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A deep understanding of the material parameters and the behavior of sandwich panels, which are used in the construction industry as roof and façade cladding, is important for the design of these construction components. Due to the constant changes in the polyurethane (PU) foams used as a core material, the experimental database for the current foams is small. Nowadays, there is an increasing number of failures of façade and roof panels after installation. This article presents a variety of experimental investigations on sandwich panels from two manufacturers with a core of polyisocyanurate (PIR) rigid foam (density: 40 kg/m3). As part of this study, compression, tension, shear, and bending tests were performed in several spatial directions and over the range required by the standard. The results of the tests showed the orthotropy of the core material and the dependence of the material on the direction and type of load. The stress-strain curves showed linear and non-linear areas. Using the data from this experimental study, a numerical model was implemented which utilized the Hill yield criterion to represent the orthotropy of the core material. The present investigation suggests that the classical von Mises failure criterion, used in many studies, is not suitable for the foam system applied in these sandwich panels. Instead, the Tsai–Wu criterion is more appropriate for defining the failure stresses. [ABSTRACT FROM AUTHOR]

Sandwich panels in the construction industry are used as roof and facade elements and usually consist of two thin face layers of steel and a thicker core of polyurethane (PU) or mineral wool in between. The PU core material is constantly being further developed. In addition to improvements in the physical properties, this further development also leads to changes in the mechanical properties. As a result, the design rules that were established for older foam systems must be reviewed at regular intervals. There is a great need for research into the temperature‐dependent behavior of the foam system. As these elements are used as roof and facade elements, they are directly exposed to climatic conditions. High temperatures are generated on the cover sheets due to solar radiation. The PU rigid foam changes its mechanical properties in this temperature range. Tests on small parts and components show a change in the stiffnesses and strengths, as well as the load‐bearing behavior under elevated temperature. Consideration of the temperature in the design is therefore of great importance. In view of the continuous further development of the foam system, statements regarding the core material from older research must be reconsidered. [ABSTRACT FROM AUTHOR]

Determination of the shear properties of sandwich core materials A comparison of the core materials of sandwich panels has revealed inconsistent relationships between their stiffness moduli at different core thicknesses. Therefore, two test methods for determining the shear properties of the core material of sandwich panels were assessed theoretically and experimentally. The results show that for the shear beam test according to EN 14509 a more precise definition of the load distribution plates is necessary and that the usual neglect of the indentation at the support is only justified for thin and medium panel thicknesses. The investigations on the square shear test have shown the influence of the eccentricity between the joint plane and the top edge of the specimen and resulted in the development of a new test setup. The findings from the investigations provide the basis for more realistic modelling of the load‐bearing behavior of sandwich panels in the future. [ABSTRACT FROM AUTHOR]

Sandwich panels with a core of corrugated cardboard The goal of a research project of the Institute for Steel Construction and Materials Mechanics was to determine the utilization of corrugated cardboard as a core material for sandwich panels for roof and wall cladding. In contrast to common core materials, corrugated cardboard is recyclable and consists of renewable raw materials. The bearing behaviour depends mainly on the paper types and on the orientation of the anisotropic material inside the panel. The weakest orientation has similar stiffness and strength as common core materials. However, these can be exceeded many times by other core orientations. Investigations of the most important building physical parameters have shown that the fire behaviour is slightly better than that of most PU‐sandwich panels. The thermal conductivity in the weakest core orientation is comparable to that of mineral wool, the stronger core orientations show higher thermal conductivity. [ABSTRACT FROM AUTHOR]

Within the scope of a research project, the pull‐through resistance of direct fixings of sandwich panels under cyclic loading was determined on small‐scale sandwich specimens. The tests were carried out on wall panels with lined steel face sheets. Various core materials (PU foam, mineral wool), face sheet thicknesses, panel depths and various screw manufacturers were combined. From the test results, cyclic reduction factors for fixings on the mid and end support were determined according to prEN 14509‐2. [ABSTRACT FROM AUTHOR]