Process for producing composite panels

A process for producing a sandwich composite panel comprising at least one cellular core having opposite faces provided with skins of fiber/resin composite material which are fastened to said cellular core, said process comprising the steps of:

• (a) giving the peripheral flank of said cellular core a given profile;
• (b) forming a sandwich composite panel preform by covering the faces of said cellular core with flexible plies of fibers impregnated with a first thermosetting resin, said flexible plies extending beyond said peripheral flank of said cellular core and being brought together so that at least one of them is in contact with said peripheral flank and so that, beyond said flank, they are superposed in order to form a projecting peripheral flange;
• (c) forming at least one strip from a flexible sheet of a composite material comprising fibers impregnated with a second thermosetting resin, the profile of said strip corresponding to that of the peripheral flank of said preform and including two external portions connected by an intermediate portion, said first and second thermosetting resins being chosen so that, during a temperature rise, curing of said second resin occurs before that of said first resin;
• (d) placing said strip into place on the border of said preform so that, simultaneously, said external portions are respectively applied against one face of said preform and against said flange, while said intermediate portion is applied against the flank of said preform;
• (e) subjecting said preform, provided with said at least one strip on said border, to a temperature rise, without positive pressure being applied, until said second resin has cured;
• and then
• (f) subjecting said preform to a continuation of said temperature rise, with positive pressure being applied, the application of temperature and positive pressure being continued until said first resin has fully cured.