The results of a recent design study indicate that layup of glass-fiber prepregs, rather than infusion of dry glass reinforcements, is a more cost-effective and weight-efficient process for fabrication of spar caps, the major load-bearing structures in composite wind turbine blades. Conducted by composite materials supplier Hexcel (Dublin, Calif.) and wind turbine manufacturer aerodyn Energiesysteme GmbH (Rendsburg, Germany), the study focused on the aerodyn 50.3m/165-ft 2.5 MW Windclass III blade design. The blade was selected because it is already commercialized and in use on operating turbines. Aerodyn was selected as the trial partner, says Hexcel, based on its successful track record as a turbine manufacturer with units in service on all five continents.
Hexcel’s trademarked HexPly M9.6F/32 percent/1600+50/G+F prepreg was selected for the comparative trials. The 1600 g/m² unidirectional glass material uses 2400 tex E-glass filament rovings and contains a 50 g/m² glass fleece to support the evacuation of air during cure of the layup. Following a number of tests conducted by IMA Dresden GmbH, an accredited independent testing laboratory based in Dresden, Germany, the aerodyn study concluded that replacing a resin-infused glass-fiber spar cap with a unidirectional glass prepreg design results in a weight reduction of approximately 400 kg/880 lb in spar structures, or 3 to 4 percent of the total blade weight, due primarily to the greater strength and stiffness that the prepregs provide in both tensile and compression modes. The use of prepreg in place of infused reinforcements, therefore, could save in the neighborhood of €1,300/$1,700 (USD) per blade, based on predicted reductions in the cost of materials and labor. Learn more about the study by contacting Hexcel’s Manfred Schoeflinger; E-mail: firstname.lastname@example.org.