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Non Destructive Testing and Evaluation of Aerospace Composite Structures

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (25 May 2018) | Viewed by 79079

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Special Issue Editors

Dr. Nico P. Avdelidis

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Guest Editor

Computer Vision and Systems Laboratory (CVSL), Department of Electrical and Computer Engineering, Laval University, Quebec City, QC G1V 0A6, Canada
Interests: NDT; health diagnostics; non-invasive imaging; autonomous systems inspections; composites; structures; thermal imaging; monitoring
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Xavier Maldague

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Guest Editor

Faculty of Science and Engineering, Department of Electrical and Computer Engineering, Université Laval, Québec, QC, Canada
Interests: infrared thermography; NonDestructive Evaluation (NDE) techniques and vision / digital systems for industrial inspection
Special Issues, Collections and Topics in MDPI journals

Prof. Theodore E. Matikas

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Guest Editor

University of Ioannina, Ioannina, Greece
Interests: nondestructive techniques for damage assessment and life prediction of engineering materials and structures; structural helth monitoring; infrared thermography; ultrasonics; nonlinear acoustics; acoustic emission; fiber bragg gradings; vibrometry; metal matrix and ceramic matrix composites; cement based materials; coatings; nano-structured materials; multi-functional and intelligeant materials; smart sersors
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Composite materials have become increasingly popular among conventional, well-studied engineering materials, as they possess favourable strength-to-weight ratios along with enhanced design potential. Moreover, their higher stiffness, superior corrosion resistance, and improved fatigue performance have encouraged their use in several operating structures, orientating industrial interests, especially in the aeronautical and transport fields, regarding the use of these materials. Nevertheless, contrary to the advantages that composite materials have, their integrity can be impaired in several ways during fabrication, assembly, and on-life stages from various defect types that affect their performance. As a result, the wide use of these materials has created the need for the development and implementation of rapid and of field level non-destructive inspections, both for quality assurance during the manufacturing process, as well as for long-term condition monitoring of in-field performance. These testing procedures must provide inspectors with the ability not only to detect defects, but also the means to quantify these defects for continuous monitoring and comparison. For this reason, a large amount of work has been carried out focusing on the development of rapid and of large area inspection capabilities methods, able to detect damage by suitable Non Destructive Testing and Evaluation (NDT&E) techniques. Nondestructive testing and evaluation (NDT&E) is an essential part of comprehensive management of any aerospace system. NDT&E techniques are broadly employed to monitor materials and safety-critical components used in aerospace industry throughout their life-cycle, either in design or as part of a maintenance program. The development of novel NDE methodologies is essential, driven by the use of new materials, as well as new manufacturing processes in aerospace applications.

This Special Issue focuses on fostering improvements and new developments of technology in areas related to novel NDT&E techniques and approaches for characterization and real-time monitoring of aerospace composites, including use of advanced smart sensors and sensor networks, as well as strategies for data utilization for overall system safety and health management. We would like to invite original research articles, as well as review articles, that contain theoretical, analytical, and experimental investigations covering all aspects of NDT&E in aerospace composites and composite structures. Potential topics include, but are not limited to:

NDT&E (thermal, infrared, terahertz, optical, acoustic, vibration, electrical, electro-magnetic, radiographic, microwave, etc.) and damage assessment of composite materials and structures, coatings, multi-functional materials and nano-structured materials.
Sensor technologies for NDT&E, sensor networks and smart systems for evaluation, detection, monitoring and control of aerospace composites.
Continuous NDT&E and real time results for improving measurement accuracy and/or inspection technologies.
Integration of multiple NDT&E approaches for improving interpretation of results.
Modeling, simulation and technology development concerning NDT&E at multiple scales ranging from nano- and micro- scales to realistic aerospace structures.
Signal and/or image processing, data fusion, and energy harvesting for NDT&E and sensor monitoring.
Interdisciplinary approaches and applications for NDT&E.

Prof. N P Avdelidis
Prof. X P V Maldague
Prof. T E Matikas
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

nondestructive
structures
sensors
composites
coatings
nano-structured materials
multi-functional materials
aerospace
imaging
structural health monitoring

Published Papers (12 papers)

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18 pages, 8971 KiB

Open AccessArticle

Detection and Characterization of Damage in Quasi-Static Loaded Composite Structures Using Passive Thermography

by Joseph Zalameda and William Winfree

Sensors 2018, 18(10), 3562; https://doi.org/10.3390/s18103562 - 20 Oct 2018

Cited by 22 | Viewed by 3777

Abstract

Real-time nondestructive evaluation is critical during composites load testing. Of particular importance is the real time measurement of damage onset, growth, and ultimate failure. When newly formed damage is detected, the loading is stopped for further detailed characterization using ultrasound inspections or X-ray computed tomography. This detailed inspection data are used to document failure modes and ultimately validate damage prediction models. Passive thermography is used to monitor heating from damage formation in a hat-stiffened woven graphite epoxy composite panel during quasi-static seven-point load testing. Data processing techniques are presented that enable detection of the small transient thermographic signals resulting from damage formation in real time. It has been observed that the temperature rise due to damage formation at the surface is composed of two thermal responses. The first response is instantaneous and conforms to the shape of the damage. This heating is most likely due to irreversible thermoelastic, plastic deformation, and microstructural heating. The second response is a transient increase in temperature due to mechanical heating at the interface of failure. Two-dimensional multi-layered thermal simulations based on quadrupole method are used to investigate the thermal responses. In particular, the instantaneous response is used as the transient response start time to determine damage depth. The passive thermography measurement results are compared to ultrasonic measurements for validation. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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16 pages, 5104 KiB

Open AccessArticle

Analysis of Errors in the Estimation of Impact Positions in Plate-Like Structure through the Triangulation Formula by Piezoelectric Sensors Monitoring

by Eugenio Marino-Merlo, Andrea Bulletti, Pietro Giannelli, Marco Calzolai and Lorenzo Capineri

Sensors 2018, 18(10), 3426; https://doi.org/10.3390/s18103426 - 12 Oct 2018

Cited by 12 | Viewed by 3111

Abstract

The structural health monitoring (SHM) of critical structures is a complex task that involves the use of different sensors that are also aimed at the identification of the location of the impact point using ultrasonic sensors. For the evaluation of the impact position, reference is often made to the well-known triangulation method. This method requires the estimation of the differential time of arrival (DToA) and the group velocity of the Lamb waves propagating into a plate-like structure: the uncertainty of these two parameters is taken into consideration as main cause of localization error. The work proposes a simple laboratory procedure based on a set-up with a pair of sensors that are symmetrically placed with respect to the impact point, to estimate the uncertainty of the DToA and the propagation velocity estimates. According to a theoretical analysis of the error for the impact position, the experimental uncertainties of DToA and the propagation velocity are used to estimate the overall limit of the SHM system for the impact positioning. Because the error for the DToA estimate depends also on the adopted signal processing, three common methods are selected and compared: the threshold, the correlation method, and a likelihood algorithm. Finally, the analysis of the positioning error using multisensory configuration is reported as useful for the design of the SHM system. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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17 pages, 5365 KiB

Open AccessArticle

Thermochromic Polymer Film Sensors for Detection of Incipient Thermal Damage in Carbon Fiber–Epoxy Composites

by Ryan Toivola, Sei-Hum Jang, Shawn Baker, Alex K. -Y. Jen and Brian D. Flinn

Sensors 2018, 18(5), 1362; https://doi.org/10.3390/s18051362 - 27 Apr 2018

Cited by 6 | Viewed by 4416

Abstract

Carbon fiber–epoxy composites have become prevalent in the aerospace industry where mechanical properties and light weight are at a premium. The significant non-destructive evaluation challenges of composites require new solutions, especially in detecting early-stage, or incipient, thermal damage. The initial stages of thermal damage are chemical rather than physical, and can cause significant reduction in mechanical properties well before physical damage becomes detectable in ultrasonic testing. Thermochromic fluorescent probe molecules have the potential to sense incipient thermal damage more accurately than traditional inspection methods. We have designed a molecule which transitions from a colorless, non-fluorescent state to a colorful, highly fluorescent state when exposed to temperature–time combinations that can cause damage in composites. Moreover, this molecule can be dispersed in a polymer film and attached to composite parts as a removable sensor. This work presents an evaluation of the sensor performance of this thermochromic film in comparison to ultrasonic C-scan as a method to detect incipient thermal damage in one of the most widely used carbon fiber–epoxy composite systems. Composite samples exposed to varying thermal exposures were used to evaluate the fluorescent thermal sensor films, and the results are compared to the results of ultrasonic imaging and short-beam shear tests for interlaminar shear strength. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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14 pages, 8384 KiB

Open AccessArticle

Simulation Analysis of Fluid-Structure Interaction of High Velocity Environment Influence on Aircraft Wing Materials under Different Mach Numbers

by Lijun Zhang and Changyan Sun

Sensors 2018, 18(4), 1248; https://doi.org/10.3390/s18041248 - 18 Apr 2018

Cited by 7 | Viewed by 5491

Abstract

Aircraft service process is in a state of the composite load of pressure and temperature for a long period of time, which inevitably affects the inherent characteristics of some components in aircraft accordingly. The flow field of aircraft wing materials under different Mach numbers is simulated by Fluent in order to extract pressure and temperature on the wing in this paper. To determine the effect of coupling stress on the wing’s material and structural properties, the fluid-structure interaction (FSI) method is used in ANSYS-Workbench to calculate the stress that is caused by pressure and temperature. Simulation analysis results show that with the increase of Mach number, the pressure and temperature on the wing’s surface both increase exponentially and thermal stress that is caused by temperature will be the main factor in the coupled stress. When compared with three kinds of materials, titanium alloy, aluminum alloy, and Haynes alloy, carbon fiber composite material has better performance in service at high speed, and natural frequency under coupling pre-stressing will get smaller. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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16 pages, 2176 KiB

Open AccessArticle

Machine Learning and Infrared Thermography for Fiber Orientation Assessment on Randomly-Oriented Strands Parts

by Henrique Fernandes, Hai Zhang, Alisson Figueiredo, Fernando Malheiros, Luis Henrique Ignacio, Stefano Sfarra, Clemente Ibarra-Castanedo, Gilmar Guimaraes and Xavier Maldague

Sensors 2018, 18(1), 288; https://doi.org/10.3390/s18010288 - 19 Jan 2018

Cited by 20 | Viewed by 5236

Abstract

The use of fiber reinforced materials such as randomly-oriented strands has grown in recent years, especially for manufacturing of aerospace composite structures. This growth is mainly due to their advantageous properties: they are lighter and more resistant to corrosion when compared to metals and are more easily shaped than continuous fiber composites. The resistance and stiffness of these materials are directly related to their fiber orientation. Thus, efficient approaches to assess their fiber orientation are in demand. In this paper, a non-destructive evaluation method is applied to assess the fiber orientation on laminates reinforced with randomly-oriented strands. More specifically, a method called pulsed thermal ellipsometry combined with an artificial neural network, a machine learning technique, is used in order to estimate the fiber orientation on the surface of inspected parts. Results showed that the method can be potentially used to inspect large areas with good accuracy and speed. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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2639 KiB

Open AccessArticle

Enhanced Infrared Image Processing for Impacted Carbon/Glass Fiber-Reinforced Composite Evaluation

by Hai Zhang, Nicolas P. Avdelidis, Ahmad Osman, Clemente Ibarra-Castanedo, Stefano Sfarra, Henrique Fernandes, Theodore E. Matikas and Xavier P. V. Maldague

Sensors 2018, 18(1), 45; https://doi.org/10.3390/s18010045 - 26 Dec 2017

Cited by 23 | Viewed by 4982

Abstract

In this paper, an infrared pre-processing modality is presented. Different from a signal smoothing modality which only uses a polynomial fitting as the pre-processing method, the presented modality instead takes into account the low-order derivatives to pre-process the raw thermal data prior to applying the advanced post-processing techniques such as principal component thermography and pulsed phase thermography. Different cases were studied involving several defects in CFRPs and GFRPs for pulsed thermography and vibrothermography. Ultrasonic testing and signal-to-noise ratio analysis are used for the validation of the thermographic results. Finally, a verification that the presented modality can enhance the thermal image performance effectively is provided. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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7246 KiB

Open AccessArticle

Redundancy Analysis of Capacitance Data of a Coplanar Electrode Array for Fast and Stable Imaging Processing

by Yintang Wen, Zhenda Zhang, Yuyan Zhang and Dongtao Sun

Sensors 2018, 18(1), 31; https://doi.org/10.3390/s18010031 - 24 Dec 2017

Cited by 16 | Viewed by 4118

Abstract

A coplanar electrode array sensor is established for the imaging of composite-material adhesive-layer defect detection. The sensor is based on the capacitive edge effect, which leads to capacitance data being considerably weak and susceptible to environmental noise. The inverse problem of coplanar array electrical capacitance tomography (C-ECT) is ill-conditioning, in which a small error of capacitance data can seriously affect the quality of reconstructed images. In order to achieve a stable image reconstruction process, a redundancy analysis method for capacitance data is proposed. The proposed method is based on contribution rate and anti-interference capability. According to the redundancy analysis, the capacitance data are divided into valid and invalid data. When the image is reconstructed by valid data, the sensitivity matrix needs to be changed accordingly. In order to evaluate the effectiveness of the sensitivity map, singular value decomposition (SVD) is used. Finally, the two-dimensional (2D) and three-dimensional (3D) images are reconstructed by the Tikhonov regularization method. Through comparison of the reconstructed images of raw capacitance data, the stability of the image reconstruction process can be improved, and the quality of reconstructed images is not degraded. As a result, much invalid data are not collected, and the data acquisition time can also be reduced. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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4642 KiB

Open AccessArticle

Hybrid Signal Processing Technique to Improve the Defect Estimation in Ultrasonic Non-Destructive Testing of Composite Structures

by Kumar Anubhav Tiwari, Renaldas Raisutis and Vykintas Samaitis

Sensors 2017, 17(12), 2858; https://doi.org/10.3390/s17122858 - 09 Dec 2017

Cited by 56 | Viewed by 8804

Abstract

This work proposes a novel hybrid signal processing technique to extract information on disbond-type defects from a single B-scan in the process of non-destructive testing (NDT) of glass fiber reinforced plastic (GFRP) material using ultrasonic guided waves (GW). The selected GFRP sample has been a segment of wind turbine blade, which possessed an aerodynamic shape. Two disbond type defects having diameters of 15 mm and 25 mm were artificially constructed on its trailing edge. The experiment has been performed using the low-frequency ultrasonic system developed at the Ultrasound Institute of Kaunas University of Technology and only one side of the sample was accessed. A special configuration of the transmitting and receiving transducers fixed on a movable panel with a separation distance of 50 mm was proposed for recording the ultrasonic guided wave signals at each one-millimeter step along the scanning distance up to 500 mm. Finally, the hybrid signal processing technique comprising the valuable features of the three most promising signal processing techniques: cross-correlation, wavelet transform, and Hilbert–Huang transform has been applied to the received signals for the extraction of defects information from a single B-scan image. The wavelet transform and cross-correlation techniques have been combined in order to extract the approximated size and location of the defects and measurements of time delays. Thereafter, Hilbert–Huang transform has been applied to the wavelet transformed signal to compare the variation of instantaneous frequencies and instantaneous amplitudes of the defect-free and defective signals. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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4740 KiB

Open AccessArticle

Fatigue Damage Evaluation of Short Carbon Fiber Reinforced Plastics Based on Phase Information of Thermoelastic Temperature Change

by Daiki Shiozawa, Takahide Sakagami, Yu Nakamura, Shinichi Nonaka and Kenichi Hamada

Sensors 2017, 17(12), 2824; https://doi.org/10.3390/s17122824 - 06 Dec 2017

Cited by 9 | Viewed by 5059

Abstract

Carbon fiber-reinforced plastic (CFRP) is widely used for structural members of transportation vehicles such as automobile, aircraft, or spacecraft, utilizing its excellent specific strength and specific rigidity in contrast with the metal. Short carbon fiber composite materials are receiving a lot of attentions because of their excellent moldability and productivity, however they show complicated behaviors in fatigue fracture due to the random fibers orientation. In this study, thermoelastic stress analysis (TSA) using an infrared thermography was applied to evaluate fatigue damage in short carbon fiber composites. The distribution of the thermoelastic temperature change was measured during the fatigue test, as well as the phase difference between the thermoelastic temperature change and applied loading signal. Evolution of fatigue damage was detected from the distribution of thermoelastic temperature change according to the thermoelastic damage analysis (TDA) procedure. It was also found that fatigue damage evolution was more clearly detected than before by the newly developed thermoelastic phase damage analysis (TPDA) in which damaged area was emphasized in the differential phase delay images utilizing the property that carbon fiber shows opposite phase thermoelastic temperature change. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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8678 KiB

Open AccessArticle

Demonstration and Methodology of Structural Monitoring of Stringer Runs out Composite Areas by Embedded Optical Fiber Sensors and Connectors Integrated during Production in a Composite Plant

by Carlos Miguel Giraldo, Juan Zúñiga Sagredo, José Sánchez Gómez and Pedro Corredera

Sensors 2017, 17(7), 1683; https://doi.org/10.3390/s17071683 - 21 Jul 2017

Cited by 6 | Viewed by 7240

Abstract

Embedding optical fibers sensors into composite structures for Structural Health Monitoring purposes is not just one of the most attractive solutions contributing to smart structures, but also the optimum integration approach that insures maximum protection and integrity of the fibers. Nevertheless this intended integration level still remains an industrial challenge since today there is no mature integration process in composite plants matching all necessary requirements. This article describes the process developed to integrate optical fiber sensors in the Production cycle of a test specimen. The sensors, Bragg gratings, were integrated into the laminate during automatic tape lay-up and also by a secondary bonding process, both in the Airbus Composite Plant. The test specimen, completely representative of the root joint of the lower wing cover of a real aircraft, is comprised of a structural skin panel with the associated stringer run out. The ingress-egress was achieved through the precise design and integration of miniaturized optical connectors compatible with the manufacturing conditions and operational test requirements. After production, the specimen was trimmed, assembled and bolted to metallic plates to represent the real triform and buttstrap, and eventually installed into the structural test rig. The interrogation of the sensors proves the effectiveness of the integration process; the analysis of the strain results demonstrate the good correlation between fiber sensors and electrical gauges in those locations where they are installed nearby, and the curvature and load transfer analysis in the bolted stringer run out area enable demonstration of the consistency of the fiber sensors measurements. In conclusion, this work presents strong evidence of the performance of embedded optical sensors for structural health monitoring purposes, where in addition and most importantly, the fibers were integrated in a real production environment and the ingress-egress issue was solved by the design and integration of miniaturized connectors compatible with the manufacturing and structural test phases. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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Review

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37 pages, 10483 KiB

Open AccessReview

Recent Advances in Active Infrared Thermography for Non-Destructive Testing of Aerospace Components

by Francesco Ciampa, Pooya Mahmoodi, Fulvio Pinto and Michele Meo

Sensors 2018, 18(2), 609; https://doi.org/10.3390/s18020609 - 16 Feb 2018

Cited by 313 | Viewed by 23535

Abstract

Active infrared thermography is a fast and accurate non-destructive evaluation technique that is of particular relevance to the aerospace industry for the inspection of aircraft and helicopters’ primary and secondary structures, aero-engine parts, spacecraft components and its subsystems. This review provides an exhaustive summary of most recent active thermographic methods used for aerospace applications according to their physical principle and thermal excitation sources. Besides traditional optically stimulated thermography, which uses external optical radiation such as flashes, heaters and laser systems, novel hybrid thermographic techniques are also investigated. These include ultrasonic stimulated thermography, which uses ultrasonic waves and the local damage resonance effect to enhance the reliability and sensitivity to micro-cracks, eddy current stimulated thermography, which uses cost-effective eddy current excitation to generate induction heating, and microwave thermography, which uses electromagnetic radiation at the microwave frequency bands to provide rapid detection of cracks and delamination. All these techniques are here analysed and numerous examples are provided for different damage scenarios and aerospace components in order to identify the strength and limitations of each thermographic technique. Moreover, alternative strategies to current external thermal excitation sources, here named as material-based thermography methods, are examined in this paper. These novel thermographic techniques rely on thermoresistive internal heating and offer a fast, low power, accurate and reliable assessment of damage in aerospace composites. Full article

(This article belongs to the Special Issue Non Destructive Testing and Evaluation of Aerospace Composite Structures)

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