Various methods and systems of making inorganic fiber/flake reinforced composites having a thermoplastic matrix are disclosed. The methods use systems similar to those used to make inorganic fiber/flake reinforced products having a thermoset matrix, but the systems and methods are modified to use thermoplastic precursor monomer(s) followed by in situ polymerization of the monomer(s) during and/or following forming of the desired shape of the products. These methods permit the manufacture of superior inorganic fiber reinforced thermoplastic matrix composites in large and very large shapes heretofore not possible, or practical.