Quantification of Void-Like Defects Using X-Ray Tomography in Elastomers Exposed to Different Hydrogen Environments

Elastomeric O-rings used for sealing in hydrogen infrastructure applications are subjected to demanding pressure-cycling environments with rapid compression and decompression steps that can generate new voids or cracks or exacerbate pre-existing manufacturing defects. X-ray computed tomography (CT) has been found to be a valuable tool in identifying and evaluating damage evolution in polymers under typical hydrogen exposure conditions. Previous X-ray CT work from Sandia on commercial elastomers exposed to hydrogen under static conditions presented evidence of damage within the polymer samples, emphasizing the dependence of hydrogen performance on composition of the polymer and conditions of exposure (cycling vs static) in fueling operations. This effort is focused on utilizing X-ray tomography data towards quantification of voids and defects seen in materials after exposure to hydrogen environments. This is seen as the first step towards relating defect formation to defect growth potential which would be useful in comparing different materials and predicting their lifetimes for use in hydrogen components. For this, we will evaluate and develop a suite of X-ray tomography tools and methods that can provide the basis for both accurate detection and quantification of defects in materials for hydrogen use. Our goal is to establish a deeper understanding of defect evolution over long-term hydrogen exposure towards developing metrics for predicting the lifetimes of common polymers in these environments as applicable to the hydrogen infrastructure.