Polymer composites have progressively found applications in sectors such as automotive, aerospace and energy storage. Their high performance can be mainly attributed to their compositions (e.g. the types of fillers and matrices) and structures (e.g. the orientation and dimension of fillers). Filler orientation has long been a crucial subject for the composite community. While the emerging discontinuous fillers offer new attributes to the next generation composites and new composite manufacturing techniques such as additive manufacturing, their orientation, however, has been much less understood and controlled as compared to that of the continuous fillers, mainly due to their small scales. Focusing on the role of filler orientation in the processing-structure–property relationships of polymer composites, the present Review critically discusses recent progress on the modelling, characterization, control and applications of the orientation of discontinuous fillers, with the advantages and disadvantages of the representative approaches analyzed. Their correlations are revealed under a proposed theoretical framework based on the rotational degree of freedom and translational degree of freedom of the fillers. Some selection criteria are proposed to guide future selection of composite manufacturing techniques for customized filler orientation. Finally, unaddressed fundamental issues and future perspectives on research and development in this field are highlighted.

中文翻译：

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聚合物复合材料中不连续填料的取向：建模、表征、控制和应用


聚合物复合材料已逐渐应用于汽车、航空航天和储能等领域。它们的高性能主要归因于它们的成分（例如填料和基体的类型）和结构（例如填料的方向和尺寸）。长期以来，填充物定向一直是复合材料社区的一个重要主题。虽然新兴的非连续填料为下一代复合材料和新的复合材料制造技术（如增材制造）提供了新的属性，但与连续填料相比，它们的取向受到的理解和控制要少得多，这主要是因为它们的规模小。本综述侧重于填料取向在聚合物复合材料的加工-结构-性能关系中的作用，批判性地讨论了不连续填料取向的建模、表征、控制和应用的最新进展，并分析了代表性方法的优缺点。在基于填料的旋转自由度和平动自由度的拟议理论框架下揭示了它们的相关性。提出了一些选择标准，以指导未来为定制填料方向选择复合材料制造技术。最后，强调了该领域未解决的基本问题和未来研发前景。