COARSE GRAINED MOLECULAR DYNAMICS SIMULATIONS ON THE UNIAXIAL STRESS STRAIN RESPONSE OF PMR 15

摘要

PMR-15 has a glass transition temperature of about 347 C and is widely used as a matrixmaterial for structural composites suitable for high temperature applications. The stress strainresponse of PMR-15 at 316 C [1] shows that PMR-15 can sustain loads of the order of 20-30MPa, undergo large deformations and is highly rate sensitive at temperatures even close to itsglass transition temperature. In this work, we initiate the task of developing atomisticallyinformed uniaxial constitutive models for this polymer with a view to gain insights into theinterplay between mechanical properties like strain rate hardening and thermal softening with themolecular architecture and crosslinking pathways of PMR15. To this end, we start by developingreliable coarse grained (CG) models of PMR15 that can then be used in large scale MolecularDynamics simulations to simulate its uniaxial response. The basic steps involved in the coarsegraining of the bonded part of the force field follow the procedure outlined in [2]. The nonbonded interactions of CG model for PMR15 is proposed to be calibrated using force matchingmethods similar to those employed by [3] for polystyrene. We have developed a method toenhance the validity of calibrated potentials by adding constraints for matching the virialsimultaneously. This methodology will enable more accurate CG simulations to highlight theconnections between key mechanical properties and the molecular details.