enters the market in 2016, will be the newest entrant in general aviation's personal jet segment. Tis fve-plus passenger, single-engine, V-tailed aircraft is 9.4m long, has a wingspan of 11.7m, a maximum takeof weight of 2,722 kg and features a maximum cruise speed of 300 KTAS. Te piggyback- mounted Williams International engine ofers 1,800 lb of thrust and helps put jet-aircraft performance within reach of private fying enthusiasts. Te SF50 airframe features 350 parts — including stabilizer, fuselage and wing structure — manufac- tured primarily using carbon fber composites fabri- cated with out-of-autoclave (OOA) processes that help make this craft mechanically robust and durable. Tony Snyder, engineering manager of manufac- turing operations at Cirrus, says the company chose OOA for the SF50 after it was successfully used to make structures for its SR2X series of piston and propeller-based single-engine personal aircraft. Snyder says of the decision to use OOA processes, "Te capital avoidance savings are signifcant, as well as the reduction in operational costs." High on the list of the latter is the cost of autoclave nitrogen consumption. Te material used in the SF50 is TC275, a carbon fber/epoxy prepreg supplied by TenCate Advanced Composites (Morgan Hill, CA, US). It is hand-layed and ranges in thicknesses from 1 mm to 127 mm. Parts are vacuum bagged and then cured in an oven at 135°C for about 10 hours. Ticker parts are run through an additional debulking cycle as well. Ovens are supplied by Gehnrich (now Wisconsin Oven, E. Troy, WI, US) and Rapid Engineering (Comstock Park, MI, US). Cirrus has done a great deal of process devel- opment in order to optimize OOA operations for the myriad parts made, says Eric Olson, materials engineer for airframe engineering. Tis included development of cure profles specifc to part size, tool type and part geometry, which built fexibility into the system. "Lots of investigation was done to better understand how resin was fowing within the fber bed during cure," he says. "Tis included fow- indicating layers on test parts, image analysis, micro CT and DOEs [designs of experiments]. Much of the trial-and-error work was aimed at quantifcation of the variables impacting laminate quality and getting a better understanding of resin fow." Post-mold fnishing, routing and drilling is performed using the company's 5-axis CNC machine supplied by Diversifed Machining Systems (Colorado Springs, CO, US). Te fuselage, as the photos show, is fabricated in sections and then assembled via bonding and fasteners. Bonding is done with Huntsman Advanced Materials' (Te Woodlands, TX, US) Epibond two-part structural adhesive. Many fnished parts are assessed via nondestruc- tive testing (NDT) using ultrasonic pulse/echo VBO prepreg payoff This fve-plus passenger, single-engine, V-tailed personal jet will sport an OOA-composites-enabled low maximum takeof weight of 2,722 kg. Source (all photos) | Cirrus Aircraft By Jef Sloan / Editor-in-Chief OUT OF AUTOCLAVE SUPPLEMENT