In this work, the effect of seawater ageing on mode I and mode II interlaminar fracture toughness ( G I C and G IIC ) of prepreg-based woven glass fiber/epoxy laminates with and without multiwall carbon nanotubes (MWCNTs) has been investigated. The first part of the investigation reports the moisture absorption behavior of multiscale composite laminates exposed to seawater ageing for ∼3912 h at 70 °C. Then, the results of mode I and mode II fracture tests are presented and a comparison of G I C and G IIC for each type of material group and condition is made. Experimental results showed the significant effect of seawater ageing on G I C of multiscale composite laminates due to matrix plasticization and fiber bridging. The improvement in G I C of the wet glass fiber/epoxy laminate was about 50% higher than that of the neat laminate (without MWCNTs) under dry condition. It was also found that the presence of MWCNTs into composite laminates promotes a moderate increase (8%) in their G IIC as a result of the additional toughening mechanisms induced by CNTs during the delamination process. Scanning electron microscopy analysis conducted on fracture surface of specimens reveals the transition from brittle (smooth surface) to ductile (rough surface) in the morphology of composite laminates due to the influence of seawater ageing on the polymeric matrix and fiber/matrix interface.

中文翻译：

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海水对多壁碳纳米管改性玻璃纤维/环氧树脂层压板层间断裂韧性的影响

在这项工作中，研究了海水老化对具有和不具有多壁碳纳米管 (MWCNT) 的预浸料基编织玻璃纤维/环氧树脂层压板的 I 型和 II 型层间断裂韧性（ GIC 和 G IIC ）的影响。研究的第一部分报告了在 70°C 下暴露于海水老化约 3912 小时的多尺度复合层压板的吸湿行为。然后，介绍了模式 I 和模式 II 断裂试验的结果，并对每种类型的材料组和条件进行了 GIC 和 G IIC 的比较。实验结果表明，由于基体塑化和纤维桥接，海水老化对多尺度复合层压板的 GIC 有显着影响。在干燥条件下，湿玻璃纤维/环氧树脂层压板的 GIC 改进比纯层压板（无 MWCNTs）高约 50%。还发现，由于 CNT 在分层过程中引起的额外增韧机制，复合层压板中 MWCNT 的存在促进了其 G IIC 的适度增加（8%）。对试样断裂表面进行的扫描电子显微镜分析揭示了由于海水老化对聚合物基体和纤维/基体界面的影响，复合材料层压板的形态从脆性（光滑表面）向韧性（粗糙表面）转变。还发现，由于 CNT 在分层过程中引起的额外增韧机制，复合层压板中 MWCNT 的存在促进了其 G IIC 的适度增加（8%）。对试样断裂表面进行的扫描电子显微镜分析揭示了由于海水老化对聚合物基体和纤维/基体界面的影响，复合材料层压板的形态从脆性（光滑表面）向韧性（粗糙表面）转变。还发现，由于 CNT 在分层过程中引起的额外增韧机制，复合层压板中 MWCNT 的存在促进了其 G IIC 的适度增加（8%）。对试样断裂表面进行的扫描电子显微镜分析揭示了由于海水老化对聚合物基体和纤维/基体界面的影响，复合材料层压板的形态从脆性（光滑表面）向韧性（粗糙表面）转变。