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Issue link: https://ct.epubxp.com/i/178128
CompositE aDVantagE's uniVErsal CamEl for u.s. naVy submarinE bErths Rope ties Wing wall EXPLODED VIEW Deck • Must withstand lifting mass in excess of 45 metric tonnes (100,000 lb) • Must withstand berthing submarine velocity of 0.4 ft/sec (0.12m/sec) or ~200 ft-kip of energy FRONT VIEW Upper box 25 ft/76m 11.5 ft/3.5m Rubber fenders Wing wall Wing wall Lower box Wing wall 9 ft/2.7m Front module TOP VIEW Front module w/ fenders Illustration | Karl Reque DEsign solution: Design a composite camel that meets the U.S. Navy's requirements for energy absorption, stability and long service life and can berth submarines of all classes. A modular composite sandwich construction that allows camel ballast to be customized to meet trim and freeboard requirements while absorbing the energy of berthing submarines. densities, can vary and must be considered to establish precise fotation calculations." Working with CA, WR&A; developed a design that comprises fve composite structures, or modules, that are assembled on site to build the 25 f by 9 f by 11.5 f (7.6m by 2.7m by 3.5m) camel. CA president Scott Reeve says the two largest modules, the upper and lower main boxes, are stacked (see photos). Two others, called wing walls, are installed on each side of the stack, and a third module is front mounted to provide the surface that faces the submarine. Attached to this front surface are the rubber fenders that contact the submarine. On the backside of the camel, a series of ultrahigh molecular weight polyethylene rubbing strips provide a contact surface where the camel meets the fxed dock structure. Te modules are made by assembling and bonding composite panels. Most panels have a sandwich construction, featuring 3.5-inch/89-mm thick TYCOR foam core (Milliken & Co., Spartanburg, S.C.) faced and edged with 0.3-inch/7.62-mm thick layers of uniaxial and triaxial glass fber fabric from V2 Composites (Auburn, Ala.). Tis structure is hand layed, vacuum bagged and infused with Hetron 992 or Derakane 610 vinyl ester resin, supplied by Ashland Performance Materials (Dublin, Ohio). Te foam core incorporates fberglass shear webs, spaced at 1.5 inch/38.1 mm intervals. Where the panels are subjected to biaxial bending or signifcant shear forces, a bidirectional core is used. Tis consists of unidirectional core that is cut into short lengths (perpendicular to the shear webs) and wrapped in additional fberglass fabric, thus providing shear webs in both directions. Reeve says some of the camel's primary contact points — those that see the most physical and mechanical stress — are designed for impact resistance as 1.5-inch/38.1-mm thick solid laminates. Each module and, later, the entire camel structure, is bonded together with an adhesive provided by SCIGRIP (Durham, N.C.). Structural analysis of the camel included a 3-D fnite element analysis (FEA) of the entire structure, using RISA-3D FEA modeling sofware developed by RISA Technologies (Foothill Ranch, Calif.). Te model consisted primarily of a series of meshed plate CT oCTober 2013 EnginEEring ChallEngE: 47