M. Valentino

Analysis of low-velocity impact damage in reinforced carbon fiber composites by HTS-SQUID magnetometers

Composite materials are susceptible to damage which can be induced by service loads and accidental impacts. The detection of any signature produced by damage is critical to maintaining the integrity of aircraft parts during routine maintenance. A high critical temperature SQUID magnetometer has been successfully employed in the evaluation of the behavior of multi-ply carbon fibers reinforced composite panels for aeronautical applications under low-velocity impacts. Measurements of the induced magnetic field have been carried out above specimen damaged with energy impact from 1 to 40 J. A quasi-linear behavior in two different regimes between the SQUIDs response and the energy of the impact has been found. This suggests a correspondence to the detection of intrinsically different damage that occurs in the laminates at different energies.

Non Destructive Evaluation of Advanced Composite Materials for Aerospace Application Using HTS SQUIDs

The main advantage of a HTS SQUID magnetometer in NDE applications is represented by its unrivalled magnetic flux sensitivity down to very low frequencies, which allows the detection of weak magnetic field variations due to defects also in materials characterized by a very low electrical conductivity. The imaging obtained by means of the magnetic flux variations can be an useful technique for an easier interpretation of SQUID magnetic responses getting along without post-processing algorithms and independent of the operator. Therefore, the SQUIDs NDE system output is compatible with the other conventional non destructive testing equipment for data fusion of aircraft inspections.

Experimental and numerical results of electromagnetic nondestructive testing with HTc SQUIDS

We present here recent results on detection of surface and subsurface artificial features in Al-Ti planar structures, to show current performance of our eddy-current nondestructive evaluation system based on HTc SQUIDs. The anomalous magnetic fields generated by flaws with known electromagnetic characteristics have been modeled by three-dimensional codes based on finite element method and volume integral formulation and developed for the investigated problem. Both numerical solutions have correctly predicted the shape of the complicated magnetic field response which is mainly the result of the shape of the defect, the geometry of the inducing coil and the characteristics of the SQUID gradiometer.

Monitoring Composites under Bending Tests with Infrared Thermography

The attention of the present paper is focused on the use of an infrared imaging device to monitor the thermal response of composite materials under cyclic bending. Three types of composites are considered including an epoxy matrix reinforced with either carbon fibres (CFRP) or glass fibres (GFRP) and a hybrid composite involving glass fibres and aluminium layers (FRML). The specimen surface, under bending, displays temperature variations pursuing the load variations with cooling down under tension and warming up under compression; such temperature variations are in agreement with the bending moment. It has been observed that the amplitude of temperature variations over the specimen surface depends on the material characteristics. In particular, the presence of a defect inside the material affects the temperature distribution with deviation from the usual bending moment trend.

Eddy Current Technique Based on

In this work we present non-destructive evaluation measurements on fiber/metal laminate specimen by using eddy current techniques employing HTc SQUID (superconductive quantum interference device) and giant magneto-resistive (GMR) sensors. Our aim is to compare the performance and the capability of HTc SQUID and GMR sensors to detect the presence of damage inside FML composite materials. Experimental results concerning the detection of artificial defects in aeronautical structures with high magnetic sensitivity by using HTc SQUID, and with high spatial resolution using GMR, will be presented and discussed.

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We find an unambiguous relationship between disorder-driven features in the temperature dependence of the resistance and the behavior, as functions of the temperature, of the parameters necessary to describe some of the relaxation processes in the photoinduced differential time-resolved reflectivity of three samples of Nd

-SQUID and GMR Sensors for Non-Destructive Evaluation of Fiber/Metal Laminates

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Disorder-sensitive pump-probe measurements on Nd 1.83 Ce 0.17 CuO 4 ± δ films

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GMR SECOND ORDER ELECTRONIC GRADIOMETER AS EDDY CURRENT PROBE IN NDE APPLICATIONS

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Electromagnetic non-destructive evaluation of fiberglass/aluminum laminates using HTS SQUID magnetometers

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