Search

In this work, the use of advanced thermographic techniques for the post-impact defect detection in basalt fibre reinforced composite laminates was investigated. The laminates were previously impacted at different energies, namely 7.5, 15 and 22.5 J and then subjected to accelerated environmental aging or to a coating process in order to conceal the previous damage due to low velocity impact. In both cases the defects could be identified using infrared thermography in the mid-wave infrared (MWIR) spectrum even after the treatments. In addition, short-wave infrared (SWIR) results were employed with the aim to clearly identify unsuspected resin-rich areas. Therefore, the non-thermal part of the infrared spectrum (SWIR) can be coupled with the thermal part (MWIR) providing a complete infrared vision beyond what is perceptible to the naked eye, i.e., in the visible spectrum.

The prerequisite for more competent and cost-effective aircraft has led to the evolution of innovative testing and evaluation procedures. Smart methods for assessing the integrity of an aircraft structure are essential to both reduce manufacturing costs and out-of-service time of aircraft due to maintenance. Nowadays, thermal non-destructive testing (NDT) is commonly used for assessing aircraft composites. In this work, certain applications of transient thermal NDT relating to the assessment of aircraft composites are presented. In particular, the following features were studied: (a) Notches under multi-ply composite patching (bonded with FM73 adhesive film to the surface of Al 2024-T3) and a simulated delamination between two plies on a multi-ply composite repair. (b) Drilling induced defects on multi-ply laminates of HEXCEL AS4/8552 carbon fibre composites. (c) Impact damage on carbon fibre reinforced plastic (CFRP) panels and honeycomb sandwich structures (bonded with AF-163-2U.03 adhesive film). (d) Through skin sensing assessment of CFRP. Real-time monitoring of all features was obtained using pulsed thermography. However, in the composite repairs cases thermal modelling and pulsed-phase thermography were also used with the intention of providing supplementary results, whilst in the case of through skin imaging thermal modelling was also used in order to demonstrate the importance of thermal contact resistance between two surfaces (skin and strut). The thermal NDT approaches used in this work gave satisfactory results in all instances.

In numerous research domains where imaging plays a pivotal role in analysing specific objects or processes, it is crucial to quantitatively evaluate the performance of acquisition systems and processing algorithms in differentiating the target from its background. This paper presents the Multi-Scale Contrast-to-Noise Ratio (MS-CNR) metric, a novel tool for precise defect quantification across various imaging modalities. The MS-CNR metric employs the Laplacian of Gaussian (LoG) operator to analyse contrast at multiple scales, allowing for effective quantitative defect characterisation without relying on predefined regions for defects or noise. Through comprehensive evaluation with synthetic and real data, the MS-CNR metric demonstrates a strong correlation with human visual perception and other well-established SNR metrics. It provides consistent and reproducible results, outperforming traditional SNR metrics that may be affected by specific types of noise. The MS-CNR metric’s robust performance and alignment with visual assessments make it a valuable addition to imaging analysis, offering a reliable and automated approach for evaluating defect visibility. [ABSTRACT FROM AUTHOR]

The conservation of artworks is playing an increasingly important role in society today. Non-destructive investigation can provide the potential to identify deterioration as early as possible. In this research, transmission mid-wave infrared (MWIR) vision and air-coupled ultrasound (ACU) were used to investigate two paintings on canvas made from different textile support materials. An X-ray technique was used in the work for validation. It was found that the transmission mode can probe deeper and the differences in absorption due to the different textile support materials can be distinguished. This paper summarises advantages of the transmission inspection mode and compares and analyses images from the two techniques from a physical point of view. [ABSTRACT FROM AUTHOR]