Characterization of rate-dependent behaviors of 3d printed material under shear impact

Abstract

A thumbtack-shaped specimen is proposed to characterize mechanical properties of material under shearing loads via both static and dynamic compression experiments. The shear strain rate varies in a large range from ∼0.001–1 s^-1 to ∼1000 s^-1. The specimen consists of three parts: a hard phase thumbtack-shaped nail and hard phase base joined via a softer tubular layer. By compressing the top nail part, the softer tubular layer is under a simple shear stress state. Thus, we named the sample the “thumbtack” specimen, and the type of experimentation it undergoes, the “Nail-It” experiment for characterizing shear-rate dependency of the tubular layer material. Under overall static and dynamic compression with different loading rates, materials in the softer tubular layer can achieve both low and high shearing strain rates accordingly. An analytical solution is derived to quantify the shearing response of the layer under both static and dynamic loading. Thumbtack specimens are fabricated via multi-material polymer jetting. Design guidelines of thumbtack specimen are explored via experiments on the 3D printed specimens. A series of impact tests are performed via a drop tower to characterize the shear-rate dependent behavior of the 3D printed soft layer material. This type of experiment offers a cost-effective, controlled, and highly reproducible approach to characterizing the dynamic shear response of materials, particularly 3D-printed materials/structures, under impact loading, providing more reliable, application-specific, and scalable material characterization compared to existing methods.