CompositesWorld
Issue link: https://cw.epubxp.com/i/742140
47 CompositesWorld.com Although the fiber architecture details are proprietary, ±45° biaxial noncrimp glass fabrics from Vectorply (Phenix City, AL, US) were selected for the skins, because they would best handle the shear loads over the dome's cored field regions, a conclu- sion confirmed by the FE model. "Because this simulator would operate in the basement of a hospital building, it had to meet building fire codes," DiEdwardo adds, particularly to avoid fire spread to upper floors. erefore, Airex foam core material, 13-19 mm thick and supplied by 3A Composites Core Materials (Colfax, NC, US), was chosen for its fire-retardant properties. AOC's (Collierville, TN, US) Firepel polyester infusion resin, also was selected, in part, for its fire-resistance properties. DiEdwardo reports that early manufacturing discussions with Design Concepts focused on keeping costs down through open mold/hand layup. But as the design matured, it became apparent that the weight budget would be tough to meet by that route. Design Concepts suggested that vacuum-infusing the parts, which typically costs more than hand layup, would better control resin volume and, therefore, part weight. To keep infusion costs as low as possible, Design Concepts CNC-machined the molds for each segment from expanded polystyrene (EPS) foam. e shaped EPS was sheathed with fiber- glass and resin, then overlaid with syntactic, which was machined to the final dimensions of the dome's inside surface. Given the small part count, the low-cost foam molds saved time and cost but posed the potential for lack of vacuum integrity during infusion. at problem was solved with Diamondback tooling gel coat from Polycryl (Oakland, TN, US). For the production parts, Hawkeye Industries' (Bloomington, CA, US) Duratech vinyl ester in-mold primer was applied over the prepped mold surfaces prior to dry layup, to enable cured parts to be painted with fire-resistant paint. Before final parts were fabricated, PEI and Design Concepts infused test panels using the selected materials and performed coupon-level B-basis tension, compression and shear strength tests in accordance with ASTM International (W. Conshohocken, PA, US) methods. Says DiEdwardo, "Stresses determined using the FE model were compared to the test allowables to ensure we would get the performance we needed from the structure." One of the project's biggest challenges was the door and door frame design, says DiEdwardo. "It's tough when designing simula- tors to replace the lost stiffness when you have to cut an aperture in the structure," he explains. e door frame was designed around existing hard points on the motion platform, and includes an additional aluminum frame, mechanically attached to the dome segment via post-bonded flat FRP panels (see drawing, p. 61). e composite door itself was hand-fitted to the frame by Design Concepts' technicians, to ensure the seal was light-tight for best projection performance, and the frame serves as a stiffening element to help keep the door alignment consistent. A unique product "e FRP weight ended up being 1,000 kg, including ventilation ducting," DiEdwardo reports, "so we met the weight requirements without issue and also used cost-effective materials to meet the cost budget." e dome also successfully completed factory accep- tance testing by IDT and TRI-UHN prior to installation. And the fully outfitted DriverLab was finally lowered through floor grates in front of the TRI-UHN hospital into CEAL's underground research facility in August of this year. PEI is hopeful that the success of DriverLab will open up new opportunities for more driving simulators. Driving Simulator Dome Fig. 3 Focus on interior surface optics Strict optical requirements outlined by simulation engineering firm International Development of Technology BV (Breda, The Netherlands) governed the design of the dome's interior (tool-side) surface, which functions as the image projection surface. The projectors are visible, here, mounted to the inside of the dome's cap. Sara Black is CW's technical editor and has served on the CW staff for 19 years. sara@compositesworld.com ABOUT THE AUTHORS CW senior editor Ginger Gardiner has an engineering/materials background and has more than 20 years in the composites industry. ginger@compositesworld.com