Effects of Natural Sunlight on Fiberglass Reinforced Polymers for Crossarms

Fiberglass crossarms have been successfully used in the electrical utility industry to improve grid reliability over the past 25 years. Because they are engineered with fiberglass reinforced polymer (FRP) materials, they are well suited to meet the demands of continuous outdoor use while in service, provided they are properly engineered and protected from the effects of outdoor weathering, including ultraviolet (UV) exposure from natural sunlight. Most fiberglass crossarm manufactures purport the use of synthetic veils and UV inhibitors formulated into the resin system as features to mitigate the effects of outdoor weathering. Some fiberglass crossarm manufactures include the use of an outer UV coating to provide further protection from the effects of outdoor weathering. This paper explores the effects of natural sunlight based on accelerated outdoor weathering test per ASTM G90 on test coupons cut from commercially available fiberglass crossarms which were either with or without a UV coating. The paper will present side-by-side testing results including images of samples with or without exposure to sunlight under ASTM G90, total color change, and analysis from a material performance perspective as well as an application perspective, and will address factors which can affect the service life of fiberglass crossarms.