CompositesWorld
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NEWS CompositesWorld.com 33 Carbon/Glass Spar Cap Design drivers for new products: uncertainties and risk Next, the design was driven by LM's uncertainty management strategy. "is approach tackles the highest uncertainties first — the worst failures that can be conceived," explains Lund-Laverick. It starts with LM's failure modes effects analyses (FMEAs). An FMEA is a formal analysis tool for evaluating the risk for a design (dFMEA) or a process (pFMEA). is consists, first, of engineers verbally brainstorming possible risks before turning to computer assistance. "In this way, we manage new projects by managing their risks, relying on the company's deep engineering knowledge, experience and communication to define the key showstoppers. Our engineers think about all the doom-and-gloom things that could possibly happen, and then think of tests and engineered solutions to ensure those things do not happen," Lund-Laverick explains. e discoveries of these FMEA sessions determine what real tests and trials need to be conducted — actual sample parts are made and tested to verify design limits and failure modes before computer modeling and analysis begins. "e computer models are then based on a kind of reality," Lund-Laverick says, instead of preliminary theory — no matter how astute that theory may be. After wind class, design limits and failure modes were estab- lished, engineers used LM Blades, the company's suite of design programs and 3D modeling software, to bring the big blade within established limits for static and dynamic fatigue load Markov Matrices (for variations over time); buckling of the large aero panels; Puck fracture criteria for strength of unidirectional fiber/ matrix (Alfred Puck, Immenhausen, Germany); and other mechan- ical/strength and chemical/environmental requirements. Hybrid carbon/glass fiber, the best of both worlds LM's hybrid technology consists of the company's standard glass fiber/polyester base shell laminate strengthened by a hybrid carbon/glass fiber main spar cap. Glass fabrics for the shell are woven to LM's specifications by a variety of glass and fabric suppliers, typically including H-glass fiber, supplied by Owens Corning (Toledo, OH, US). e shell laminate is a structural sandwich with a balsa wood core, infused with LM's standard polyester resin. Model Length (m) Rotor dia(m) Swept area (m 2 ) Blade mass (MT) Bolt circle dia. (m) Maximum Chord (m) Projected Blade area (m 2 ) Nominal power output (MW) LM88.4 P 88.4 181 25,734 34 4.2 5.9 333 8 LM73.5 P 73.5 151 17,910 28 3.2 4.2 188 6 Percentage Difference 120% 120% 144% 121% 131% 140% 177% 133% IEC Wind Classes I (High Wind) II (Medium Wind) III (Low Wind) IV (Very Low Wind) Reference Wind Speed (max.) 50 m/s 42.5 m/s 37.5 m/s 30 m/s Annual Average Wind Speed (max.) 10 m/s 8.5 m/s 7.5 m/s 6 m/s 50-year Return Gust 70m/s 59.5 m/s 52.5 m/s 42 m/s 1-year Return Gust 52.5 m/s 44.6 m/s 39.4 m/s 31.5 m/s On April 20, 2017, General Electric announced final acquisition of Kolding, Denmark-based LM Wind Power. Although LM will continue to operate as an independent blade manufacturer, Jérôme Pécresse, president and CEO of GE Renewable Energy (Fairfield, CT, US), says, "The completion of the LM Wind Power acquisition provides us with the operational efficiencies necessary to support the growth of our wind turbine business, which is the fastest growing segment of power generation. With LM's technology and blade engineering, we are now able to improve the overall performance of our wind turbines, lowering the cost of electricity and increasing the value for our customers. Together, we are set to capitalize on the expansion of renewable energy and be a growth engine for GE." To date, GE has installed more than 30,000 wind turbines worldwide, using blades supplied by LM and other blade manufacturers. LM Wind Power now part of General Electric SIDE STORY FIG. 3 IEC Wind Classes LM built the LM 88.4 P blades for Wind Class 1, according to the class system estab- lished by the International Electrotechnical Commission (IEC, Geneva, Switzerland). FIG. 2 Blade comparison Statistics comparison, LM 73.5 P (glass/polyester construction) with LM 88.4 P (featuring the hybrid carbon spar), for IEC Wind Class 1.