Session: SYMP 3-4: Programming and Modeling

Paper Number: 141593

141593 - Programming of Nonlinear Heterogeneous Metamaterial for Shock and Vibration 

Mechanical metamaterials are artificial material systems that are constructed with unique internal structure at micro or nanoscale to achieve superior mechanical properties than conventional materials. In many applications such metamaterial can be tuned in advance to fit in the demand of specific engineering property that cannot be found in nature, such as negative stiffness. This work expand upon the concept of a metamaterial with digital elements, which modified the behavior of elastomer by inserting higher modulus elastic members to permit a spectrum of material behavior from the host structure and introduce a heterogeneity in the elastomer matrix. While each of the 72 symmetric configurations identified is allowed to achieve its unique stiffness value, interests are developed on the behavior of system towards nonlinear stiffness region since elastomer matrix is chosen as the host structure. 

To properly obtain experimental results, cyclic compression tests have been implemented to eliminate Mullin’s effect and hysteresis is found to be consistent across all the 72 symmetric configurations, while the identified configurations may have different compression limits and therefore are classified into individual ranks accordingly. Meanwhile, drop tests are also conducted to further investigate the stability as well as energy absorption ability of unit cell model upon sudden impact. And with the finite element models developed in ABAQUS using hyperelastic material property obtained for elastomer matrix, both tests’ results for all the configurations are simulated and validated numerically. In general, although lower maximum strain can be reached as rank elevates, steeper stress-strain curve is expected, implying larger potential for energy absorption. Exceptions exist because certain configurations create considerable plateau region on stress-strain plot, which lowers the overall toughness. Moreover, higher rank suggests higher energy absorption ability except rank 0 and 5, where rank 0 has no elastic member and thus can be compressed for 27% more than rank 1 to further absorb energy. And rank 5 configurations are filled with too many elastic members to be compressed at a similar level to previous ranks, or even initiate geometric deformation, before elastic members to be bent or flipped. Nevertheless, the proportion of nonlinear region toughness to overall toughness rises from 15.71% at rank 0 to 69.49% at rank 4, which indicates over 4 times energy absorption ability at nonlinear region than that of a solely elastomer matrix without any enhancing elastic members and implies huge potential at nonlinear stiffness region for energy absorption. And such a nonlinear heterogeneous programming matrix can be easily expanded to a variety of sizes and the corresponding nonlinear region toughness contribution is expected to dominate its energy absorption ability for any higher ranks. 

Presenting Author: Qianyu Zhao Purdue University

Presenting Author Biography: Qianyu is doctoral student at Purdue University. His research interests include dynamics of nonlinear systems, additive manufacturing, and metamaterials.

Authors:

Qianyu Zhao
Hongcheng Tao
James Gibert