Session: MR-1-5: Mechanisms Synthesis and Analysis

Paper Number: 118199

118199 - Mechanics of a Chevron Shaped Unit Cell With Tape Spring Arms 

Architected materials have been shown to exhibit solid-state energy dissipation without undergoing 
irreversible deformation which makes these materials suitable for applications ranging from football 
helmets to seismic protection of structures. Materials comprising a chevron shaped unit cell with tape 
spring arms can provide dissipation in samples with as few as a single row of unit cells  unlike other 
architected materials which need samples with O(10) rows or more to exhibit  meaningful dissipation.  
In this work we explore the mechanics of this unit cell when it is subject to quasi-static compression. 
Geometrically non-linear, explicit dynamic finite element simulations in Abaqus are used for this study.  
The thin, transversely curved tape segment legs give rise to a deformation process that combines axial 
compression, bending and twisting. The force-displacement response of the unit cell exhibits four 
distinct limit points during loading and three limit points during unloading.  The limit points demarcate 
the following five deformation regimes during loading: 1) linear force-displacement regime with positive 
stiffness until a twist buckling event occurs, 2) a second nearly linear force-displacement regime with a 
smaller positive stiffness than the first one until a partial fold is nucleated, 3) a linear negative stiffness  
regime which ends when the partial fold has propagated across the width of the tape segment to form a 
complete fold, 4) a nearly linear negative stiffness regime during which the tape segments untwist, and 
finally 5) a nonlinear negative stiffness regime corresponding to the bending collapse of the segments. 
The loading and unloading branches are separated, with the deviations between these branches 
corresponding to the forward and reverse limit point traversals. This gives rise to solid-state energy 
dissipation even when the deformation of the tape segments is entirely reversible.

Presenting Author: Pablo Zavattieri Purdue University

Presenting Author Biography: Pablo Zavattieri is the Jerry M. and Lynda T. Engelhardt Professor in Civil Engineering in the Lyles School of Civil Engineering at Purdue University. His contributions in the industry and in the academia focus on the boundary between solid mechanics and materials engineering. His current active research program includes elements of multiscale computational modeling of advanced and sustainable structural materials bridging the gap between atomistic and structural mechanics, mechanics of smart materials, hard biological materials and bio-inspired materials design. His engineering and scientific curiosity lies on the fundamental aspects of how Nature makes better and more sustainable materials.

Authors:

Nilesh Mankame General Motors Global Research & Development
Kristiaan Hector Purdue University
Pablo Zavattieri Purdue University