Anisotropic properties of 3D-printed rock-like materials under dynamic Brazilian disc tests

Rock materials are commonly endowed with anisotropic structures, like beddings, flaws and fillers, which makes it difficult to predict their strength, deformation and fracturing properties under dynamic loading. Considering the structural complexity and randomness in rock materials, it is difficult to obtain two rock specimens with exactly the same structures for experimental study. As an emerging method, 3D printing (3DP) shows some promise in being able to replicate the complicated meso- and micro- structures and repetitively fabricate identical “rock” specimens. In this study, 3D printed rock-like specimens are fabricated into bedded Brazilian discs (diameter: 50 mm and thickness: 25 mm) using extrudable geomaterials with an extrusion width of 1 mm and a layer thickness of 0.5 mm. By combining a split Hopkinson pressure bar and two high-speed cameras, Brazilian disc tests were conducted on 3DP specimens with bedding angles α (i.e. angle between impact direction and bedding orientation) of 0, 30, 60 and 90 to investigate their anisotropic mechanical and fracture properties under dynamic loading. Results show that the dynamic indirect tensile strength decreases as the bedding angle β increases from 0 to 30 and then increases when β is increased from 30 to 90. Failure patterns of 3DP specimens exhibit tensile dominated failure at bedding angles of 0 and 90, and the mixed tensile-shear failure in other bedding angles (30 and 60). The experimental results are consistent with a previous study using natural rock materials, indicating that the 3D printing technology is applicable to the replication study of rock-like materials under dynamic loadings, allowing an artificial design process and a repeatability in the structures, avoiding the inconsistencies in natural rock specimens.