Method and device for stiffener protection, and corresponding composite panel

The stiffeners of a composite material panel may be protected by a structural section having a configuration absorbing edge impacts without propagation of impact energy to the protected structure. Each composite panel with protected parallel stiffeners has a multiply front face coming to an edge and extending between two lateral flanks of outside plies, symmetrically relative to a median plane (Pm). A device for protecting each stiffener includes a structural section that caps the stiffener symmetrically relative to this median plane (Pm). This structural section consists of an upper section formed above the edge and configured to envelop a space above the edge, a lower section framing the lateral flanks by longitudinal walls (Pi) fastened to these flanks, and an intermediate section bearing at least partially on the edge via transverse walls (Pb) so as to minimize the propagation of impact forces to the lower section.