- 學位論文
以微波加熱奈米碳管方式修補纖維強化複合材料
Repairing fiber-reinforced polymer composites by microwave heating of carbon nanotubes
摘要
Abstract Up to 3 wt% multi-walled carbon nanotubes (MWNTs) was mixed with a single part high temperature curing epoxy by a three-roll mill to form adhesives that can be heated by microwave radiation. The adhesives were then used for rapid repairing and joining fiber-reinforced polymer composites by microwave heating. The addition of MWNTs improved the mechanical properties of epoxy adhesives. Comparing with neat epoxy adhesive, there are 4.6% increase in the tensile strength and 6.2% increase in the Young’s modulus. By microwave irradiation, the well dispersed MWNTs act as heat sources that provide a more homogeneous and effective heating. Therefore, the curing time of MWNTs filled epoxy adhesive by microwave heating can be reduced to less than 1/3 of that by conventional heating. The addition of MWNTs into epoxy can reduce the voids size and strengthen the epoxy matrix by impeding the crack growth in the material. However, in curing with conventional heating, the addition of MWNTs can also reduce the cross-link density manifested by lowering of the glass transition temperature (Tg) of the cured adhesive. Therefore, the strength of conventional cured MWNTs/epoxy resin adhesive reached maximum with 1 wt% MWNTs addition and getting lower with more MWNTs added. In contrast, by microwave heating, the cross-link reaction was not impeded by MWNTs since the polymer chains of epoxy resin and hardener around the heated MWNTs were cross-linked firstly. Therefore, the cross link density did not decrease and the glass transition temperature did not change obviously. As a result, the strength of the MWNTs filled epoxy adhesives increased with increasing the content of MWNTs over 1 wt% to 3 wt%. 56 % increase of the bonding strength from 16 MPa for neat epoxy to 24.9 MPa for 3 wt% MWNTs addition was observed. The patch repair strengths with the use of MWNTs/epoxy resin adhesives were higher by microwave heating than those by conventional heating. By using 3 wt% MWNTs/epoxy resin adhesive and microwave curing with a patch longer than 20 mm, the bending strength of the damaged composite material with a 2 mm deep through crack can be higher than the initial good composites.
並列摘要
摘要 本論文研究以三軸滾輪機混合多壁奈米碳管及高溫固化型環氧樹脂來製作可微波加熱的複合材料接著劑，以微波加熱的方式來達到快速接著以及修補複合材料的效果。與未添加奈米碳管的環氧樹脂膠比較，添加多壁奈米碳管的環氧樹脂膠其拉伸強度可以提高約4.6 %，而楊氏係數可以提高約6.2 %。此外，奈米碳管具有優異的微波吸收特性，因此在微波加熱中可將吸收微波的能量轉換成熱能，形成熱源可均勻地加熱膠料。研究中發現利用微波加熱奈米碳管的方式相較於傳統加熱方式，可以使接著所需的時間減少為1/3以下。 由重疊剪切測試發現添加多壁奈米碳管可以降低膠層內孔洞大小及阻礙裂縫成長，因而提高接著的強度。利用傳統加熱的方式，因為多壁奈米碳管的添加會降低環氧樹脂的交聯密度，而使其接著強度在1 wt%時有最大值，其後接著強度反隨碳管含量增加而減少。而利用微波的方式，因其加熱較均勻且不會明顯降低環氧樹脂的交聯密度，相較於以傳統加熱的方式，不但有較高的接著強度，而且接著強度繼續隨奈米碳管含量增加至3 wt%以上。相較於純環氧樹脂16 MPa 的接著強度，含3 wt%奈米碳管膠料的接著強度可提高56 % 而達 24.9 MPa 。 在複合材料修補的實驗中，以三點彎曲試驗量測修補過後複合材料的強度，發現以微波加熱的方式具有較佳的修補強度，同時增加補片的長度可提高修補強度，以20 mm長的補片修補含2 mm深穿越裂縫的5 mm彎曲試片，其強度就可以比原始的複合材料還要來得高。