Effect of Fiber Surface Structure on Absorption Properties of Carbon Fiber Reinforced Composites

doi:10.3724/SP.J.1077.2013.12182

Abstract

Abstract:

Carbon fibers with different surface structures were obtained through changing the treatment intensities in the process of electrochemical oxidation, and then oxidized carbon fibers were used as reinforcements to manufacture carbon fiber/epoxy composites. The relationship between fiber surface structure and the moisture absorption of carbon fiber/epoxy composites after hygrothermal aging treatment was studied. Results show that a significant increase happen to the surface activity of carbon fiber after electrochemical oxidation, and there is also a large extent of elevation in the relative content of oxygen-containing functional groups especially -OH group which increases from 18.62% to 34.84%. The moisture absorption mechanism of carbon fiber/epoxy composites varies with the change of hygrothermal aging conditions. Temperature is considered to be a leading factor in the moisture absorption process. Results also indicate that the higher the surface activity of carbon fiber, the greater composite materials get the equilibrium moisture content. There is an obvious decline in the ILSS values of carbon fiber/epoxy composites with the increase of moisture uptake content.

Key words: carbon fiber, composites, surface structure, hygrothermal performance

CLC Number:

TB332

QIAN Xin, ZHI Jian-Hai, WANG Xue-Fei, ZHANG Yong-Gang, YANG Jian-Xing. Effect of Fiber Surface Structure on Absorption Properties of Carbon Fiber Reinforced Composites[J]. Journal of Inorganic Materials, 2013, 28(2): 189-194.

Figures/Tables 8

Fig. 1 Hygrothermal aging process of carbon fiber/epoxy composites under a condition of variable temperature and constant humidity

Fig. 2 Surface morphological changes of carbon fibers before and after electrochemical oxidation

Table 1 Elemental composition of carbon fiber surface before and after electrochemical oxidation

Current density/ (A·m^-2)	Relative content of surface chemical elements/%					Atomic ratio
Current density/ (A·m^-2)	C1s	N1s	O1s	Si2p	Na1s	N/C	O/C
0	94.977	1.121	3.096	0.643	0.163	0.0118	0.0326
5	82.058	3.307	11.197	1.654	0.851	0.0403	0.1365
12	81.925	4.578	12.940	0.487	0.070	0.0559	0.1579
20	78.456	5.960	13.071	0.650	0.181	0.0760	0.1666

Fig. 3 XPS C1s spectra of oxidized carbon fibers vs different current density

Fig. 4 Moisture absorption curves of carbon fiber/epoxy composites with the treating conditions of (a) constant temperature and humidity (b) variable temperature and constant temperature

Table 2 Saturated moisture uptake and diffusion coefficient of carbon fiber/epoxy composites with the change of hygrothermal aging modes

Current density /(A·m^-2)	Saturated moisture uptake/%		Diffusion coefficient /(×10^-5, mm²·s^-1)
Current density /(A·m^-2)	C.T.	V.T.	C.T.	V.T.
5	1.205	0.890	2.12	1.20
12	1.392	1.017	1.94	1.21
20	1.454	1.192	2.52	1.23

Fig. 5 Changes in ILSS values of carbon fiber/epoxy composites before and after hygrothermal aging treatment

Fig. 6 Cross-section and vertical-section images of composites after interlaminar shear damage((a),(d))untreated carbon fiber reinforced composites((b),(e))oxidized carbon fiber reinforced composites((c),(f)) after hygrothermal aging treated composites

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