Study of microstructure of dielectric polymer nanocomposites subjected to electromagnetic fields for development of self-toughening, self-awareness li

在复合材料中提出一种可控的预应力/增韧技术是极其复杂的，因为在超过聚合物屈服点的压缩中，基体容易开裂。为了克服这一点，EPSRC资助的项目自调谐纤维增强聚合物自适应纳米复合材料（STRAINcomp; EP/R 016828/1）旨在开发一种新的微压缩方法，通过EM暴露将被动压缩应力场局部均匀地引入介电增强复合材料的基体微结构。在分子尺度上增强形成网络的聚合物的性质的介电纳米材料的分散严重地降低了颗粒分子移动性/振动。在其玻璃化的固体基质中，一旦纳米增强聚合物暴露于介电场（例如微波），则在与基质的界面处引入应力，因为分子振动突然增加，这将应力引入到其周围的基质。这种压缩应力增强了微尺度下的裂纹闭合能力，防止基质开裂，从而能够通过调节介电场来调节应力水平。因此，基体的机械性能将得到改善，从而产生自调谐自适应材料。然而，除了一些孤立的稀缺研究（例如Odegard等人，2015年，J. Polymer），对纳米材料-聚合物界面如何以及在何种可量化程度上对EM场微机械响应的理解在现有文献中仍然存在很大的知识差距。这样的理解和量化是拟议的博士项目的基础。这一发现将导致一种自调整技术，该技术响应迅速，辐射吸收体积大，可应用于各个领域的刚性复合材料结构。建立了三种不同材料粘接系统多物理场问题的新的理论本构方程（纳米材料，聚合物和界面）与机械载荷和EM场的边界条件，为了关联材料的介电性能，界面结构和电磁驱动的偶极矩与系统的机械性能，从而性能，例如由连续介质力学定律表示，其中应力和应变张量，是材料常数矩阵，采用两种多尺度模型对电磁场作用下三材料系统的细观力学性能进行了数值研究。MD模拟模型将使用LAMMPS开发，连续模型将由Abaqus/Intel-Fortran驱动（用于模拟纳米材料-聚合物局部应变和变形的细观尺度），基于目标1中开发的本构律。(Data从MD模型中获得的界面性能将被输入到中尺度模型中，用于模拟三种材料的相互作用），并在STFC钻石光源和曼彻斯特罗伊斯研究所的X射线成像设施中使用原位X射线断层扫描，光栅干涉测量和重叠断层扫描对纳米材料-聚合物界面进行实验研究。这些测量（现场机械测试和EM暴露）不仅有助于博士生和团队了解变形机制，结合质量，形态效应和界面水平暴露期间分子结构演变的任何可能性，还将为MD和中尺度模型参数的校准和开发提供数据。

Proposing a controllable pre-stressing/toughening technique in composites is extremely complex being susceptible to matrix cracking in compression beyond the polymers yield point. To overcome this, the EPSRC funded project Self-Tuning Fibre-Reinforced Polymer Adaptive Nanocomposite (STRAINcomp; EP/R016828/1) aims to develop a novel micro-compression method to locally and uniformly introduce a passive compressive stress field to the matrix microstructure of dielectric enhanced composites via EM exposure. Incorporating dielectric nanomaterials to enhance the properties of the polymer forming networks at a molecular scale severely reduces particles molecular mobility/vibration. In its vitrified solid matrix, stress is introduced at the interface with the matrix once the nano-enhanced polymer is exposed to a dielectric field (e.g. microwave), since the molecular vibration abruptly increases which introduces stress to their surrounding matrix. This compressive stress enhances the crack closure capability at microscale preventing matrix cracking, enabling adjusting the levels of the stress via adjusting the dielectric field. As a result, the mechanical properties of the matrix will be improved resulting in a self-tuning adaptive material. However, except some isolated scarce research (e.g. Odegard et al. 2015, J. Polymer), an understanding of how, and to what quantifiable extent, the nanomaterial-polymer interface responds to an EM field micromechanically has remained a big knowledge gap in the extant literature. Such an understanding and quantification is the foundation of the proposed PhD project. This discovery will lead to a self-tuning technology which is swift in response, volumetric in radiation absorption, and can be applied to rigid composite structures across various sectors. Develop novel theoretical constitutive material equations for the Multiphysics problem of three bonded dissimilar materials system (nanomaterial, polymer and interface) with boundary conditions of mechanical loading and EM field, in order to correlate the materials dielectric properties, interface structure and the EM driven dipole moment with the system's mechanical properties and thus performance e.g. expressed by the continuum mechanics law of where the stress and strain tensors respectively and is material constants matrix.Numerically study the micromechanical performance of the three-material system in the presence of an EM field using two multiscale modelling. The MD simulation model will be developed using LAMMPS and continuum model will be driven by Abaqus/Intel-Fortran (at meso-scale for modelling the nanomaterial-polymer localised straining and deformation) based on the constitutive law developed in Objective 1. (Data obtained from the MD model for the interface performance will be fed into the meso-scale model for modelling the three-material interaction), and Experimentally study the nanomaterial-polymer interface using in-situ X-ray tomography, grating interferometry and ptycho-tomography at the STFC Diamond Light source and The X-ray Imaging facility at the Royce Institute, Manchester. Such measurements (in-situ with mechanical testing and EM exposure) not only assist the PhD student and the team to understand the deformation mechanisms, bonding quality, morphological effects and any possibility of molecular structural evolution during exposure at the interface level, they will also provide data for calibration and development of the MD and meso-scale models' parameters.