高聚物/金属界面动态力学行为的多尺度研究

The quantitative study on the interface mechanical behavior subjected to impact loadings, which is of great importance to determine the adhesive structure property, faces many challenges such as difficulty on getting physical parameters, complexity of strain-rate effect and size effect. In the present project, bi-material adhesive structure with poly epoxy resin under dynamic condition is proposed as the research object. Utilizing multi-level simulations composed with Molecular dynamics (MD), Coarse-grained dynamics (CGD) and finite element method (FEM), the analyses of interface damage evolution and failure mode will be carried out. The key point that should be focused on is obtaining the multi-scale interactions between atom-atom, bead-bead and condensed phase-phase. Correspondingly, the basic physical data can be provided bottom-up level by level. In addition, the effects of influential factors, such as strain-rate, adhesive thickness, crosslinking degree, impedance matching of bi-material and interface stress state et al., on the interface failure will be also examined. Subsequently, the control parameters to govern the interface strength and failure mode can be determined. Furthermore, the phase diagram of interface failure modes will be provided. According to the establishment of micro-meso-macroscopic analysis method, the methods of interface strength evaluation and light-weight design will be explored, which will provide the analysis tool and method support for engineering applications.

界面的力学行为是决定粘接结构性能的关键，其在冲击载荷下的定量化研究存在着物性参数获取困难、复杂的应变率效应及尺寸效应等诸多挑战。本项目以动态条件下高聚环氧树脂为粘接剂的双材料粘接结构为研究对象，以分子动力学、粗化粒子动力学及有限元等多层次模拟为研究手段，开展界面损伤演化与失效模式的研究。重点是获取原子间-粒子间-凝聚态相间的多尺度相互作用，自下而上逐层提供物性基础数据，关注应变率、界面层厚度、界面材料聚合度、双材料间的阻抗匹配特性及界面应力状态等因素对界面失效的影响规律，进而掌握影响界面强度及失效模式的主控参量，并给出界面失效模式相图。基于界面力学行为微-介-宏观分析方法的搭接，探索界面强度评估与粘接结构轻量化设计方法，为工程技术提供分析工具和方法支撑。

本项目结合动态实验与多尺度分析方法，对典型高聚物块体材料及其约束条件下的界面体系进行界面失效过程及控制参量影响规律的研究。主要研究内容包括四个方面：一是获得了典型高聚物块体材料宽域加载应变率下的动态力学性能及应力波衰减规律，提供了丰富的物理图像和基础参数；二是建立了高聚物界面微结构参量演化与失效过程之间的对应关系；发展了一种界面体系稳定性和能量状态的预示方法，并确定了二面角分布状态对界面失效的决定性作用，进而给出应力应变曲线以及体系能量演化特征点的机理性解释；三是发现了界面屈服强度的厚度依赖性，提出了描述聚合物分子链搭桥和缠结效应的表征参量，发现界面强度的厚度依赖性由搭桥效应所主导；在一定范围内给出了界面失效模式关于聚合物层厚和加载率的图谱，并发现界面失效模式由加载率主控；四是发展了一种计算加速较全原子模型达4个量级的粗粒化势函数，复现出了与实验观测一致的“硬段基团条带状”聚集构型，量化了有效粗粒度及计算加速比，进而形成了一种在扩展时空尺度上的有效分析方法。通过上述研究工作，为界面失效机理的明晰和有效的预测和调控提供了方向和思路。