Molecular dynamics simulations are used to obtain mode I and mode II fracture energies and cohesive laws for bulk epoxy and interfaces formed between epoxy and single-layer graphene (SLG), multilayer graphene (MLG), and multilayer graphene oxide (MLGO). The elastic moduli and ultimate tensile and shear strengths of epoxy–graphene interfaces are calculated from uniaxial tension and simple shear loadings. The results show that Young’s modulus and the ultimate tensile strength increase relative to bulk epoxy, whereas the shear modulus and ultimate shear strength are reduced. Failure of epoxy–graphene interfaces in tension occurs due to the formation of voids in the epoxy. Failure in shear is due to tangential slipping at the interface. Under mixed-mode conditions, the shear modulus and shear strength decrease with increasing tensile load. The critical energy release rate \(G_{\text{c}}\) for the studied epoxy–SLG/MLG/MLGO systems is obtained using a continuum fracture mechanics approach and is found to be significantly lower than for bulk epoxy. All of the results are combined to define mode I and II cohesive laws for bulk epoxy and epoxy–SLG/MLG/MLGO interfaces that can be used in theoretical models and numerical methods, such as finite elements, that employ cohesive zones.

分子动力学模拟用于获得本体环氧树脂和环氧与单层石墨烯（SLG），多层石墨烯（MLG）和多层石墨烯氧化物（MLGO）之间形成的界面的模式I和模式II断裂能和内聚规律。环氧-石墨烯界面的弹性模量以及极限拉伸强度和剪切强度是根据单轴张力和简单剪切载荷计算得出的。结果表明，相对于本体环氧树脂，杨氏模量和极限拉伸强度增加，而剪切模量和极限剪切强度降低。环氧-石墨烯界面在拉伸中的失效是由于在环氧树脂中形成空隙而引起的。剪切失败是由于界面处的切向滑动。在混合模式条件下，剪切模量和剪切强度会随着拉伸载荷的增加而降低。使用连续断裂力学方法获得了研究的环氧树脂–SLG / MLG / MLGO系统的\（G _ {\ text {c}} \\），发现它远低于散装环氧树脂。所有结果组合在一起，定义了散装环氧树脂和环氧-SLG / MLG / MLGO界面的模式I和II内聚规律，这些理论可用于理论模型和数值方法，例如采用内聚区的有限元。