Impact Absorption in Soft Gyroid Structures

Numerical Analysis and Digital Fabrication

United States
Created on 2020.06.26 261 views
In this project, we use Abaqus to analyze the dynamic response of gyroid structures subjected to impact loads.     Gyroid structures are a class of triply periodic minimal surfaces (TPMS) with repeating, curved microstructure, and are known for high strength to weight ratio. Though practical from a theoretical standpoint, they are challenging to fabricate unless additive manufacturing methods (3D printing) are used. We came up with the idea for this project while squeezing a 3D printed soft gyroid sample in our hands, and noticing how much the gyroid structure is able to conform to an applied load. Since the materials that we printed the gyroid structure with are very viscous, we wondered how well the gyroid structure would absorb and dissipate energy from a high-velocity impact.     We created our analysis geometry by computing an isosurface through an implicit function representing the TPMS and remeshing to optimize for regularity of triangles. We use triangular shell elements (Abaqus type S3R) to mesh our geometry, which proved to be very robust to large distortion. We used a Neo-Hookean hyperelasticity model and a Prony series viscoelasticity model for the gyroid structure, with properties taken from datasheets for 3D printed flexible material. In our simulation, one face of the gyroid was fixed (full encastre), and a spherical projectile with very high rigidity was initialized with a uniform velocity field pointed toward the gyroid. General contact was enabled, and Abaqus effectively captured contact between the sphere and gyroid, as well as self-contact between interior regions of the gyroid.     A gyroid specimen was printed on a Stratasys J750 industrial 3D printer from Statasys Agilus material. In order to gauge qualitative agreement between our simulations and reality, we contrived a safe way to create a high-speed impact between the gyroid and a projectile from the comfort of our apartment. We glued the gyroid to a wooden plank and constructed a 3-meter pendulum by suspending a billiard ball from a balcony, and recorded slow-motion video of the impact.      This was an exciting project that highlights how well Abaqus handles nonlinear materials, dynamic analysis, extreme deformations, and dense contact problems. We hope you enjoy it!
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LS Lawrence Smith
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