CompositesWorld
Issue link: https://cw.epubxp.com/i/620463
CompositesWorld.com 27 NEWS N E W S N S N E W S E N W S W Composite Spiral Staircase 6 Following wedge installation, technicians put the spiral spar in a rotisserie fxture that faciltiated application of the fnal visual carbon fabric plies to the spiral spar and, after cure, application of a clearcoat. 7 Stair units were assembled and bonded, one by one, onto the wedges. Note the molded-in grooves at inner and outer edges. designed to receive the glass balustrades. same Gurit low-temperature-cure epoxy resin. Ten the spar layup was re-bagged and put through another 6-hour cure. Te wedges were positioned on the spar using the central MDF fxture and bonded in place with PRO-SET 176/276 structural epoxy adhesive (Step 5, p. 26). Each marked where a stair would be located. Its position was checked, using lasers, against the compass rose and plumb baseplate. At this point, the staircase resem- bled a tall corkscrew with sawteeth. Te center scafold and halo fxturing were disassembled and the stairway was mounted into a rotisserie fxture made from steel boxstock (Step 6, p. 27), which enabled easy rotation of the structure as the spar surface was faired (made smooth) with epoxy fller and then received two fnal plies of 200-g/m 2 2x2 twill CF prepreg to provide the visual carbon surface. "We actually turned the whole stairs upside down to make it easy to apply the cosmetic layer and get the fber orientation right for the aesthetic appearance," says Dunham. Envelope bagging and cure in the temporary oven were repeated, followed by a fnal 6-hour post-cure at 90°C. After demolding, multiple layers of high-gloss clearcoat were applied. Finishing steps Te spar with wedges was again repositioned, vertically (right side up), and ftted with another central MDF fxture, but this one was narrower to accommodate location and placement of the 91-cm-wide stairs. Each stair unit had been molded with a groove at both inner and outer edges to eventually receive the glass balustrades (see opening image, p. 24) upon installation in the residence (Step 7, p. 27). Finally, 19 stair units and one Fig. 2 On to the next step(s) The completed CFRP staircase structure was transported, mounted in the rotisserie fxture used in Step 6, to a subcontractor's facility, where it was ftted with white oak veneers (above) on step surfaces before transporta- tion to the residential installation site. Final instal- lation was scheduled at the customer's residence (as CW went to press) for January. Source | Charlie Lovely