Health monitoring and damage prognosis of aircraft composite structures

通过充分预测复合材料结构的剩余使用寿命进行健康监测是航空界感兴趣的一个主要领域，因为不断增长的维护费用估计每年在全球范围内达到100亿美元，这可能会缩短其经济寿命。拟议研究计划的目标是设计和制造与光纤传感器集成的先进复合材料，以监控制造过程，并使用相同的传感器网络开发一种损伤预测方法，以逐步取代当前的基于计划的维护任务，其中部件在预先确定的循环次数后进行检查，通过基于状态的维护来进行，其中部件在达到不足的剩余使用寿命之前进行维护。目前可用于监测飞机部件健康状况的系统和技术大多基于负荷监测系统，这些系统确定飞行参数，并能够通过射线照相、涡流、超声波或其他适当方法等小区域扫描过程得出关于飞行期间发生的负荷水平或定期维护的结论。现有的方法费时费力。因此，提供一种非破坏性评估技术，使结构健康评估成为飞机部件的组成部分，即结构健康监测，对于减少与维护部件可靠性相关的时间和成本至关重要。结构健康监测是一项新兴技术，致力于以最少的人力投入开发用于结构的连续监测、检查和损伤检测的技术和系统。(I)结构中损伤的存在及其类型，(Ii)损伤是局部的还是全局的(例如，材料中分布的大的孤立裂纹或许多小缺陷)，(Iii)损伤的位置，无论损伤是在材料中还是在节点和连接中(或两者都是)，以及(Iv)最终确定结构是否可能由于存在损伤而失效。

Health monitoring through adequate prediction of the remaining useful life of composite structures is a major area of interest for the aerospace community where the growing maintenance costs, estimated to $10 billion worldwide annually, can reduce their economic life. The objective of the proposed research program is to design and manufacture advanced composites integrated with fiber optic sensors to monitor the manufacturing process and to use the same sensor network to develop a damage prognostic approach to gradually replace current schedule-based maintenance tasks, where components are inspected after a pre-established number of cycles, by condition-based maintenance, where components are maintained prior to attaining an insufficient remaining useful life. The current systems and technologies available for monitoring the health of the aircraft components are mostly based on load monitoring systems that determine flight parameters, and enable conclusions to be drawn concerning the load levels occurred during the flight, or scheduled maintenance by means of small area scanning processes such as radiography, eddy currents, ultrasonic or other appropriate methods. The existing methods are time consuming and cost intensive. Therefore, the availability of a non-destructive evaluation technology, which makes the structural health assessment an integral part of the aircraft components, known as Structural Health Monitoring, is crucial in terms of reducing time and cost associated with maintaining reliability of components. SHM is an emerging technology, dealing with the development of techniques and systems for the continuous monitoring, inspection and damage detection of structures, with minimum labor involvement. The SHM focuses on finding answers to the very critical questions on: (i) damage existence in a structure and its type, (ii) whether the damage is local or global (e.g., a large isolated crack or many small defects distributed in the material), (iii) the location of the damage whether the damage is in the material or in the joints and connections (or both), and (iv) finally find out whether the structure is likely to fail due to the presence of damage.