NOVELTY - A polyurethane-forming system comprises a) isocyanate component having viscosity at 25 degrees C of 20-300 mPas containing di-/poly-isocyanate; b) isocyanate-reactive component containing at least one polyol having viscosity at 25 degrees C of 20-850 mPas, and hydroxyl (OH) number of 200-600, flow additive (up to 6 wt.%), and drying agent (2-6 wt.%); and optionally additives (up to 1 wt.%) which do not cause foaming, where components (a) and (b) are reacted in amounts such that isocyanate index is 99-110 to form polyurethane having green strength to be de-molded at ambient temperature in not greater than 6 hours.    USE - As a polyurethane-forming system, used in the production of fiber-reinforced polyurethane composite in the form of wind turbine blade (claimed).    ADVANTAGE - The system has viscosity at 25 degrees C of less than 600 (preferably less than 400, especially 250-300) mPas for at least 30 minutes, a gel time at ambient temperature of greater than 60 (preferably greater than 180) minutes, and a water content of less than 0.06 wt.%. The fiber-reinforced polyurethane composite has fatigue tensile strength as determined by ASTM E647-05 of at least twice as long as that of a fiber-reinforced epoxy composite; and has inter-laminar fracture toughness as determined by ASTM D5528 of at least double the inter-laminar fracture toughness of a fiber-reinforced epoxy composite. The system produces large composites such as wind turbine blade having excellent physical properties; and is effectively infused into a reinforcing material by a vacuum infusion process.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) production of a fiber-reinforced polyurethane composite from the system by vacuum infusion involving de-gassing each of components (a) and (b), combining the de-gassed components (a) and (b) to obtain a polyurethane-forming reaction mixture, and applying vacuum pressure to a dry fiber-reinforcement material in a manner such that the fiber-reinforcement material is infused with the polyurethane-forming reaction mixture; and    (2) a fiber-reinforced polyurethane composite produced by the process.