Abstract: The present invention relates to a composite cellulose material, comprising: —a layer of a cellulose material, —a starch-based reinforcement grid which is positioned on at least one surface of the layer of cellulose material, the reinforcement grid comprising a plurality of meshes which are delimited by grid wires, the composite cellulose material having a relief in three dimensions comprising folds in the positioning zones of the reinforcement grid, and relief bumps on either side of the plane of the grid which are delimited by the folds.

Abstract: A method for fixing a first surface to a second surface. The method comprises depositing a first layer of nanocellulose on the first surface; bringing the first layer of nanocellulose into contact with the second surface or with a second layer of nanocellulose deposited on the second surface; and fixing the first layer of nanocellulose to the second surface, the second surface containing cellulose, or to the second layer of nanocellulose by a step of ultrasonic welding, which results in a first zone comprising the first layer of nanocellulose, where the first surface is fixed to the second surface, and a second zone around the first zone, where the first surface is not fixed to the second surface.