3D thermoformed element

An assembly comprising:

• a three-dimensional structural element having a curved shape and/or reliefs and depressions, interposed between an external environment and an internal volume to be thermally and/or acoustically protected, and
• an inner lining element for lining the three-dimensional structural element, the inner lining element comprising a thermally insulating element which is interposed between the external environment and the internal volume to be protected, the thermal insulating element being bent-shaped and/or having reliefs and depressions, engaged at least partly with respectively the curved shape and/or the depressions and the reliefs of the structural element, in order to substantially follow at least part of a contour thereof,
• the thermal insulating element comprising:
• a structure made of a three-dimensional porous material,
• an envelope closed in an airtight manner,
• comprising an airtight barrier wall,
• in which envelope is enclosed the three-dimensional porous material whose shape is followed by the airtight barrier wall, and
• in which envelope, at outside ambient temperature and pressure, a pressure of between less than 105 Pa and more than 10−2 Pa prevails,
• wherein:
• the barrier wall is thermoformable and being thermoformed,
• the structure is compressed,
• the bent-shaped is defined by a bending of said thermal insulating element, and/or the reliefs and the depressions are defined by embossings and the thermal insulating element, and wherein between two major surfaces of the barrier wall, the structure has thick zones having a first thickness and thin zones having a second thickness lower than the first thickness, the thin zones having a density of the three-dimensional porous material that is higher than a density at the thick zones of the three-dimensional porous material, a minor surface of a wall being a sealing zone where the sheets, or portions of sheets, forming the barrier wall are interbonded and sealed together to close the envelope, complementarily, the major surface of the same wall being an area of the envelope bounded by this sealing zone.