The effect of cement material properties on the fracture patterns developing within cement-covered brittle sphere under impact

Dynamic loading experiments of single glass bead cement-covered by epoxy resins of different compositions demonstrate the existence of diverse fracture patterns under similar impact velocities and high strain rates. A comparison of these fracture patterns between different resin compositions highlights two distinctive fracture mechanisms, namely cement-focused fracture and grain-focused fracture mechanisms, which is affected by the interface adhesion toughness. The transition between those patterns is characterised by the damage of the cement/grain interface adhesion. Using Fourier transform of the X-ray micro-computed tomography images, the details of the locality of the damage within the cemented bead are then quantitatively analysed, as well as the preferential crack orientation. Several sporadic curved cracks are observed near the cement/grain interface region in the cement-focused fracture cases, roughly along the interface. However, for grain-focused fracture cases, damage is most likely to occur along the central loading axis area of the cemented bead and prevailingly forms diametric cracks along the impact direction. The results of this study are expected to help advancing the development of models that predict the deterioration of brittle cemented geomaterials under impact.