Inspection Of Composites Research Articles

On distant neutron logging (laser methods)

We discuss the concept of remote inspection of the isotopic composition of objects in space by products of nuclear reactions (including the fission of heavy isotopes), initiated by directed accelerated beams of ultracold neutrons. Despite the partial unavailability of quantitative estimates of specific situations, the proposed approach is internally consistent. We emphasise the urgency of development the problem in question and offer directions for further research.

Evolution of industrial laser-ultrasonic systems for the inspection of composites

For nearly 30 years, laser ultrasonics has been under investigation and development for the inspection of complex composites for the aeronautic industry; however, this technology has failed to achieve widespread adoption. The authors of this paper use their combined experience of over 40 years in the development and use of laser-ultrasonic systems in industrial environments to review the characteristics that appeared to have limited the widespread use of laser ultrasonics in the aeronautic industry. The authors review various technologies that they have explored and developed over the years to address those issues. Finally, a novel laser-ultrasonic approach is described and its capabilities are discussed.

Testing of composite materials using advanced NDT methods

PurposeThe purpose of this paper is to present capabilities of terahertz imaging technology in case of various composite materials and to propose a new defect detection algorithm.Design/methodology/approachThis paper first discusses an applicability of the terahertz technique in composite materials inspection. It then describes source of terahertz radiation (photoconductive antenna) and general structure of terahertz time domain imaging system. Next the terahertz imaging results of composite anticorrosion coating, glass‐ and carbon‐fiber‐reinforced laminates are presented. Then the signal processing and identification scheme based on time domain A‐scan signal equalization and C‐scan thresholding is presented. Data processed in this way are parameterized and defect identification database is prepared. The proposed procedure is verified using the exemplary inspection results of glass‐fiber laminate delamination. Finally, some comparison of terahertz time domain inspection with low energy digital radiography is presented.FindingsThis paper shows terahertz imaging as a well‐suited technique for composite structures inspection. The terahertz imaging results of composite anticorrosion coating, glass‐ and carbon‐fiber‐reinforced laminates are presented. An application of proposed signal processing algorithm enables accurate defects detection and effective data collection for identification database purpose.Originality/valueThe paper provides an insight into the potential of terahertz imaging of various composite structures. Proposed signal processing and defects detection scheme is applicable to wide range of composite structures.

Fabrication of a Multi-Physics Integral Structural Diagnostic System Utilizing Nano-Engineered Materials

Composites present additional challenges for inspection due to their heterogeneity and anisotropy, and since damage often occurs beneath their surface. Currently successful laboratory non-destructive methods, such as X-ray and C-scans, are impractical for inspection of large integrated structures. It is clear that new approaches for inspection of composites need to be developed. During the present research, multiple carbon nanotube (CNT) based NDE & SHM techniques were investigated to resolve these issues. Aligned CNTs offer excellent mechanical toughness improvements for traditional composite laminates, and additionally enable multifunctional capabilities through piezoresistive properties and greatly enhanced electrical and thermal conductivity. This paper introduces the fabrication of fuzzy-fiber reinforced plastic (FFRP) composite laminates uses CNTs, and presents results for multiple CNT-enhanced laminates that were electroded using direct-write techniques and subject to impact damage. A resistive-based method was used to create a detailed damage map of the effected zone. Finally, demonstrations are also described for multiple alternative CNT-based NDE approaches that were explored.

Surface preparation of Si(1 0 0) by thermal oxide removal in a chemical vapor environment

The preparation of Si(1 0 0) surfaces in chemical vapor environments suitable for subsequent epitaxial III–V integration by chemical vapor deposition (CVD) involving metal-organic precursors was investigated by surface sensitive instruments accessible through a dedicated sample transfer to ultra high vacuum (UHV). Using X-ray photoelectron spectroscopy for inspection of the chemical surface composition, we verified the ability to obtain clean Si(1 0 0) free of oxygen or other contaminants. Annealing for 30 min in a pure hydrogen atmosphere of 950 mbar pressure was found to be sufficient if the surface temperature reached at least 950 °C. We characterized the crucial annealing step comprehensively regarding reliability, dependency on essential process parameters (such as annealing time and surface temperature). Our results verified significant differences to established Si(1 0 0) UHV preparation routines and therefore indicated a major influence of the process gas in the SiO 2 removal process, hence we also considered a chemically active role of the hydrogen ambient in the deoxidation reaction. A complementary assessment of the general structure and the atomic configuration of our CVD-prepared Si(1 0 0) surfaces included low energy electron diffraction and scanning tunnelling microscopy and confirmed atomically flat surfaces with two-domain (2×1)/(1×2) reconstruction typical for completely deoxidized Si(1 0 0) as well as for a monohydride termination.

Reannotation of protein‐coding genes based on an improved graphical representation of DNA sequence

Over annotation of protein coding genes is common phenomenon in microbial genomes, the genome of Amsacta moorei entomopoxvirus (AmEPV) is a typical case, because more than 63% of its annotated ORFs are hypothetical. In this article, we propose an improved graphical representation titled I-TN (improved curve based on trinucleotides) curve, which allows direct inspection of composition and distribution of codons and asymmetric gene structure. This improved graphical representation can also provide convenient tools for genome analysis. From this presentation, 18 variables are exploited as numerical descriptors to represent the specific features of protein coding genes quantitatively, with which we reannotate the protein coding genes in several viral genomes. Using the parameters trained on the experimentally validated genes, all of the 30 experimentally validated genes and 63 putative genes in AmEPV genome are recognized correctly as protein coding, the accuracies of the present method for self-test and cross-validation are 100%, respectively. Twenty-eight annotated hypothetical genes are predicted as noncoding, and then the number of reannotated protein coding genes in AmEPV should be 266 instead of 294 reported in the original annotations. Extending the present method trained in AmEPV to other entomopoxvirus genomes directly, such as Melanoplus sanguinipes entomopoxvirus (MsEPV), all of the 123 annotated function-known and putative genes are recognized correctly as protein coding, and 17 hypothetical genes are recognized as noncoding. The present method could also be extended to other genomes with or without adaptation of training sets with high accuracy.

Impact of Waveguide Filling Material on Near-Field Microwave Inspection of Carbon-Loaded Composites

The advent of carbon loaded composite materials gave a boost to many industries. This is because of their light weight, durability and strength. As new structures utilizing carbon loaded composites are built, the need for a reliable nondestructive testing technique increases. A carbon-loaded composite testing poses a challenge to most nondestructive testing and evaluation (NDT&E) techniques. Microwave NDT&I techniques main challenge is the lossy nature of carbon, especially at high microwave frequencies. Lower frequencies penetrate deeper in carbon-loaded composites, however, to operate at lower frequencies the size of the waveguide probe increases significantly which degrades the resolution rapidly. Open-ended rectangular waveguide sensors filled with a dielectric material will be used to inspect carbon-loaded composites. The filling of the waveguide reduces the frequency of operation and keeps the small size of the waveguide (i.e. increases the penetration depth and maintains the resolution). However, varying the waveguide filling material dielectric properties will have an impact on the measurement parameters optimization process and consequently on the detection sensitivity. In this paper, the use of the waveguide filling material as an optimization parameter will be investigated. Carbon-loaded composites with disbonds will be inspected and the variation of the dielectric properties of the loading material of rectangular waveguide probes for carbon loaded composites inspection will be assessed.

Degradation of CoSb3 in Air at Elevated Temperatures

Degradation of CoSb3 in air was studied at 500, 600 and 700 °C. The type and extent of degradation was evaluated on the basis of specimen mass change, scale thickness, visual inspection and systematic analysis of chemical composition, phase composition and microstructure of specimen surfaces, fractures and cross-sections. It has been found that at the investigated temperatures, CoSb3 is neither sufficiently stable nor oxidation-resistant. Antimony and cobalt react readily with oxygen by 500 °C. The oxide scales are complex, with the predominant constituents being cobalt-antimony oxides, CoSb2O4 and CoSb2O6. A tentative reaction mechanism is proposed.

Surface molecular degradation of 3D glass polymer composite under low earth orbit simulated space environment

Epoxy resin reinforced with 3D parabeam glass fibre was subjected to low earth orbit (LEO) simulation conditions comprising ultra high vacuum, temperature cycling (TC), and ultraviolet (UV) radiation and atomic oxygen (AO) bombardment. Inspection of the same composite using only a selection of these hazardous conditions provided comparison measures to identify the effect of each condition on the surface degradation of the resin composite. Each of the individually selected conditions showed a different degradation mechanism that is accelerated by the presence of other conditions. X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy (SEM) were used to provide surface information. The resin composite samples suffered surface oxidation that increased the oxygen content to 17.24% in comparison with the untreated sample (only 14.2%). The samples that were treated with AO showed higher C–O and C O functional groups on the surface in comparison with the rest of the samples (as indicated by XPS). Molecular information (from ToF-SIMS) showed that surface oxidation differs with different conditions and in comparison with the use of all conditions. All treated samples were shown to suffer significant chain scission and loss of volatiles as a result of the LEO conditions. The extent of the chain scission reaction for each condition can be indicated by the extent of the reduction of the relative concentration of the aliphatic hydrocarbon ions. The relative intensity of the C 4H 11N 4O 2 + ion showed that AO bombardment accelerated the oxidation of the surface. The AO effect is doubled when UV and TC are also present. SEM results indicated that sample surfaces were eroded and roughened upon exposure to LEO conditions. Presence of AO and UV in the LEO conditions introduced white deposits onto the surface, believed to be crosslinked formations.

Micro gear validation: improving the correlation between virtual and physical testing

Downsizing mechanical systems requires the consideration of technological environment and restrictions. Nominal dimensions can be miniaturized, but shape and material deviations cannot be scaled down in the same way. In design these effects have to be considered and thus analyzed and evaluated in the very early activities. Simulation and test methods have to be adapted to the special characteristics of microtechnology. The present paper provides a strategy to validate micromechanical systems by means of virtual and physical testing. A standard test approach in macroscopic gear metrology, the tangential composite inspection, is used as validation tool for both test approaches. The results are very promising and show a good correlation between both miniaturized tests procedures.

Review of models and simulators for NDT reliability (POD)

With the use of probabilistic and risk-based methods by industry it is often necessary to estimate and input values for the reliability of inspection methods typically in terms of probability of detection (POD). In many cases this has been based on expert judgement. In recent years a more structured approach has developed using multi-parameter POD models. POD models have been around since the early 1990s. Inspection reliability has featured recently in a number of important legal cases, which has focused attention on the factors affecting reliability and approaches used to estimate reliability in practical circumstances. This paper will review the development of models for POD in Europe and the USA in the last decade and the current state-of-the-art in inspection reliability modelling by ESR Technology and others. Examples will include models for composite inspection developed for the European Space Agency and a specific model-based and simulator 'POD Generator' approach developed in the offshore industry through the HOIS joint industry project. This allows the POD for corrosion mapping and radiography inspections to be estimated and parametric studies undertaken to estimate the reliability of commercial inspection eguipment in real situations. Other model-based approaches will be assessed. These include model-assisted POD approaches developed in the US aerospace industry, use of transfer functions to extend hit/miss and â versus a POD trial data to new applications, simulated POD trials, the addition of POD modules to established 3D and CAD inspection models and the use of NDT simulators. There are analogies now for POD modelling for NDT methods to the use of finite element analysis for stress analysis. In the early 1990s, FE analysis was treated with some suspicion and normal practice was to carry out expensive large-scale component tests. Nowadays, FE analysis is widely accepted and large-scale testing is carried out as the exception to validate the FE models. The use of model-assisted and model-derived methods to derive POD data has gained significant acceptance and arguably is becoming the preferred method to generate POD values, with POD trials providing model validation. Empirical methods developed in NNDTC to correct POD data for human and environmental effects are also discussed.

TN curve: A novel 3D graphical representation of DNA sequence based on trinucleotides and its applications

In this paper, a novel 3D graphical representation of DNA sequence based on trinucleotides is proposed. This representation allows direct inspection of composition as well as distribution of trinucleotides in DNA sequence for the first time and avoids loss of information, from which one can obtain more information. Based on this novel model, six numerical descriptors of DNA sequence are deduced without complicated calculations, and the applications in similarities/dissimilarities analysis of coding sequences and conserved genes discrimination illustrate their utilities. In addition, two simple methods for similarities/dissimilarities analysis of coding sequences among different species are exploited by using two vectors composed of 64 and six components, respectively, which can provide convenient sequence alignment tools for both computational scientists and molecular biologists.

NEWSDESK: New CT imaging facility at Manchester University; Terahertz system for Iowa State; Sophisticated metals analyser helps protect power station pipes; Outstanding ‘world first’ achievement for vibration analysis expert; Museum digitally analyses art using GE technology; GE works with Boeing to develop new composite inspection solution

NEWSDESK: New CT imaging facility at Manchester University; Terahertz system for Iowa State; Sophisticated metals analyser helps protect power station pipes; Outstanding ‘world first’ achievement for vibration analysis expert; Museum digitally analyses art using GE technology; GE works with Boeing to develop new composite inspection solution

Results of Nondestructive Inspection of Layered Composites Using IR Thermography and Ultrasonics

Polymeric layered composites exhibit a variety of damages following in service loading conditions, like delamination, matrix cracking or even fibre breaking. Detection of such damages and assessing their extension and severity is vital during maintenance cycle, in view of keeping the normal operational reliability. For local inspections, IR thermography and ultrasonic scanning are among the best valued NDT methods. The paper describes the inspections performed by IR active thermography, in different variants, and pulse-echo ultrasonic scanning on GFRP. A variety of layered composites and defects/damages were inspected and the results are evaluated independently, in some cases being compared each other, with valuable conclusions for the users of the mentioned NDI techniques.

Time delay comb transducers for aircraft inspection

AbstractAn ultrasonic guided wave technique based on time delay comb transducers is introduced for aircraft inspection. It is demonstrated that for isotropic plate structures the time delay comb transducers with appropriate excitation are capable of performing discontinuity detections without knowing the precise isotropic material properties of the objects being inspected. Fibre-reinforced composite plates are also considered. The wave skew effects are investigated using both the slowness curve and the Poynting vector. A composite inspection technique that takes advantage of the skew effects is proposed. Using time delay comb transducers to excite the guided wave modes with different skew angles, the proposed technique is capable of scanning the composite plate in different directions without moving or rotating the transducers. By contrast with the applications in the isotropic cases, knowledge of the material properties and other necessary information that is needed to produce dispersion curves is generally required. Experimental results are provided as a validation of the proposed techniques.

Non-destructive Inspection of Composites Using Step Heating Thermography

The article explores the use of step heating thermography for defect identification in glass fiber reinforced composites. Step heating methods have potential for increasing the maximum detectable defect depth as compared with pulse heating methods. Inspection of thick fiberglass composites containing flat-bottom holes and resistive embedded defects using step heating thermography is investigated using 1-D analytical models, axisymmetric finite element modes, and experimental methods. 1-D heat transfer models of embedded defects under step heating are developed based on results from previous research of pulse heating thermography. Finite element models are used to explore the range of validity of defect identification techniques based on correlation with 1-D analytical methods, and it is found that accurate results are obtained for a defect radius to thickness ratio greater than two. Experimental results demonstrate the validity of the 1-D models for high defect resistance cases. For low resistance defects, detection is more difficult due to reduction of signal strength. A simple procedure is proposed to simultaneously determine defect depth and thermal resistance from the early time surface temperature profile based a two-point correlation with one-dimensional resistive defect solutions.

An integrated approach for validating micro mechanical systems based on simulation and test

Miniaturization of macroscopic mechanical systems enables the opening of new areas of application for micro technological systems. Because of technological restrictions, especially when applying miniaturized conventional manufacturing techniques, shape and material deviations cannot be scaled down in the same dimension like micro parts. Thus, the long-term objective is to ensure the functioning by appropriate design measures. In doing so, determination of the transfer behavior by modeling and simulation is required. This work presents two ways for ensuring the required properties of micro gears and describes how the results do correlate. The experimental way uses the radial composite inspection as it is used in the macroscopic world. The simulative way deploys a rolling simulation by utilization of finite element analysis. The virtual prototypes are originated on measured real test gears. When comparing experiment and simulation of the rolling behavior, in some short and long wave areas deviations can be recognized. These can be ascribed to the reduction from three to two dimensions when modeling. Other deviations might be based on inaccuracies when mounting into the test rig. In other areas quite good correlations of test and simulation could be ascertained.

Validation of micromechanical systems

For a reliable function of micro-mechanical systems the behavior of the used gear wheels is of extreme importance. But up to now there is no general available method for quality assurance of them. In this paper an adoption of the tangential and radial composite inspection as defined in standards for macroscopic gear wheels to the special needs and boundary conditions in micro technology is proposed. It is based on an examination of the differing results if the same gear wheels are mated with varying angles of rotation. Additionally special test rigs are presented which are able to test micro gear wheels. Finally some exemplary results are shown.

Accordion fringe interferometry: a revolutionary new digital shape‐scanning technology

PurposeThis paper seeks to describe an innovative new technology for digitizing the shapes of 3D objects quickly and accurately, which uses accordion fringe interferometry (AFI).Design/methodology/approachLaser beams cast fringe patterns on objects, a digital camera captures images and software constructs point clouds of data. A software package then analyzes the point cloud to extract information such as dimensions or variations in shape for subsequent operations.FindingsThe AFI approach has already been applied to a number of applications such as: inspection of jet engine airfoils, repair of composite structures and inspection of very delicate objects.Practical implicationsPoint cloud digital shape scanning will find an ever increasing number of applications which will benefit from this fast, accurate and non‐contact three‐dimensional digitizing technology.Originality/valueUsers now have a totally new means for capturing dense, three‐dimensional data.

OS3-5-1 Stress wave scattering: an enemy or a friend of concrete non destructive testing?

Cementitious materials are by definition inhomogeneous containing cement paste, sand, aggregates as well as air voids. Wave propagation in such a material is characterized by scattering phenomena. Damage in the form of micro or macro cracks certainly enhances scattering influence. Its most obvious manifestation is the velocity variation with frequency and excessive attenuation. The influence becomes stronger with increased mis-match of elastic properties of constituent materials and higher crack content. Therefore, in many cases of large concrete structures, field application of stress waves is hindered since attenuation makes the acquisition of reliable signals troublesome. However, measured wave parameters, combined with investigation with scattering theory can reveal much about the internal condition and supply information that cannot be obtained in any other way. The size and properties of the scatterers leave their signature on the dispersion and attenuation curves making thus the characterization more accurate in case of damage assessment, repair evaluation as well as composition inspection. In this paper, three indicative cases of scattering influence are presented. Namely, the interaction of actual distributed damage, as well as the repair material injected in an old concrete structure with the wave parameters. Other cases are the influence of light plastic inclusions in hardened mortar and the influence of sand and water content in the examination of fresh concrete. In all the above cases, scattering seems to complicate the propagation behavior but also offers the way for a more accurate characterization of the quality of the material.