Method for open-mold production of a semi-crystalline thermoplastic polyamide matrix fiber-reinforced composite. The matrix has Tg>80° C. and Tf between 280° C. and 200° C. The matrix is prepared in-situ by molten state bulk polycondensation of a reactive precursor composition including A: a first polyamide prepolymer A1 each carrying two identical functions and a second polyamide prepolymer A2 each carrying two identical functions different from and coreactive with those of A1. The reactive precursors may alternatively include B: a prepolymer carrying (on the same chain) two different functions coreactive with each other. The reactive precursors may alternatively include a precursor composition that is a mixture of (A+B). The method involves successive steps of i) preparing the reactive mixture, ii) continuously coating the fibers by deposition-impregnation with the reactive mixture, iii) in-situ bulk polycondensation in an open heated die, and iv) cooling the composite.