Physical properties of 3D printed materials and their applicability as proxies for heterogeneous geomaterials

3D printing is a rapidly evolving technology that has proven useful for a wide variety of disciplines and industries. However, knowledge of its applicability to the fields of rock and soil physics remains limited. 3D printing allows the design of samples with any desired microstructural composition, enabling independent control of properties such as pore space fabric, size, and density; a feat impossible to accomplish with naturally occurring geomaterials. The use of 3D printed samples is therefore highly attractive for relating the effective properties of heterogeneous materials to their microstructural arrangement, a key subject in the fields of rock and soil physics.

This study aims to characterize the physical properties of 3D printed materials (i.e., elasticity parameters, porosity, permeability) and evaluate whether they are suitable to be used as proxies for heterogeneous geomaterials. Two distinct 3D printing technologies were employed for this purpose: the Fused Deposition Modelling (FDM), and Stereolithography (SLA) methods. The FDM method constructs 3D objects by superposing layers of polymer-based filament through a heated nozzle, whereas the SLA method, also known as resin 3D printing, uses a laser light source to cure liquid resin into hardened plastic.

Samples with a variety of pore shapes (sphere, needle, penny shaped), sizes, and pore densities were designed and printed as cylindrical samples of 25 mm diameter and 62.5 mm height. Samples were then subjected to uniaxial compression to measure their effective elastic parameters (elasticity modulus and Poisson’s ratio), and these measurements were compared with theoretical predictions. Preliminary results indicate that the FDM printing method is inadequate for representing a heterogeneous solid composed of an isotropic matrix and void space, due to the intrinsically anisotropic fabric resulting from the layer-by-layer printing method. Additionally, samples with a porous microstructure appear to be effectively stiffer than the intact material, which is attributed to enhanced material sintering surrounding the edges of the void spaces. On the other hand, SLA printing appears to hold more promise and be able to represent a composite material composed of an isotropic matrix with a heterogeneous void space. Further measurements need to be made to confirm these preliminary findings, and this work is currently in progress.