Investigations into the multiaxial material behaviour of ETFE‐foils subjected to strain‐controlled multiaxial loading in bubble inflation tests

Abstract

The recently published DIN CEN/TS 19102 provides guidelines to design membrane structures and distinguishes between two limit states: ultimate limit state (ULS) and serviceability limit state (SLS). DIN CEN/TS 19102 provides strength characteristics based on uniaxial short‐term tensile tests, whereas most membrane structures are subjected to multiaxial stress. Thus, the multiaxial material behaviour should be decisive for design, which can be analysed in bubble inflation tests – at least for structures made of ETFE‐foils. In the past, bubble inflation tests on ETFE‐foils were performed based on a predefined pressure rate, leading to different strain rates during testing. Thus, multiaxial stress‐strain curves cannot be directly compared to uniaxial short‐term tensile tests with constant strain rates. To fill this gap, a novel test setup has been developed enabling strain‐controlled bubble inflation tests. The determined multiaxial stress‐strain curves can be directly compared to uniaxial short‐term tensile tests. The comparisons show distinct differences in the strength and deformation capabilities of ETFE‐foils in uni‐ and multiaxial stress states. The present contribution addresses circular bubble inflation tests (stress ratio 1:1) on ETFE‐foils from two different producers with interesting results for the design of ETFE‐foil structures.