Composite structural housing with integrated thermal management

随着现代旋翼机设计从传统动力转向更多的电气系统，对有效热调节的需求从未如此之高。系统目前已经到位，以打击这在旋翼机，但他们将受益于更高的集成和优化。实现这一目标的关键可能在于进一步利用航空航天工业中已经司空见惯的材料：复合材料。复合材料，即碳纤维和玻璃纤维增强复合材料（CFRP/GFRP）在现代飞机中具有广泛的应用，并且可以包括多达40-50%的结构部件。复合材料的流行主要是由于它们的高强度重量比和刚度剪裁能力。然而，由于其较差的热性能，它们在温度关键区域受到限制。这意味着它们通常不适合需要大量散热的组件周围的结构应用。然而，如果这些复合材料的热性能可以得到改善，而不损害材料本身的机械性能，那么好处将是多方面的。该项目旨在研究改善复合材料热特性的方法，以帮助从温度关键部件中移除热量。目前有一些新的概念可以在小规模上做到这一点，但目前的文献和研究领域是稀缺的。这可能意味着必须使用新技术或技术组合来实现这一点。可以使用两种类型的技术：被动冷却和主动冷却。被动冷却系统将采用微结构或几何特征，并利用周围环境来促进散热，而不需要消耗能量。在微观结构上，这可以包括将导热添加剂添加到复合材料基质中或改善基质内的结晶度。在几何上，这可能涉及利用周围条件和转子产生的空速的通风特征。然而，可能最有前途的概念将是使用用于簇绒（缝合）的z-钉扎来改善复合材料在整个厚度方向上的热导率。这将在具有更多传导材料（诸如碳或金属）的结构内创建导热路径。从机械性能的角度来看，这两种技术已经有了用途，但它们的热效应尚未在研究中进行过研究。作为该项目的一部分，已经进行了初步实验来研究z钉扎，并取得了令人鼓舞的初步结果。主动冷却系统将需要一些能量消耗手段以从系统中移除热量。这将最容易通过在结构的表面周围泵送冷却流体来完成。在现代旋翼机中存在一些类似的系统，但是集成到复合结构中是非常复杂的。然而，通道可以嵌入复合材料中，以创建一个“血管网络”，通过该网络可以泵送冷却剂。根据有限的文献，这种技术提供了最有潜力实现所需的冷却效果，并将形成本项目的大部分实验工作。通道的尺寸、构造和制造方法以及冷却剂和流速的选择都是需要进一步研究的因素。这些变量将为研究创造一个强有力的起点。该项目将采用双管齐下的方法，在确定具有最高潜力的概念之前，对被动和主动系统进行实验评估。然后将对这一概念进行更详细的评估，并考虑到具体的应用，希望提高TRL水平，并为未来的项目进一步研究。

As modern rotorcraft design shifts away from conventional power and towards more electrical systems, the need for efficient thermal regulation has never been higher. Systems are currently in place to combat this in rotorcraft but they would benefit from higher integration and optimisation. The key to achieving this may lie in further utilisation of materials that are already commonplace in the aerospace industry; composites. Composite materials, namely carbon and glass fibre reinforced composites (CFRPs/GFRPs) have widespread applications in modern aircraft and can comprise as much as 40-50% of structural components. The prevalence of composite materials is mainly due to their high strength-weight ratio and stiffness tailoring ability. They are however limited in temperature critical areas due to their poor thermal performance. This means they are generally unsuitable for structural applications around components that require a large amount of heat removal. However, if the thermal performance of these composite materials could be improved without compromising the mechanical properties of the material itself, the benefits would be numerous. This project aims to investigate ways to improve the thermal characteristics of composite materials in ways that would aid the removal of heat from temperature critical components. There are currently a few novel concepts that can do this on a small scale, but current literature and research into the area is scarce. This likely means a new technique, or a combination of techniques would have to be used to achieve this. There are two types of techniques that could be used; passive and active cooling. A passively cooled system would employ microstructural or geometric features and take advantage of the surrounding environment to promote heat dissipation without the need for energy consumption. Microstructurally, this may include thermally conductive additives into the composite matrix or improved crystallinity within the matrix. Geometrically, this may involve ventilation features that take advantage of the surrounding conditions and the airspeed produced by the rotors. Possibly the most promising concept however would be to improve thermal conductivity in the through-thickness direction of the composite using z-pinning for tufting (stitching). This would create thermally conductive pathways within the structure with more conductive materials such as carbon or metals. These two techniques already have uses from a mechanical performance perspective, but their thermal effects have not been investigated in research. Preliminary experiments have already been carried out to investigate z-pinning as part of this project, with promising initial results. An actively cooled system would require some means of energy consumption in order to remove heat from the system. This would most easily be done by pumping a cooling fluid around the surface of the structure. Some similar systems exist in the modern rotorcraft but integration into composite structures is very complex. Channels can however be embedded within the composite to create a 'vascular network' through which coolant can be pumped. Based on the limited literature, this technique offers the most potential to achieve the cooling effect required, and will form the bulk of the experimental work of this project. The size, configuration, and fabrication method of the channels are all factors that need to be investigated further, as well as choice of coolant and flow velocity. These variables will create a strong starting point for research. The project will use a two pronged approach to evaluate both passive and active systems experimentally, before identifying the concept with the highest potential. This concept will then be evaluated in more detail and with a specific application in mind, in the hopes of raising the TRL level and furthering the research for future projects.