In this study, two types of specimens, woven [0, 90]s and unidirectional [0]s glass/epoxy composites, were studied. Acoustic emission (AE) monitoring with wavelet-based signal processing technique and Fuzzy C-Means (FCM) clustering method was used to detect the different fracture mechanisms during delamination in quasi-static three-point bending test. The three-point bending test simulates thrust force, the most effective factor in delamination, throughout the process of drilling without backup plate. The obtained AE signals were decomposed into various wavelet levels and classified using FCM. Scanning Electron Microscopy (SEM) observation was used to determine the different fracture mechanisms. The results show that the energy of AE signals has been concentrated in two significant components for both types of specimens, and the dependency percentage of damages in the two specimens is different.
TagliaferriVCaprinoGDiterlizziA. Effect of drilling parameters on the finish and mechanical properties of GFRP composites. Int J Mach Tool Manuf1989; 30: 77–84.
2.
KoenigWWulfCGrassPWillersheidH. Machining of fiber reinforced plastics. Ann CIRP1985; 34: 536–548.
3.
ChenW. Some experimental investigations in the drilling of carbon fiber-reinforced plastic (CFRP) composite laminates. Int J Mach Tools Manuf1997; 37: 1097–1108.
4.
SimleyAJPipesRB. Rate effect on mode I interlaminaire fracture toughness in composites materials. J Comp Mat1987; 21: 670–678.
5.
HochengHTsaoCC. Comprehensive analysis of delamination in drilling of composite materials with various drill bits. J Mater Process Technol2003; 140: 335–339.
6.
PappasYZMarkopoulosYPKostopoulosV. Failure mechanisms analysis of 2D carbon/carbon using acoustic emission monitoring. NDT&E Int1998; 31: 157–163.
7.
Ronnie KM. Acoustic emission. In: McIntire P (ed.) Handbook of nondestructive testing. Vol. 5, 2nd edn. Columbus, Ohio: American Society for Nondestructive Testing, 1987, pp. 560–572.
8.
ASTM. Definitions of terms relating to acoustic emission. E610-98A, 1991.
BenmedakheneSKenaneMBenzeggaghML. Initiation and growth of delamination in glass/epoxy composites subjected to static and dynamic loading by acoustic emission monitoring. Compos Sci Technol1999; 59: 201–208.
11.
SironOChollonGTsudaHYamauchiHMaedaKKosakaK. Microstructural and mechanical properties of filler-added coal-tar pitch-based C/C composites: the damage and fracture process in correlation with AE waveform parameters. Carbon2001; 39: 2065–2075.
12.
Ramirez-JimenezCRPapadakisNReynoldsNGanTHPurnellPPharaohM. Identification of failure modes in glass/polypropylene composites by means of the primary frequency content of the acoustic emission event. Compos Sci Technol2004; 64: 1819–1827.
13.
OskoueiARZucchelliAAhmadiMMinakG. An integrated approach based on acoustic emission and mechanical information to evaluate the delamination fracture toughness at mode I in composite laminate. Mater Des2011; 32: 1444–1455.
14.
MinakGMorelliPZucchelliA. Fatigue residual strength of circular laminate graphite–epoxy composite plates damaged by transverse load. Compos Sci Technol2009; 69(9): 1358–1363.
15.
QiGBarhorstAHashemiJKamalaG. Discrete wavelet decomposition of acoustic emission signals from carbon-fiber-reinforced composites. Compos Sci Technol1997; 57: 389–403.
16.
LoutasTHKostopoulosVRamirez-JimenezCPharaohM. Damage evolution in center-holed glass/polyester composites under quasi-static loading using time/frequency analysis of acoustic emission monitored waveforms. Compos Sci Technol2006; 66: 1366–1375.
17.
PhilippidisTPNikolaidisVNAnastassopoulosAA. Damage characterization of carbon/carbon laminates using neural network techniques on AE signals. NDT&E Int1998; 31: 329–340.
18.
YanTHolfordKCarterDBrandonJ. Classification of acoustic emission signatures using a self-organization neural network. J Acoust Emission1999; 17: 49–59.
19.
GodinNHuguetSGaertnerRSalmonL. Clustering of acoustic emission signals collected during tensile tests on unidirectional glass/polyester composite using supervised and unsupervised classifiers. NDT&E Int2004; 37: 253–264.
20.
de OliveiraRMarquesAT. Health monitoring of FRP using acoustic emission and artificial neural networks. Comput Struct2008; 86: 367–373.
21.
HaykinS. Neural networks—a comprehensive foundation. New York: Macmillan College, 1994.
22.
SureshSOmkarSNManiVMenakaC. Classification of acoustic emission signal sources using genetic programming. Int J Aerospace Sci Technol2004; 56: 26–40.
23.
SelimSZIsmailMA. K-means type algorithms: A generalized convergence theorem and characterization of local optimality. IEEE Trans Pattern Anal Mach Intell1984; 6: 81–87.
24.
GodinNHuguetSGaertnerR. Integration of the Kohonen's self-organising map and K-means algorithm for the segmentation of the AE data collected during tensile tests on cross-ply composites. NDT&E Int2005; 38: 299–309.
25.
Omkar SN, Suresh S, Raghavendra TR and Mani V. Acoustic emission signal classification using fuzzy C-means clustering. Proceedings of the 9th International Conference on Neural Information Processing (ICONIP’02), Singapore 4, pp. 1827–1831.
26.
MarecAThomasJHGuerjoumaEl. Damage characterization of polymer-based composite materials: multivariable analysis and wavelet transform for clustering acoustic emission data. Mech Syst Signal Process2008; 22: 1441–1464.
NiQQIwamotoM. Wavelet transform of acoustic emission signals in failure of model composites. Eng Fract Mech2002; 69: 717–728.
29.
VelayudhamAKrishnamurthyRSoundarapandianT. Acoustic emission based drill condition monitoring during drilling of glass/phenolic polymeric composite using wavelet packet transform. Mater Sci Eng Part A2005; 412: 141–145.
30.
RaoRMBopardikarAS. Wavelet transforms introduction to theory and applications. Amsterdam: Addison-Wesley, 1998.
31.
SomanKPRamachandranKI. Insight into wavelets from theory to practice. India: Prentice-Hall, 2004.
32.
WojtaszczykP. A mathematical introduction to wavelets. London: Cambridge University Press, 1997.
33.
RefahiOAAhmadiMHajikhaniM. Wavelet-based acoustic emission characterization of damage mechanism in composite materials under mode I delamination at different interfaces. Exp Polym Lett2009; 3: 804–813.
