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.

作为总称，膜结构包括由本申请中涉及的技术织物和技术箔制成的结构，两者都具有非常低的自重，这意味着它们用于屋顶区域中的宽的、无支撑的表面跨度。到目前为止，只有一种类型的薄膜用于由箔制成的膜结构：由乙烯-四氟乙烯制成的箔，简称 ETFE 箔结构是另一种相对年轻的结构类型。薄膜材料是乙烯-三氟氯乙烯，简称ECTFE，尚未用于膜结构中，但目前对ETFE薄膜在单轴和双轴拉伸试验中表现出非线性粘弹性材料行为的了解。已经使用的箔材料 ETFE 和新的箔材料 ECTFE 都缺乏变化的边界条件，例如温度或负载速度。该提案的中心研究目标是弥合有关表征和建模的知识的基本差距因此，必须从根本上研究和记录 ETFE 和 ECTFE 箔在单轴和双轴短时拉伸试验中的应力应变行为，包括所有材料参数（弹性模量、泊松比、屈服应力和应变）。 、拉伸强度、断裂伸长率等）此外，由于膜结构始终是多轴的，因此需要在长期拉伸试验中研究两种箔的单轴和双轴蠕变和松弛行为。由于双轴材料特性需要付出相当大的努力，因此双轴材料行为对于设计至关重要，因此研究目标之一是开发单轴和双轴材料行为之间的相关性并对其进行分析描述。研究目标，详细检查拉伸载荷行为（单轴/双轴）以及蠕变和松弛行为（单轴/双轴），同时考虑材料厚度、样本几何形状、温度、应变率、应力等影响参数双轴应力状态下的比率包括来自不同制造商的材料的特性值和强度值作为同弹、抗弹和平面结构的设计相关值，并根据分析模型进行描述。开发了单轴和双轴状态下的非线性、粘弹性应力-应变以及蠕变和松弛行为，所开发的方法和模型还将在现有大型组件试验台上的大型组件测试中得到验证，并通过数值扩展。有限元参数研究。