Molecular Simulation On Structure And Interface Of High Performance Thermoplastic Composites

In the world, high performance thermoplastic composites is the emphases of research in the field of composites, but most of the research focus on molding technics and macroscopical properties. Therefore, we will study the structure and interface of high performance thermoplastic resin——PES, PEEK, PPEK, PPES and their composites by molecular simulation.First, we constructed single molecular model of PES, PEEK, PPEK and PPES in vacuum with 12 polymerization degree, and a combinative anneal simulation with molecular mechanics(MM) and the molecular dynamics(MD) are applied to optimize the structure, the anneal temperature from 298K to 598K,then we get the steady frames at 298K. The pair correlation function of oxygen in the matrix after anneal simulation has been investigated. We also discuss the change of the energy. The result show that electrostatic energy is the primary factor in the energy change, according to the analysis of internal energy of matrix, we find angle and torsion result in the frames transformation and energy reducing.Secondly, we constructed amorphous cells of PES, PEEK, PPEK and PPES in the three-dimensional period boundary condition. After the anneal simulation, we analyze the mean squared displacement(MSD) of the four kinds of matrix. It is shown that following the volume and rigidity of chain increase, activation of the matrix becomes lower. The cohesive energy density and solubility parameter are calculated.Finally, basing on unoxygenated carbon fibre(CF) and oxygenated CF(connect with -OH) models, we constructed comparable interface models of CF/PES, CF/PEEK, CF/PPEK and CF/PPES (marked interface model 1 and interface model 2), and applied anneal simulation. According to the MSD of the composite CF/PPES and CF/PPEK in the comparable models, find that the attraction force of model 1 is larger than model 2. The interfacial energy in the different models of the composite CF/PES, CF/PEEK, CF/PPEK and CF/PPES have been calculated. Also we analyze the variety of concentration of matrix in the composite CF/PPEK and CF/PPES. Results show that interfacial of model 1 is larger than model 2. the interfacial energy is caused by attraction between the carbon fibre and benzene in the matrix. So oxygenating on CF is found to benefit soakage, but cause reduction of interfacial energy.