Abstract: A method for manufacturing a part made from composite material includes the steps of: applying, to a tool, layers of prepreg composite material for constituting a preform; installing a cover on the preform and sealingly connecting this cover to the tool with sealant; applying a vacuum to the enclosure delimited by the cover and the tool containing the preform; and heating the assembly to a given temperature for a predetermined time period in order to polymerise the layers of prepreg composite material. Also, a step of applying at least one silicone patch to geometrically complex zones of the tool and/or the preform may be performed before installing the cover. The cover may include at least one polyimide and/or at least one compound from the phthalonitrile family.