Abstract Thermosetting epoxy polymers exhibit excellent stiffness and strength and are commonly utilized as matrices to make fiber reinforced composites. However, epoxy thermosets are brittle and typically possess a low fracture toughness that restricts their applications. One promising mechanism for improving mechanical properties of epoxy is the integration of micro- and nano-scale fillers. MXenes, a large family of 2D transition-metal carbides, carbonitrides, and nitrides, can be used to produce multifunctional polymer nanocomposites due to their excellent electrical, thermal, and mechanical properties. We employed density functional theory and coarse-grained molecular dynamics simulations to evaluate binding energy and microscopic mechanisms of fracture under uniaxial tension for MXene-epoxy composites. The simulation results were verified by manufacturing Ti3C2Tx MXene-epoxy composites and studying their structure and fracture surfaces. MXene-epoxy binding energies are largely unaffected by MXene type (Ti2CTx or Ti3C2Tx). Binding between Ti3C2Tx and epoxy becomes stronger with less hydrogen coverage of Ti3C2Tx surface due to increase in favorable electrostatic interactions. The Young's modulus of MXene-epoxy composites is greater compared to the neat epoxy which originates from stress transfer between the matrix and the nanofiller, the modulus linearly increases with the filler loading up to 1 vol %. At higher filler contents, the increase of the modulus is reduced due to filler aggregation. Void formation was detected near edges of the particles in MXene-epoxy composites under deformation from both experimental and simulation studies of the fracture surfaces. From these observations, we expect the MXene fillers to improve epoxy toughness and enhance its mechanical performance.

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MXene-环氧纳米复合材料的界面结合和力学性能

摘要 热固性环氧聚合物表现出优异的刚度和强度，通常用作制造纤维增强复合材料的基体。然而，环氧树脂热固性材料脆且通常具有低断裂韧性，这限制了它们的应用。改善环氧树脂机械性能的一种有前景的机制是微米级和纳米级填料的整合。MXenes 是一大类二维过渡金属碳化物、碳氮化物和氮化物，由于其优异的电学、热学和机械性能，可用于生产多功能聚合物纳米复合材料。我们采用密度泛函理论和粗粒分子动力学模拟来评估 MXene-环氧树脂复合材料在单轴拉伸下的结合能和微观断裂机制。通过制造 Ti3C2Tx MXene-环氧树脂复合材料并研究它们的结构和断裂表面来验证模拟结果。MXene-环氧结合能在很大程度上不受 MXene 类型（Ti2CTx 或 Ti3C2Tx）的影响。由于有利的静电相互作用增加，Ti3C2Tx 和环氧树脂之间的结合随着 Ti3C2Tx 表面的氢覆盖减少而变得更强。MXene-环氧树脂复合材料的杨氏模量与纯环氧树脂相比更大，后者源自基体和纳米填料之间的应力传递，模量随填料负载量线性增加至 1 vol%。在较高的填料含量下，由于填料聚集而降低了模量的增加。根据断裂表面的实验和模拟研究，在变形下 MXene-环氧树脂复合材料中的颗粒边缘附近检测到空隙形成。从这些观察中，我们预计 MXene 填料可以提高环氧树脂的韧性并增强其机械性能。