A skin-stiffened composite panel extending essentially along a common plane, said panel comprising: - at least two essentially longitudinal stiffeners arranged distant to each other in said plane, said at least two essentially longitudinal stiffeners having each at least one base flange (11, 13), - a skin of a planar outer continuous composite layer and an inner continuous composite layer, the at least two essentially longitudinal stiffeners being each bonded unilaterally by means of said at least one base flange (11, 13) to one side of the inner continuous composite layer of the skin, wherein the at least two essentially longitudinal stiffeners have a height a perpendicular to the skin, characterized by - at least two sandwich assemblies in said common plane along each one of the at least two essentially longitudinal stiffeners, said at least two sandwich assemblies comprising each the planar outer and the inner continuous composite layers (9, 10) and a foam module, with the foam modules on the same side of the planar outer continuous composite layer as the essentially longitudinal stiffeners between the inner continuous composite layer and the planar outer continuous layer and the foam modules each having a height b less than 3.5 mm, perpendicular to the planar outer continuous composite layer, the foam module having a grid-type structure with openings and flat ribs along first and second angled directions (12, 14) in said plane, the width c of the flat ribs being at least 5 times larger than the height b of the foam modules, the inner continuous composite layer and the planar outer continuous layer being connected to each other within the openings of the foam module and along at least two interstices between the at least two sandwich assemblies for the at least two essentially longitudinal stiffeners. - at least two essentially longitudinal stiffeners arranged distant to each other in said plane, said at least two essentially longitudinal stiffeners having each at least one base flange (11, 13), - a skin of a planar outer continuous composite layer and an inner continuous composite layer, the at least two essentially longitudinal stiffeners being each bonded unilaterally by means of said at least one base flange (11, 13) to one side of the inner continuous composite layer of the skin, wherein the at least two essentially longitudinal stiffeners have a height a perpendicular to the skin, characterized by - at least two sandwich assemblies in said common plane along each one of the at least two essentially longitudinal stiffeners, said at least two sandwich assemblies comprising each the planar outer and the inner continuous composite layers (9, 10) and a foam module, with the foam modules on the same side of the planar outer continuous composite layer as the essentially longitudinal stiffeners between the inner continuous composite layer and the planar outer continuous layer and the foam modules each having a height b less than 3.5 mm, perpendicular to the planar outer continuous composite layer, the foam module having a grid-type structure with openings and flat ribs along first and second angled directions (12, 14) in said plane, the width c of the flat ribs being at least 5 times larger than the height b of the foam modules, the inner continuous composite layer and the planar outer continuous layer being connected to each other within the openings of the foam module and along at least two interstices between the at least two sandwich assemblies for the at least two essentially longitudinal stiffeners.