Method for shaping a film of a material that has low resistance to traction, and mirror comprising such a film

Method for shaping a sheet of a material that has low resistance to traction and having a thickness Ev, comprising the steps of:

• applying and adhering onto a first surface of the sheet a layer of a first material withstanding higher tensile stresses than those of said sheet of material, said layer having a thickness E1 such that, when this complex is subjected to bending, the neutral fiber is moved by more than 20% of the sheet's thickness Ev;
• elastically deforming the complex comprising the sheet coated with the first layer of material into the final shape, such that the sheet is principally subjected to compression relative to the initial shape because of the neutral fiber having moved;
• applying a layer of a second material, resistant to compression stresses, on a free surface of the layer of the first material opposite to the sheet, the layer of the second material adopting a final shape of said surface of the layer of first material, the layer of second material shaping the complex into the final shape;
• and
• adhering the layer of the second material onto the layer of the first material and dimensionally stabilizing the final shape.

Mirror comprising a sheet, a layer of a first material adhering to a first surface of the sheet and a layer of a second material adhering to a surface of the layer of the first material opposite to the sheet, wherein:

• a constitutive material of the sheet is principally subjected to compression;
• the material of the layer of first material is mainly subjected to traction;
• and
• the material of the layer of second material is subjected to compression.