Mechanical anisotropy of 3D-printed digital materials at large strains

TL;DR

This study investigates the anisotropic mechanical behavior of 3D-printed digital materials, revealing how microstructural features and printing orientation influence their nonlinear deformation and energy dissipation at various strains.

Contribution

It combines experimental, microscopic, and micromechanical modeling approaches to elucidate the deformation mechanisms underlying anisotropy in 3D-printed digital materials.

Findings

Stable compression of aligned inclusions causes initial elastic anisotropy.

Buckling and plastic deformation of high-aspect-ratio domains affect large-strain behavior.

Printing orientation impacts resilience and energy dissipation capabilities.

Abstract

3D-printed digital materials whose mechanical behavior travels between those from thermoplastic to rubbery polymers have become increasingly important. However, their mechanical functionalities have not been fully exploited due to intrinsic mechanical anisotropy resulting from microstructural heterogeneity. Here, we combine mechanical testing, microscopy analysis and micromechanical modeling for a comprehensive understanding of complex deformation mechanisms responsible for the printing-orientation-dependent nonlinear mechanical behavior of digital materials at small to large strains. Towards this end, we construct representative volume elements that account for highly anisotropic microstructural features resulting from the printing-orientation-dependent diffusion and mixing between photocurable base resins. We then demonstrate, through micromechanical analysis, that stable compressive deformation of well-aligned elliptical hard thermoplastic inclusions embedded within the surrounding soft rubbery matrix gives rise to initial elastic anisotropy. Our experimental and micromechanical modeling results also show that the interplay between buckling instability and plastic deformation of the high-aspect-ratio hard domains governs mechanical anisotropy at large strains as well as the printing-orientation-dependent resilience and energy dissipation capabilities in these digital materials.