Application of NDT thermographic imaging of aerospace structures

The application of fiber-reinforced polymer (FRP) composites is continuously increasing due to their superior mechanical properties and the associated weight advantage. However, they are susceptible to more complex types of damage, and advanced damage characterization systems are required to prevent catastrophic failures. Various non-destructive testing and evaluation (NDT&E) and in-situ structural health monitoring (SHM) techniques have been applied for damage detection in FRP composites. These techniques have been continuously developed to achieve reliable inspections, especially for safety-critical applications such as the aerospace industry. This review presents recent advances in NDT&E techniques and SHM techniques, particularly for damage diagnosis in FRP composites. For selecting the most suitable NDT technique based on specific criteria, the analytical hierarchy process is applied as a decision-making tool to evaluate and rank the NDT techniques. The size of the specimen is found to be the most important criterion that significantly affects technique selection. Finally, the importance of developing in-situ SHM systems is outlined, and different in-situ SHM systems are then reviewed and discussed. This review provides progress of the recent damage characterization techniques and enables researchers to devise selection criteria to select the most appropriate technique for their own work.

Advancements in fiber-reinforced polymer composite materials damage detection methods: Towards achieving energy-efficient SHM systems

A nonlinear ultrasonic SHM method for impact damage localisation in composite panels using a sparse array of piezoelectric PZT transducers.

Eddy current nondestructive testing (ECT) method is an efficient method based on electromagnetic induction for quantitative nondestructive evaluation of defects in the pipeline structure, due to its advantages of high detectability, non-contact and quick scanning. How to realize the probe scanning is a key issue for the long distance pipe inspection when the probe is located inside the tube. To address this problem, in this paper, a novel type of magnetic force transmission eddy current array split type probe has been proposed and developed to detect the defects in the pipeline structure. Firstly, the magnetic force transmission eddy current probe is proposed and designed, which includes excitation device outside the pipe and pickup device inside the pipe. The whole probe can simultaneously move along the pipe under the function of magnetic force. Secondly, the advantage of this proposed split type probe is validated through numerical simulation and experiment, which is that the detection signal cannot be saturated for deep buried defect, compared to the reflection type probe. Thirdly, the array structure pickup probe is designed and its merit is verified through simulation and experiment, which is that the detection sensitivity and efficiency are improved significantly. Finally, the proposed magnetic force transmission eddy current array probe is applied to detect one aluminum pipe with crack defects. The depth, axial position and circumferential position of the cracks can be successfully determined according to the proposed novel probe in this study.

A novel magnetic force transmission eddy current array probe and its application for nondestructive testing of defects in pipeline structures

This work aims to address the effectiveness and challenges of non-destructive testing (NDT) by active infrared thermography (IRT) for the inspection of aerospace-grade composite samples and seeks to compare uncooled and cooled thermal cameras using the signal-to-noise ratio (SNR) as a performance parameter. It focuses on locating impact damages and optimising the results using several signal processing techniques. The work successfully compares both types of cameras using seven different SNR definitions, to understand if a lower-resolution uncooled IR camera can achieve an acceptable NDT standard. Due to most uncooled cameras being small, lightweight, and cheap, they are more accessible to use on an unmanned aerial vehicle (UAV). The concept of using a UAV for NDT on a composite wing is explored, and the UAV is also tracked using a localisation system to observe the exact movement in millimetres and how it affects the thermal data. It was observed that an NDT UAV can access difficult areas and, therefore, can be suggested for significant reduction of time and cost.

Comparison of Cooled and Uncooled IR Sensors by Means of Signal-to-Noise Ratio for NDT Diagnostics of Aerospace Grade Composites.

Development of a thermal excitation source used in an active thermographic UAV platform

An intelligent and agile wireless communication scheme is a key factor in provision of efficient air-to-ground (A2G) communication for unmanned aerial vehicles (UAVs) operations. For this purpose we review and propose an architecture for aeronautical cognitive communication system (ACCS) that will be providing command, control and communication (C3) link between ground control stations (GCSs) and multiple UAVs utilizing cognitive radio (CR) concept. The factors reviewed and accounted for in the design process are the topology of cognitive detectors, connectivity between cognitive detector and control agency, connection with unmanned traffic management (UTM) system, data link requirements imposed by cognitive scheme, failure notification and recovery, etc. The proposed ACCS is suitable for supporting UAV operations and features a distributed non-communication architecture consisting of GCS network in the ground zone, hybrid data link with the static uplink and the flexible downlink, demonstrating a dynamic nature overall with the frequency handoff scheme generated periodically in accordance with current spectrum environment.

Alex Williamson

Papers

Application of NDT thermographic imaging of aerospace structures

Comparison of Cooled and Uncooled IR Sensors by Means of Signal-to-Noise Ratio for NDT Diagnostics of Aerospace Grade Composites.

Development of a thermal excitation source used in an active thermographic UAV platform

Cognitive Communication Scheme for Unmanned Aerial Vehicle Operation

Autonomous Architecture for UAV-based Agricultural Survey