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

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.