Electrical degradation diagnosis of aerospace carbon fibre composites

减少飞机上金属结构的使用，代之以更轻的碳纤维增强聚合物(CFRP)，可以优化飞机的重量。优化飞机的重量至关重要，这包括电力推进系统的优化，其中最大的挑战是电力系统的重量。具有电力推进的近期飞机的一个例子是电力垂直起降(EVTOL)飞机，例如CityAirbus。CFRP具有优异的机械性能，但与铝相比导电性较差(约为铝的1000倍)。由于对电流传导引起的碳纤维复合材料失效阈值以及以非破坏性方式检测这些阈值的方法认识不足，导致行业标准要求碳纤维复合材料与电气设备和电缆在物理上保持分离。这确保了在电气故障(例如，由于绝缘故障)的情况下，电气故障电流不会流经CFRP结构。这导致了体积和重量的损失：布线基础设施增加了30%的重量；电力电子重量的10%；固态断路器重量的30%是由于金属外壳；电机重量的25%是由于金属端板和外壳。在这些部件中使用CFRP实现这些功能将为设备带来~5%-10%的重量减轻。本项目将研究部件所承受的焦耳加热水平与由于热降解而导致的机械性能下降之间的相关性。该项目的一个主要内容是使用无损检测方法评估退化程度，并与持续的焦耳加热程度相关联。首先，这开发了一种更有效的评估退化的方法。这是至关重要的，因为有一组广泛的可变参数可能会影响CFRP对焦耳加热的响应。其次，这为今后对已通电的CFRP部件进行在役评估提供了一个平台。2.审查使用的碳纤维类型、电负载特性和电推进飞机中碳纤维的机械阈值(例如，EVTOL)。设计测试矩阵，对CFRP的电加载导致不同程度的降解。电载荷作用下CFRP降解数据集的实验捕获。使用非破坏性测试方法评估退化程度，并通过机械测试进行验证。根据观察到的退化阈值，提出设计和制造改进，以将退化保持在失效阈值以下(例如，铺层、电结合、制造方法)。

Reducing the use of metallic structures on aircraft, by replacement with lighter weight carbon fibre reinforced polymer (CFRP), enables optimisation of aircraft weight. Optimisation of weight for aircraft is critical and this includes the optimisation of the electrically powered propulsion system, where the biggest challenge is electrical power system weight. An example of a near-term aircraft with electrical propulsion is an electrical vertical take-off and land (eVTOL) aircraft, e.g. CityAirbus.CFRP has excellent mechanical properties, but it has poor conductivity compared to aluminium (~1000 times less). A gap in knowledge on the thresholds for failure of CFRP due to electrical current conduction, and methods to detect these in a non-destructive manner, results in industry standards requiring that CFRP and electrical equipment and cables are kept physically separate. This ensures that in the event of an electrical fault (e.g., due to insulation failure), electrical fault current will not flow through CFRP structures. This leads to volume and weight penalties: additional 30% weight on wiring infrastructure; 10% of power electronic weight, and 30 % of solid state circuit breaker weight is due to metallic casings; 25 % of motor weight is due to metallic end plates and casing. The use of CFRP for these functions in these components will bring weight reductions for the equipment of ~5 - 10 %.This project will investigate the correlation between the level of Joule heating sustained by a component and the reduction in mechanical properties due to thermal degradation. A major element of the project is the use of NDT methods to assess the level of degradation, and correlate to the level of Joule heating sustained. First, this develops a more efficient route to assessing degradation. This is critical, as there are a wide set of variable parameters which may influence the response of CFRP to Joule heating. Second, this provides a platform for future in-service assessment of CFRP components which have conducted electrical current.Key Objectives1. Review types of CFRP used, characteristics of electrical loading, and mechanical thresholds of CFRP in aircraft with electrical propulsion (e.g., EVTOL).2. Design test matrix for electrical loading of CFRP to lead to different levels of degradation.3. Experimental capture of datasets for degradation of CFRP due to electrical loading.4. Assessment of level of degradation using non-destructive test methods, verified by mechanical testing.5. From degradation thresholds observed, propose design and manufacture modifications to keep degradation below failure thresholds (e.g. layup, electrical bonding, manufacturing method).