Abstract This research investigates the toughness of poly(butylene terephthalate) (PBT) nanocomposites, based on mechanical characterizations and subsequent microstructural observations. Montmorillonite (MMT) and nano-precipitated calcium carbonate (NPCC) were selected as nano-reinforcing phases. Notched Izod impact test, tensile test as a quasi-static loading, and mode-I fracture toughness test, were conducted to evaluate the toughness. The corresponding fracture surfaces were analyzed using scanning electron microscopy (SEM). Tensile test results were linked with the morphologies of corresponding tensile-fractured surfaces. The results indicated that massive fibrillation in PBT/MMT nanocomposites dissipated lower energy relative to the large plastic deformation that was induced in the fracture surface of pure PBT. For PBT/NPCC samples, however, surface roughening mechanism was observed to increase the toughness in the tensile test, as compared to plain PBT. The fracture morphology of compact tension (CT) specimens exhibited a low extent of plastic deformation for pure PBT. However, the crack initiation zone of both nanocomposites showed a fibrillated morphology, leading to the increase of stress intensity factor up to 57% and 45% with the application of MMT and NPCC, respectively, as compared to pure PBT. The crack propagation region was, however, associated with shallow fibrils for MMT and local polymer yielding for NPCC.

中文翻译：

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聚对苯二甲酸丁二醇酯纳米复合材料的韧性评价

摘要 本研究基于机械表征和随后的微观结构观察，研究了聚对苯二甲酸丁二醇酯 (PBT) 纳米复合材料的韧性。蒙脱石（MMT）和纳米沉淀碳酸钙（NPCC）被选为纳米增强相。进行缺口悬臂梁冲击试验、作为准静态载荷的拉伸试验和I型断裂韧性试验以评价韧性。使用扫描电子显微镜（SEM）分析相应的断裂表面。拉伸试验结果与相应的拉伸断裂表面的形态有关。结果表明，相对于纯 PBT 断裂表面引起的大塑性变形，PBT/MMT 纳米复合材料中的大量原纤化耗散的能量较低。然而，对于 PBT/NPCC 样品，与普通 PBT 相比，观察到表面粗糙化机制增加了拉伸试验中的韧性。致密拉伸 (CT) 试样的断裂形态显示纯 PBT 的塑性变形程度较低。然而，与纯 PBT 相比，两种纳米复合材料的裂纹萌生区均表现出原纤维化形态，导致应力强度因子在应用 MMT 和 NPCC 后分别增加了 57% 和 45%。然而，裂纹扩展区域与 MMT 的浅原纤维和 NPCC 的局部聚合物屈服有关。与纯 PBT 相比，两种纳米复合材料的裂纹萌生区均显示出原纤化形态，导致应力强度因子在应用 MMT 和 NPCC 后分别增加了 57% 和 45%。然而，裂纹扩展区域与 MMT 的浅原纤维和 NPCC 的局部聚合物屈服有关。与纯 PBT 相比，两种纳米复合材料的裂纹萌生区均显示出原纤化形态，导致应力强度因子在应用 MMT 和 NPCC 后分别增加了 57% 和 45%。然而，裂纹扩展区域与 MMT 的浅原纤维和 NPCC 的局部聚合物屈服有关。