Session: 01-07-01: Nonlinear Problems in Aerospace Structures

Paper Number: 114925

114925 - High-Temperature Material Models for the Lightning Strike Damage Predictions in Polymer Matrix Composites 

The survivability of carbon fiber reinforced polymer (CFRP) composites under high temperature environments is limited. It is well known that at temperatures above the glass transition temperature, a rapid thermal decomposition (pyrolysis) of the polymer matrix occurs, which results in deterioration of the thermal and mechanical properties. Prediction of the high-temperature properties of CFRPs is a fundamental problem that arises in many applications including lightning strike, laser-induced damage, and thermal protection systems.

In this work a micromechanics-based framework for determining high-temperature thermophysical and mechanical properties of CFRPs undergoing pyrolysis is presented. The framework enables investigating the effects of the mass loss and material phase changes (i.e. formation of the secondary char and gas phases) and endothermic pyrolysis reactions on the overall material properties.

The framework includes physics-based models accounting for phase transitions and formation of solid pyrolytic (char) and gaseous phases in the composite material were incorporated in the micromechanics-based numerical homogenization of the RVEs performed using FEA. First-order Arrhenius kinetics were used to model thermal degradation in the AS4/3501-6 composite material. This gives temperature-dependent volume fractions of the constituent phases. All phases (polymer, char, pores filled with pyrolysis gas, and fibers) were assumed to coexist at a given temperature and microstructure evolves with temperature. Temperature and heating rate dependent evolving microstructures were captured using information about volume fractions of phases based on the thermal decomposition rate. Microstructure generation algorithms were developed to create highly packed particle filled microstructures. Pyrolysis and consequent release and/or absorption of heat were modeled using UMATHT subroutine in Abaqus. Heat of decomposition was found to be significant enough to affect the effective specific heat of the material. Two-step numerical homogenization of representative volume elements (RVEs) was performed to determine overall material properties. Macroscale and microscale analyses are bridged to investigate the effect of the endothermic reactions occurring during pyrolysis on the overall material properties.

The computational results for the overall thermal and mechanical properties were obtained for the AS4/3501-6 composite in a temperature range up to 700 K. Results showed good agreement with experimental data and lie within bounds.

The micromechanics-based models of the overall properties were used in the FEA-based multiphysics modeling of lightning strike damage in CFRP composites. Computational studies were performed to analyze lightning strike induced thermal damage in a CFRP composite panel.

Presenting Author: Olesya Zhupanska University of Arizona

Presenting Author Biography: Dr. Olesya Zhupanska is a Professor in the Department of Aerospace and Mechanical Engineering at the University of Arizona.

Authors:

Olesya Zhupanska University of Arizona