Ion López

Bio: Ion López is an academic researcher. The author has contributed to research in topics: Interferometry & Electronic speckle pattern interferometry. The author has an hindex of 9, co-authored 16 publications receiving 328 citations.

Aeronautics composite material inspection with a terahertz time-domain spectroscopy system

Abstract: The usability of pulsed broadband terahertz radiation for the inspection of composite materials from the aeronautics industry is investigated, with the goal of developing a mobile time-domain spectroscopy system that operates in reflection geometry. A wide range of samples based on glass and carbon fiber reinforced plastics with various types of defects is examined using an imaging system; the results are evaluated both in time and frequency domain. The conductivity of carbon fibers prevents penetration of the respective samples but also allows analysis of coatings from the reflected THz pulses. Glass fiber composites are, in principle, transparent for THz radiation, but commonly with significant absorption for wavelengths >1 THz . Depending on depth, matrix material, and size, defects like foreign material inserts, delaminations, or moisture contamination can be visualized. If a defect is not too deep in the sample, its location can be correctly identified from the delay between partial reflections at the surface and the defect itself.

Feature extraction and analysis for automatic characterization of impact damage in carbon fiber composites using active thermography

Abstract: The use of composite materials in the industry has increased in the past few decades due to their high strength and stiffness to weight ratios. However, composite materials have a serious weakness: their sensitivity to impact damage. This work proposes a method to automatically characterize impact damage in carbon fiber composites using active thermography. Shape and amplitude features are extracted from the defects detected using image processing. The analysis of these features provides relevant conclusions about their relation to the impact energy, and the influence of number of plies and the type of core of the composite. Finally, a classifier based on neural networks is proposed to automatically characterize the detected defects caused by impact damage according to impact energy. Tests carried out over several specimens that contain impact damage of different energies show excellent performance for the classifier.

Combined holography and thermography in a single sensor through image-plane holography at thermal infrared wavelengths

Abstract: Holographic interferometry in the thermal wavelengths range, combining a CO(2) laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and surface shape information about objects. This is due to the fact that the holograms are affected by the thermal background emitted by objects at room temperature. We explain the setup and the processing of data which allows decoupling the two types of information. This natural data fusion can be advantageously used in a variety of nondestructive testing applications.

A quantitative comparison of stimulation and post-processing thermographic inspection methods applied to aeronautical carbon fibre reinforced polymer

Abstract: Active thermographic inspection is a very powerful tool for many areas of science. However, there is no agreement about the proper stimulation and post-processing method for a particular material and defect type, which forces technicians to carry out trial and error tests. This study presents a comparison of three stimulation and six post-processing thermographic inspection methods applied to aeronautical carbon fibre reinforced polymer with different kind of simulated defects. The obtained results have been quantitatively assessed using the signal-to-noise ratio metric. Conclusions provide recommendations for technicians interested in thermographic inspection of this type of material.

Infrared thermography for temperature measurement and non-destructive testing.

Abstract: The intensity of the infrared radiation emitted by objects is mainly a function of their temperature. In infrared thermography, this feature is used for multiple purposes: as a health indicator in medical applications, as a sign of malfunction in mechanical and electrical maintenance or as an indicator of heat loss in buildings. This paper presents a review of infrared thermography especially focused on two applications: temperature measurement and non-destructive testing, two of the main fields where infrared thermography-based sensors are used. A general introduction to infrared thermography and the common procedures for temperature measurement and non-destructive testing are presented. Furthermore, developments in these fields and recent advances are reviewed.

A review of non-destructive testing methods of composite materials

Abstract: A review provided about non-destructive testing (NDT) methods for the evaluation of composites. The review considers the capabilities of most common methods in composite NDT applications such as Visual Testing (VT or VI), Ultrasonic Testing (UT), Thermography, Radiographic Testing (RT), Electromagnetic Testing (ET), Acoustic Emission (AE), and Shearography Testing with respect to advantages and disadvantages of these methods. Then, methods categorized based on their intrinsic characteristics and their applications.

Review of terahertz photoconductive antenna technology

Abstract: Photoconductive antennas (PCAs) have been extensively utilized for the generation and detection of both pulsed broadband and single frequency continuous wave terahertz (THz) band radiation. These devices form the basis of many THz imaging and spectroscopy systems, which have demonstrated promising applications in various industries and research fields. The development of THz PCA technology through the last 30 years is reviewed. The key modalities of improving device performance are identified, and literature is reviewed to summarize the progress made in these areas. The goal of this review is to provide a collection of all relevant literature to bring researchers up to date on the current state and remaining challenges of THz PCA technology.