Nanoscale mechanical properties of 3D printed gypsum-powder-based rocks by nanoindentation and numerical modeling

Abstract

Purpose Evaluating mechanical properties of simply made samples by 3D printing technology at nanoscale provides a clear path to better understand larger-scale responses of complex natural rocks. Therefore, to realize the similarity between synthetically manufactured materials and natural geomaterials, this study focused on nanoscale mechanical characterization of a 3D printed object with only two constituent components (gypsum powder and infiltrant). Design/methodology/approach The study method includes nanoindentation technique combined with numerical simulation via discrete element method (DEM). Findings Four typical load-displacement curves were identified from nanoindentation of total test points indicating a typical elastic-plastic behavior of the 3D printed gypsum rock sample. Mechanical parameters such as Young’s modulus and hardness were calculated by energy-based methods and a positive correlation was observed. The infiltrant was found to considerably be responsible for the majority of the sample nano-mechanical behavior rather than the gypsum particles, thus expected to control macroscale properties. This was decided from deconvolution and clustering of elastic modulus data. Particle flow modeling in DEM was used to simulate the nanoindentation process in a porous media yielding rock-alike mechanical behavior. Originality/value The results show a matching load-displacement response between experimental and simulation results, which verified the credibility of simulation modeling for mechanical behavior of 3D printed gypsum rock at nanoscale. Finally, differential effective medium theory was used to upscale the nanoindentation results to the macroscale mechanical properties, which provided an insight into the geomechanical modeling at multiscale.

Probing Nanomechanical Properties of a Shale with Nanoindentation: Heterogeneity and the Effect of Water–Shale Interactions

“…Former studies reported that mechanical properties of rocks at the submicron scale can be determined by nanoindentation techniques, such as Young’s modulus, hardness, fracture toughness, and creep behavior. − Previous investigations found that the mechanical responses of the rock-forming minerals are significantly different. , These minerals demonstrate clear elasticity- or plastic-preferred characteristics to the load and show various degrees of irrecoverable deformation. − The mechanical differences among the minerals, either relatively hard granular particles or soft kerogens, have been shown to have a crucial impact on the bulk mechanical properties of shale. , In addition, it is found that the mechanical properties such as its strength, stiffness, and fracture roughness are orientation-dependent, and the multiscale anisotropy of shale is attributed to mechanisms corresponding to the observed scale. ,,− For the purpose of ultimate application in the industry, upscaling the nano- or micromechanical properties to the engineering scale is a key step. Although still in infancy, some studies have tried to upscale the nanoscale strength of shale rock to bulk strength by homogenizing the multiphase elastic composites using the Mori–Tanaka model. ,− …”