Session: 15-01-01: ASME International Undergraduate Research and Design Exposition

Paper Number: 100693

100693 - Design and Manufacturing of Metastructures for Different Applications 

Metastructure designs have attracted significant research interest due to their tunability of mechanical response and potential to exhibit higher strength, toughness, and energy absorption capability with reduced weight. Metastructures can be separated into three categories: strut-based lattices, skeletal-TPMS-based lattices, and sheet-TPMS-based lattices. This research project focuses on the geometric modeling of strut-based lattice metastructures, including octet-truss unit cell and re-entrant auxetic unit cell, respectively.

An octet-truss unit cell is a type of metastructure with a single octahedral inner cell surrounded by eight tetrahedral cells. Key features of this unit cell include near-isotropic behavior, resulting in an increased linear stiffness scaling with lower density. The tunable properties of the octet-truss structure make it a multifunctional configuration adaptable to various industry applications. Likewise, the re-entrant auxetic unit cell is characterized by its versatility. Its negative Poisson ratio behavior allows the unit cell to contract transversely under uniaxial compression, while the honeycomb geometry displays superior shear and fracture resistance and improved energy absorption. Its mechanical properties can be further tuned by controlling the characteristic strut ratio and re-entrant angle. It is found that certain hybrid metastructure configurations that consist of a carefully designed network of octet-truss and re-entrant auxetic unit cells can exhibit higher stiffness and strength than the homogenous octet-truss and auxetic lattices. Both finite element analysis and uniaxial compression tests are carried out for
mechanical property evaluation.

The unique features of metastructures lend themselves to various industry applications. One application is the metastructure-based pressure sensors (MBPS), where a thin film of an electrically conductive coating is applied to the surface of the metastructure template. The sensitivity/mechanical properties of the MBPS are primarily dictated by the metastructure configuration, with the octet-truss unit cell identified as an appropriate template for the sensor surface due to its high strength-weight ratio. An in-situ compression-resistance test was conducted to investigate the resistance evolution,
deformation characteristics, and load-displacement response of an octet-truss metastructure coated in a conductive layer using the Deben MT5000 tensile stage. It is found that increasing the number of unit cells within the cubic metastructure can lead to decreased nominal resistance and enhanced electrical conductivity and sensor sensitivity. Metastructure can also lead to more pronounced power generation with frequency tunability. One example in this study concerns the implementation of metastructure in a cantilever beam piezoelectric energy harvester (PEH). It is found that the PEH with re-entrant auxetic metastructure can yield about ten times higher electrical power than the traditional bulk beam design.

Keywords: metastructure design, finite element analysis

Presenting Author: Anisia Tiplea Dartmouth College

Presenting Author Biography: My name is Anisia Tiplea, and I am a junior student from Romania at Dartmouth College studying Engineering Sciences with a minor in French. My research interests lie in materials science, biomedical materials, and medical imaging. On campus, I am involved with the first-generation student office and the college feminist online magazine, Spare Rib. I also work as a writing tutor and social media manager for the women, gender, and sexuality studies department.

Authors:

Anisia Tiplea Dartmouth College
Huan Zhao Dartmouth College
Xiangbei Liu Dartmouth College
Julia Huddy Dartmouth College
William Scheideler Dartmouth College
Yan Li Dartmouth College