Characterization of fracture behavior under impact-like loading conditions of elastomeric grades for high-pressure gas applications

Rapid gas decompression (RGD) is a major concern for elastomeric sealing components in cyclic gas exposure conditions as it generates cracks and can even cause total mechanical damage threatening the sealing integrity. Therefore, to analyze the fracture behavior of elastomeric grades under impact-like loading conditions, a test methodology was developed using a single edge notch in tension (SENT) specimen. To gain more insights into the behavior of differently formulated four nitrile butadiene rubber (NBR) grades (carbon black (CB) or Silica-filled, with different curing characteristics), tests were conducted at a wide range of temperatures, -20, 23, and 80 degrees C and under a wide range of loading rates (0.2-5 m/s). The single fracture parameters, strain energy release rate (G) at stable crack initiation and G at maximum load, as well as multiple fracture parameters from crack resistance curves (R-curves), G-Delta a and crack growth rate vs crack extension curves, da/dt-Delta a, were derived. All the grades showed distinct temperature and loading rate sensitivity on fracture behavior, however, the effect was more pronounced in sulfur-cured grades. Higher cross-link density, delivered a lower resistance to fracture and a uniform higher crack growth rate, conversely higher filler loading improved the fracture resistance. Within the tested conditions, the component-level instrumented tests on RGD failure revealed a similar ranking to the tested grades and it emphasizes the importance and relevance of intrinsic fracture properties. The generated information on single fracture parameters and crack growth kinetics is vital in phenomenological modeling attempts of the actual failure of components as well.