<p>Non-penetrated openings are among the most common structural defects in natural rock and have a critical influence on the stability and safety of rock engineering structures. In this study, a series of Brazilian splitting tests were performed on sandstone specimens with varying penetration depths of central circular openings. The digital image correlation (DIC) technique was employed to quantitatively capture the crack initiation and propagation processes. The energy evolution and conversion characteristics of the specimens during tensile failure were compared across different opening penetration depths. The results show that the maximum hoop stress of the Brazilian discs exhibits an exponential decay law with increasing opening penetration depth, while the overall failure mode remains tensile-dominated. The strain evolution of tensile cracks shows that the crack initiation time, crack initiation location, and crack propagation path are different for both sides of the Brazilian disc containing non-penetrated opening. The strain field spatial and temporal non-uniformity indicators are defined, demonstrating that the two sides of Brazilian discs with non-penetrated opening exhibit significant asymmetry in strain field evolution, whereas other specimens show nearly symmetrical behavior. The presence of the opening weakens the ability to absorb, store, and convert energy in the Brazilian disc specimens, and the greater the opening penetration depth is, the greater the weakening, which is related to the initial damage of the specimen.</p>