A skin-stiffened composite panel (1) comprising at least two essentially longitudinal stiffeners (3) arranged distant to each other in a plane with a skin (2) of a planar outer continuous composite layer (9) and an inner continuous composite layer (10). The at least two essentially longitudinal stiffeners (3) have a height “a” perpendicular to the skin (2). At least two sandwich assemblies (4) in said plane are along each one of the at least two essentially longitudinal stiffeners (3), said at least two sandwich assemblies (4) comprising each the planar outer and the inner continuous composite layers (9, 10) and a grid-type foam module (8) with openings and with a height “b”, with the foam modules (8) on the same side of the planar outer continuous composite layer (9) as the essentially longitudinal stiffeners (3) between the inner continuous composite layer (10) and the planar outer continuous layer (9).