Dimensionally stable polyurethanes and composites

A composite comprising a continuous resin phase and 8 to 85% by weight, based on the weight of the composite, of a discontinuous phase comprising filler particles, reinforcing fibers or both filler particles and reinforcing fibers, wherein the continuous resin phase is a cured polyurethane which is the reaction product of a polyurethane-forming reaction mixture characterized by an isocyanate index of 95 to 150, the reaction mixture comprising

• A) an aromatic polyisocyanate or mixture of aromatic polyisocyanates, the aromatic polyisocyanate or mixture of aromatic polyisocyanates having an isocyanate functionality of 2 to 4 and an isocyanate equivalent weight of 80 to 175;
• B) a mixture of polyols, the mixture of polyols having an average hydroxyl equivalent weight of 125 to 275 and an average hydroxyl functionality of 2.5 to 4 hydroxyl groups per molecule,
• wherein triisopropanolamine constitutes 12 to 33 weight percent of the mixture of polyols,
• wherein the reinforcing fibers are selected from one or more of a group consisting of glass fibers, boron fibers, ceramic fibers, carbon fibers, and metal fibers, and
• wherein the cured polyurethane has a glass transition temperature of at least 80° C.