CompositesWorld
Issue link: https://cw.epubxp.com/i/697353
JULY 2016 24 CompositesWorld WORK IN PROGRESS 2.1 mm. Blanks were placed between two plates in a press shuttle equipped with infrared lamps, heated to 400°C (with thermocouple control) then quickly shuttled into the press for a 5-minute forming cycle. Omega-shaped (or hat-shaped) stringers were chosen to simulate typical fuselage structure; T-shaped stifeners also were formed, but in an autoclave process. Troubleshooting the methodology "Te manufacturing of the stringers using the thermoforming press involved solving several issues, including working temperature, time, heating rate, transfer time when the laminate is melted and the cooling rate," Rodriguez explains. Te legacy AS4/APC2 thermo- plastic prepreg material, required by Airbus for the project, presented some challenges, including variations in fber wetout and tape thick- ness. To achieve very low void content with the in-situ methods used in the project, he explains, the tape must have a uniform fber/resin distribution. (Going forward, more tapes, impregnated with PEKK and PAEK polymers, from a proprietary list of suppliers, will be tested as part of the current OUTCOME project.) FIDAMC developed a custom, internally heated steel layup tool, 800 mm by 600 mm, consisting of a fat table-like surface with a 10-mm deep, 100-mm wide and 800-mm long central longitudinal countersunk "valley" or recess, and underlying support structure. Into the recess, a formed carbon fber/PEEK stringer could be placed upside-down, with its fat fanges positioned fush with the fat tool surface. Says Rodriguez, "Te tooling allows us to place a consolidated thermoplastic within the hollow, and lay up the skin above it with the automated machine." Te thermoplastic skin would be deposited by the laser-heated head in a quasi-isotropic layup sequence at the same nominal thickness as the stringers. Initially, however, this, too, posed challenges: Because the PEEK material has no tack, it would not adhere to the tool. "We had to add a vacuum system to the layup tool, to help hold the frst ply down," explains Rodriguez. "Ten the Anticipating fuselage panels In addition to fat demonstrators, curved test panels also were produced. Source | FIDAMC Tool recesses accommodate stringers for co-molding The ISINTHER project produced a heated, modular layup tool that can accommodate several stringer shapes. Holes for the vacuum system are visible, and the recesses or "valleys" into which the prepared stringers are placed are shown here, covered with the tooling blocks that ft inside the stringers to create a fat layup surface. In the inset photo (right), note how the block fts inside the fnished stringer. Source (both photos) | FIDAMC