Understanding and Interpreting Stress-Strain Curves from Molecular Dynamics Simulation of Amorphous Polymers

The phenomenon associated with load/deflection behavior of structures has been investigated for centuries, with many theories and methods developed for analyzing such behavior. In the nineteenth century the behavior of polymers started to be studied experimentally. In addition, during the latter half of the twentieth century simulation of polymers via molecular dynamics began to flourish due to access to greater and greater computing power following Moore’s Law. Both experimental studies and simulation studies of polymers typically rely on interpretations of stress-strain plots for deriving mechanical properties. The American Society for Testing and Materials (ASTM) have developed best practices for analyzing stress-strain curves. However, the methods still involve manual human interpretation of the stress-strain curves and don’t directly apply to molecular-scale behavior. To fully remove all subjectivity from a stress-strain analysis the physics and data processing of stress-strain curves need to meet in a synergistic relationship. In this work a new and novel method called the Regression Fringe Response method (RFR) has been developed for analyzing stress-strain curves. The RFR-method was tested using molecular dynamics loading simulations for a variety of amorphous polymers. The simulated stress-strain curves were analyzed with the RFR-method and results were compared to experimentally determined values. The results of this study ultimately show that the novel RFR method has been validated and is ready to use for automatically interpreting a large range of stress-strain curves for automatic mechanical property predictions.