Investigation of material properties of thermoplastic and thermoset polymer materials at cryogenic temperatures using molecular dynamics

Cryogenic fluids, such as liquid hydrogen and liquid oxygen, are critical for space operations as rocket fuel and life support. The fluids need to be contained in tanks that can withstand the effects of cyclic thermal and pressure loading throughout their lifecycle. Polymer matrix composites (PMCs) are prime candidates for these tanks because of their low mass, which is important for fuel savings. Although advanced PMC systems have been developed for a wide range of engineering applications, insight is still needed to identify optimal polymer matrix materials for cryogenic structural applications. The objective of this study is to use molecular dynamics simulations to provide physical insight into polymer performance in terms of thermal shrinkage, mechanical property response, and free volume at cryogenic temperatures. Molecular dynamics is particularly well-suited in this regard for its efficiency in predicted material behavior for a wide range of temperatures. The results of this study indicate that high-performance thermoplastic systems; particularly polyetheretherketone (PEEK), low-melt polyaryletherketone (LM PAEK), and polyimide; are well-suited for use as the matrix component of PMCs used in cryogenic tanks. This study is important for establishing the suitability and performance of these materials over a range of temperatures for aerospace applications.