Hot/wet properties of high temperature composites

在一系列工业中，用先进的复合材料代替金属已经变得司空见惯。这是由于其优异的比刚度和强度，广泛的可用成分和制造工艺阵列，使其适用于多种应用，包括在航空航天和能源领域。由于复合材料在更极端的环境中使用，人们对能够承受高温和高温的有机基质产生了相当大的兴趣。因此，研究已经进行了开发新型热固性系统与增强的热湿耐用性。由于氰酸酯具有树脂注入和高玻璃化转变温度所需的粘度特性，使其适用于一系列应用，因此对氰酸酯具有特殊的兴趣。虽然对纯树脂的行为有一些了解，但在复合层压板中集成时，对其性能的了解很少。分层，即层间的分离，是复合材料的主要破坏机制。断裂韧性是衡量材料抗分层能力的指标。这些新材料的大多数试探性应用涉及在热和湿的存在下循环组件，这加速了降解机制。因此，必须了解这些热固性体系的层间断裂韧性特性，特别关注它们在热湿条件下的反应，然后才能在复合材料中常规使用。该项目将重点对一种领先的航空级环氧基复合材料IM7-8552，以及含有新型热固性树脂的复合材料进行实验测试。这将允许获得一组基线属性，以便与新开发的材料进行性能比较。虽然有关于试样湿度调节的规定，但对于获得复合材料在高温和高湿度下的断裂性能，还没有普遍接受的测试标准。因此，该项目的一个关键目标是开发一种更强大、更可靠的方法，用于在极端环境下进行测试，同时获得裂缝本身的特性。测试将首先在静态和准静态条件下进行，然后进行疲劳测试，以模拟材料在高温环境下连续循环和振动暴露所经历的条件。断口学分析将用于创建断裂表面的定性测量，开发易于识别的视觉指标，以确定材料在每种测试条件下是如何失效的，以便将来进行比较。一旦对复合材料中新型热固性系统的行为有了更深入的了解，并通过该项目的严格测试得到支持，其应用将在劳斯莱斯开发的涡扇发动机中得到应用。然而，如果这些材料被证明在高温下反复循环的环境中具有增强的耐久性，这将使它们在更广泛的应用中得到应用。这些可能包括传统的燃气轮机、先进的混合电力推进系统、电动机、发电机和储氢罐。在高温和高湿度条件下进行静态、准静态和疲劳试验的规程的开发将对断裂力学研究领域做出重大贡献。随着高温复合材料的使用范围不断扩大，能够在这些条件下自信地生成性能测试数据集对于高温复合材料的发展至关重要。

The replacement of metals with advanced composite materials within a range of industries has become commonplace. This is due to their excellent specific stiffness and strength, wide range of available constituents and array of manufacturing processes, making them suitable for a multitude of applications, including within the aerospace and energy sectors. As composites are employed in more extreme environments, there has been considerable interest in organic matrices that are able to withstand high temperatures and humidities. Thus, research has been conducted to develop novel thermoset systems with enhanced thermal and moisture durability properties. There has been specific interest in cyanate esters due to their desirable viscosity properties for resin infusion and high glass transition temperatures, making them suitable for a range of applications. Although there is some understanding of the behaviour of the neat resin, there is little knowledge on its performance when integrated within composite laminates. Delamination, the separation of layers, is the primary failure mechanism within composites. Fracture toughness is a measure of a material's resistance to delamination. Most tentative applications for these novel materials involve cycling components in the presence of heat and moisture which accelerates degradation mechanisms. Therefore, it is imperative to understand the interlaminar fracture toughness properties of these thermoset systems, with a particular focus on how they react in hot-wet conditions, before they can become routinely used within composites. This project will focus on the experimental testing of a leading aerospace-grade epoxy-based composite material, IM7-8552, in conjunction with composites containing the novel thermoset resins. This will allow a baseline set of properties to be acquired for performance comparison with the newly developed materials. Although regulations for moisture conditioning of test specimens exist, there is no universally accepted testing standard for acquiring fracture properties of composites at elevated temperatures and humidities. For this reason, a key objective of this project is to develop a more robust, reliable method for testing within extreme environments, along with obtaining the fracture properties themselves. Testing will initially be conducted in static and quasi-static conditions, followed by fatigue testing performed to mimic the conditions experienced by materials in-service under continuous cycling and vibration exposure whilst in high temperature environments. Fractographic analyses will be conducted to create qualitative measures of fractured surfaces, developing easily identifiable visual indicators of how the material failed in each set of testing conditions for future comparison. Once the behaviour of the novel thermoset systems within composites is more thoroughly understood, supported through rigorous testing within this project, the envisaged application for their use is within the turbofan engines developed by Rolls Royce. However, if these materials prove to have enhanced durability within environments involving repeated cycling at elevated temperatures, this will open them up for use within a broad spectrum of applications. These could include conventional gas turbines, advanced hybrid electric propulsion systems, motors, generators, and hydrogen storage tanks. The development of a vigorous protocol for static, quasi-static and fatigue testing in elevated temperatures and humidities will be a significant contribution to the fracture mechanics research field. The ability to confidently produce a data set of properties tested within these conditions is essential for the progression of high temperature composites as the boundaries for their use continue to be broadened.