The introduction of nanostructured interlayers is one of the most promising strategies for interlaminar reinforcement in structural composites. In this work, we study the failure mechanism and interlayer microstructure of aerospace-grade structural composites reinforced with thin veils of carbon nanotube produced using an industrialised spinning process. Samples of unidirectional carbon fiber/epoxy matrix composites interleaved with different composition CNT veils were prepared using hot press method and tested for interlaminar fracture toughness (IFT), measured in Mode-I (opening) and Mode-II (in-plane shear), and for interlaminar shear strength (ILSS), evaluated by the short beam shear (SBS) test. The crack propagation mode could be directly determined through fractography analysis by electron microscopy and resin/CNT spatial discrimination by Raman spectroscopy, showing a clear correlation between interlaminar reinforcement and the balance between cohesive/adhesive failure mode at the interlayer region. Composites with full resin infiltration of the CNT veils give a large increase of Mode II IFT (88%) to 1500 J/m² and a slight enhancement of apparent interlaminar shear strength (6.5%), but a decrease of Mode I IFT (−21%). A toughening factor, defined as the relative increase in toughness per interleaf-to-ply thickness ratio, give a record-high value of 15.8 for Mode II IFT. The results help establish the role of interlayer infiltration, interlaminar crossings and formation of a carbon fiber bridgings, for interlaminar reinforcement with interleaves.

纳米结构夹层的引入是结构复合材料中层间增强的最有希望的策略之一。在这项工作中，我们研究了用工业化纺丝工艺生产的用碳纳米管薄面纱增强的航空级结构复合材料的破坏机理和层间微观结构。使用热压法制备交织了不同成分CNT面纱的单向碳纤维/环氧树脂基复合材料样品，并测试了层间断裂韧性（IFT），以模式I（开口）和模式II（面内剪切）测量，对于层间剪切强度（ILSS），通过短梁剪切（SBS）测试进行评估。裂纹扩展模式可以通过电子显微镜的断层分析和拉曼光谱法直接确定树脂/ CNT的空间分辨力来确定，显示出层间增强与层间区域内聚/内聚破坏模式之间的平衡之间存在明显的相关性。树脂完全渗透到CNT面纱中的复合材料使II型IFT大幅提高（88％）至1500 J / m²和表观层间剪切强度略有提高（6.5％），但I型IFT降低（-21％）。增韧因子定义为每层夹层与层厚度之比的相对增韧，对于模式II IFT给出了创纪录的15.8值。结果有助于确立层间渗透，层间交叉和形成碳纤维桥接物的作用，以增强层间夹层。