CompositesWorld
Issue link: https://cw.epubxp.com/i/930524
FEBRUARY 2018 34 CompositesWorld WORK IN PROGRESS and a downwind (lower) half — which are mated after cure. Each blade half carries a hybrid spar cap. e manufacturing strategy for the hybrid carbon development consists of a two-stage infusion process, based on VARTM: In the first stage, the shell, which includes all elements of the blade except the spar cap, is built up in the following sequence: • Gel coat applied to 88.4m mold (Fig. 4, above). • External biaxial fiberglass shell coverage layers are arranged. • Root and edge reinforcements are applied, primarily UD materials. • Balsa core is positioned in place for sandwich panel construction and retained with small fasteners (Fig. 5, above). • Internal biaxial layers are added (Fig. 6, above). • Vacuum bag is attached and standard LM poly- ester resin is infused via VARTM process. For the spar cap, uniaxial carbon/H-glass hybrid fabric is manu- factured by Devold AMT AS (Langevaag, Norway), a subsidiary of SAERTEX GmbH & Co. KG (Saerbeck, Germany), which received LM's Most Innovative Partner 2017 award for this fabric. Fiber architecture for both the base shell and the spar cap consists of a mixture of ±45° biaxial fabric, 0°, ±45° combination fabrics, and 0° unidirectional (UD) fabrics in differing areal weights. Devel- oped with the LM team, this fabric was used for the first time in the 88.4m blade, infused with an unidentified, but proven LM resin to achieve target blade properties. e proprietary resin system used for spar cap infusion is based on the chemical backbone of other systems that have shown excellent chemical attachment and adhesion to the polyester resin used in the shell structure, Lund- Laverick says. Hybrid carbon manufacturing strategy e blade is constructed in two halves — an upwind (upper) half FIG. 4 In-mold finishing Workers spray gel coat onto mold in preparation for fiberglass base shell layup, eliminating the need for a post-mold painting step. FIG. 5 Core placement The balsa core is fixed in place by workers. FIG. 6 Dry fabric layup A semi-automated machine lays lengths of dry fabric along flat center of the mold. The hybrid carbon layup is shown in this photo.