Abstract

Acoustic Impact Technique (AIT), commonly known as “coin-tapping,” has been applied by previous investigators as a nondestructive evaluation technique to study disbonds in composite honeycomb structures. The experimental configuration adopted by previous investigators was somewhat restricted. In this study, a different approach to AIT is developed. This was done to overcome the experimental constraints encountered in the previous approaches. This paper presents experimental results obtained in the evaluation of defects commonly found in graphite based composite structures, such as delamination, fiber breakage, and misaligned fibers. The experimental approach adopted in this work has two main features. Primarily, the force-time history of the specimen's response to a low magnitude input pulse in different regions of the specimen is compared. Secondly, an Acoustic Emission (AE) wide band sensor was used in conjunction with the conventional acoustic impact technique. The combination of the AE sensor and AIT enabled the study of the material interaction with stress waves generated in the vicinity of the tapped region. Gross defects such as delaminations were identified through the change in the pulse width of the force input, while defects such as fiber breakage and misaligned fibers were successfully identified using AIT in conjunction with AE.

References

1.
Cawley
,
P.
and
Adams
,
R. D.
, “
The Mechanics of the Coin-Tap Method for Nondestructive Testing
,”
Journal of Sound and Vibration
 0022-460X,
1988
, Vol.
122
, No.
2
, pp.
299
-
316
.
2.
Adams
,
R. D.
and
Cawley
,
P.
, “
Vibration Techniques in Nondestructive Testing
,”
Research Techniques in Nondestructive Testing
, Vol.
VIII
,
Sharpe
R. S.
, Ed.,
Academic Press Inc. (London) Ltd.
,
1985
, pp.
303
-
360
.
3.
Vaidya
,
U. K.
and
Murthy
,
C. R. L.
, “
Defect Characterization in Glass Fiber Reinforced Composites (GFRC) Using the Acoustic Impact Technique (AIT)
,”
Journal of Non-destructive Evaluation
, ISNT, Vol.
10
, No.
2
, April–June 1990, pp.
30
-
40
.
4.
Schroeer
,
R.
,
Roward
,
R.
, and
Kamm
,
H.
, “
The Acoustic Impact Technique—A Versatile Tool for Nondestructive Evaluation of Aerospace Structures and Components
.”
Materials Evaluation
 0025-5327,
1979
, pp.
237
-
243
.
5.
Murthy
,
C. R. L.
and
Mohindru
,
J. I.
, “
Detection and Sizing of Bond Defects by Acoustic Impact Technique
,”
Department of Aerospace Engineering Indian Institute of Science
, Bangalore, India,
1988
(unpublished work).
6.
Reynolds
,
W. N.
, “
Nondestructive Testing (NDT) of Fiber Reinforced Composite Materials
,”
SAMPE Quarterly
 0036-0821, Vol.
16
, No.
4
,
07
1985
, pp.
1
-
16
.
7.
Cawley
,
P.
and
Adams
,
R. D.
, “
An Automated Coin-Tap Technique for the Non-destructive Testing of Composite Structures
,”
Proceedings of 2nd International Conference on Testing, Evaluation, and Quality Control of Composites
, TEQC-87,
University of Surrey, Guildford
, Sept. 22–24, 1987, pp.
11
-
15
.
8.
Cawley
,
P.
and
Adams
,
R. D.
, “
Sensitivity of the Coin-Tap Method of Nondestructive Testing
,”
Materials Evaluation
 0025-5327, Vol.
47
,
05
1989
, pp.
558
-
563
.
9.
Vaidya
,
U. K.
, “
Nondestructive Evaluation of Defects in Glass Fibre Reinforced Composites by Acoustic Impact Technique
,” Master's thesis,
Department of Mechanical Engineering, Walchand College of Engineering
, Sangli, India,
1988
.
10.
Raju
,
P. K.
,
Vaidya
,
U. K.
,
Crocker
,
M. J.
, and
Valaire
,
B. T.
, “
Nondestructive Evaluation of Graphite Epoxy Composites Using Acoustic Techniques
,”
NDE of Materials and Structures Using Vibration and Acoustic Techniques
, Vol.
6
,
Raju
P. K.
, Ed.,
ASME
,
1989
, pp.
29
-
38
.
11.
Vaidya
,
U. K.
,
Raju
,
P. K.
, and
Kowbel
,
W.
, “
Material Damping Studies on Carbon-Carbon Composites
,”
Carbon
 0008-6223, Vol.
30
, No.
6
,
1992
, pp.
925
-
929
.
12.
Murthy
,
C. R. L.
,
Hegde
,
L. M.
,
Ravindra
,
K. M.
, et al
, “
Micro-processor Based Instrumentation for Acoustic Impact Testing
,”
NDE of Materials and Structures Using Vibration and Acoustic Techniques
, Vol.
6
,
Raju
P. K.
, Ed.,
ASME
,
1989
.
13.
Cawley
,
P.
, “
The Sensitivity of the Mechanical Impedance Method of Nondestructive Testing
,”
NDT International
 0308-9126, Vol.
20
, No.
4
,
08
1987
.
14.
Acoustic-Ultrasonics—Theory and Application
,
Duke
,
J. C.
, Ed.,
Plenum Press
,
New York
,
1988
.
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