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

膜结构用 ETFE 和 ECTFE 箔的非线性粘弹性材料行为表征

• 批准号: 427405088
• 负责人: Professorin Dr.-Ing. Natalie Stranghöner
• 金额: --
• 依托单位: Institut für Metall- und Leichtbau
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427405088?language=en
• 关键词: Characterisation; nonlinear; viscoelastic; material; behaviour

As an umbrella term, membrane structures comprises structures made both of technical textiles and technical foils dealt with in the present application. Both have a very low dead weight, which means that they are used for wide, unsupported spans of surfaces in the roof area and in the façade. So far, only one type of film has been used for membrane structures made of foils: foils made of ethylene-tetrafluoroethylene, ETFE for short. ETFE foil stuctures are a comparatively young type of construction. Another possible foil material is ethylene-chlorotrifluoroethylene, or ECTFE for short, which has not yet been used in membrane structures. ETFE foils exhibit nonlinear viscoelastic material behavior in both mono- and biaxial tensile tests. At present, however, basic knowledge of the mechanical behaviour under varying boundary conditions such as temperatures or load speeds is lacking both for the already used foil material ETFE and for the new foil material ECTFE.The central research objective of this proposal is to close fundamental gaps in knowledge regarding the characterisation and modelling of mechanical material behaviour. Therefore, the stress-strain behaviour of ETFE and ECTFE foils in mono- and biaxial short-time tensile tests has to be fundamentally studied and recorded, including all material parameters (moduli of elasticity, poisson’s ratios, yield stresses and strains, tensile strengths, elongation at break, etc.). In addition, the mono- and biaxial creep and relaxation behaviour of both types of foil are to be investigated in long-term tension tests. Since membrane structures are always multi-axially tensioned, the biaxial material behaviour is decisive for the design. Since biaxial material characterization is associated with considerable effort, one research goal is also to develop a correlation between the mono- and biaxial material behaviour and to describe it analytically.In order to achieve the research objectives, both the tensile load behaviour (mono-/biaxial) and the creep and relaxation behaviour (mono-/biaxial) are examined in detail, taking into account the influencing parameters of material thickness, specimen geometry, temperature, strain rate, stress ratio in the biaxial stress state and load history. Materials from different manufacturers are included. Characteristic values as quality features and strength values as design relevant values for synclastic, anticlastic and plane structures are determined on the basis of the experimental results. Analytical models to describe the nonlinear, viscoelastic stress-strain as well as the creep and relaxation behaviour in the mono- and biaxial state are developed. The developed methods and models will also be validated in large scale component tests on an existing large component test stand and extended by numerical FE parameter studies.

作为伞术，膜结构包括在本应用中处理技术纺织品和技术箔的结构。两者的重量都非常低，这意味着它们用于屋顶区域和立面的宽，无支撑的表面跨度。到目前为止，仅将一种类型的膜用于由箔制成的膜结构：由乙二醇甲基乙烯制成的箔，简称ETFE。 Etfe箔结构另一种可能的足球材料是乙二醇富集甲基乙烯，即简称ECTFE，尚未用于膜结构中。在单轴和双轴拉伸试验中，ETFE箔暴露于非线性粘弹性材料行为。然而，目前，对于已经使用的箔材料ETFE和新的铝材材料ECTFE缺乏不同边界条件（例如温度或载荷速度）的机械行为的基本知识。该提案的中心研究目标是在有关机械材料行为的特性和建模的知识方面的基本差距。因此，单轴和双轴短期拉伸测试中ETFE和ECTFE箔的应力 - 应变行为必须从根本上进行研究并记录，包括所有材料参数（弹性的模量，Poisson的比率，比率，屈服应力和菌株，拉伸强度，拉长等）。此外，在长期张力测试中，将研究两种类型的箔的单轴和双轴蠕变和放松行为。由于膜结构始终是多轴张力的，因此针对设计决定了双轴材料行为。由于双轴材料表征与考虑的努力有关，因此一个研究的目标也是建立单一物质行为和双轴物质行为之间的相关性并进行分析描述。为了实现研究目标，拉伸负荷行为（单次/双轴）（单/双轴）以及蠕动和放松行为（单一/双疗法）都在详细范围内进行了影响，以详细介绍材料的参数，并详细介绍了详细的参数。双轴应力状态和负载病史中的温度，应变率，应力比。包括来自不同制造商的材料。特征值作为质量特征和强度值作为突触，反和平面结构的设计相关值，是根据实验结果确定的。开发了描述非线性，粘弹性应激 - 应变以及单轴和双轴状态的蠕变和松弛行为的分析模型。开发的方法和模型也将在现有大型组件测试台上的大型组件测试中进行验证，并通过数值FE参数研究扩展。