Abstract Composite materials are more and more used in high technology industries owing to their unique mechanical properties. For such heterogeneous and quasi-periodic materials, classical non-destructive evaluation (NDE) methods prove very unsatisfactory, and even often inapplicable. Our aim here is to investigate the particular case of ultrasonic NDE of fibre-reinforced composite materials. When using the classical A-scan echography method, it is difficult to interpret time diagrams. This is mainly due to the heterogeneous nature of the materials, the complexity of the diagrams being especially increased by the occurrence of distributed defects (like porosities). Using spectral analysis techniques (ultrasonic spectroscopy), information may be extracted from these intricate time diagrams, In particular, the occurrence of a selective absorption frequency in both the transmitted and reflected energy spectra is evident. This absorption phenomenon is clearly related to the material structure and periodicity and advantage may then be taken of its characteristics (centre frequency, bandwidth and relative depth of the absorption dip in the spectrum) to characterize the material and identify the presence of defects of porosities.
[1]
J. C. Bell,et al.
The application of broadband ultrasonic spectroscopy to the study of layered media
,
1978
.
[2]
B. Auld,et al.
Acoustic fields and waves in solids
,
1973
.
[3]
P. Cielo,et al.
Laser Generation of Convergent Acoustic Waves and Applications to Materials Evaluation
,
1986,
IEEE 1986 Ultrasonics Symposium.
[4]
O. R. Gericke,et al.
Determination of the Geometry of Hidden Defects by Ultrasonic Pulse Analysis Testing
,
1963
.
[5]
F. Chang,et al.
Spectral analysis technique of ultrasonic ndt of advanced composite materials
,
1974
.
[6]
W. R. Scott,et al.
Ultrasonic spectrum analysis for nondestructive testing of layered composite materials
,
1977
.
[8]
Subhendu K. Datta,et al.
Calculated elastic constants of composites containing anisotropic fibers
,
1984
.