CompositesWorld
Issue link: https://cw.epubxp.com/i/450689
FEBRUARY 2015 36 CompositesWorld INSIDE MANUFACTURING Doudican explains the unis were used on the box beam's top and bottom, formed by the 6-mm thick C-channels, while the 2-mm thick side plates were shear-driven, and so used the 12K twill. He notes, "All of the parts used plain weave on the outer surfaces to enable good bonded joints and fnish coating. Unfortunately, we had to paint it with intumescent paint, so you couldn't see the carbon fber surfaces." For the resin, the team chose its own No Oven, No Autoclave (NONA) RT-177 two-part epoxy, says Dietsch, "because we had a a rudimentary design using standard-modulus CF to see if it would even work," says Doudican. Because the two weeks prior to getting the contract had been spent analyzing all available of-the-shelf tooling and fabrication materials options, the team was able to place orders on day one with suppliers Composites One (Arlington Heights, IL, US) and North American Composites (Hampton, NH, US). "We ended up with a mix of plain-weave carbon fabric, a 12K 2x2 twill and a 24K 630-g/m 2 unidirectional broadgood — all standard modulus," he says. 1 Tooling for beam sections was machined from high-temperature polyurethane foam backed by wood substructures. All 14 tools for the beam sections were completed in one week. 2 Beam manufacturing required two teams working simultaneously. The frst performed layup of dry reinforcements. The shear-driven side plates used a 12K 2x2 twill carbon fabric while C-channels featured 24K unidirectional reinforcements. Both used plain-weave carbon fber fabric on outer surfaces. 3 A second team, working in parallel with the layup crew, bagged and infused completed layups for as many as four parts at one time. C-channels (shown here) and sidewall plates were infused with NONA RT-177 epoxy resin in 35-40 minutes. Overlapping Steps 2 and 3 saved signifcant time in processing. 4 Here, infused parts cure inside insulated boxes, custom-built from readily available hardware-store foam and fberglass insulation, to contain the heat generated during resin exotherm. The NONA-developed epoxy infusion resin reached peak exotherm in about two hours and required no additional heat source. Cool-down took another four hours. All laminated parts were completed in two weeks.