Title: Tunable Mechanical Metamaterial with Constrained Negative Stiffness for Improved Quasi-Static and Dynamic Energy Dissipation

Abstract

This paper presents the computational design, fabrication, and experimental validation of a mechanical metamaterial in which the damping of the material is significantly increased without decreasing the stiffness by embedding a small volume fraction of negative stiffness (NS) inclusions within it. Unlike other systems that dissipate energy primarily through large‐amplitude deformation of nonlinear structures, this metamaterial dissipates energy by amplifying linear strains in the viscoelastic host material. By macroscopically tuning the pre‐strain of the metamaterial via mechanical loading, the embedded NS inclusions operate about a constrained buckling instability. When further macroscopic vibrational excitation is applied, the inclusions amplify the strains of the surrounding viscoelastic medium. This results in enhanced dissipation of mechanical energy when compared to voided or neat comparison media. Microstereolithography, an emerging high‐resolution additive manufacturing (AM) technology, is employed to fabricate the deeply subwavelength inclusions which ensures broadband damping behavior. The mechanically induced broadband energy dissipation and manufacturing approach further differentiate the metamaterial from other approaches that exploit resonances, large deformations, or non‐mechanical instabilities. The computational design, fabrication, and experimental evaluation reported is the first dynamic demonstration of such a mechanically tunable NS metamaterial, potentially enabling components with integrated structural and damping capabilities.

Authors:

Morris, Clinton ^[1]; Bekker, Logan ^[2]; Spadaccini, Christopher ^[2]; Haberman, Michael ^[3]; Seepersad, Carolyn ^[3]

---

+ Show Author Affiliations

1. Palo Alto Research Center Incorporated, Palo Alto, CA (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
3. Univ. of Texas, Austin, TX (United States)

Publication Date:

Tue Apr 09 00:00:00 EDT 2019

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); US Department of the Navy, Office of Naval Research (ONR)

OSTI Identifier:

1828127

Alternate Identifier(s):

OSTI ID: 1505872

Report Number(s):

LLNL-JRNL-824979
Journal ID: ISSN 1438-1656; 1022011

Grant/Contract Number:  

AC52-07NA27344; CMMI-1435548; N00014-13-1-0631; IM# 944586

Resource Type:

Accepted Manuscript

Journal Name:

Advanced Engineering Materials

Additional Journal Information:

Journal Volume: 21; Journal Issue: 7; Journal ID: ISSN 1438-1656

Publisher:

Wiley

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; mechanical metamaterial; materials design; negative stiffness; microsterolithography