《复合材料 Composites》课程教学资源（学习资料）第二章增强体_glass fiber-4 Tensile behaviors of ECR-glass and high strength glass fibers after NaOH treatment.pdf_大学文库

Availableonlineatwww.sciencedirect.com Science Direct CERAMICS CrossMark INTERNATIONA ELSEVIER Ceramics International 39(2013)9173-9178 www.elsevier.com/locate/ceramint Tensile behaviors of ECR-glass and high strength glass fibers after Naoh treatment Jianxun Liu, Ming Jiang, Yang Wang, Gang Wu b, Zhishen Wu.b, is International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China National Local United Engineering Research Center of"Basalt fiber production and application Southeast University Received 24 March 2013: received in revised form 4 May 2013; accepted 5 May 201 Available online 14 May 2013 Abstract ECR-glass and high strength glass(S-glass)fibers were treated in 2 mol NaOH solution up to 5 h. The strength maintenance ratio and mass loss ratio of the fibers after treatment were investigated. The surface morphologies were characterized using scanning electron microscopy, and changes of chemical composition were analyzed by energy dispersive X-ray spectroscopy and Fourier transform infrared spectrometry. The alkali resistance and tensile strength of the S-glass fibers are higher compared to those of the ECR-glass fibers as they received less alkaline attack because of the more compact SiO2 network and the formation of a protective layer on the S-glass fiber surface. The S-glass fibers have a higher mass loss due to the smaller diameter and thinner corrosion layer. e 2013 Published by Elsevier Ltd and Techna Group S.r.L. Keywords: Glass fibers; Alkali corrosion; Tensile strength; Mass loss: Microstructure 1. Introduction Some studies have been performed on the durability of the E-glass fibers and certain high performance fibers in alkaline High performance filaments are widely used as the reinfor- environment [6-9]. They suggested that the alkali solution cement of the composites due to their excellent properties very aggressive to the fibers surface, and the corrosion process [1-4]. It is accepted that the fibers in the composites can confer is the breaking of Si-o bonds in the glass network by hydroxyl trength and rigidity to the weak matrix. Fibers commonly ions. However, these experimental studies about the fiber used are glass fibers, ceramic fibers, carbon fibers, etc. The corrosion behavior are not complete because only a few kinds composites fiber reinforced are unavoidably applied in alkaline of fibers are systematically compared environments, but they are very sensitive to alkaline corrosion The ECR-glass fiber is a new fiber which is similar to the e- and show limited mechanical properties. Previous publications glass fiber but without boron and fluorine, thus having better reveal that the component responsible for corrosion failures in strength, chemical resistance and temperature resistance [10] the composites appears to be the fiber rather than the resin, as High strength glass fiber(s-glass fiber)is a stronger and stiffer the resin appears to play a protective role by shielding the version of the E-glass fiber. It has a higher modulus of fibers from the corrosive environment [5]. Thus, in order to elasticity due to high contents of Sio2 and Al2O3. Both the igure out how to improve the alkali resistance of the ECR-glass and S-glass fibers are suitable for all the applica- omposites, the fiber behavior during alkaline environment tions that E-glass suits. The research covering the alkaline should be understood resistance for the two fibers is limited by far. In this work, the strength maintenance ratio and mass loss ratio of the ECR-glass and S-glass fibers after NaoH treatment were Corresponding author at: Intemational Institute for Urban Systems Engineering. examined. The surface morphologies and changes of chemical Southeast University, Nanjing 210096, China. Tel: +86 25 83793232 composition were analyzed. The purpose is to investigate the effect E-mail address: zswu( mx ibaraki ac jp(ZS. Wu of Naoh on the performance of the ECR-glass and S-glass fibers 02728842 ront matter e 2013 Published by Elsevier Ltd and Techna Group S.r.L. http://dx.doiorg/10.1016/j-ceramint201305.018

CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 9173–9178 Tensile behaviors of ECR-glass and high strength glass fibers after NaOH treatment Jianxun Liua,b , Ming Jiangb , Yang Wangb , Gang Wua,b , Zhishen Wua,b,n a International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China b National & Local United Engineering Research Center of “Basalt fiber production and application”, Southeast University, Nanjing 210096, China Received 24 March 2013; received in revised form 4 May 2013; accepted 5 May 2013 Available online 14 May 2013 Abstract ECR-glass and high strength glass (S-glass) fibers were treated in 2 mol/l NaOH solution up to 5 h. The strength maintenance ratio and mass loss ratio of the fibers after treatment were investigated. The surface morphologies were characterized using scanning electron microscopy, and changes of chemical composition were analyzed by energy dispersive X-ray spectroscopy and Fourier transform infrared spectrometry. The alkali resistance and tensile strength of the S-glass fibers are higher compared to those of the ECR-glass fibers as they received less alkaline attack because of the more compact SiO2 network and the formation of a protective layer on the S-glass fiber surface. The S-glass fibers have a higher mass loss due to the smaller diameter and thinner corrosion layer. & 2013 Published by Elsevier Ltd and Techna Group S.r.l. Keywords: Glass fibers; Alkali corrosion; Tensile strength; Mass loss; Microstructure 1. Introduction High performance filaments are widely used as the reinforcement of the composites due to their excellent properties [1–4]. It is accepted that the fibers in the composites can confer strength and rigidity to the weak matrix. Fibers commonly used are glass fibers, ceramic fibers, carbon fibers, etc. The composites fiber reinforced are unavoidably applied in alkaline environments, but they are very sensitive to alkaline corrosion and show limited mechanical properties. Previous publications reveal that the component responsible for corrosion failures in the composites appears to be the fiber rather than the resin, as the resin appears to play a protective role by shielding the fibers from the corrosive environment [5]. Thus, in order to figure out how to improve the alkali resistance of the composites, the fiber behavior during alkaline environment should be understood. Some studies have been performed on the durability of the E-glass fibers and certain high performance fibers in alkaline environment [6–9]. They suggested that the alkali solution is very aggressive to the fibers' surface, and the corrosion process is the breaking of Si–O bonds in the glass network by hydroxyl ions. However, these experimental studies about the fiber corrosion behavior are not complete because only a few kinds of fibers are systematically compared. The ECR-glass fiber is a new fiber which is similar to the Eglass fiber but without boron and fluorine, thus having better strength, chemical resistance and temperature resistance [10]. High strength glass fiber (S-glass fiber) is a stronger and stiffer version of the E-glass fiber. It has a higher modulus of elasticity due to high contents of SiO2 and Al2O3. Both the ECR-glass and S-glass fibers are suitable for all the applications that E-glass suits. The research covering the alkaline resistance for the two fibers is limited by far. In this work, the strength maintenance ratio and mass loss ratio of the ECR-glass and S-glass fibers after NaOH treatment were examined. The surface morphologies and changes of chemical composition were analyzed. The purpose is to investigate the effect of NaOH on the performance of the ECR-glass and S-glass fibers. www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Published by Elsevier Ltd and Techna Group S.r.l. http://dx.doi.org/10.1016/j.ceramint.2013.05.018 n Corresponding author at: International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China. Tel.: +86 25 83793232. E-mail address: zswu@mx.ibaraki.ac.jp (Z.S. Wu)

9174 J. Liu et al. Ceramics intemational 39(2013)9173-9178 able 1 Mechanical properties of the ECR-glass and S-glass fibers. ECR-glass fiber S-glass fiber Elastic modulus(GPa) Elongation at failure(%) Filament diameter(um) ECR-glass fiber Yarn fineness(tex 4800 S-glass fiber The materials used for the present investigation are the ECR-glass fibers(produced by Corning Incorporated, US) and high strength glass fibers(S-glass fibers, produced by Nanjing Treating time(h) Fiberglass R&D Institute, China). Their basic properties are Fig. 1. Mass loss ratio of the fibers as a function of treating time. shown in Table 1 The two kinds of fibers were treated in naoh solution with concentration of 2 mol/. Before the treatment. fibers were pre-treated in acetone for size removal in order to avoid that the sizing agent influences the measurement results The 一ECR- glass fiber experimental temperature during the treatment was kept to be S-glass fiber 95C, and the treating time ranged from 1 to 5 h. After the treatment, the samples were rinsed four times in deionised (Di) water and dried. The mass losses of fibers after the treatment were examined using an electronic analytical balance with a precision of 0.0001 g. Control specimens were cut at intervals along the roving. Tensile strength test of the fibers before and after the treatment was performed at a crosshead speed of 20 mm/min by using a YG(B)026H-1000 Bundle Fiber Strength Tester (Wenzhou, China). The distance between the two clampers before the test was maintained to be 100 mm. The surface morphologies of the ECR-glass and S-glass fibers Treatin before and after the treatment were characterized with a FEl-Sirion Fig. 2. Strength maintenance ratio of the fibers as a function of treating time. scanning electron microscope (SEM). To check any significa chemical modification of the fibers, the specimens were analyzed using energy dispersive X-ray spectroscopy(EDX) and TEN- value, the strength of both fibers drops dramatically until l h SOR27 Fourier transform infrared spectrometer(FT-IR). It reduced to 31%o for the ECR-glass fibers, and 51%o for the S-glass fibers. After I h, the strength of both fibers falls slowly 3. Results and discussion The strength maintenance ratio of the S-glass fibers is higher than that of ECR-glass fibers. According to the results of 3 Mass loss Figs. I and 2, there is no close relationship between the mass loss ratio and strength maintenance ratio for the two fibers Fig. I shows the mass loss ratio as a function of treating Since fiber strength is an important parameter that controls the time for the ECR-glass and S-glass fibers. For both types of fracture behavior of composites [Il, strength maintenance fibers, the mass loss ratio increases sharply before I h. After ratio is able to represent the durability of the fibers. Therefore, I h, it changes slowly. Moreover, the mass loss ratio of the the alkali resistance of the S-glass fibers ECR-glass fibers first decreases and then increases. On the compared to that of the ECR-glass fibers. One of the reasons contrary, it first increases and then decreases for the S-glass may be that the density of framework(mainly composed of Si fibers. After 5 h, the mass loss ratio of the ECR-glass fibers is and Al) for the S-glass fibers is higher than that for the ECR much lower than that of the S-glass fibers glass fibers It is known that the glass fiber corrosion in alkaline media is mainly controlled by dissolving the SiOz-network The hydro 3. 2. Strength maintenance ratio xyl ions of the solution may disrupt the siloxane bonds in the glass [8,9, 12), as shown below: Fig. 2 shows the strength maintenance ratio of the two types of fibers after NaOH treatment. Compared with the original [-Si-o-Si-]+OH--[-Si-OH]+[] (1)

2. Experimental The materials used for the present investigation are the ECR-glass fibers (produced by Corning Incorporated, US) and high strength glass fibers (S-glass fibers, produced by Nanjing Fiberglass R&D Institute, China). Their basic properties are shown in Table 1. The two kinds of fibers were treated in NaOH solution with a concentration of 2 mol/l. Before the treatment, fibers were pre-treated in acetone for size removal in order to avoid that the sizing agent influences the measurement results. The experimental temperature during the treatment was kept to be 95 1C, and the treating time ranged from 1 to 5 h. After the treatment, the samples were rinsed four times in deionised (DI) water and dried. The mass losses of fibers after the treatment were examined using an electronic analytical balance with a precision of 0.0001 g. Control specimens were cut at intervals along the roving. Tensile strength test of the fibers before and after the treatment was performed at a crosshead speed of 20 mm/min by using a YG (B) 026H-1000 Bundle Fiber Strength Tester (Wenzhou, China). The distance between the two clampers before the test was maintained to be 100 mm. The surface morphologies of the ECR-glass and S-glass fibers before and after the treatment were characterized with a FEI-Sirion scanning electron microscope (SEM). To check any significant chemical modification of the fibers, the specimens were analyzed using energy dispersive X-ray spectroscopy (EDX) and TENSOR27 Fourier transform infrared spectrometer (FT-IR). 3. Results and discussion 3.1. Mass loss Fig. 1 shows the mass loss ratio as a function of treating time for the ECR-glass and S-glass fibers. For both types of fibers, the mass loss ratio increases sharply before 1 h. After 1 h, it changes slowly. Moreover, the mass loss ratio of the ECR-glass fibers first decreases and then increases. On the contrary, it first increases and then decreases for the S-glass fibers. After 5 h, the mass loss ratio of the ECR-glass fibers is much lower than that of the S-glass fibers. 3.2. Strength maintenance ratio Fig. 2 shows the strength maintenance ratio of the two types of fibers after NaOH treatment. Compared with the original value, the strength of both fibers drops dramatically until 1 h. It reduced to 31% for the ECR-glass fibers, and 51% for the S-glass fibers. After 1 h, the strength of both fibers falls slowly. The strength maintenance ratio of the S-glass fibers is higher than that of ECR-glass fibers. According to the results of Figs. 1 and 2, there is no close relationship between the mass loss ratio and strength maintenance ratio for the two fibers. Since fiber strength is an important parameter that controls the fracture behavior of composites [11], strength maintenance ratio is able to represent the durability of the fibers. Therefore, the alkali resistance of the S-glass fibers should be higher compared to that of the ECR-glass fibers. One of the reasons may be that the density of framework (mainly composed of Si and Al) for the S-glass fibers is higher than that for the ECRglass fibers. It is known that the glass fiber corrosion in alkaline media is mainly controlled by dissolving the SiO2-network. The hydroxyl ions of the solution may disrupt the siloxane bonds in the glass [8,9,12], as shown below: [−Si–O–Si−]+OH−-[−Si–OH]+[−SiO]− (1) Table 1 Mechanical properties of the ECR-glass and S-glass fibers. Property ECR-glass fiber S-glass fiber Strength (cN/tex) 43.5 112.9 Elastic modulus (GPa) 70 84 Elongation at failure (%) 4.5 2.4 Filament diameter (mm) 24 14 Yarn fineness (tex) 4800 480 012345 0 2 4 6 8 10 ECR-glass fiber S-glass fiber Treating time (h) Mass loss ratio (%) Fig. 1. Mass loss ratio of the fibers as a function of treating time. 012345 0 20 40 60 80 100 ECR-glass fiber S-glass fiber Treating time (h) Strength maintenance ratio (%) Fig. 2. Strength maintenance ratio of the fibers as a function of treating time. 9174 J. Liu et al. / Ceramics International 39 (2013) 9173–9178

Liu et al. Ceramics International 39(2013)9173-9178 91 Fig. 3. SEM images of ECR-glass fibers before and after treatment in NaOH solution:(a)original fiber, (b) after I h treatment, and (c. d)after 5 h treatment. Thus the strength of the fibers after treatment in alkali Table 2 solution is decreased considerably. The S-glass fibers have The EDX results of ECR-glass fiber surface before and after NaOH treatment very integrated and compact SiO2 network due to high (wt%; n =not detectable) contents of Sioz and Al2O3. Even though the hydroxyl ion can break the Si-o-Si linkage in NaOH solution, there should be munificent SiO2-network remained. Therefore, the S-glass Original fiber 8.837.33.00.40.3 fibers have higher strength maintenance ratio after naoH After I h treatment 2.6 treatment. Nevertheless, the contents of Sio, and Al,Oz in the After 5 h treatment 45.0 6.4 44.4 4.2 n. n ECR-glass fibers are lower, thus the amount of Sio2 network reserved should not be munificent in the ECR-glass fibers after alkali corrosion. Consequently, the strength maintenance ratio Fig 4 shows the SEM images of the S-glass fibers before of the ECR-glass fibers is lower after NaOH treatment. and after NaoH treatment The edX results of the fiber surface (Fig. 4)are given in Table 3. There is a corroded layer on the 33. Microstructure surface of the S-glass fibers after NaOH treatment which is as same as the ECr-glass fibers. The thickness of corroded layer ig.3 shows the SEM images of the ECR-glass fibers before also increases with increasing treatment time. Compared with and after NaOH treatment. Before the treatment, the surfaces the ECR-glass fibers, the corroded layer is thinner. From the of the fibers are very smooth although some fibers display EDX results, a decrease in Si and an increase in Mg contents surface defect, probably due to abrasion during the manufac- are observed in the corroded layer, whereas the Al content turing(as shown in Fig. 3(a). After I h treatment, the glass stays the same. After 5 h treatment, the contents of Si, Al and fiber surface becomes rough due to chemical interactions and it Mg are 52.5%0, 19.4%o and 28.1%o, respectively is covered by reaction products. The corrosion products have Although the chemical composition of the fibers is different, an amorphous or gel-like appearance. With the treatment time both the fibers should react in a similar way. Therefore, it can increasing, the thickness of the corroded layer increases. After be deduced that the formation of corrosion layer is typical for 5 h treatment, there are some cracks on the corroded layer the treatment in naoh solution some alkali metal released by Fig. 3(c)), and some parts of the layer are separated from the the glass through a network breakdown, is partly retained by ber surface(see Fig. 3(d). The EDX analysis results of the adsorption at the surface and formed corrosion layer. Taking fiber surface(Fig 3)are given in Table 2. Before I h, the into consideration the high amount of Ca in the ECR-glass concentrations of Si and Al of the fiber surface drastically fibers, a passivation Ca-Si-layer was formed on the fiber reduce, whereas the Ca content increases. Then the contents of surface. For the S-glass fibers, an insoluble Si-Mg-Al-layer Si, Al and Ca slightly decrease with increasing treatment time. was formed on the fibers because they have high concentra- After 5 h, the contents of Si. Al, and Ca are 45%, 6.4% and tions of Mg and Al. The corrosion layer becomes more 44.4%, respectively and compact with increasing treatment time, which may delay

Thus the strength of the fibers after treatment in alkali solution is decreased considerably. The S-glass fibers have very integrated and compact SiO2 network due to high contents of SiO2 and Al2O3. Even though the hydroxyl ion can break the Si–O–Si linkage in NaOH solution, there should be munificent SiO2-network remained. Therefore, the S-glass fibers have higher strength maintenance ratio after NaOH treatment. Nevertheless, the contents of SiO2 and Al2O3 in the ECR-glass fibers are lower, thus the amount of SiO2 network reserved should not be munificent in the ECR-glass fibers after alkali corrosion. Consequently, the strength maintenance ratio of the ECR-glass fibers is lower after NaOH treatment. 3.3. Microstructure Fig. 3 shows the SEM images of the ECR-glass fibers before and after NaOH treatment. Before the treatment, the surfaces of the fibers are very smooth although some fibers display surface defect, probably due to abrasion during the manufacturing (as shown in Fig. 3(a)). After 1 h treatment, the glass fiber surface becomes rough due to chemical interactions and it is covered by reaction products. The corrosion products have an amorphous or gel-like appearance. With the treatment time increasing, the thickness of the corroded layer increases. After 5 h treatment, there are some cracks on the corroded layer (see Fig. 3(c)), and some parts of the layer are separated from the fiber surface (see Fig. 3(d)). The EDX analysis results of the fiber surface (Fig. 3) are given in Table 2. Before 1 h, the concentrations of Si and Al of the fiber surface drastically reduce, whereas the Ca content increases. Then the contents of Si, Al and Ca slightly decrease with increasing treatment time. After 5 h, the contents of Si, Al, and Ca are 45%, 6.4% and 44.4%, respectively. Fig. 4 shows the SEM images of the S-glass fibers before and after NaOH treatment. The EDX results of the fiber surface (Fig. 4) are given in Table 3. There is a corroded layer on the surface of the S-glass fibers after NaOH treatment which is as same as the ECR-glass fibers. The thickness of corroded layer also increases with increasing treatment time. Compared with the ECR-glass fibers, the corroded layer is thinner. From the EDX results, a decrease in Si and an increase in Mg contents are observed in the corroded layer, whereas the Al content stays the same. After 5 h treatment, the contents of Si, Al and Mg are 52.5%, 19.4% and 28.1%, respectively. Although the chemical composition of the fibers is different, both the fibers should react in a similar way. Therefore, it can be deduced that the formation of corrosion layer is typical for the treatment in NaOH solution. Some alkali metal released by the glass through a network breakdown, is partly retained by adsorption at the surface and formed corrosion layer. Taking into consideration the high amount of Ca in the ECR-glass fibers, a passivation Ca–Si-layer was formed on the fiber surface. For the S-glass fibers, an insoluble Si–Mg–Al-layer was formed on the fibers because they have high concentrations of Mg and Al. The corrosion layer becomes more thick and compact with increasing treatment time, which may delay Fig. 3. SEM images of ECR-glass fibers before and after treatment in NaOH solution: (a) original fiber, (b) after 1 h treatment, and (c, d) after 5 h treatment. Table 2 The EDX results of ECR-glass fiber surface before and after NaOH treatment (wt%; n.¼not detectable). Element Si Al Ca Mg K Na Original fiber 50.2 8.8 37.3 3.0 0.4 0.3 After 1 h treatment 45.7 7.1 44.6 2.6 n. n. After 5 h treatment 45.0 6.4 44.4 4.2 n. n. J. Liu et al. / Ceramics International 39 (2013) 9173–9178 9175

Liu et al. Ceramics International 39(2013)9173-9178 9177 a 三 b3295 1500 1500 1 Fig. 6. FT-IR spectra of two fibers before(upper curves)and after (lower curves)5 h treatment in NaoH solution:(a) ECR-glass fiber and(b)S-glass fiber. NaO solution. There are three obvious absorption bands in The results indicate the better alkali resistance of the S-glass the spectra for the two fibers before the treatment. The strong fibers and thus point out their potential in future design of band attributed to Si-O is Si-O-Si stretching at around composite materials. 1100 cm [13]. The weak absorption band at around 620 cm is assigned to o-si-o stretching in [SiO4) or O-Al-O stretching in[AlO4][14 A strong absorption peak Acknowledgments at about 434-547 cm is due to Si-o-Si or Al-O-Al bending vibrations [15, 16]. The absorption peaks related to Si-O-Si The authors wish to thank the National Key Technology R&D and/or Al-O-Al decreased in intensity after 5 h NaoH Program of the Ministry of Science and Technology(Grant no treatment. It indicated that the SiO2-network is partially 201 1BAB03B09)for financial support. destroyed for both fibers after the alkali corrosion. Since Sio2 act as glass structure formers, their depletion can disturb References the glass structure, therefore reducing the strength of the fibers. Meanwhile, aluminum ions can either occupy the holes [11 D Ratna, Toughened FRP composites reinforced with glass and carbon between the SiO4 tetrahedra or join the SiO2-network to act fiber, Composites: Part A 39(3)(2008)462-469. as part of the glass matrix [17, 18]. Its depletion can also [2] T. Cziga'ny, Special manufacturing and characteristics of basalt fiber disrupt the continuity of the SiO2-network, further resulting in reinforced hybrid polypropylene composites: mechanical properties and the fiber strength reduction. In addition, the decline changes of the absorption peaks of the S-glass fibers are much smaller 3)C. Tascioglu, B. Goodell, R. Lopez-Anido, M. Peterson, W.Halteman, than that of the ECR-glass fibers. It may be explained by less J. Jellison, Monitoring fungal degradation of E-glass/phenolic fiber alkaline attack because of the more compact SiO2 network and reinforced polymer (FRP) composites forming a protective layer on the S-glass fiber surface International Biodeterioration Biodegradation 51 (3)(2003)157-165 4 J M. Yang. K.H. Min, H.O. Shin, Y.S. Yoon, Effect of steel and synthetic fibers on fexural behavior of high-strength concrete beams reinforced with FRP bars, Composites: Part B 43(3)(2012)1077-1086 H.B. Li, M L. Yan, D.T. Qi, S.H. Zhang. N. Ding. X H. Cai, Q. Li, X. 4. Conclusions M. Zhang. J. L. Deng. Corrosion of E-glass tiber in simulated oilfield environments, Joumal of Petroleum Science and Engineering 78(2) The ECR-glass and S-glass fibers would be damaged greatly in 2 mol/l NaOH solution. The tensile strength of both fibers [6] B. Wei, H.L. Cao, S.L. Song, Environmental resistance and mechanical performance of basalt and glass fibers, Materials Science and Engineering decreases with increasing treatment time. There are different A27(18-19)(2010)4708-4715. corrosion product layers on the surfaces of two fibers due to [7] H. Gu, Tensile behaviours of some high performance filaments after lifferent chemical compositions. A Ca-Si-layer was formed on NaoH treatment, Materials and Design 29(10)(2008)1893-1896 the ECR-glass fibers, and a Si-Al-Mg-layer was formed on (81 B. Wei, H.L. Cao, S.H. Song, Tensile behavior contrast of basalt and the S-glass fibers. Based on microstructure and FTIR analysis lass fibers after chemical treatment, Materials and Design 31(9)(2010) hydroxyl ions can disrupt the continuity of the glass network, [9] M. Friedrich, A Schulze, G Prosch, C. Walter. D. Weikert, N.M.Binh, thus reducing the fiber strength. The alkali resistance of the D.R.T. Zahn, Investigation of chemically treated basalt and glass fibres, S-glass fibers is higher than that of the ECR-glass fibers as Mikrochimica Acta 133(1-4)(2000)171-174. they received less alkaline attack because of the more compact [10] L. Kumosa, M. Kumosa, D. Armentrout, Resistance to stress corrosion SiOz network and forming a protective layer on the S-glass cracking of unidirectional ECR-glass/polymer composites for high oltage composite insulator applications, Composites: Part A 34(1)

NaOH solution. There are three obvious absorption bands in the spectra for the two fibers before the treatment. The strong band attributed to Si–O is Si–O–Si stretching at around 1100 cm−1 [13]. The weak absorption band at around 620 cm−1 is assigned to O–Si–O stretching in [SiO4] or O–Al–O stretching in [AlO4] [14]. A strong absorption peak at about 434–547 cm−1 is due to Si–O–Si or Al–O–Al bending vibrations [15,16]. The absorption peaks related to Si–O–Si and/or Al–O–Al decreased in intensity after 5 h NaOH treatment. It indicated that the SiO2-network is partially destroyed for both fibers after the alkali corrosion. Since SiO2 act as glass structure formers, their depletion can disturb the glass structure, therefore reducing the strength of the fibers. Meanwhile, aluminum ions can either occupy the holes between the SiO4 tetrahedra or join the SiO2-network to act as part of the glass matrix [17,18]. Its depletion can also disrupt the continuity of the SiO2-network, further resulting in the fiber strength reduction. In addition, the decline changes of the absorption peaks of the S-glass fibers are much smaller than that of the ECR-glass fibers. It may be explained by less alkaline attack because of the more compact SiO2 network and forming a protective layer on the S-glass fiber surface. 4. Conclusions The ECR-glass and S-glass fibers would be damaged greatly in 2 mol/l NaOH solution. The tensile strength of both fibers decreases with increasing treatment time. There are different corrosion product layers on the surfaces of two fibers due to different chemical compositions. A Ca–Si-layer was formed on the ECR-glass fibers, and a Si–Al–Mg–layer was formed on the S-glass fibers. Based on microstructure and FTIR analysis, hydroxyl ions can disrupt the continuity of the glass network, thus reducing the fiber strength. The alkali resistance of the S-glass fibers is higher than that of the ECR-glass fibers as they received less alkaline attack because of the more compact SiO2 network and forming a protective layer on the S-glass surface. The results indicate the better alkali resistance of the S-glass fibers and thus point out their potential in future design of composite materials. Acknowledgments The authors wish to thank the National Key Technology R&D Program of the Ministry of Science and Technology (Grant no. 2011BAB03B09) for financial support. References [1] D. Ratna, Toughened FRP composites reinforced with glass and carbon fiber, Composites: Part A 39 (3) (2008) 462–469. [2] T. Cziga´ny, Special manufacturing and characteristics of basalt fiber reinforced hybrid polypropylene composites: mechanical properties and acoustic emission study, Composites Science and Technology 66 (16) (2006) 3210–3220. [3] C. Tascioglu, B. Goodell, R. Lopez-Anido, M. Peterson, W. Halteman, J. Jellison, Monitoring fungal degradation of E-glass/phenolic fiber reinforced polymer (FRP) composites used in wood reinforcement, International Biodeterioration & Biodegradation 51 (3) (2003) 157–165. [4] J.M. Yang, K.H. Min, H.O. Shin, Y.S. Yoon, Effect of steel and synthetic fibers on flexural behavior of high-strength concrete beams reinforced with FRP bars, Composites: Part B 43 (3) (2012) 1077–1086. [5] H.B. Li, M.L. Yan, D.T. Qi, S.H. Zhang, N. Ding, X.H. Cai, Q. Li, X. M. Zhang, J.L. Deng, Corrosion of E-glass fiber in simulated oilfield environments, Journal of Petroleum Science and Engineering 78 (2) (2011) 371–375. [6] B. Wei, H.L. Cao, S.L. Song, Environmental resistance and mechanical performance of basalt and glass fibers, Materials Science and Engineering A 27 (18–19) (2010) 4708–4715. [7] H. Gu, Tensile behaviours of some high performance filaments after NaOH treatment, Materials and Design 29 (10) (2008) 1893–1896. [8] B. Wei, H.L. Cao, S.H. Song, Tensile behavior contrast of basalt and glass fibers after chemical treatment, Materials and Design 31 (9) (2010) 4244–4250. [9] M. Friedrich, A. Schulze, G. Prosch, C. Walter, D. Weikert, N.M. Binh, D.R.T. Zahn, Investigation of chemically treated basalt and glass fibres, Mikrochimica Acta 133 (1–4) (2000) 171–174. [10] L. Kumosa, M. Kumosa, D. Armentrout, Resistance to stress corrosion cracking of unidirectional ECR-glass/polymer composites for high voltage composite insulator applications, Composites: Part A 34 (1) (2003) 1–15. 500 1000 1500 Wavenumber(cm-1) Relative Intensity (ua) 500 1000 1500 Wavenumber(cm-1) Relative Intensity (ua) Fig. 6. FT-IR spectra of two fibers before (upper curves) and after (lower curves) 5 h treatment in NaOH solution: (a) ECR-glass fiber and (b) S-glass fiber. J. Liu et al. / Ceramics International 39 (2013) 9173–9178 9177

《复合材料 Composites》课程教学资源（学习资料）第二章 增强体_glass fiber-4 Tensile behaviors of ECR-glass and high strength glass fibers after NaOH treatment

《复合材料 Composites》课程教学资源（学习资料）第二章增强体_glass fiber-4 Tensile behaviors of ECR-glass and high strength glass fibers after NaOH treatment