碳纖維水泥質複合材料於應變量測之可行性研究

Feasibility Study of Carbon Fiber Reinforced Cementitious Composite on Strain Measurement

連婉佑(Wan-Yu Lien)

指導教授 ： 張國鎮

共同指導教授 ： 廖文正

國立臺灣大學/工學院/土木工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00635

摘要

結構物監測是現今土木工程界重要的議題之一，纖維混凝土是目前主要的補強材料，具有高抗張強度、高彈性模數、韌性佳與減少裂縫產生等優點，可增加結構耐震能力與安全性。在混凝土中添加纖維可改善混凝土抗彎、抗張、易脆等特性，進而發展出纖維混凝土材料。現今土木工程界常用之纖維混凝土包括鋼纖維混凝土、玻璃纖維混凝土與碳纖維混凝土(Carbon Fiber Reinforced Concrete, CFRC)等。目前工程界及學術界常用之監測方式，主要是將電子感測元件置入試體內部或是被覆於試體表面上，以進行物理量量測。然而感測元件的有效期限通常遠低於結構物之使用壽命，耐久性較差。為使感測元件的使用壽命與所監測之結構物相近，本研究嘗試以碳纖維砂漿作為結構監測之元件。由於碳纖維本身為導體，加入砂漿之後會使砂漿的電阻值大大地降低，使碳纖維砂漿成為一個導體，將其通入電流後，當結構受力時，造成碳纖維與砂漿之間的拉拔(pull-out)或推進（push-in），前者將使電阻值提高，後者則是使電阻值降低，而兩者的電阻變化與應變皆存在著一定的線性關係，此線性關係可用於量測應變；而當試體即將發生破壞時，電阻值的變化量會較彈性階段時大許多，此時可藉由此現象得知結構體的損壞程度是否已達到破壞，近一步達成監測及預警的目的。
然而，考慮實際應用時的經濟性，本研究僅使用0.2 vol.%之碳纖維添加量，其約為文獻中用量的一半，且經實驗結果得知，在此碳纖維含量之下對於材料之導電率不但能有明顯之提升，亦能達成量測與預警之目的，其量測範圍較文獻廣，再者，塗層試體之實驗結果亦能作為將來應用之參考。

關鍵字

Gauge Factor ； 碳纖維 ； 電阻變化率 ； 甲基纖維 ； 塗層

並列摘要

Structural monitoring system is important in civil engineering. There are some advantages in carbon fiber reinforced concrete, such like high tensile strength, high ductility which increase seismic capacity and security of structures. The traditional structural monitoring system has some disadvantage such as the life of sensor is shorter than structures. To find a sensor with long life as structure, in this research we used CFRCC (Carbon Fiber Reinforced Cementitious Composite) as the structural monitoring sensor. CFRCC with the functionality similar to piezoresistivity material can be used as a self-sensing material for strain measurement and damage detection. It is based on the reversible effect of strain on the volume electrical resistivity and the irreversible effect of damage on the resistivity. The strain sensing behavior is such that the resistivity decreases reversibly upon compression due to the slight push-in of crack-bridging fibers and the consequent decrease of the contact electrical resistivity of the fiber-cement interface. Similarly, the resistivity increases reversibly upon tension due to the slight pull-out of crack-bridging fibers and the consequent decrease of the contact resistivity.
To consider the economic, the fiber content is only 0.2 vol.% less than half of the amount of 0.48 vol.% used in references【14】【15】【17】. The experimental results shows that the conductivity of materials is significantly improved and CFRCC can be used as a strain measurement and damage detection in the fiber content of 0.2 vol.%. Moreover, the experimental results of coating beams can be the database for applications in the future.

並列關鍵字

Gauge Factor ； Carbon fiber ； Fractional change in electrical resistance ； Methyl cellulose ； Coating

參考文獻

【28】 林靖淳, 碳纖維水泥複合材料受力應變與電阻特性之探討, July, 2011.

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【2】 Manuela Chiarello, Raffaele Zinno, Electrical Conductivity of Self-Monitoring CFRC, Cement and Concrete Composites 27 (2005) 463-469

【3】 Rose Mary Chacko, Nemkumar Banthia, Aftab A. Mufti, Carbon-Fiber-Reinforced Cement-Based Sensors, Canadian Journal of Civil Engineering 34 (2007) 284-290.

【4】 D.D.L. Chung, Dispersion of Short Fibers in Cement, Journal of Materials in Civil Engineering (2005) 379-383.