Nowadays, the application of glass-fibre composites in light-weight structures is growing. Although mechanical characterizations of those structures are commonly performed in testing, chemical changes of materials under stresses have not yet been well documented. In the present work coupon tests and Hyperspectral Imaging (HSI) have been used to categorise possible chemical changes of glass-fibre reinforced polymers (GFRP) which are currently used in the aircraft industry. HSI is a hybrid technique that combines spectroscopy with imaging. It is able to detect chemical degradation of surfaces and has already been successfully applied in a wide range of fields including astronomy, remote sensing, cultural heritage and medical sciences. GFRP specimens were exposed to two different thermal loading conditions. One thermal loading condition was a continuous thermal exposure at 120°C for 24h, 48 h and 96h, i.e. ageing at a constant temperature. The other thermal loading condition was thermal cycling with three different numbers of cycles (4000, 8000, 12000) and two temperature ranges (0°C to 120°C and -25°C to 95°C). The effects of both conditions were measured using both HSI and interlaminar shear (ILSS) tests. No significant changes of the physical properties of the thermally cycled GFRP specimens were detected using interlaminar shear strength tests and optical microscopy. However, when using HIS, differences of the surface conditions were detected. The results showed that the different thermal loading conditions could be successfully clustered in different colours, using the HSI linear unmixing technique. Each different thermal loading condition showed a different chemical degradation level on its surface which was indicated using different colours.
Optical coherence tomography (OCT) is a contactless and non-destructive testing (NDT) technique based on low-coherence interferometry. It has recently become a popular NDT-tool for evaluating cultural heritage. In this study, protective coatings on wood and their penetration into the wood structure were measured with a customized infrared fiber optic OCT instrument. In order to enhance the understanding of the OCT measurements of coatings on real wooden samples, an optimization of the measuring and analyzing methodology was performed by developing an averaging approach and by post-processing the data. The collected information was complemented by data obtained with hyperspectral imaging to allow data from local OCT A-scans to be used in mapping the coating thicknesses over larger areas.
Deterioration of artwork, in particular paintings, can be produced by environmental factors such as temperature
fluctuations, relative humidity variations, ultraviolet radiation and biological factors among others. The effects of these
parameters produce changes in both the painting structure and chemical composition. While well established analytical
methodologies, such as those based in Raman Spectroscopy and FTIR Spectroscopy require the extraction of a sample
for its inspection, other approaches such as hyperspectral imaging and 3D scanning present advantages for in-situ, noninvasive
analysis of artwork. In this paper we introduce a novel system and the related methodology to acquire process,
generate and analyze 4D data of paintings. Our system is based on non-contact techniques and is used to develop
analytical tools which extract rich 3D and hyperspectral maps of the objects, which are processed to obtain accurate
quantitative estimations of the deterioration and degradation present in the piece of art. In particular, the construction of
4D data allows the identification of risk maps on the painting representation, which can allow the curators and restorers
in the task of painting state evaluation and prioritize intervention actions.
The SYDDARTA project is an on-going European Commission funded initiative under the 7th Framework Programme. Its main objective is the development of a pre-industrial prototype for diagnosing the deterioration of movable art assets. The device combines two different optical techniques for the acquisition of data. On one hand, hyperspectral imaging is implemented by means of electronically tunable filters. On the other, 3D scanning, using structured light projection and capturing is developed. These techniques are integrated in a single piece of equipment, allowing the recording of two optical information streams. Together with multi-sensor data merging and information processing, estimates of artwork deterioration and degradation can be made. In particular, the resulting system will implement two optical channels (3D scanning and short wave infrared (SWIR) hyperspectral imaging) featuring a structured light projector and electronically tunable spectral separators. The system will work in the VIS-NIR range (400-1000nm), and SWIR range (900-2500nm). It will be also portable and user-friendly. Among all possible art work under consideration, Baroque paintings on canvas and wooden panels were selected as the project case studies.
Cavity-enhanced ellipsometry, using nanosecond pulsed lasers and without moving parts, is demonstrated to have
submicrosecond time resolution. The ellipsometric phase angles are measured from the Fourier transform of the cavity
ring-down experimental signals, with a sensitivity 0.01 degrees. The technique is applied to highly reflective surfaces,
including total internal reflection, where the samples are placed within the evanescent wave. The technique can be
generalized to broadband sources, such as from supercontinuum generation, allowing spectral resolution of thin films
and monolayer samples.
A new portable spectral imaging system is herein presented capable of acquiring images of high resolution (2MPixels)
ranging from 380 nm up to 950 nm. The system consists of a digital color CCD camera, 15 interference filters covering
all the sensitivity range of the detector and a robust filter changing system. The acquisition software has been developed
in "LabView" programming language allowing easy handling and modification by end-users. The system has been tested
and evaluated on a series of objects of Cultural Heritage (CH) value including paintings, encrusted stonework, ceramics
etc. This paper aims to present the system, as well as, its application and advantages in the analysis of artworks with
emphasis on the detailed compositional and structural information of layered surfaces based on reflection & fluorescence
spectroscopy. Specific examples will be presented and discussed on the basis of system improvements.