Sandwich Panel Fire Resistance via Stiffening Layers
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Solution Overview
Problem
Existing building elements with sandwich structures face issues of poor fire resistance, insufficient strength, and load-bearing ability, leading to structure-borne sound propagation and risk of collapse during fires, especially when used in load-bearing floor structures or walls without additional support structures.
Innovation Solution
A building element with a sandwich structure comprising a first and second cover layer connected to opposite sides of an intermediate core, where the cover layers have stiffening layers with high modulus of elasticity, and the core materials are selected for fire resistance and sound/heat insulation, with a fire-resistant adhesive providing a shear-resistant connection to maintain load-bearing ability during fires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal sheets are used as cover layers in sandwich structure building elements, then the structure provides initial strength and stability, but it rapidly loses load-bearing ability when exposed to high temperatures during fire
Solution Approach 1:
A fire-resistant board (gypsum or wood fibre) is introduced as an intermediary layer between the metal cover sheet and the insulating core. This board acts as a thermal barrier that delays heat transfer to the core material during fire, maintaining the sandwich structure's load-bearing capacity for a specified period (e.g., 15 or 30 minutes). The board partially carbonizes (wood fibre) or vaporizes crystal water (gypsum) to absorb heat and protect the core.
Solution Approach 2:
The building element uses a composite sandwich structure combining metal cover sheets, fire-resistant boards, and insulating core materials (polystyrene or polyurethane foam). This multi-material composite design leverages the strength of metal, the fire resistance of gypsum/wood fibre boards, and the insulation properties of the core material to achieve both structural integrity and fire safety.
2Strength
If additional supporting structures (wood or metal ribs, frameworks) are added to increase strength and load-bearing ability, then the building element can be used in load-bearing applications, but the risk of structure-borne sound propagation increases
Solution Approach 1:
Instead of adding rigid supporting ribs or frameworks throughout the structure, the patent uses locally optimized sandwich panel design with carefully selected core materials and thicknesses that provide sufficient load-bearing capacity without requiring additional stiffening elements. The insulating core itself is configured to provide both structural support and sound insulation where needed.
3Ease of manufacture
If the insulating core material is directly exposed to external heat during fire, then the structure simplifies construction, but the core material softens or vaporizes causing the sandwich structure to collapse
Solution Approach 1:
A fire-resistant board is positioned as a protective intermediary between the external fire environment and the insulating core material. This board serves as a thermal shield that delays heat penetration, preventing the core material (polystyrene or polyurethane foam) from reaching its softening or vaporization temperatures during fire exposure, thereby maintaining structural integrity.
4Strength
If stiffening layers with high modulus of elasticity are added to cover layers, then the building element gains sufficient strength for load-bearing applications, but the device complexity increases
Solution Approach 1:
The fire-resistant board (gypsum or wood fibre) serves dual functions: it acts as a thermal barrier for fire protection and simultaneously provides stiffening reinforcement to the metal cover sheet, enhancing the overall load-bearing capacity of the sandwich panel without requiring separate stiffening elements.
Solution Approach 2:
The fire-resistant board performs multiple functions within a single layer: fire protection (thermal barrier), structural reinforcement (stiffening), and potentially sound insulation. This multi-functional design eliminates the need for separate components for each function, reducing overall structural complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the building element's strength, load-bearing capacity, sound insulation, and fire resistance, allowing it to be self-supporting in load-bearing applications while minimizing structure-borne sound and heat insulation risks, and maintaining load-bearing ability during fires.
Implementation Method 1
one or several stiffening layers having a thickness of at least 5 mm and a modulus of elasticity which is higher than 3000 MPa and higher than the moduli of elasticity of said core materials
Implementation Method 2
said fire-resistant adhesive covers at least 5 % of the area of the inwardly facing surface of the respective cover layer in order to provide a shear-resistant connection
Implementation Method 3
the first core material has a higher modulus of elasticity than the modulus of elasticity of the second core material, which has a modulus of elasticity lower than 10 MPa
Implementation Method 4
meets the high demands for sound insulating ability and also heat insulating ability placed on the construction of modern houses
Data Source
Figure 1~2
Figure 3~4
AI summary
Building element with cover layers (11, 19) connected to opposite sides of a core of a first (12, 13, 14, 15, 16) and a second (17, 18) core material. The cover layers (11; 19) comprise at least one stiffening layer having a thickness of at least 5 mm and a modulus of elasticity higher than 3000 MPa. The first core material (12, 13, 14, 15, 16) has a higher modulus of elasticity than the second core material (17, 18), whose modulus of elasticity is lower than 10 MPa. Edge pieces (12, 13, 15, 16) of the first core material surround intermediate pieces (17, 18) of the second core material, which cover at least 60 % of the area inside the edge pieces (12, 13, 15, 16). The cover layers (11, 19) are connected to the edge pieces (12, 13, 15, 16) by means of a fire- resistant adhesive, which covers at least 5 % of the area of the cover layers (11, 19) for a shear-resistant connection where the cover layers (11, 19) are at least 70 mm from each other with the first core material (12, 13, 15, 16) as a spacing element.