The rapid NDT of composite aircraft components remains an important issue for the passenger aircraft industry. This paper presents the use of two thermal techniques for the rapid in-service inspection of impact damaged composite aircraft components. The apparatus required for the currently established lock-in halogen lamp technique and the newly developed lock-in ultrasonic transducer technique is described together with an appreciation of the relevant theory. Experimental samples were prepared to simulate Barely Visible Impact Damage (BVID) in composite laminates to represent material flaws in the in-service environment. The samples were then evaluated using the two thermal methods and verified using ultrasonic c-scans. The paper concludes that ultrasonic lock-in thermography is a more powerful technique to detect BVID than halogen lamp lock-in thermography. Although thermal NDT techniques do not provide a comprehensive solution to all of the rapid NDT requirements they may eventually find application for use in combination with hand held ultrasonic equipment. It is also demonstrated that thermal NDT is up to 10 times quicker than underwater ultrasonic c-scanning and may ultimately provide a solution to the problem of rapid quantitative in-service and manufacturing process inspection of composite aircraft components.

Although acceptance of pulsed thermography as a tool for nondestructive inspection continues to increase, standards and metrics for performance assessment and procedure development have been slow to follow. Consequently, practical application development is often left to the experience and intuition of the supervisor, and decisions such as heating input power, surface preparation, acquisition time, camera wavelength, integration time, and sensor type are made on a subjective, qualitative basis. Furthermore, quantitative thermographic methods that have been reported generally rely on the ability of the operator to identify a defect free region of the sample, as well as high-speed laboratory cameras that are not practical for many field inspection applications. Because of these limitations, practical application of pulsed thermography is often limited to use as a qualitative complement to conventional point inspection methods (e.g. ultrasound). We have developed a metric for characterization of active thermographic system performance that defines a Thermal Modulation Transfer Function (TMTF), which allows complete characterization of the IR NDE system performance for a given sample type. The TMTF approach allows accurate prediction of peak contrast times, and best-case contrast for defects of a given diameter and depth. We will use the TMTF approach to demonstrate how detection limits and ranges can be established, and how these limits can be improved using TMTF based signal processing algorithms.

This paper describes current efforts to apply spatially and temporally localized microwave processing techniques to ensure uniformity of material properties in polymer composite materials. In large polymer composite structures, high temperatures caused by exothermic resin cure can degrade the mechanical properties of the composite. In this work, resin cure temperature data was obtained during microwave processing from a series of thermocouples embedded at various lateral locations relative to the microwave source and uniformly through the thickness of the composite structure. Using this temperature information, the potential for localized microwave-accelerated cure to reduce the occurrence of material degradation from resin over-temperature was evaluated.

A series of epoxy carbon fiber development panels manufactured as part of a BAE SYSTEMS, Airbus, Composite Wing Development program were evaluated using Acoustography, a new ultrasonic Non Destructive Evaluation (NDE) method being developed by Santec Systems Inc, as an alternative to the conventional point-by-point ultrasonic C-scan. This study provides details on a novel wide area Acousto-optic (AO) sensor that can be used to nondestructively evaluate materials and components in near real-time. A description of the technology and how it compares to conventional ultrasonic methods is provided. The results of 4 experiments are also provided. The first experiment involves performing ultrasonic and Acoustography tests on thick graphite/epoxy composite panels that have embedded inclusions of known sizes. The objective of this experiment is to determine if the capabilities (i.e. resolution) of Acoustography are comparable to those of conventional ultrasonic techniques. The second experiment involves applying ultrasonics and Acoustography to evaluate a 10 mm thick graphite/epoxy composite panel containing defects associated with the manufacturing process. The third and fourth experiments detail the inspection of complex shaped composite parts representative of aerospace applications. Effort has been conducted towards demonstrating the effectiveness of the technology and establishing a baseline for projected inspection times.

Capabilities and expertise related to the development of links between nondestructive evaluation (NDE) and finite element analysis (FEA) at Glenn Research Center (GRC) are demonstrated. Current tools to analyze data produced by computed tomography (CT) scans are exercised to help assess the damage state in high temperature structural composite materials. A utility translator was written to convert velocity (an image processing software) STL data file to a suitable CAD-FEA type file. Finite element analyses are carried out with MARC, a commercial nonlinear finite element code, and the analytical results are discussed. Modeling was established by building MSC/Patran (a pre and post processing finite element package) generated model and comparing it to a model generated by Velocity² in conjunction with MSC/Patran Graphics. Modeling issues and results are discussed in this paper. The entire process that outlines the tie between the data extracted via NDE and the finite element modeling and analysis is fully described.

The analysis of acoustic emission signals has been widely applied to damage detection and damage characterization in composites. Features of acoustic emission signals, such as amplitude, frequency, and counts, are usually utilized to identify the type of a damage. Recently, time-frequency distribution techniques, such as the wavelet transform and the Choi-Williams distribution, have also been applied to characterize damage. A common feature of these approaches is that the analysis is on the acoustic emission signal itself. Nevertheless, this signal is not the wave source signal as it has been modulated by the signal transfer path. Real information on damage is actually hidden behind the signal. To reveal direct information on damage, a blind deconvolution method has been developed. It is a quefrency domain method based on the cepstrum technique. With the method, acoustic emission signal is demodulated and information on the wave source can be revealed and thus damage can be identified. This paper presents preliminary test data to assess the validity of the proposed methodology as a means of identifying specific damage modes in fiber reinforced composites.

An in-situ technique to measure sound velocity, ultrasonic attenuation and acoustic nonlinear property has been developed for characterization and early detection of fatigue damage in aerospace materials. For this purpose we have developed a computer software and measurement technique including hardware for the automation of the measurement. New transducer holder and special grips are designed. The automation has allowed us to test the long-term stability of the electronics over a period of time and so proof of the linearity of the system. Real-time monitoring of the material nonlinearity has been performed on dog-bone specimens from zero fatigue all the way to the final fracture under low-cycle fatigue test condition (LCF) and high-cycle test condition (HCF). Real-time health monitoring of the material can greatly contribute to the understanding of material behavior under cyclic loading. Interpretation of the results show that correlation exist between the slope of the curve described by the material nonlinearity and the life of the component. This new methodology was developed with an objective to predict the initiation of fatigue microcracks, and to detect, in-situ fatigue crack initiation as well as to quantify early stages of fatigue damage.

The conventional methods of measuring displacement and strain are severely taxed especially when long-term stability is needed in a situation involving temperatures above 1000 degrees Celsius. Optical techniques are attractive for measurements in these difficult situations because of their remote, non-contacting and non-destructive capability. The objective of this study was to develop a speckle based laser interferometry system to evaluate whole field out-of-plane deformation of a very small region (less than 1 mm) of an object at elevated temperatures in real time. The optical system (1) was capable of measuring very small displacements in a small area; (2) was used at high temperatures; and (3) was able to take 250 frames per second. A long distance microscope was used in the system in order to focus onto very small areas on the object and a high-speed camera to take real-time measurements. A CO₂ laser was employed to irradiate a circular thin aluminum oxide plate (object) locally and to generate local deformation as well as a crater. Laser radiation with the power density exceeding the critical power density q_c produces melting and plasma. The plasma appears as a very bright spot and it reduces speckles that give information about surface deformation of the object. As a result, the bright spot limits deformation measurement with the designed laser interferometry system. Some preliminary quantitative data on the form of images and deformation profiles will be presented. The laser interferometry system designed is significant because very small out-of-plane deformations from a small region were measured in real-time with up to 250 frames per second although the object's temperature was locally very high (approximately 2000 degrees Celsius).

This study focused on the application of the Thermoelastic Stress Analysis (TSA) technique as a tool for assessing the residual stress state of structures. TSA is based on the fact that materials experience small temperature changes when compressed or expanded. When a structure is cyclically loaded, a surface temperature profile results which correlates to the surface stresses. The cyclic surface temperature is measured with an infrared camera. Traditionally, the amplitude of a TSA signal was theoretically defined to be linearly dependent on the cyclic stress amplitude. Recent studies have established that the temperature response is also dependent on the cyclic mean stress (i.e., the static stress state of the structure). In a previous study by the authors, it was shown that mean stresses significantly influenced the TSA results for titanium and nickel based alloys. This study continued the effort of accurate direct measurements of the mean stress effect by implementing newly developed temperature correction curves. In addition, a more in-depth analysis was conducted which involved analyzing the second harmonic of the temperature response. By obtaining the amplitudes of the first and second harmonics, the stress amplitude and the mean stress at a given point on a structure subjected to a cyclic load can be simultaneously obtained. The experimental results showed good agreement with the theoretical predictions for both the first and second harmonics of the temperature response. As a result, confidence was achieved concerning the ability to simultaneously obtain values for the static stress state as well as the cyclic stress amplitude of structures subjected to cyclic loads using the TSA technique. With continued research, it is now feasible to establish a protocol that would enable the monitoring of residual stresses in structures utilizing the TSA technique.

Optical fiber sensors are rapidly emerging as viable alternatives to piezoelectric devices as effective means of detecting and quantifying acoustic emission (AE). Compared to traditional piezoelectric-based sensors, optical fiber sensors offer much smaller size, reduced weight, ability to operate at temperatures up to 2000 degrees Celsius, immunity to electromagnetic interference, resistance to corrosive environments, inherent safety within flammable environments, and the ability to multiplex multiple sensors on a single fiber. The authors have investigated low-profile fiber optic- based AE sensors for non-destructive evaluation (NDE) systems. In particular, broadband optical fiber sensors were developed for monitoring acoustic emission for NDE of pressurized composite vessels. The authors conducted experiments by surface attaching sensors to aluminum compact tension specimens using a piezoelectric transducer as a reference sensor. Both the fiber optic and piezoelectric sensors accurately measured a representative acoustic event. The response of the fiber optic AE sensors were also compared to existing piezoelectric sensors during pencil lead break tests on an aluminum panel. The results indicate that optical fiber AE sensors can be used as highly sensitive transducers in many applications where conventional piezoelectric transducers are not suited.

This paper highlights three advantages of infrared thermography as a nondestructive, non-contact and in real-time technique. It permits first observation of the physical manifestation of damage and the mechanism of failure of concrete, second detection of the occurrence of intrinsic dissipation localization, and third evaluation of the fatigue strength in a very short time, compared to traditional testing techniques. In addition, infrared thermography readily describes the damage location and the evolution of structural failure. The investigated parameter is heat generation due to intrinsic dissipation of concrete subject to compressive loading. Owing to the thermomechanical coupling, this technique provides a simple means for evaluating fatigue strength and for discriminating diverse dissipative phenomena.

The Impact-Echo (IE) method has been widely used to evaluate the integrity of concrete structures. In this method, the P- wave velocity of concrete is a crucial parameter in determining the thickness of concrete lining and the location of cracks or other defects. In this paper, Spectral Analysis of Surface Wave (SASW) method was employed to determine P-wave velocity of concrete, and IE-SASW method was suggested by combining two nondestructive testing methods. IE method was used for the detailed nondestructive evaluation of concrete whereas SASW method was employed for the measurement of the average P-wave velocity and for the status evaluation of concrete. The feasibility study of IE-SASW method was performed by using finite element method. Experimental studies were also performed in the slab type concrete model specimens in which various types of defects or boundaries were included at known locations. SASW tests showed the potential of determining the P-wave velocity of concrete accurately and IE tests were able to determine the thickness of structures and locations of defects. Based on both experimental and numerical studies, the feasibility of the proposed method was verified.

The pavement elastic modulus of each layer was usually assumed not to be dependent on the environmental factors when the backcalculation of asphalt pavement was conducted from the measured surface deflections of FWD. However, it is well known that the elastic modulus of asphalt layer changes with the variation of temperature. Considering the influence of atmospheric temperature and radiant heat, the temperature distribution is nonlinear along the asphalt layer thickness, and has always been changed. Therefore, the distribution of elastic modulus in the asphalt layer has been considered to change as well. In this paper, we assume the elastic modulus distribution of the asphalt layer to vary with its temperature in terms of the exponential form. Based on the finite element method forward analysis, we propose a method to estimate a standard elastic modulus and temperature coefficient at 20 degrees Celsius for the asphalt layer from the backcalculation analysis. The corresponding FEM backcalculation program using Gauss-Newton method was developed to determine the pavement layer moduli and temperature dependent coefficient, in which the singular value decomposition (SVD) was used for the inverse analysis with scaling of unknown parameters. This method results in a smaller condition number that contributes to improvement of numerical stability. Both numerical simulation and measured data from FWD testing are used to demonstrate the potential applications of this method. As a result, the backcalculation procedure is less dependent on the user's initial values, fast in convergence rate and effective in the pavement engineering.

Despite recent advances in the development of new materials, wood continues to be used globally for the support of overhead cable networks used by telecommunications and electrical utility companies. As a natural material, wood is subject to decay and will eventually fail, causing disruption to services and danger to public and company personnel. Internal decay, due to basidomycetes fungi or attack by termites, can progress rapidly and is often difficult to detect by casual inspection. The traditional method of testing poles for decay involves hitting them with a hammer and listening to the sound that results. However, evidence suggests that a large number of poles are replaced unnecessarily and a significant number of poles continue to fail unexpectedly in service. Therefore, a more accurate method of assessing the structural integrity of wooden poles is required. Over the last 25 years there have been a number of attempts at improving decay detection. Techniques such as ultrasound, drilling X rays etc. have been developed but have generally failed to improve upon the practicality and accuracy of the traditional testing method. The paper describes the use of signal processing techniques to analyze the acoustic response of the pole and thereby determine the presence of decay. Development of a prototype meter is described and the results of initial tests on several hundred poles are presented.

We present shearographic imaging of the interaction of A_O waves with defects in plates. The images are good when the plates are composite plates, due to some attenuation of the waves which prevents reflections. Those images contain information on the interaction between waves and defects. Nevertheless, this information is very difficult to extract and this extraction need numerical models. Here we show some examples of interaction. It is expected that this images will help to better understand the wave-defect interaction and will help to define and optimize health monitoring systems for carbon-epoxy plates and sandwich plates.

This paper describes the initial phase of the development of a nondestructive, multi-sensor approach for detecting, quantifying and monitoring degradation of organic coatings applied to aircraft aluminum frame structures. Two ultrasonic techniques are discussed: the well-established pulse/echo scanning acoustic microscopy, employing a 200 MHz transducer with a focusing lens and, as a proposed alternative, continuous acoustic wave measurements with a probe in contact to the sample. The High spatial and depth resolution of scanning acoustic microscopy provides the possibility to obtain information about coating inhomogeneities, e.g. density variations due to non uniform curing of the polymeric coating or interface voids, e.g. sites of weak adhesion. This is achieved by altering the probe/sample-distance, i.e. changing the focus point of the lens. Since the echoes from the topsurface and the interface can be separated, thickness measurements are possible, too. However, only down to a thickness of 10 - 15 micrometer. Here, continuous acoustic wave measurements can be considered to be a good alternative for acoustic measurements in the pulsed regime. The method enables very accurate thickness evaluation, but can not reach the excellent lateral resolution of scanning acoustic microscopy.

Frequency shift, due to quartz crystal resonator aging, has been identified as one of the most important quality control problems of quartz crystal products. The problem becomes more significant due to the device miniaturization and high precision standards for telecommunication applications. Since aging induced frequency shift occurs during a long time frame, it is necessary to predict the long-term behavior of the devices based on the short-term data obtained under an accelerated environment. On the other hand, frequency shift is associated with quite large random variation, and thus, a proper probabilistic theory should be used for analyzing test data and for developing a reliable prediction model. Accelerated testing was performed for various types of crystal resonators under elevated temperatures. The frequency shifts of the devices were measured at different testing periods. Markov chain model was used to characterize the frequency shift of the devices. The obtained short-term test results were used for calibrating the probabilistic transition matrix of Markov chain model. The model can then be used for predicting the long-term frequency shift. The time-temperature superposition principle in viscoelasticity was adopted to address the shift in time under different temperatures.

The implementation of temporal phase unwrapping within a real- time phase stepped shearing speckle interferometer is presented. Speckle phase maps obtained with a shearing speckle interferometer, representing an object before and after deformation, reveal sub-surface defects or damage, after subtracting the images. Phase information is only known modulo 2(pi) , and has to be unwrapped for a true representation of the deformation map. Results are easier to interpret during the deformation process when the images are unwrapped; phase unwrapping also facilitates automatic detection of suspected areas. It is shown that, compared to the more common spatial* phase unwrapping methods, temporal phase unwrapping is much faster, and can be implemented in a real-time system. In addition, this method offers an increased measuring range, reduces sensitivity for speckle decorrelation, handles discontinuities in the object, and is very reliable, even when used with noisy data. Processing strategies for the selective removal of unwanted image components, and for automatic defect detection are presented. Examples of results obtained for artificial defects in metallic and composite aeronautical components are shown. Measurements have been carried out with our phase stepped shearography system under laboratory and industrial conditions, showing improved performance under non- ideal conditions. It has been shown during these experiments that shearography cannot only be used for detection of defects, but also for characterization.

The present article reports a technique to characterize small portions in the order of a few micron of a soft anisotropic material. The heart muscle was selected for specimen as an example of the soft material. The heart muscle was cut by a microtome and coated on a substrate. The thickness of the specimen was substantially 3 micrometer. For the substrate, fused quartz was used because its elastic properties are known and stable. The spherical acoustic lens was used to determine the position for the measurement. Considering the anisotropy of the specimen, the cylindrical lens was used to measure velocities of the Rayleigh waves propagating within the specimen. The frequency of 400 MHz was used for both the visualization and the measurement. The generation of the Rayleigh waves in the above conditions was confirmed by numerical calculations based on the wave propagation theory for layered media. As a result, the variation of the velocities representing the anisotropy of elastic properties were obtained and found to be about 7%.

The objective of this study is to provide details on a novel wide area acousto-optic (AO) sensor that can be used to nondestructively evaluate materials and components in near real-time. A description of the technology and how it compares to conventional ultrasonic methods is provided. The results from three experiments provide details on how acoustography compares to conventional ultrasonics when applied to the inspection of composite parts. The first experiment involves performing ultrasonic and acoustography tests on a standard graphite/epoxy composite panel that has embedded inclusions of known sizes. The objective of this experiment is to determine if the capabilities (i.e. resolution) of acoustography are comparable to those of conventional ultrasonic techniques. The second experiment applied acoustography and ultrasonic techniques to evaluate the effects of low impact damage in composite materials. The third experiment involves applying ultrasonics and acoustography to evaluate a complex shaped composite part. The purpose of this experiment is to show the strengths and weaknesses of both techniques as applied to real world problems.

Corrosion of structures is a serious problem involving man and material safety. Over the years, though several methods of monitoring corrosion have been devised with some success, but there is a persistent need for devising non-destructive and in-situ techniques for monitoring corrosion in structures. Fiber optic techniques are capable of meeting these requirements, besides offering several other important advantages. Fiber optic corrosion sensors have thus become quite attractive and are currently being investigated to address the high costs associated with the existing structural maintenance procedures. Fiber optics based direct absorption spectroscopic techniques investigated by some groups for estimating corrosion have used single fiber elements for recording the signal reflected from specimen at different wavelengths. As the light coupling efficiency of the single fiber elements is relatively poor in comparison with that of fiber bundles and the signal available for processing is weak, the paper presents a simple and alternate technique based on the color matching principle of fiber optic colorimetry to detect corrosion induced color changes. It employs a thin Y- shaped fiber optic bundle which increases the quantity of light energy coupled from a whitelight source. The light reflected off the sample is made incident on a PIN photo- detector through a complementary filter. A series of such probes can be safety embedded and or bonded to structures at pre-determined locations. The experimental set up for this sensor was implemented and feasibility of in-situ corrosion detection in structures demonstrated. Measurement data was acquired for steel samples corroded both in concrete embedded and open ambience conditions and results analyzed.

In this paper, the image preprocessing techniques are studied in detail combining with the characteristics of real-time radiography. In view of the characteristics of radiant attenuation, an image processing method is presented to make the relationship between image gray scale and workpiece thickness linear. In order to get better image contrast, an image stretching method based on fuzzy transformation is designed by which the image is effectively enhanced. Meanwhile, another algorithm is also proposed to avoid the complexity of above method. Moreover, the study is carried out to the influence of radiation source focus, which is a very important factor to image quality in real-time radiography. The mathematical model is established for the influence of radiation source focus on real-time radiography image. On the basis of this model, the corresponding algorithm is proposed to eliminate its influence. All these algorithms are studied in detail with corresponding results presented.

The application of embedded sensors for use in monitoring the cure of composite snowboards during manufacturing was demonstrated. Ultrasonic and capacitive sensors were used and the results compared. Both techniques showed indications of the end of cure in the evaluation of plots of wave attenuation versus time and change in capacitance versus time.

One of the most important issues in liquid composite molding (LCM) is the complete saturation of the preform by the resin to eliminate voids or dry spots in the structure which could later adversely affect the structural integrity of the part. While there have been efforts in developing reliable mold filling simulations for LCM, very few successful flow sensing systems exist for detecting actual resin arrival during mold filling. In this study, the feasibility of using optical fibers with long period gratings (LPG) as sensors for monitoring flow in the LCM process was investigated. An advantage of using LPGs is that they are more robust and less susceptible to background noise than simple bare fibers. Furthermore, the location of resin arrival can be easily identified as the signals from each LPG uniquely correspond to predetermined wavelengths along the source spectrum. The LPGs are sensitive to changes in the refractive index and register a strong signal change when covered with resin. In this study, the LPG sensors were placed in the middle of a preform stack inside a mold and the sensor response after the mold was properly closed, and when the resin covered a particular LPG was monitored. An assortment of preforms, which included random mats and unidirectional fabrics, with a series of fiber volume fractions were used to determine their effects on the sensor response.

Precise control of temperature is needed in pharmaceutical glass containers manufacture during the different stages of moulding process. A slightly incorrect temperature produces dimensional tolerances above the allowed limits in pharmaceutical industry. The paper introduces the complete development of an infrared measurement system which measures the temperature for the different critical points in moulding process. This system is able to measure temperatures between 500 degrees Celsius and 1300 degrees Celsius for maximum rates about 150 containers per minute and 2 mm focus diameter. The system detects the presence of a container directly through the measurement, without needing any proximity detectors. During the usage, the system has showed high reliability and repeatability in its measurements, becoming an essential system for both the adjusting stage of the machine and the supervision of its working. The paper analyses the keys of the design, including the sensor even the measurement analysis software, highlighting the main factors which determine the repeatability in measurements, as this is the most important parameter in order to assure a correct machine supervision.

A relational database is a powerful tool for collecting and analyzing the vast amounts of inner-related data associated with the manufacture of composite materials. A relational database contains many individual database tables that store data that are related in some fashion. Manufacturing process variables as well as quality assurance measurements can be collected and stored in database tables indexed according to lot numbers, part type or individual serial numbers. Relationships between manufacturing process and product quality can then be correlated over a wide range of product types and process variations. This paper presents details on how relational databases are used to collect, store, and analyze process variables and quality assurance data associated with the manufacture of advanced composite materials. Important considerations are covered including how the various types of data are organized and how relationships between the data are defined. Employing relational database techniques to establish correlative relationships between process variables and quality assurance measurements is then explored. Finally, the benefits of database techniques such as data warehousing, data mining and web based client/server architectures are discussed in the context of composite material manufacturing.

Techniques are being developed worldwide for non-contact ultrasonic inspection of composite materials. These include laser generation and optical detection of ultrasound; both with interferometers and simpler beam deflection techniques, air coupled transducers are also used as generators and/or detectors of ultrasound. This paper compares the generation efficiency and damage thresholds of a range of different laser types: A fundamental Nd:YAG laser (1.06 micrometer), a TEA CO₂ laser (10.6 micrometer normally preferred for carbon- fiber reinforced composites) and a Nd:YAG laser with an Optical Parametric Oscillator (OPO) tunable up to 4 micrometer. The laser energy is absorbed with the optical absorption depth, the temperature rise is affected by the wavelength and laser pulse duration. It is essential to remain in the thermoelastic regime in order not to damage the material. A modified Michelson interferometer is used to detect the absolute displacement of the ultrasound. Optical beam deflection techniques and air-coupled transducers are also evaluated as detectors.

On-line monitoring of the Liquid Composite Moulding (LCM) process is a key element to improve quality and to reduce manufacturing cost for complex parts. In this context, direct current (DC) resistance measurement is a promising sensing technique allowing to track both flow front position and degree of curing of the resin during injection. One possible geometrical configuration to measure DC resistance in a mould is to dispose two electrically conductive fiber grids orthogonally on non-intersecting planes (DC-SMARTweave^TM technique). On-line resistance measurement of the sensing gap between two wires crossing (i.e. node) allows to determine the presence of resin and the degree of curing at this node location. An original measurement technique (LDC: Linear Direct Current) based on the same physical principle was developed to record the flow front position continuously. Linear DC allows to track the flow front position on the overall length of two contiguous wires and not only at discrete nodes location. Two experiments were conducted in a 2D-glass tool in order: (1) to evaluate the potentiality and reliability of the standard DC-SMARTweave^TM technique. (2) to test in-house developed software, based on LabVIEW, which allows to quantify the time discrepancy between DC-measurement and LCM-simulation. Results and comparison between video capture, LCM-simulation and DC-resistance monitoring has shown a good agreement (see appendix A). A first measurement in a 1D-flow channel was conducted to quantify the sensitivity of the Linear DC (LDC) technique and test an in-house developed software which permits to give, before an injection, the LDC geometrical set-up to optimize data acquisition and data processing. The permeability of the fibers laid-up in the 1D- flow channel can be calculated, first based on the video capture K _visual of the flow front position and second directly based on the output voltage of the LDC-measurement K_LDC. A discrepancy smaller than 1% between K_visual and K_LDC has shown a good potential of this original LCM- monitoring technique and need to be tested later on a production part to characterize local variation of the permeability due to drape of the fiber material.

The technique described in this paper is for one-side thermal diffusivity measurement. A single stripe-shaped pulse provided by a flash lamp is used to heat the front surface of a specimen slab. Classical methods for estimating a parameter out of a distribution involve fitting the temperature distribution with its theoretical model. With the technique described in this paper the evolution of the temperature distribution along a line perpendicular to the heated stripe is analyzed in the frequency domain. An estimate of the thermal diffusivity is then obtained from comparison of the phase component behavior with an abacus similarly built from the theoretical model. This technique is valid for any shape of flash lamp pulse (i.e. laser spot), and can be used also for estimating the thermal diffusivity of anisotropic materials. The choice of the stripe shape is due to the limitations of the simulation environment used.

The focus of this investigation is to develop an Ultrasonic Position Indication System (UPIS) that is capable of determining one-dimensional target location in a steel- contained pressurized gaseous medium. The combination of the very high acoustical impedance of steel (45.4 MRay1) and the very low impedance of air (0.0004MRay1) causes extremely high- energy losses upon transmission. In addition to the energy loss, propagation through a steel plate produces many internal reflections in the plate. The strategy of this investigation is to develop a self-contained ultrasonic transducer that is capable of replacing a small portion of a high temperature- pressure boundary. In building such a transducer, sufficient acoustic matching layers for the steel-gas interface, a mechanically and acoustically competent housing, a sufficient piezoelectric element, and backing materials are all developed and tested. The results include a successful housing design, high-temperature acoustic matching layers, and subsequent successful waveforms. Target location through 9.6'(24.5 cm) of ambient air was successful, with a steel pressure boundary 0.4566' (1.1598 cm) thick, and using one matching layer.