CompositesWorld
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NEWS 43 CompositesWorld.com Aeris Energy, Brazil conduct nondestructive testing, assessing, in particular, bondline quality. Lolli says that about 90% of all blade failures can be traced to bond failures, so Aeris must check every bondline against design allow- ables, and then decide if remediation is required. "Rework is very expensive," Lolli notes. "Not to deliver the product is the most expensive." Workers in the finishing building also remove excess paste from the bond lines, fill in small holes in the blades, adjust and trim the root, attach an aluminum tip at the end of the blade, and sand the entire surface of each blade skin. Each blade is then transferred to a massive booth to be painted. is is the noisiest, smell- iest, dustiest, dirtiest process that Aeris performs, but it is vital to creating a blade surface that, when installed on a turbine, most optimally captures wind energy. It is in the finishing building that Lolli pauses at the tip of a finished wind blade. He points out the unique curvature of the blade as we look down its length, and he emphasizes the importance of a strong adhesive to maintain blade integrity. Our tour is joined here by Johannes Meunier, Hexion's global segment leader, wind/ composites, who is a member of a larger technical team from Hexion that has provided critical technical support to Aeris as it has developed its wind blade manu- facturing (see the Side Story, "Wind blade economics" on p. 40). Meunier points (Fig. 8, p. 41) out that the leading edge, particularly near the tip, is the part of the blade most subject to abuse in service. On a turbine with blades 56.9m long, rotating at 15 rpm, tip speed is 200 mph/322 kmh. Even half way along that blade, rotational speed is 100 mph/161 kmh. at leading edge, there- fore, is being impacted at high speeds and quickly eroded by dust, insects, hail and a variety of other materials. Protection against that erosion is a massive challenge for any wind blade manufacturer, Meunier says. And it's a problem not yet solved. Vestas operations Notably, Aeris Energy's facility is the second in the world at which Vestas allows its blades to be manufactured by a non- Vestas entity. In fact, the wind turbine DeWAL's pressure-sensitive PTFE tapes and films are known for tightly sealing carbon-fiber composites and cleanly releasing parts from molds. Use them to separate epoxy resins from laminates or to seal vacuum bags up to 500°F. DeWAL PTFE tapes and films offer minimal elongation and temperature-resistant silicone-based adhesion. UL-recognized 204-HD films are both skived and tensilized for higher tensile strength, lower elongation and higher dielectric strength. 204-HD films range from 0.5 to 21.5 inches wide and are as long as 108 feet, with tensile strength up to 13,000 psi at 500°F. They are in stock in 2, 3 and 5 mil thicknesses, as are other 36" width DeWAL tapes and films for composites. Whether you are doing open or closed molding, whether your process is lay-up, compression molding, resin transfer or continuous lamination, DeWAL will share a solution with you. 15 Ray Trainor Drive Narragansett, RI 02882 www.dewal.com usa1@dewal.com 800-366-8356 (International: 001-401-789-9736) Quality of Product...First DeWAL PTFE Tapes & Films — for tighter vacuum seals and cleaner mold separation. Used as an alternative to sanding and painting Used as peel-ply on molds Used between a mold and a carbon-fiber composite DW 134 DW 204-HD DW 202 & DW 2000 manufacturer is famous for the stringent control is exerts over its manufacturing operations. us, Aeris must make Vestas blades to the same exacting standards Vestas maintains in its internal operations. All Vestas operations — cutting, kitting, molding, assembly, finishing — are confined to one building. And there, everything is done to the Vestas spec, as if it were done by Vestas itself. To accomplish this, Aeris sent teams of employees, for weeks at a time, to the Vestas blade manufacturing facility in Windsor, CO, US, where they learned Vestas production standards and practices. In addition, Vestas placed in the Aeris plant two employees of its own to oversee operations. Cutting and kitting, as with non-Vestas blades, is done on another large Eastman Machine cutting table.