碳纤维表面结构对复合材料吸湿性能的影响

doi:10.3724/SP.J.1077.2013.12182

摘要/Abstract

摘要：

通过改变阳极氧化处理程度得到了具有不同表面结构的碳纤维, 然后将其与环氧树脂加工成碳纤维/树脂基复合材料, 研究了碳纤维的化学结构与湿热环境下复合材料吸湿之间的关系。结果显示: 阳极氧化处理后碳纤维表面的活性显著提高, 碳纤维表面含氧官能团的含量大幅增加, 尤其是-OH由处理前18.62%提高到处理后的34.84%。随着湿热处理条件的改变, 复合材料的吸湿机理也有所差异, 且温度是影响复合材料吸湿的重要因素。碳纤维表面活性越高, 复合材料达到吸湿平衡时的平衡吸湿量越大, 而平衡吸湿量的增加又会导致复合材料层间剪切强度(ILSS)下降幅度增大。

关键词: 碳纤维, 复合材料, 表面结构, 湿热性能

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

中图分类号:

TB332

钱鑫, 支建海, 王雪飞, 张永刚, 杨建行. 碳纤维表面结构对复合材料吸湿性能的影响[J]. 无机材料学报, 2013, 28(2): 189-194.

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.

图/表 8

图1 碳纤维/树脂基复合材料的变温恒湿处理过程

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

图2 阳极氧化处理前后碳纤维表面的物理形貌变化阳极氧化处理前后碳纤维表面化学元素组成的变化如表1所示。未处理碳纤维的表面碳元素含量高达94.977%, 而活性元素如氧、氮等相对较低, 表明处理前碳纤维表面呈现较高的惰性。随着电流密度的提高, 碳元素含量逐渐降低, 氧、氮活性元素含量增加明显[15], 当电流密度为20 A/m2时, 与未处理纤维相比, 氧、氮元素分别提高了322%、432%。表1中列举了元素比值, 其中n(O)/n(C)比越大, 说明碳纤维的表面活性越高, 其与树脂基体发生的化学反应越好。

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

图3 不同氧化条件下碳纤维表面的XPS C1s图谱

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

图4 恒温恒湿处理(a)及变温恒湿处理(b)时碳纤维/树脂基复合材料的吸湿曲线

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

图5 湿热处理前后碳纤维/树脂基复合材料的ILSS强度变化

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

图6 剪切破坏后((a)、(d))未经氧化处理碳纤维增强复合材料的截面及剖面形貌((b)、(e))氧化处理碳纤维增强复合材料的截面及剖面形貌((c),(f))恒温恒湿处理复合材料的截面及剖面形貌

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

参考文献 20

[1]	Pillay S, Vaidya U K, Janowski G M. Effects of moisture and UV exposure on liquid molded carbon fabric reinforced nylon 6 composite laminates. Composites Science and Technology, 2009, 69(6): 839-846.
[2]	Ray B C. Temperature effect during humid ageing on interfaces of glass and carbon fibers reinforced epoxy composites. Journal of Colloid and Interface Science, 2006, 98(1): 111-117.
[3]	Zai B A, Park M K, Choi H S, et al. Effect of moisture absorption on damping and dynamic stiffness of carbon fiber/epoxy composites. Journal of Mechanical Science and Technology, 2009, 23(11): 2998-3004.
[4]	Pavlidou S, Papaspyrides C D. The effect of hygrothermal history on water sorption and interlaminar shear strength of glass/polyester composites with different interfacial strength. Composites : Part A, 2003, 34(11): 1117-1124.
[5]	Choi H S, Ahn K J, Nam J D, et al. Hygroscopic aspects of epoxy/ carbon fiber composite laminates in aircraft environments. Composites : Part A, 2001, 32(5): 709-720.
[6]	Khan L A, Nesbitt A, Day R J. Hygrothermal degradation of 977-2A carbon/epoxy composite laminates cured in autoclave and quickstep. Composites: Part A, 2010, 41(8): 942-953.
[7]	Bao L R, Yee A F. Effect of temperature on moisture absorption in a bismaleimide resin and its carbon fiber composites. Ploymer, 2002, 43(14): 3987-3997.
[8]	Bao L R, Yee A F. Moisture diffusion and hygrothermal aging in bismaleimide matrix carbon fiber composites—part I: uni-weave composites. Composites Science and Technology, 2002, 62(16): 2099-2110.
[9]	Olmos D, Lopez-Moron R, Gonzalez-Benito J. The nature of the glass fibre surface and its effect in the water absorption of glass fibre/epoxy composites. The use of fluorescence to obtain information at the interface. Composites Science and Technology, 2006, 66(15): 2758-2768.
[10]	Vaddadi P, Nakamura T, Singh R P. Inverse analysis for transient moisture diffusion through fiber-reinforced composites. Acta Materialia, 2003, 51(1): 177-193.
[11]	Hough J A, Karad S K, Jones F R. The effect of thermal spiking on moisture absorption, mechanical and viscoelastic properties of carbon fibre reinforced epoxy laminates. Composites Science and Technology, 2005, 65(7/8): 1299-1305.
[12]	Tsenoglou C J, Pavlidou S, Papaspyrides C D. Evaluation of interfacial relaxation due to water absorption in fiber-polymer composites. Composites Science and Technology, 2006, 66(15): 2855-2864.
[13]	Cauich-Cupul J I, Perez-Pacheco E, Valadez-Gonzalez A, et al. Effect of moisture absorption on the micromechanical behavior of carbon fiber/epoxy matrix composites. Journal of Material Science, 2011, 46(20): 6664-6672.
[14]	Paiva M C, Bernardo C A, Nardin M. Mechanical, surface and interfacial characterisation of pitch and PAN-based carbon fibers. Carbon, 2000, 38(9): 1323-1337.
[15]	Guo Y X, Liu J, Liang J Y. Modification mechanism of the surface- treated PAN-based carbon fiber by electrochemical oxidation. Journal of Inorganic Materials, 2009, 24(4): 853-858.
[16]	Yue Z R, Jiang W, Wang L, et al. Surface characterization of electrochemically oxidized carbon fibers. Carbon, 1999, 37(11): 1785-1796.
[17]	Bao L R, Yee A F, Lee Charles Y C. Moisture absorption and hygrothermal aging in a bismaleimide resin. Polymer, 2001, 42(17): 7327-7333.
[18]	ASTM D5229/D5229M-92, Standard Test Method for Moisture Absorption PropertiesEquilibrium Conditioning of Polymer Matrix Composite Materials. D5229/D5229M-92, Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials.
[19]	Bryan Harris. Engineering Composite Materials, 2nd Edition. London: The Institute of Materials, 1999: 99.
[20]	Chevali V S, Dean D R, Janowski G M. Effect of environmental weathering on flexural creep behavior of long fiber-reinforced thermoplastic composites. Polymer Degradation and Stability, 2010, 95(12): 2628-2640.