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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/10321

Title: 碳奈米管/環氧樹脂複合材料疲勞性質之研究 (III)
A Study on Fatigue Property of CNT/Epoxy Resin Composite Materials (III)
Authors: 任貽明
Contributors: NTOU:Department of Mechanical and Mechatronic Engineering
國立臺灣海洋大學:機械與機電工程學系
Keywords: 碳奈米管/環氧樹脂複合材料;溫度;濕度;疲勞;缺口;疲勞缺口因子;缺口敏感度;疲 勞裂縫成長速率;應力強度因子
carbon nanotube/epoxy composite;temperature;humidity;fatigue;notch;fatigue notch factor;notch sensitivity;fatigue crack propagation rate;stress intensity factor
Date: 2010-08
Issue Date: 2011-06-28T07:38:25Z
Publisher: 行政院國家科學委員會
Abstract: 摘要:在本計畫第三年度中之研究方法及步驟可分為兩大部分:第一部份是在不同溫濕度條件下,針對不同碳奈米管含量及不同缺口尺寸的奈米複材缺口試片進行疲勞實驗;並以數學模型來描述缺口試片的疲勞壽命曲線。得到的缺口試片之疲勞壽命曲線將與本計畫第一年度所獲得之無缺口試片疲勞壽命曲線相比,藉此找出碳奈米管/環氧樹脂複合材料的疲勞缺口因子及缺口敏感度。此疲勞缺口因子及缺口敏感度預期將與碳奈米管含量及缺口尺寸等實驗參數有關。缺口敏感度的測定將對於具應力集中效應的碳奈管/環氧樹脂複合材料結構之疲勞設計有重要的幫助。第二部份則是利用不同碳奈米管含量的碳奈米管/環氧樹脂複合材料製作CT 試片(Compact Tension Specimen),進行疲勞裂縫成長速率的測量實驗;並討論疲勞裂縫成長速率及應力強度因子範圍之間的關係。本計畫使用硝酸改質之碳奈米管,製成三種不同含量(0 wt%、0.5 wt%和1.0 wt%)之碳奈米管/環氧樹脂複合材料,再將其加工成具四種不同缺口孔徑之試片。在進行疲勞實驗之前,首先對具缺口之碳奈米管/環氧樹脂複合材料試片進行靜態拉伸實驗,其結果發現:具缺口試片之缺口孔徑越大,其靜態拉伸極限強度越小。另外,在碳奈米管含量為0.5 wt%時,會有最高之極限強度。所有疲勞實驗均為負荷控制,波形負荷比為0.1。疲勞實驗結果發現,在任何固定的碳奈米管含量下,其試片缺口孔徑越大,疲勞壽命有明顯下降之趨勢。且試片缺口孔徑越大,其缺口敏感因子也越大。此外,缺口敏感因子以0.5 wt%碳奈米管/環氧樹脂複合材料試片為最高,1.0 wt%之碳奈米管/環氧樹脂複合材料試片次之,0 wt%之碳奈米管/環氧樹脂複合材料試片為最低。本文並成功地利用Peterson模型來描述缺口敏感因子與缺口尺寸及材料常數之間的關係,並發現此材料常數與材料的靜態極限強度有關。最後,本計畫利用實體顯微鏡與場發射掃瞄式電子顯微鏡對試片之破斷面進行觀察,藉此了解具缺口之碳奈米管/環氧樹脂複合材料之疲勞破壞機制。另外,本計畫之結果也發現在較低的固定應力強度因子範圍下,添加碳奈米管將有效降低疲勞裂縫成長速率,但過多的碳奈米管添加,則對裂縫成長的抑制無明顯之作用。此結果與該奈米複合材料之疲勞強度與碳奈米管含量間之趨勢相同。
abstract:The research work in the third year includes two main parts. The first part of the project is to study the notch effect on the fatigue strength of the CNT/Epoxy composites. The contents of CNTs and sizes of notches are the considered variables in the study. By integrating with the smooth-specimen data achieved in the first year of this project, the fatigue notch factors and the notch sensitivity for the nanocomposites can be obtained. The second part of this research is to investigate the crack growth rates for the studied nanocomposites using the compact tension specimens. The relationship between the crack propagation rates and the stress intensity factor ranges will be observed and discussed. The experimental results show that the static ultimate strengths of the studied notched nanocomposites decrease with increasing the notch sizes. Furthermore, adding 0.5 wt.% CNTs significantly increases the static strength of the epoxy material. However, adding 1.0 wt.% CNT can not improve the strength effectively because the stress concentrations resulting from the agglomerates of CNTs decrease the strength of the studied nanocomposites. Similar to the static behavior, the fatigue strengths of the notched CNT/epoxy composite specimens decrease with increasing the notch sizes of the specimens. Peterson’s model was employed to relate the notch sensitivity factors of the notched specimens with the notch sizes and a material constant. The material constant was found to be related to the ultimate strength of the studied nanocomposites, and a power law model was proposed herein to relate the material constant and the ultimate strength of the nanocomposite. The fatigue damage was found to initiate from the defect located near the notch root, and propagated along the plane normal to the specimen axis. The CNT bridging across the cracked matrix transferred the loads from the epoxy matrix to the CNTs and the pullout of the CNTs is the main fatigue failure mechanism observed in the fatigue tests. Furthermore, the addition of CNTs can reduce the crack propagation rate of the epoxy resin effectively. However, the excessive addition of CNTs can not improve the resistance of fatigue crack growth. This observation can successfully explain the trend between the fatigue strength and the CNT content.
Relation: NSC99-2221-E019-056
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/10321
Appears in Collections:[機械與機電工程學系] 研究計畫

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