Researchers at Colorado State University and University of Denver have developed a polyurea-coated polymer-matrix-composite panel for impact protection of critical power grid assets, especially large power transformer (LPT) tanks. In simulations, adding a 3 mm polyurea coating to selected 10.8 mm composite laminates, arrested a 400 m/s steel projectile while reducing required thickness, mass, and cost relative to comparable uncoated designs. The technology is especially attractive where utilities need lighter protective structures than conventional steel-based solutions.
Large power transformers are critical grid assets, and prior incidents of vandalism have increased interest in impact-resistant protection. Conventional LPT tanks are typically built from about 10 mm mild steel, but prior cited studies show that steel plates in this thickness range can remain vulnerable to high-energy projectile attack. Polymer matrix composites (PMCs) offer a lightweight structural alternative, but uncoated composite panels can require substantially greater thickness to stop a projectile. This technology adds a polyurea coating to the composite structure to improve impact resistance without simply making the panel much thicker.
Researchers used validated finite-element models to evaluate carbon-fiber-reinforced polymer (CFRP), glass-fiber-reinforced polymer (GFRP), and hybrid CFRP/GFRP laminates, with and without a polyurea (PU) coating, under impact from a 4340 steel projectile traveling at 400 m/s. Before running the design comparisons, the composite model was checked against a published ballistic experiment to confirm the model gave a conservative but reasonable prediction of impact response.
For the uncoated baseline, 10.8 mm CFRP, 10.8 mm GFRP, and 10.8 mm hybrid laminates were all perforated in simulation. To prevent full penetration without a coating, the required composite thickness increased to about 19.8 mm for CFRP and 22.2 mm for GFRP. With a 3 mm PU coating added, a 13.8 mm total panel based on 10.8 mm CFRP fully arrested the projectile, and a 13.8 mm hybrid PU/CFRP/GFRP design also fully arrested the projectile. A 13.8 mm PU + GFRP design came very close but was reported as partial penetration, meaning that configuration would need a small additional increase in coating or substrate thickness for full arrest.
Researchers also found that the PU coating changed the impact dynamics significantly. In the coated hybrid case, the projectile decelerated from 400 m/s to 200 m/s in about 15 microseconds, compared with about 45 microseconds for the uncoated hybrid. Based on the modeled configurations, researchers concluded that the PU coating was about three times more effective than adding extra composite thickness alone. Results also suggest lower modeled mass and lower estimated material cost for coated arrest-capable designs than for several uncoated alternatives.
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US Provisional Patent
Babajide Williams
Maciej Kumosa
Paul Predecki
Joe Hoffman
Aly Hoeher
Aly.Hoeher@colostate.edu
970-491-7100