Mechanical and fracture behaviour of epoxy polymer under extreme low temperature and high strain rate conditions

Abstract

Low-temperature studies are crucial in material science, cryogenic, and aerospace engineering, where materials endure extreme temperatures. High strain rate loading at low temperatures significantly affects material performance and integrity. This article investigates the dynamic mechanical response of EPOFINE®-1564, a Bisphenol-A-based liquid epoxy resin, using Split Hopkinson Pressure Bar (SHPB) and Modified Hopkinson Pressure Bar (MHPB) at high strain rates. An in-house built liquid nitrogen environment chamber was used to attain low temperatures. Dynamic experiments under compressive loading were conducted at strain rates of 710–2051 s⁻¹ and temperatures between −120 °C and −25 °C, while under tensile loading, the experiments were performed at strain rates of 1125–2194 s⁻¹ and temperatures between −70 °C and −40 °C. The results revealed an increase of strength and stiffness by 12.3 % and 16.66 %, respectively, for compressive loading with a decrease in temperature from −25 °C to −120 °C. Similarly, these properties increased by 9.28 % and 2.6 % for tensile loading with the decrease in temperature from −40 °C to −70 °C. Additionally, MHPB was employed to investigate the fracture behaviour of the epoxy resin under dynamic loading (6 m/s – 12 m/s) using Three-Point Bend (TPB) specimens. High-speed imaging and 3D Digital Image Correlation (DIC) revealed that dynamic fracture toughness decreased with temperature, weakening intermolecular interactions, and reducing crack resistance. Analyzing the fracture surface using scanning electron microscopy revealed the disappearance of stretch zones and crazes as brittleness increased with decreasing temperature.