Experimental and Numerical Characterization of Polymer Nanocomposites for Solid Rocket Motor Internal Insulation.

摘要

Research objective is to develop a modeling framework for simulating the insulative behavior of thermoplastic polyurethane elastomer nanocomposites (TPUNs) for solid rocket motors (SRMs). This research combines numerical modeling and experimental characterization of TPUNs for SRM insulation. Two families of TPUNs based on nanoclay, carbon nanofiber (CNF), and multiwall carbon nanotubes (MWNT) were developed. TGA experiments were conducted on Kevlar-EPDM, TPU, TPUN-clay, TPUN-CNF, and TPUN-MWNT in both air and nitrogen at low heating rates. Kinetics was calculated using isoconversion technique. High heating rate TGA was conducted on selective TPUNs. Flammability tests indicated TPUN-clay has the toughest char, followed by TPUN-MWNT, then TPUN- CNF. We connected the population balance framework to atomistic calculations to determine what aspects of the atomistic simulations would likely affect the meso-scale evolution. We focused on understanding the role that the scission kernel has on the overall degradation process and also on the role of the stoichiometry parameter has on the overall degradation kinetics. We began using the atomistic simulation code RXN MD to compute scission kinetics parameters. We recognized that the critical issue in characterizing a particular materials ablation rate could be captured by investigating the steady state ablation process. The meso-scale (mechanistic) modeling is integral to understanding what pyrolysis products form during the decomposition process and how these products affect the char.