NOVELTY - A thermoplastic composite material-forming composition comprises reinforced fiber, thermoplastic matrix polymer, reactive polyamide prepolymer and nonreactive polyamide polymer. The thermoplastic matrix polymer is a semicrystalline polyamide polymer comprising amide units (Z), (10T) and (6T), where amide unit (Z) is derived from condensation of diamine and 4-18C diacid, amide unit (10T) is derived from condensation of decanediamine and terephthalic acid, and amide unit (6T) is derived from condensation of 6C diamine and terephthalic acid.    USE - Composition is used for forming thermoplastic composite material used in manufacture of mechanical components and structural components for automobiles, electrical/electronic components, rail components, marine structures, wind power, photovoltaic cells, solar cells, solar panels, solar power components, sporting products, aerospace component, trucks, civil engineering and construction materials, panels, recreation components and wind turbine components (all claimed).    ADVANTAGE - The composition is manufactured with high productivity by simple process, and provides mechanical components and structural components having excellent creep resistance.    DETAILED DESCRIPTION - A thermoplastic composite material-forming composition comprises reinforced fiber, thermoplastic matrix polymer, reactive polyamide prepolymer and nonreactive polyamide polymer. The thermoplastic matrix polymer is a semicrystalline polyamide polymer comprising amide units (Z), (10T) and (6T), where amide unit (Z) is derived from condensation of diamine and 4-18C (preferably 10-12C) diacid, amide unit (10T) is derived from condensation of decanediamine and terephthalic acid, and amide unit (6T) is derived from condensation of 6C diamine, preferably hexanediamine and terephthalic acid. The composition has a heat deflection temperature of less than 260 degrees C, preferably 210 degrees C to less than 240 degrees C, and melting point of 270 degrees C or less, preferably 260 degrees C. The content of amide unit (Z), amide unit (10T) and amide unit (6T) is 0-30 mol%, 40-95 mol% and 5-60 mol%, respectively. The total content of amide units (Z), (10T) and (6T) is 100 mol%. INDEPENDENT CLAIMS are included for the following:    (1) polymer, which is obtained using prepolymer and chain extender; and    (2) manufacture of thermoplastic composite material, which involves molding the composition.