CompositesWorld
Issue link: https://cw.epubxp.com/i/841219
NEWS CompositesWorld.com 33 that can help reduce blade production cycle times while also cutting nonconformance costs due to irregular wet out of larger blades," says Shreve. "It's all about lowering the levelized cost of energy [LCOE]," Klausen contends. "If we can make blades 10-15% cheaper to produce while decreasing their weight and enabling them to perform well at increasingly longer lengths, then we can drop LCOE even further." Early promise, long development In 2009, Covestro, then Bayer MaterialScience (Leverkusen, Germany), received a grant from the US Department of Energy (DoE) to research PU composites for use in wind turbine blades. Researcher Marcio Loos at Case Western Reserve University (Cleveland, OH, US) investigated the processing and proper- ties of a 0.74m-long wind blade made using infusion, glass fiber fabrics and PU resin. In 2011, Loos reported that the PU composite bested glass fiber/epoxy, lasting eight times longer in fatigue testing and showing a fracture toughness roughly eight times higher in delamination tests. Further, fracture growth rates were shown to be a fraction of those for epoxy and vinyl ester composites. e following list of additional ways PU bests epoxy were compiled in a 2012 presentation by Loos' co-researcher Usama Younes at Sandia National Laboratories (Albuquerque, NM, US), based on multiple investigations of PU with glass and carbon fiber, including resin infusion molding of a thick, glass/PU root ring for a 42m long wind blade: • 34% less time required for infusion of thick (50-ply) laminates. • >17% greater tensile strength. • Almost double the interlaminar fracture toughness. • 30% lower stress crack growth rate. • Better adhesion to glass fiber. at same year, Bayer announced it would establish a global wind energy competence and development center in Otterup, Denmark. e facility would go on to spearhead and coordi- nate global development of Covestro's advanced materials for wind energy applications (after the name change in 2015) under Klausen's leadership, then managing director of Bayer Materi- alScience A/S, Denmark. Although the idea to use polyurethane as an infusion resin originated in the US, Klausen notes that today, develop- ment and optimization of the PU resin chemistry are being performed cooperatively by Covestro's Polymer Research PU-infused Wind Blades FIG. 1 PU blade an industry first Covestro recently built the first polyurethane (PU) composite wind turbine blade in Asia (seen here, in process), a 37.5m long resin-infused blade designed for a 1.5-MW turbine installed in China. Source | Covestro