Xue Mengchi Wu Jian Gao Anmin Ju Zhigang Xu Shan
Hengtong Optic-electric Co., Ltd
Suzhou, Jiangsu, P.R.China
+86-512-63800592, xuemc@htgd.com.cn
Abstract
Basalt fiber(BF fiber) is continuous fiber manufactured by drawing melted natural basalt mineral 1450-1500℃. It has some advantages such as excellent high temperature resistant, high strength, incombustible and chemical stability, especially the better cost and performance advantages compared with glass fiber and aramid. Its temperature range can reach -200℃～+650℃, young′s modulus can reach 90～110Gpa. Therefore BF fiber gains increasingly popular among cable manufacturing enterprises and is introduced into optical fiber cables as reinforcing material. This paper studies application of basalt fiber reinforcement in cables, compares BF fiber reinforcement with other major reinforcements in cables. Through the design and performance test of several typical products, the advantages of basalt fiber reinforcement and the possibility of fully replacing mainstream non-metallic reinforcements are verified and analysed. At last it briefly introduces the upcoming Chinese standard YD/T 1181.5 “Basalt fiber yarns and reinforced plastic rods for optical fiber cables”.
Key words: Basalt fiber; non-metallic reinforcements; Experimental verification
1. Introduction
As the structure is relatively unitary and the material tends to be stable, the new structure and the innovation of materials will be an important direction of the future development of optical fiber cable technology. At present glass fiber and aramid fiber are the mainly non-metallic reinforcements in cables, glass fiber has the advantage of low cost, but it also has the drawback, the great limitations of specific strength, hygroscopicity, chemical stability (especially in alkaline medium). The advantage of aramid yarn is high specific strength, but the drawback is the high cost. Therefore, the current market needs a high quality, low-cost reinforced fiber to meet the mechanical properties of the optical cables and the large-scale application.
Basalt fiber is continuous fiber manufactured by drawing melted natural basalt mineral 1450-1500℃.The monofilament diameter is between a few microns to dozens of microns. Products are shown in figure 1. Basalt fiber has so many advantages such as high strength, resistance to high and low temperature, thermal isolation, corrosion resistance, flame retardant, resistance to ultraviolet radiation, low moisture absorption, excellent insulation performance and high cost performance. Continuous basalt fiber is the only pure natural new high-tech fiber which doesn’t add any other material. It represents the development direction of green material in the world. Because of the better cost and performance advantage compared with glass fiber and aramid yarn, basalt fiber can be introduced as stable non-metallic reinforcement in optical fiber cables.
Our company uses basalt fiber and rod as reinforcement in cables, carry on the test first and the testing is good. The following is the detailed introduction.
Figure 1. Basalt mineral and the resulting fiber and rod
2. The properties of basalt fiber and rod and the experimental verification
2.1 Mechanical and physical properties
Comparisons of physical properties between basalt continuous fiber and other fibers are shown in table 1, the measured values are shown in table 2. Comparisons of physical properties between basalt fiber reinforced plastic rod (BFRP) and other plastic rods are shown in table 3, the measured values are shown in table 4. Through the comparisons and our measured values, we can see that the elastic modulus of basalt continuous fiber is a few percent lower than aramid yarn but 30-60% higher than glass fiber yarn, and the heat-resistant property is the most excellent.
Table 1. Comparison of physical properties between basalt continuous fiber and other fibers
Table 2. Measured values of basalt fiber
Figure 2. Tensile test curve of 5 glass fiber yarns of 785tex
The tensile strength of basalt fiber is 1.5~2 times of metal,1.2~1.5 times of E glass fiber. From the comparison of the measured values from figure 2 and table 2 we can find that single glass fiber of 785tex can only provide about 400N tensile force, which is 470N for basalt fiber of the same type. Excellent tensile property makes the basalt fiber reinforced cable a smaller diameter to meet the same mechanical properties. It can save scare resources of pipeline and greatly improve the utilization rate of pipeline when used in pipeline.
Table 3. Main performance criteria of reinforced plastic rods
Table 4. Measured values of basalt fiber reinforced plastic rod
2.2 Environmental tolerance property
Optical fiber cable is usually oil filling structure when used in outdoor, the structure makes that the fiber reinforcement contact with filling compound for a long time. If the bearing capacity of reinforcement is decreased obviously under the effect of active medium, this will lead to an undoubtedly fatal influence on the life of cables. An experiment proved that after soaking in acid solution for 2 hours and alkaline solution for 1hour, the bearing tensile strength of basalt fiber reinforcement is reduced by 25%, which is 40% for glass fiber. This suggests that basalt fiber has a more excellent performance in active medium tolerance and its application as cable reinforcement can make sure the long lifetime of cables. Actual experiences of the cable application show that because of the special laying environment and installation requirements, cable strengthen materials creep under a lot of stress conditions. With the increase of service time, the modulus and strength of common cable strengthen material will reduce gradually. Creepage will lead to the deformation or damage of the materials and the strengthen function will eventually lose. According to the results of resistance to creep experiment of basalt fiber, the long-term loads on sample of 100MPa (20% stress level), 200MPa (40% stress level), 300MPa (60% stress level), after 1080h, the bending creep values are 0.12mm, 0.35mm and 0.45mm. It shows that basalt fiber has a good creep property. As for the long-term application, thin rods made of continuous basalt fiber has no traces of fatigue damage after a long time (more than 9 years) subjected to cyclic loading. It is unbelievable to achieve such performance for glass fiber. So basalt fiber reinforced cables have longer lifetime and better stability in using.
Hygroscopicity of basalt fiber is 6~8 times lower than the glass fiber. When in long-term laying applications used as reinforcement and auxiliary reinforcement for cables, it can effectively avoid fiber hydrogen damage caused by wet to ensure the cable transmission performance.
3. Manufacture and test of basalt fiber reinforced cable
We use basalt fiber yarns of 800tex as auxiliary reinforcement, design and manufacture the ADSS as shown in figure 3. Figure 4 is the tensile strain curve of the cable. Through the curve and our design parameters, we can measure the effective modulus of elasticity of the basalt fiber yarn is about 80GPa, which is really greater than that of glass fiber yarn.
Figure 3. Basalt fiber reinforced ADSS (2.2FRP, 20 basalt fibers of 800tex)
Figure 4. Cable strain curve of basalt fiber reinforced ADSS (2012 Nov. 6)
Tensile additional decay curve of the cable is shown in figure 5, we can see the attenuation change value is within 0.03dB. Table 5 is mechanical property test summary, table 6 is environment performance test summary, all can satisfy the requirements of relevant standards.
Figure 5. Tensile additional decay curve of basalt fiber reinforced ADSS (2012 Nov. 6)
Table 5. Mechanical property test results of basalt fiber reinforced ADSS (2012 Nov. 6)
Table 6. Environmental performance test methods and results
4. Conclusions
As for the comparison of mainstream fiber reinforcement and basalt fiber reinforcement in cables, the advantage in performance and price of basalt fiber reinforced cable is obvious. It has the possibility of fully replace the current mainstream fiber reinforced cable. At least it provides an entirely new solutions and ideas for the design and application of optical fiber cables, and its application prospect is very broad.
At present we HTGD declare China's communication industry standard YD/T 1181.5-2015 “Characteristics of non-metal reinforcement for optical fiber cables part5: Basalt fiber yarns and reinforced plastic rods” as leading organization. The drafting and publication of the standard will open a new chapter for basalt yarn and reinforced plastic rod used in cables, and will play a strategic role for the new situation of non-metallic cable design.
5. Acknowledgments
We thank our technology and quality team for tracking and testing the samples.
6. Pictures of Authors
Xue Mengchi
Mr. Xue Mengchi was born in 1972. He now works as chief engineer in Jiangsu Hengtong Optic-Electric Co., LTD. He is also a professor level senior engineer and a Master student adviser, senior member of China institute of communications, member of ITU-T SG6 and SG15 China expert team.
Wu Jian
With 20 years of experience in telecommunication, Mr. Wu Jian has been standard composer of optical fiber cable for Ministry of Industry and Information Technology of the People’s Republic of China (MIIT)
Gao Anmin
Mr. Gao Anmin was born in 1965. He now works as chairman in Jiangsu Hengtong Optic-Electric Co., LTD. He is also a senior engineer and a professor and Master student adviser of university, vice director of optical cable and cable symposium of China institute of communications, member of ITU-T SG6 and SG15 China expert team.
Ju Zhigang
Mr. Ju Zhigang joined Jiangsu Hengtong Optic-electric Co., Ltd in 2002 after Graduation from the Southwest University of Science and Technology, and has been engaged in process research of optical fiber cables. Now he is a process supervisor of Outdoor Optical Cable Technique Department.
Xu Shan
Ms. Xu Shan was born in 1989. She joined Jiangsu Hengtong Optic-electric Co., Ltd in 2011 after Graduation from Wuhan University. Now she is a technical support engineer in Outdoor Optical Cable Technique Department.
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