Thema: Kohlefaserverbund, Faseranteil
Autor/Institution: Zalameda, J.N.;Smith, B.T. /NASA Langley Res. Center, Hampton, USA;Coll. of William and Mary, Williamsburg, USA

Title: Measurement of composite fiber volume fraction using thermal and ultrasonic inspection techniques
Titel : Messung des Faseranteils in Verbunden mit thermischen und Ultraschallverfahren

Quelle : Nondestructive Characterization of Materials VI. Sixth Int. Symposium, Oahu, USA, June 7-11, 1993 1994 ; New York: Plenum Press ; ISBN 0-306-44816-5 ; S.741-748 ; 8S,7B,1T,5Q ; BAM-Z-0492/95 ; E

Abstract:

The objective of this work is to develop a nondestructive technique to determine fiber volume fraction (FVF) using a dual inspection methodology. The relationship between thermal diffusivity and fiber, matrix and void volume fractions is described in a one dimensional heat flow model where the void volume fraction is determinded ultrasonically. The use of a phase lag technique ist implemented to make quantitative measurements of thermal diffusivity. These measurements were on composite plates with varying FVF. Diffusivity measurements indicated a nonlinear relation between FVF and measured diffusivity with values ranging from .003 to .007 cm(exp 2)/s. In addition to the thermal measurements, frequency dependent relative attenuation ultrasonic measurements were made within the area to be destructively tested. Results have shown an approximate linear correlation between porosity and attenuation. Results are presented on 16 and 32 ply composite plates with lay ups of (0/90) 4s and (0/90) 8s and with FVF values ranging from 50 to 75 percent. A comparison of the measurement results to destructive testing is shown and the implementation of the thermal and ultrasonic measurement techniques is described. A modest FVF measurement improvement was obtained when correcting for the porosity. With no porosity correction the FVF measurement error compared to the destructive test results was +/- 3.6 percent. Using the linear equation resulting from combining the ultrasonic relative slope of attenuation measurements with the optical porosity values gave the best results reducing the measurement error to +/- 2.7 percent. This dual inspection technique has potential in determining FVF nondestructively in cured composites. Another advantage of this technique is that no knowledge of the ply layup is required for the measurement. .1 F33,B13,H13,A25

Database Keywords: Zerstörungsfreie Prüfung, Faserverstärkter Kunststoff, Kohlefaser, :Faseranteil, Wärmeleitfähigkeit, Mathematisches Modell, Wärmefluß, Schallschwächungsmessung, Frequenzabhängigkeit, :Akustisches Messen, Porosität 23 :Thermisches Messen, Nichtlineares Verhalten, Verfahrenskombination, Einflußgröße 24 Z:P

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Rolf Diederichs 1. Dec 1996, info@ndt.net