Experimental and DEM investigation of axially-loaded behaviours of IWP-based structures

The Schoen I-graph-wrapped package (IWP) structures are recognized as one of the best promising cellular structures because of their high specific mechanical properties and damping ratios. The axially-loaded behaviors are critical for structural safety and durability in engineering fields. In order to extend the application of IWP structures into civil engineering, this paper investigated the axially-loaded behaviors, including compressive strength, force distribution, load-deflection pattern, energy absorption and cracking pattern, of the main and secondary Skeletal-IWP structures. Firstly, a novel method for simplifying triply periodic minimal surfaces (TPMSs) has been put forward. Then the main and secondary Skeletal-IWP units are fabricated using stereolithography technology and tested. The discrete element method (DEM) is adopted, for the first time, to simulate the axially-loaded behaviors of IWP structures with different unit cell arrangements after the validation by robust experimental results. The results reveal that the secondary Skeletal-IWP structures outperform the main Skeletal-IWP structures in compressive strength. When the unit arrangement changes from single unit to 7 × 7 × 7, the compressive strength of the main and secondary Skeletal-IWP structures increases from 9 MPa to 13.4 MPa and 9.2 MPa to 14.4 MPa, respectively. The main type shows a “X”-shaped cracking pattern, and the secondary shows a “X”-shaped cracking pattern.