Characterisation of the nonlinear viscoelastic material behaviour of ETFE and ECTFE foils for membrane structures

• Applicant: Professorin Dr.-Ing. Natalie Stranghöner
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 427405088

• Final Report Year: 2024

Final Report Abstract

ETFE-foils, which are applied exclusively in tension-bearing structures, are used as lightweight and wide-span roof and façade elements in membrane structures in the building industry under heterogeneous regulations. In order to be able to define standardised regulations, the central research objective was to close the fundamental knowledge gaps with regard to the material behaviour of ETFE-foils by analysing the short- as well as the long-term tensile behaviour. The time- and temperature-dependent material properties of the ETFE-foil material under uni- and biaxial stresses were characterised. The knowledge about the biaxial material behaviour under short- and long-term tensile effects is decisive for the design and optimisation of these structures, but is much more difficult to examine. Therefore, an analytical correlation between the uni- and biaxial material behaviour under short- and long-term tensile actions was developed in order to characterise the biaxial material behaviour on the basis of uniaxial tensile tests. In addition to the material tests on the time- and temperature-dependent material behaviour, ETFE-foils of different foil thicknesses (100 µm, 250 µm) and foils from three different material producers were examined. The differences were so clear that different material classes were defined.

Publications

• European ETFE-Design – New findings and concepts, in: Proc. Structural Membranes 2021, München, Deutschland, 13-14 September, 2021
  Stranghöner, N., Surholt, F., Runge, D. & Uhlemann, J.
  
• Mechanisch-technologische Eigenschaften von ETFE-Folien und deren Schweißverbindungen, in: Stranghöner, N., Uhlemann, J. (Hrsg.), 5. Essener Membranbau Symposium, Shaker Verlag, Düren, 2022
  Surholt, F., Runge, D., Uhlemann, J. & Stranghöner, N.,
  
• Mechanisch‐technologisches Verhalten von ETFE‐Folien und deren Schweißverbindungen. Stahlbau, 91(8), 513-523.
  Surholt, Felix; Runge, Dominik; Uhlemann, Jörg & Stranghöner, Natalie
  
• Temperature and Strain Rate Effects on the Uniaxial Tensile Behaviour of ETFE Foils. Polymers, 14(15), 3156.
  Surholt, Felix; Uhlemann, Jörg & Stranghöner, Natalie
  
• Correlation Between Uniaxial and Biaxial Creep Behaviour of ETFE Foils, in: Proc. Structural Membranes 2023, Valencia, Spanien, 2-4 Oktober, 2023
  Surholt, F., Uhlemann, J. & Stranghöner, N.
  
• Defining design limits for ETFE foils determined in bubble inflation tests, in: Proc. IASS Annual Symposium 2023, Melbourne, Australien, 10-14 Juli, 2023, S. 2158-2169
  Surholt, F., Uhlemann, J. & Stranghöner, N.