Acta Materiae Compositae Sinica Vol123 No12 April 2006

Transcription

1 Acta Materiae Compositae Sinica Vol123 No12 April 2006 : (2006) , 3, (, ) :, ( FFT) :, : ; ; ; : V258 ; TB332 : A Frequency spectral analysis f or the ultrasonic attenuation of carbon f iber reinf orced plastics HUA Zhiheng, ZHOU Xiaojun 3, L I Ling ( The College of Mechanical and Energy Engineering, Zhejiang University, Hangzhou , China) Abstract : The pulse 2echo technique was used to obtain the ultrasonic measurement of two different group s of carbon fiber reinforced plastic (CFRP) samples, and FF T algorithm was used for f requency spectral analysis. The attenuation coefficient shows approximately linear behaviour with f requency over the f requency range used, and the attenuation slope increases with the void content. The attenuation effect s of voids were shown by the dropped ampli2 tude, the downshifted position and the decreased bandwidth of the center peak. : ; : :,,, E2mail : com The result s indicate that linear relationships hold between the centroid f requency shift, the attenuation slope and the void content, and these relationships will aid the model development for void content detection using f requency spectral analysis. Keywords : carbon fiber reinforced plastic ; void content ; attenuation ; f requency spectral analysis (CFRP),, [1 ] 10 M Hz,, [25 ], [6 ],,, [ 79 ],, B. G. Martin [10 ] Stone [11 ] : [12,13 ] A. P. Mouritz [ 14 ], ; H. J eong [7,8 ], D1 K1 Hsu [15 ] N. K. Batra [16 ]

2 124, D. K. Hsu [8,17 ], FF T,, : A A1 A2 A3 A4 2, 0. 8 % % 2. 8 %3. 7 % ; B B1 B2 B3 B4 SB = A i ( f ) DSe - 2 W ( f ) L e - 2 S ( f ) h R T S, 111 % 2. 6 % 4. 0 %4. 7 % 1. 2 ( 1), (),,, FF T,,, 2 ; 2, 5 M Hz, 6 mm, 5 cm Fig. 1 Experimental setup for ultrasonic measurement : DS ; TS ; S ( f ) ; h ; R, DS DW S F SB, S ( f ) : TS =, ZS = [ln ( S F/ SB ) + ln ( TS R / R) ]/ 2 h 4 ZW ZS ( ZW + ZS) 2, ZW = W V W = S V S FF T, 2 2,,,,,, S F, SB, S F SB [7,8,15 ] H. J eong [7,8 ] D. K. Hsu [15 ] N. K. Batra [16 ],, 2 (b),, p = 4. 7 %, 2 p = 1. 1 % A B : B S F = A i ( f ) DWe - 2 W ( f ) L R, B : A i ( f ) ; DW ; W ( f ) ; L ; R 2 (a) 2 (b), A, B

3 , : Fig. 2 Attenuation curves of samples wit h different void content s 2. 2,,,, 3 B B1B4 Front ; Back 3,, : (1) ; (2) ; (3) B3 B4 f c f c = f A ( f ) 2 d f A ( f ) 2 d f D ( f c ) / f 0 ( 4) : D ( f c ) ; f 0 4, A, B,, 3 B Fig. 3 Comparison for t he frequency spectra of t he echoes of group B samples

4 126 4 D( f c) / f 0 Fig. 4 Relationship between t he centroid frequency shift ( D( f c) / f 0) and t he void content 2. 3 d / df d / d f A B,, B, B,, B ( 5),,,,,, (2),,,, (3) d / d f :, D ( f c ) / f 0 d / d f : [ 1 ] Birt E A, Smit h R A. A review of NDE met hods for porosity measurement in fibre2reinforced polymer composites [J ]. N on2 Destructive Testing and Condition Monitoring, 2004, 46 (11) : [ 2 ] Bowles K H, Frimfong S. Void effect s on t he interlaminar shear strength of unidirectional graphite2fiber2reinforced com2 posites [ J ]. J ournal of Com posites M aterials, 1992, 26 : [ 3 ] Uhl K, Lucht B, Jeong H. Mechanical strengt h degradation of graphite fiber reinforced thermoset composites due to porosity [ J ]. Review of Progress in Quantitative N ondestructive Evaluation, 1988, 7B : [ 4 ] Gurdal Z, Tomasino A P, Biggers S B. Effect s of processing 3 5 d / d f Fig. 5 Relationship between t he attenuation slope (d / d f ) and t he void content (1) FF T, induced defects on laminate response : Interlaminar tensile strengt h [J ]. S A M P E J ournal, 1991, 27 (4) : [5 ],,,. [J ]., 2004, 21 (5) : Liu Ling, Lu Mingkun, Zhang Boming, et al. Effect s of po2 rosity on the ultrasonic absorption coefficient and mechanical strength of carbon/ epoxy composites [J ]. A cta M ateriae Com2 positae S inica, 2004, 21 (5) : [ 6 ] Almeida S F M, Nogueira Neto Z S. Effect s of void content on t he strengt h of composite laminates [J ]. Com p S t ruct, 1994, 28 (8) : [ 7 ] Jeong H. Effects of voids on the mechanical strength and ul2 trasonic attenuation of laminated composites [J ]. J ournal of Com posite M aterials, 1997, 31 (3) : [ 8 ] Jeong H, Hsu D K. Experimental analysis of porosity2induced ultrasonic attenuation and velocity change in carbon composites [J ]. Ult rasonics, 1995, 33 (3) :

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