An investigation into engineered thermoplastic polymer composite filament for through thickness reinforcement of laminated carbon fibre composites.

由干碳纤维预制件制成的层压复合材料越来越多地用于生产几个行业的主要结构。然而，在平面外（通过厚度）方向上的差的性能和分层一直是引起关注的原因，需要仔细分析载荷路径以限制平面外应力。此外，这对复合材料部件的设计自由度有限制作用，并可能挑战复合材料在未来空气动力学或结构概念中的使用。已经提出了几种“第一代”方法来改善面外性能，包括z钉扎、选择性夹层和混合物、保护层或树脂增韧;一种越来越成功的方法是用纤维增强复合材料，该纤维将层从层压板的上表面连接到下表面。这种方法显示出潜力，但由于缺乏可用于全厚度增强的合适材料而受到限制，迄今为止，我们仅限于碳纤维、玻璃、玄武岩、芳纶或其他聚合物纤维。此外，有一个有限的了解，涉及的机制，在平面外的速率相关的复合材料的响应。该建议旨在发展对全厚度增强的新理解，并研究生产具有设计者定义的全厚度响应的复合材料的方法。这将通过在整个厚度方向上放置具有优化特性的“第二代”制造纱线来完成，从而能够针对给定的负载情况设计最佳Ez（层压体整个厚度杨氏模量）。新纱线将通过复合挤出热塑性单丝与特定长度的碳纤维增强制成，优化材料和工艺参数，并将这些纱线用作碳纤维/环氧树脂层压板的全厚度增强材料。性能将被表征，并将开发预测分析弹性刚度模型。此外，新的全厚度纱线的粘弹性性能将与层压复合材料的横向冲击性能有关。这些主题以前没有研究过，如果成功，结果可能是变革性的，并对英国复合材料研究和工业产生全球影响。在未来，这项研究将使航空航天公司受益;由于提出了增强的面外性能，他们可能会设计一种加压混合机翼、复合材料耳片布置、桁条与蒙皮的界面和跳动、屈曲临界位置、高冲击位置等。

Laminated composites from dry carbon fibre preforms are increasingly being used to produce primary structures in several industries. However, the poor performance in the out-of-plane (through the thickness) direction, and delamination has been a cause of concern, requiring the careful analysis of load paths to limit out-of plane stress. Furthermore, this has a limiting effect on the design freedom for composite components and could challenge the use of composites for future aerodynamic or structural concepts. Several 'first-generation' methods have been proposed to improve out-of-plane performance including z-pinning, selective interlayers and hybrids, protective layers or resin toughening; one method that is becoming increasingly successful is to reinforce composites with a fibre that connects the layers together running from the upper to lower surface of the laminate. This method shows potential but has been limited by the lack of suitable materials available for through-thickness reinforcement where we have hitherto been limited to carbon fibre, glass, basalt, Aramid or other polymeric fibres. Also, there is a limited understanding of the mechanisms involved in out-of-plane rate-dependent response of composite materials. This proposal aims to develop a new understanding of through-thickness reinforcement and to research a method to produce composites with a through-thickness response which is designer defined. This will be done by placing a 'second-generation' manufactured yarn with optimised properties in the through-thickness direction, thereby enabling the design of optimum Ez (laminate through-thickness Young's modulus) for a given loading scenario. The new yarn will be made by compounding extrusion of a thermoplastic monofilament reinforced with carbon fibres of specified length, optimising material and process parameters, and using these yarns as through-thickness reinforcement in carbon fibre/epoxy laminates. The performance will be characterised and a predictive analytical elastic stiffness model will be developed. Also, the visco-elastic properties of the new through thickness yarn will be related to the transverse impact performance of the laminated composite. These subjects have not been previously researched and if successful, the results could be transformative and generate global impact for UK composites research and industry. In the future the research will benefit aerospace companies; with the proposed enhanced out-of-plane performance they could potentially design a pressurised blended wing, composite lug arrangement, stringer to skin interface and run-out, buckling critical locations, high impact locations, etc.