A grid type fibre composite structure with longitudinal stiffening elements oriented in at least two directions, comprising - a grid of polygon cell modules, each cell module comprising - two parallel polygon surfaces connected by peripheral surfaces perpendicular to said two polygon surfaces, - at least three substantially u-shaped fibre composite ribs each rib having a transverse web section corresponding to one of said peripheral surfaces and two flat cap sections (11, 12) connected to said transverse web section, each of said two flat cap sections (11, 12) extending at least partially along one of said respective polygon surfaces, wherein - a foam core is provided inside said at least three substantially u-shaped fibre composite ribs for support of said transverse web sections and said flat cap sections (11, 12), said foam core being delimited by said two parallel polygon surfaces and said peripheral surfaces and said foam core being in contact with said transverse web sections and said flat cap sections (11, 12) of each rib, - said polygon cell modules are stringed together along entire transverse web sections of equal length, - layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) are provided outside said flat cap sections (11, 12) in at least one of said polygon surfaces, said layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) being aligned with ribs in one direction of said longitudinal stiffening elements, at least one of said flat cap sections (11, 12) being allocated between at least one of said layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) and said foam core, - said longitudinal stiffening elements are provided by the grid wise mounted cell modules with the layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) along the ribs and - a skin sheet is provided, said skin sheet being unilaterally attached either to said layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) and/or to said flat cap sections (11, 12) and/or to said base of said foam core. - a grid of polygon cell modules, each cell module comprising - two parallel polygon surfaces connected by peripheral surfaces perpendicular to said two polygon surfaces, - at least three substantially u-shaped fibre composite ribs each rib having a transverse web section corresponding to one of said peripheral surfaces and two flat cap sections (11, 12) connected to said transverse web section, each of said two flat cap sections (11, 12) extending at least partially along one of said respective polygon surfaces, - a foam core is provided inside said at least three substantially u-shaped fibre composite ribs for support of said transverse web sections and said flat cap sections (11, 12), said foam core being delimited by said two parallel polygon surfaces and said peripheral surfaces and said foam core being in contact with said transverse web sections and said flat cap sections (11, 12) of each rib, - said polygon cell modules are stringed together along entire transverse web sections of equal length, - layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) are provided outside said flat cap sections (11, 12) in at least one of said polygon surfaces, said layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) being aligned with ribs in one direction of said longitudinal stiffening elements, at least one of said flat cap sections (11, 12) being allocated between at least one of said layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) and said foam core, - said longitudinal stiffening elements are provided by the grid wise mounted cell modules with the layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) along the ribs and - a skin sheet is provided, said skin sheet being unilaterally attached either to said layers (2, 3) of intersecting strips (2a, 2b, 2c, 3a, 3b, 3c) and/or to said flat cap sections (11, 12) and/or to said base of said foam core.