Eddy-current inspection of complex geometries in carbon fibre composites

为了提高生产率，已经开发了先进的复合材料制造方法，例如自动纤维放置(AFP)系统，使制造商能够为一系列工业应用制造具有更大几何复杂性的部件。这些复杂的几何形状给碳纤维复合材料的制造带来了许多挑战，包括：曲线型表面的纤维不对准、内部角落的铺层桥接以及纤维密度的变化。它也位于复杂几何形状的区域，可能会出现高应力集中，因此需要严格的无损检测(NDT)。然而，这些复杂的几何形状给一些无损检测技术带来了巨大的检测挑战。涡流检测(ECT)是无损检测工具箱的主要组成部分，即使是非常小的不连续也能提供高灵敏度。然而，涡流传感器对被检测材料的局部几何形状也高度敏感，导致在更容易出现制造错误的边缘和拐角处出现不希望看到的几何信号。这些几何信号限制了ECT测量在这些环境中的灵敏度。本项目将探索在ECT测量中消除或隔离几何信号的方法，以提高这些关键区域缺陷迹象的信噪比。将开发有限元模型来模拟复杂的环境和优化传感器设计，同时将探索先进的多频率数据处理方法。预计将开发新的涡流传感器配置来实现这些检查。这项研究将主要由布里斯托尔超声和无损检测小组的Rob Hughes博士负责监督。学生将在实验ECT检测技术、数据处理和建模方面学习有价值的技能，最好能与ECT探头制造商和/或工业制造商密切合作。布里斯托尔的工作环境将使学生接触到涡流方法之外的一系列技术和能力。

To increase production rates advanced composite manufacturing methods have been developed, such as automated fibre placement (AFP) systems, allowing manufacturers to fabricate parts with greater geometric complexity for a range of industrial applications. These complex geometries introduce a number of manufacturing challenges for carbon fibre composites including; fibre misalignment of curvi-linear surfaces, ply bridging in internal corners and variations in fibre density. It is also in regions of complex geometries where high stress concentrations can occur thereby requiring rigorous non-destructive testing (NDT). However, these complex geometries present significant inspection challenges for some NDT techniques. Eddy current testing (ECT) is a staple of the NDT toolbox, offering high sensitivity to even very small discontinuities. However, eddy-current sensors are also highly sensitive to the local geometry of the material under inspection, leading to undesirable geometric signals at edges and corners where manufacturing errors are more likely to occur. These geometric signals limit the sensitivity of ECT measurements in these environments.This project will explore methods of eliminating or isolating geometric signals in ECT measurements to improve the signal-to-noise ratio of defect indications in these critical regions. Finite element models will be developed to simulate complex environments and optimise sensor design while advanced multi-frequency data-processing methods will be explored.It is anticipated that novel configurations of eddy current sensors will be developed to enable these inspections.The research will be primarily supervised by Dr Rob Hughes in the Bristol Ultrasonics and NDT group. The student will learn valuable skills in experimental ECT inspection techniques, data-processing, and modelling, and would ideally work closely with ECT probe manufacturers and/or industrial manufacturers. The work environment at Bristol will expose the student to a range of techniques and capabilities beyond Eddy Current approaches.