基于缠结微结构的非晶态玻璃态高分子材料屈服行为的分子动力学研究

非晶态玻璃态高分子材料作为结构材料在工程领域应用广泛,其机械力学性能特别是屈服变形行为受到热处理、加载应变率和环境温度的影响.采用分子动力学模拟方法研究非晶态玻璃态高分子材料不同工况下的单轴拉伸变形,基于分子链缠结微结构的概念,阐明了非晶态玻璃态高分子材料屈服和应变软化过程的内在变形机制.结果表明,拓扑缠结具有较为稳定的空间结构,难以发生解缠,决定了非晶态高分子材料屈服后的软化平台.由相邻分子链的局部链段相互作用形成的次级缠结在一定外界条件下可发生破坏或重新生成,次级缠结微结构及其演化是非晶态高分子材料发生屈服及软化的内在物理原因.

Molecular Dynamics Simulation on the Yield Behavior of Amorphous Glassy Polymers Based on Entanglements

Amorphous glassy polymers are widely used as structural materials in engineering field. The uniaxial tensile deformation of amorphous glassy polymers was studied by molecular dynamics simulation. Based on the concept of molecular entanglements, the inherent deformation mechanisms of the yield and strain softening process of amorphous glassy polymers were interpreted. The effects of cooling rate, loading rate and temperature on the yield behavior were discussed. The results show that the topological entanglements have arelatively stable spatial structures and are rarely untangled, which determine the softening platform after yielding. The sub-entanglements formed by the interaction of local segments of adjacent molecular chains may be destroyed or regenerated under certain external conditions. The microstructure and evolution of the sub-entanglements are the internal mechanism of the yield behavior of amorphous polymers.