|Alternative Title||Molecular dynamics simulation of mechanical behavior of polymer/substrate interface at micro-/nano-scale|
|Place of Conferral||北京|
|Keyword||聚合物-异质材料界面 微观力学行为 分子动力学模拟 粗粒化 微结构演化|
Polymer/substrate interface is widely used in systems such as polymer matrix composites and adhesive bonded joint structures. Its dynamic behavior directly determines the stability and reliability of the system. Due to the presence of the interfacial phase, the physical and mechanical properties of the multiphase system are different from that of each single phase. The failure behavior of interface is determined by the intrinsic physical properties of the polymer, external loads and constrained effects simultaneously. The present study focuses on the mechanical behavior of polymers and the relating interface at micro-/nano-scale. Molecular dynamics simulation was used to capture the failure evolution process of polymer/substrate interface under tensile loading conditions. The coarse-grained molecular simulation method of polymer systems was developed and the influence of microscopic phases on the mechanical behavior of the interface was obtained. The main works of this paper are as followed.
(1) The correlation between the evolution of the microstructure parameters and the critical moments of the failure behavior during the loading process of the constrained polymer/substrate interface was established. A prediction method of the instability and energy state of the interfacial system was developed. The dihedral distribution governs the interfacial failure behavior largely. The rational mechanism explanation of the feature points of the stress-strain curve and the system energy evolution was given.
(2) The thickness-dependence of yield strength of the constrained polymer/substrate interface was illustrated. The characterization parameters used to describe the bridging and entanglement effects of polymer molecular chains were also proposed. It was concluded that the thickness dependence of the interfacial strength is dominated by the bridging effect. The non-monotonic relation between the yield strength and the loading rate was observed. In addition, a parameter describing failure mode was introduced. Accordingly, a phase diagram of failure mode with respect to polymer layer thickness and loading rate was provided within a given range. It showed that the failure mode is mainly controlled by loading rate.
(3) A coarse-grained potential function was developed to describe the physical behavior of block copolymers. The phase separation phenomenon of block copolymers was reproduced with the "strip" aggregate structure of hard segments. The loading rate dependence of the total failure strain due to the aggregation of hard segments was obtained by all-atom simulation. The microstructural interpretationwas given to explain the rate dependence phenomenon.
|孟昶宇. 聚合物-异质材料界面微纳尺度力学行为的分子动力学模拟研究[D]. 北京. 中国科学院大学,2019.|
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