Nano-enhanced matrix resin for CF wind blade spars

3M’s resurgence in the composite market was recently underscored by the release of 3M Matrix Resin 3381, a high-performance, nanoparticle-enhanced epoxy designed for use in carbon-fiber composites.

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3M’s (St. Paul, Minn.) resurgence in the composite market was recently underscored by the release of 3M Matrix Resin 3381, a high-performance, nanoparticle-enhanced epoxy designed for use in carbon-fiber composites. Compatible with prepreg processes, the resin, according to the company, has a unique chemistry that, in combination with a proprietary nano-granule additive, makes it possible for 3M formulators to avoid the traditional tradeoff between toughness/flexibility and stiffness/hardness; instead, the resin improves performance properties on both ends of the scale. Although slightly more dense than standard epoxies (1.48 g/cm² vs. 1.25 g/cm² in ASTM D792 testing), the resin reduces linear shrinkage (0.58 percent vs. 1 percent for standard epoxy), yet it increases fracture toughness by almost 50 percent with a Barcol hardness of 67, compared to 59 for standard epoxy. Moreover, the filler helps reduce the coefficient of thermal expansion (44.6 µm/m per °C vs. 59.5 µm/m per °C for standard epoxy). First applied in carbon composite fishing rods because of its effect on rod compression strength (rod owners report unprecedented flexural strength and resistance to breakage), the resin is set for commercialization in construction of carbon fiber-reinforced spar caps for wind turbine blades. Because spars on long wind blades necessarily involve thick laminates, the resin also provides the added benefit of reducing exotherm during cure by up to 40 percent. The resin cures at temperatures from 250°F to 300°F (121°C to 149°C), depending on the service requirements. The recommended cure cycle involves a vacuum at a minimum of 22 inches/Hg (85 psi/5.86 bar), a ramp to 260°F/127°C at 10°F (±5°F) per minute, followed by a two-hour hold at 260°F.

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