Department of Textiles, Ghent University , Technologiepark-Zwijnaarde 907, B-9052 Zwijnaarde, Belgium.
Department of Materials Science and Engineering, Ghent University , Technologiepark-Zwijnaarde 903, B-9052 Zwijnaarde, Belgium.
ACS Appl Mater Interfaces. 2016 May 11;8(18):11806-18. doi: 10.1021/acsami.6b02247. Epub 2016 Apr 26.
Today, fiber-reinforced polymer composites are a standard material in applications where a high stiffness and strength are required at minimal weight, such as aerospace structures, ultralight vehicles, or even flywheels for highly efficient power storage systems. Although fiber-reinforced polymer composites show many advantages compared to other materials, delamination between reinforcing plies remains a major problem limiting further breakthrough. Traditional solutions that have been proposed to toughen the interlaminar region between reinforcing plies have already reached their limit or have important disadvantages such as a high cost or the need for adapted production processes. Recently, electrospun nanofibers have been suggested as a more viable interlaminar toughening method. Although the expected benefits are numerous, the research on composite laminates enhanced with electrospun nanofibrous veils is still very limited. The work that has been done so far is almost exclusively focused on interlaminar fracture toughness tests with different kinds of nanofibers, where typically a trial and error approach has been used. A thorough understanding of the micromechanical fracture mechanisms and the parameters to obtain toughened composites has not been reported as of yet, but it is crucial to advance the research and design highly damage-resistant composites. This article provides such insight by analyzing the nanofiber toughening effect on three different levels for several nanofiber types. Only by combining the results from different levels, a thorough understanding can be obtained. These levels correspond to the hierarchical nature of a composite: the laminate, the interlaminar region, and the matrix resin. It is found that each level corresponds to certain mechanisms that result in a toughening effect. The bridging of microcracks by electrospun nanofibers is the main toughening mechanism resulting in damage resistance. Nevertheless, the way in which the nanofiber bridging mechanism expresses itself is different for each scale and dependent on parameters linked to a certain scale. The multiscale analysis of the toughening mechanisms reported in this paper is therefore crucial for understanding the behavior of nanofiber toughened composites, and as such allows for designing novel, damage-resistant, nanofiber-toughened materials.
如今，纤维增强聚合物复合材料在需要最小重量的高刚度和高强度的应用中是一种标准材料，例如航空航天结构、超轻车辆，甚至是高效储能系统的飞轮。尽管纤维增强聚合物复合材料与其他材料相比具有许多优势，但增强层之间的分层仍然是限制进一步突破的主要问题。为了增强增强层之间的层间区域，已经提出了许多传统的解决方案，但这些解决方案已经达到了极限，或者具有高成本或需要适应生产工艺等重要缺点。最近，静电纺纳米纤维已被提议作为一种更可行的层间增韧方法。尽管预期的好处很多，但增强了静电纺纳米纤维面纱的复合材料层压板的研究仍然非常有限。到目前为止，所做的工作几乎完全集中在具有不同种类纳米纤维的层间断裂韧性测试上，通常使用试错法。尚未报道对获得增韧复合材料的细观力学断裂机制和参数的透彻理解，但对于推进研究和设计高抗损伤复合材料至关重要。本文通过分析几种纳米纤维类型在三个不同层次上对纳米纤维增韧效果的影响，提供了这样的见解。只有结合不同层次的结果，才能获得透彻的理解。这些层次对应于复合材料的分层性质：层压板、层间区域和基体树脂。研究发现，每个层次都对应于某些导致增韧效果的机制。静电纺纳米纤维对微裂纹的桥接是导致抗损伤的主要增韧机制。然而，纳米纤维桥接机制在每个尺度上的表现方式不同，并且取决于与某个尺度相关的参数。本文报告的增韧机制的多尺度分析对于理解纳米纤维增韧复合材料的行为至关重要，因此允许设计新型的、抗损伤的、纳米纤维增韧材料。
