Investigation of Combined Loading Effects during Testing, Modeling and Optimization of Woven Fabrics under Uncertainty: An Application to Forming Processes

机织聚合物织物复合材料由于其易于成型以及轻质和高强度的结合，在航空航天、汽车、建筑、海洋和能源等几个主要行业得到了相当大的关注。尽管有了广泛的兴趣，但在测试和分析其在复杂载荷条件下的力学响应方面仍然缺乏知识和标准化。更具体地说，基本的材料变形机理，如纤维拉伸和织物网格化，大多是在单独的模式下进行研究的，而关于织物在同时双向拉伸和剪切等组合加载模式下行为的复杂性的信息较少。这种变形模式在实际应用中的例子包括在冲压过程中使用压边机，以及双向机织复合材料制成的充气梁的加载和卸载。 本研究的目的是通过机械测试、计算机建模、X射线层析成像和多目标逆识别方法，对机织物在复合加载模式下的多尺度行为进行新的、综合的识别，最终目的是提高加拿大和其他地方用于模拟和优化复合材料成型过程的现有宏观模型的性能。此外，在实践中，经常有两个不确定源导致不可重复的测试数据和/或不一致的部件质量。这些来源包括特定于给定变形模式/成形设置的来源，以及织物预成型件内部异质性所固有的来源。认为在利用实验室测试和相关的反演方法对纱线性能进行多目标识别时，这两组不确定度都需要更密切地关注。因此，为了增加所提出的织物模型在组合加载模式下的可靠性，本研究将通过稳健的实验设计技术来考虑不确定性影响。最终，结果将与实际成型过程进行测试，新材料数据将包括在机织织物的多标准材料选择工具中。

Woven fabric polymer composites, owing to their ease of formability along with a combination of light weight and high strength, have found considerable attention in several leading industries including aerospace, automotive, construction, marine, and energy. Despite this wide interest, there still exists a lack of knowledge and standardization in testing and analyzing their mechanical responses under complex loading conditions. More specifically, basic material deformation mechanisms such as fiber tension and fabric trellising have been mostly studied under individual modes, and there is less information on the complexity of fabrics behavior under combined loading modes such as simultaneous biaxial tension and shear. Examples of such deformation modes in practical applications include the use of a blank-holder during stamping, and the loading and unloading of inflatable beams made of bidirectional woven fabric composites. The aim of this research is to conduct a novel, integrated approach by means of mechanical testing, computer modeling, x-ray tomography and multi-objective inverse identification of multi-scale behavior of woven fabrics under combined loading modes, with an ultimate goal of enhancing the performance of existing macro-level models used for the simulation and optimization of composite forming processes in Canada and elsewhere. Furthermore, in practice there are two sources of uncertainties that often result in non-repeatable test data and/or inconsistent parts quality. These include sources that are specific to a given deformation mode/forming set-up, and those that are inherent to the heterogeneity within fabric preforms. It is deemed that both groups of uncertainties need a closer attention during multi-objective identification of yarn properties using laboratory tests and the related inverse methods. Hence, in order to add to the reliability of the proposed fabric models under combined loading modes, uncertainty effects will be accounted for in this research via a robust design-of-experiments technique. Eventually, results will be tested against an actual forming process, and new material data will be included in a multi-criteria material selection tool for woven fabrics.