Panel with a layered structure

A panel (1) having a layered structure comprising:

• a first outer layer (2);
• an intermediate layer (3);
• a second outer layer (4);
• and
• an interface layer (5) between said intermediate layer (3) and said second outer layer (4), said interface layer (5) enabling adhesion of the intermediate and second outer layers (3, 4) it is arranged between;
• wherein a fabric proper free of any matrix is used to form the second outer layer (4), the second outer layer having continuous fibres and having a tensile modulus of elasticity higher than or equal to 40 GPa as measured according to ASTM 01557 standard, and wherein a majority of the second outer layer remains the fabric proper free of any matrix after being joined to the intermediate layer;
• wherein said first outer layer (2) is made of sheet material having a flexural elasticity modulus higher than 2 GPa measured in accordance with ASTM E855 or ASTM D790 standards;
• wherein a product of a thickness of said first outer layer (2) and the flexural elasticity modulus of said first outer layer (2), measured in accordance with ASTM E855 or ASTM D790 standards, is higher than 0.4 Mpa·m;
• wherein the intermediate layer is made of a material chosen from the group consisting of:
• materials having a honeycomb structure, and
• polymer foams;
• wherein the intermediate layer has a macroscopic compressive modulus of elasticity measured with ASTM C365/C365M standard, the macroscopic compressive modulus of elasticity being measured, in a polymer foam intermediate layer, for a size greater than that of pores present in the polymer foam or, in materials with honeycomb structure. for a size greater than twice a size of a radius of cells of the honeycomb structure:
• wherein the macroscopic compressive modulus of the intermediate layer, in at least a direction parallel to the layers of the panel, is at least two orders of magnitude lower than a compressive modulus of elasticity of the first outer layer such that the intermediate layer is prevented from hindering bending of the panel in at least a direction substantially perpendicular to said direction parallel to the layers of the panel in which the intermediate layer is compressible, and wherein the compressive modulus of elasticity of the first outer layer is measured according to ASTM D3410/D3410M standard;
• wherein flexural properties of the panel are obtained by a combination of:
• the intermediate layer being configured to undergo compression, in a longitudinal direction parallel to that of the layers of the panel, and
• a reduced buckling stress of the fibres and strands constituting the second outer layer and the interface layer relative to the first outer layer. such as to allow the second outer layer to collapse locally towards an outside of the panel, and/or locally towards the intermediate layer;
• wherein when applying to the pan& at rest, a first bending moment configured to fold the panel towards the second outer layer, a variation of a curvature of the panel is produced with respect to a resting situation, with the panel bending towards the second outer layer, with the second outer layer being deformable by buckling and flexible, and the first outer layer being flexible. but substantially non-extensible, and
• wherein when applying a second bending moment to the panel with an opposite direction to the first bending moment and a same intensity as the first bending moment thereby urging the panel to bend towards the first outer layer, the panel does not undergo macroscopic deformations, substantially maintaining the panel's shape at rest, with the first outer layer withstanding compression without undergoing deformation due to buckling, and the second outer layer being substantially inextensible via the reduced buckling stress of the second outer layer relative to the first outer layer.