Multiscale Modeling of Thermoplastics Using Atomistic-informed Micromechanics

Document Type

Conference Proceeding

Publication Date

1-19-2023

Department

Department of Mechanical Engineering-Engineering Mechanics

Abstract

A multiscale model was developed for predicting the thermoelastic behavior of semi-crystalline thermoplastic materials for composite aerospace applications. At the highest scale containing the semi-crystalline spherulite in an amorphous matrix, the generalized method of cells, or high fidelity method of cells, was used to perform the homogenization calculations to obtain the effective properties. Models were developed assuming a cubic shape, or spherical shape, for the spherulite to understand if the morphology of the spherulite affects the effective thermoelastic properties. The generalized method of cells was used to model at the repeating unit cells at the subscales of the microstructure including the lamellar stacks and granular crystal blocks. The scales are integrated using the multiscale micromechanics method in the NASA Multiscale Analysis Tool. Data from molecular dynamics simulations were used as inputs for the amorphous and crystalline constituents. Convergence studies were performed to determine the best level of discretization for the repeating unit cell at the highest scale. Effective Young’s modulus, shear modulus, Poisson’s ratio, and coefficient of thermal expansion were predicted for polyether ether ketone and polyether ketone ketone, and very good agreement between the model utilizing the cubic spherulite and the experimental data, where available, was observed for polyether ketone ketone. Normalization of the data for the bulk polyether ketone ketone, against amorphous data, improved the predictions as compared to experimental data. Overall, a continuous path of crystalline subcells, resulting from the voxelization of the spherical spherulite, led to an over-predicted stiffness for these materials.

Publisher's Statement

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

Publication Title

AIAA SCITECH 2023 Forum

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