Uniaxial long‐term creep and recovery tests on ETFE‐foils

Abstract ETFE films, used as prestressed, lightweight, and transparent or translucent facade and roof constructions, withstand high wind and snow loads over a wide temperature range (Figs. 1–2). Tests on removed ETFE films show no significant changes in their optical and mechanical properties even after extended periods of use [1], [2], [3]. To demonstrate their durability and load‐bearing capacity, the long‐term mechanical behavior of the film must be known as precisely as possible. This is particularly true for single‐layer, mechanically prestressed constructions. The following presents the execution and results of long‐term laboratory tests over more than 100,000 hours on the commonly used ETFE film (NOWOFLON ET6235Z, 250 μm, clear). The objective of the long‐term investigation was to obtain data for implementation in FE simulations in order to model the time‐ and load‐dependent mechanical behavior computationally as accurately as possible and to derive an upper application limit under uniaxial prestressing. The comparison of the results of uniaxial short‐term tensile tests before and after long‐term loading should provide information on whether and to what extent the mechanical properties of the film have changed.