Enhanced Ultrasonic 3D Characterisation Of Composites Using Full Matrix Capture Of Array Data

近年来，人们越来越关注将厚截面复合材料用于安全关键部件，例如飞机主结构和航空发动机的风扇叶片。所有这些部件在制造过程中都需要进行无损评估（NDE）；这是非常耗时的，而且NDE吞吐量在国际上已经达到了极限。目前的复合无损评价（NDE）是基于定性的经验方法，即使用单个正入射超声探头从后壁反射振幅估计平均超声衰减。虽然这种方法足以接受或拒绝薄复合板，但它不能提供较大部件定量无损检测所需的缺陷表征和定位水平。工业对定量NDE技术有明确而迫切的需求，这种技术可以应用于制造和使用中的安全关键复合部件。由于成本、安全性和易于部署的原因，超声波技术是工业上的首选，但需要提高扫描速度来加快吞吐量。然而，快速扫描、高穿透深度和精确缺陷表征的矛盾需求无法通过单个正入射探针实现。相反，来自多个检测方向的数据必须结合起来。利用超声阵列可以快速有效地获得必要的原始数据，但目前还不能充分利用。这是由于缺乏(a)斜波传播和散射过程的适当正演模型，以及(b)将原始数据转化为有用信息的合适反演方案。这就是拟议研究计划的动机，其目的是开发基于安全关键航空航天复合材料特征的物理推理的超声波阵列数据处理技术。该计划要求推进复合材料中波动现象的基础科学，解决具有挑战性的反问题，最重要的是，将科学发现转化为实际的工业解决方案。

Recent years have seen increasing interest in the use of thick-section composites for safety-critical components in, for example, primary aircraft structure and fan blades in aero engines. All such components are required to undergo non-destructive evaluation (NDE) during manufacture; this is time consuming and NDE throughput is stretched to its limit internationally. Current composite Non-destructive Evaluation (NDE) is based on a qualitative empirical approach where a single normal-incidence ultrasonic probe is used to estimate the average ultrasonic attenuation from the amplitude of the back-wall reflection. While adequate for accepting or rejecting thin composite panels, this approach does not provide the level of defect characterisation and localisation necessary for the quantitative NDE of larger components.There is a clear and pressing industrial need for quantitative NDE techniques that can be applied to safety-critical composite components both at manufacture and in-service. An ultrasonic technique is the industrially preferred option for reasons of cost, safety and ease of deployment, but increased scanning speeds are required to speed up throughput. However, the conflicting demands of rapid scanning, high-penetration depth and accurate defect characterisation cannot be achieved with a single normal-incidence probe. Instead the data from multiple inspection directions must be combined. The necessary raw data can be rapidly and efficiently obtained using an ultrasonic array, but at present it cannot be exploited. This is due to the lack of (a) an appropriate forward model of oblique wave propagation and scattering processes, and (b) a suitable inversion scheme to turn the raw data into useful information. This is the motivation for the proposed research programme, the aim of which is to develop ultrasonic array data processing techniques based on physical reasoning for the characterisation of safety-critical aerospace composites. The programme requires advancement of the fundamental science of wave phenomena in composites, the solution of a challenging inverse problem and, crucially, the translation of the scientific findings into practical industrial solutions.