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

由干碳纤维预制体制成的叠层复合材料正越来越多地被用于制造几个行业的初级结构。然而，在平面外(通过厚度)方向的不良性能和分层一直是一个令人关注的问题，需要仔细分析加载路径以限制平面外应力。此外，这限制了复合材料部件的设计自由度，并可能对复合材料在未来的空气动力学或结构概念中的使用提出挑战。已经提出了几种改进平面外性能的“第一代”方法，包括Z钉扎、选择性夹层和杂化、保护层或树脂增韧；其中一种日益成功的方法是用一种纤维来增强复合材料，这种纤维将层压件从上到下表面连接在一起。这种方法显示出潜力，但由于缺乏合适的材料用于穿透加固，到目前为止，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，人们对复合材料离面速率相关响应的机理了解也很有限。这一建议旨在发展对贯穿厚度增强的新理解，并研究一种制造具有设计者定义的贯穿厚度响应的复合材料的方法。要做到这一点，可以在厚度方向放置具有优化性能的“第二代”人造纱线，从而为给定的加载方案设计最佳的EZ(层压板厚度杨氏模数)。新的纱线将通过复合挤出用指定长度的碳纤维增强的热塑性单丝，优化材料和工艺参数，并使用这些纱线作为碳纤维/环氧层压板的穿透厚度增强。将对其性能进行表征，并建立预测的解析弹性刚度模型。此外，新厚度纱线的粘弹性能将与层合复合材料的横向冲击性能有关。这些课题以前从未被研究过，如果成功，结果可能是变革性的，并对英国复合材料研究和行业产生全球影响。未来，这项研究将使航空航天公司受益；有了拟议的增强的飞机外性能，他们可能会设计出增压混合机翼、复合材料凸耳布置、纵梁与蒙皮的界面和跳动、屈曲关键位置、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.