Abstract
A new method based on Ping He’s technique for simultaneous measurement of frequency dependant thickness and attenuation was developed without any need of a priori knowledge of the material parameters. The thickness and attenuation coefficient for longitudinal wave were measured in a thin specimen of glass fiber reinforced plastic produced by Resin Transfer Molding. A 5 MHz pulse of 0.1 µs duration was used as excitation signal. Mean error and standard deviation of the frequency dependant thickness are used to compare both techniques. The new method has demonstrated to be more accurate than conventional Ping He’s technique, and can be implemented automatically thus saving processing time and increasing accuracy. Measurement of the attenuation coefficient is achieved using the frequency dependent thickness without requiring any additional parameter of the material. DOI: http://dx.doi.org/10.5755/j01.eee.20.1.4675
Highlights
The number of new composite materials has greatly increased in recent years, given to its low cost, ease of manufacture and the large number of applications they have
Ultrasound attenuation and dispersion are two material properties directly related to the characteristics of the material and widely used in non-destructive evaluation and material characterization
It can be found a lot of techniques in literature for frequency dependent attenuation measurement [1]–[5], Ping He’s technique [6], [7] is one of the most used due to its ease and because it does not need any a priori knowledge of the material characteristics
Summary
The number of new composite materials has greatly increased in recent years, given to its low cost, ease of manufacture and the large number of applications they have. Ultrasound attenuation and dispersion (changes in phase velocity with frequency) are two material properties directly related to the characteristics of the material and widely used in non-destructive evaluation and material characterization It can be found a lot of techniques in literature for frequency dependent attenuation measurement [1]–[5], Ping He’s technique [6], [7] is one of the most used due to its ease and because it does not need any a priori knowledge of the material characteristics. Using simultaneous pulseecho and through-transmission immersion measurements, it is able to provide the frequency dependent thickness and attenuation It is not an exact method and has several limitations [6], [7], but in spite of them, it still provides very useful results when the parameters of the material are unknown, which is especially interesting when analysing fiber reinforced RTM composites, whose final inner composition is difficult to control due to its fabrication process [8]–[11].
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