research

Link to paper: https://doi.org/10.1016/j.polymertesting.2021.107262 Abstract

Mode-coupling instabilities are known to trigger self-excited vibrations in sliding contacts. Here, the conditions for mode-coupling (or "flutter") instability in the contact between a spherical oscillator and a moving viscoelastic substrate are studied. The work extends the classical 2-Degrees-Of-Freedom conveyor belt model and accounts for viscoelastic dissipation in the substrate, adhesive friction at the interface and non-linear normal contact stiffness as derived from numerical simulations based on a boundary element method capable of accounting for linear viscoelastic effects.

In this paper, we discuss two problems concerning scattering and localisation of flexural waves in structured elastic plates. Firstly, we compare the scattering amplitudes of waves in a thin plate, generated by a point source, due to a single mass and to a large number of smaller masses, having the same equivalent mass and located around a circle. We show that in the second case, the scattering can be reduced, in particular in the medium- and high-frequency regimes.

dmHUB invites you to attend the Global Composites Experts Webinar Series. 

Title: Control of Reaction Fronts for Rapid Energy-Efficient Manufacturing of Multifunctional Polymers and Composites

Speaker: Dr.  Nancy R. Sottos

Time: 6/3, 11AM-12PM EST.

In situ dendrite reinforced Bulk Metallic Glass matrix composites (BMGCs) are known to overcome poor ductility and fracture response exhibited by monolithic bulk metallic glasses (BMGs). In this paper (Shear fracture in bulk metallic glass composites) recently published by our group in Acta Materialia, we report mode I and mode II fracture experiments on the above in situ BMGCs containing transforming and non-transforming dendrites.

How can we induce twist in tubular structures without applying a torque?

In nature, such behavior is enabled by material anisotropy. In our new work, we show that isotropic bi-layer tubes with twist incompatible layers can twist upon inflation and extension.
Interestingly, the direction of twist can spontaneously reverse as the load increases!

Check out our new paper at EML:
https://www.sciencedirect.com/science/article/pii/S2352431621000766

Dear colleagues,

Dear colleagues,
We invite you to see the preprint of our new paper "Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity" that will appear in PNAS. Here we present a molecular-to-continuum scale theory for the flexoelectric effect in elastomers. The theory unveils a mechanism for achieving giant flexoelectricity--which finds support in prior experimental results; it is then leveraged for designing elastomers for 1) piezoelectricity, 2) tuning the direction of flexoelectricity, and 3) flexoelectricity which is invariant with respect to spurious deformations (https://doi.org/10.1073/pnas.2102477118).

The recent literature of finite eignestrains in nonlinear elastic solids is reviewed, and Eshelby's inclusion problem at finite strains is revisited. The subtleties of the analysis of combinations of finite eigenstrains for the example of  combined finite radial, azimuthal, axial, and twist eigenstrains in a finite circular cylindrical bar are discussed. The stress field of a spherical inclusion with uniform pure dilatational eigenstrain in a radially-inhomogeneous spherical ball made of arbitrary incompressible isotropic solids is analyzed.

Mechanical performance of silicon nanopillars with homogeneous and gradient nanotwinned structures are investigated through a series of molecular dynamics simulations. The most observed Σ3 twin boundary (TB) with two preferable (lowest surface energy) planes of {111} and {001} are used to generate homogeneous and gradient nanotwinned structures. Simulations of compression and tension of nanotwinned pillars reveal an extra strengthening behavior due to the addition of Σ3 TBs when compared to the single crystalline nanopillar without any TBs.

Keep EML Webinar going by donating at: 

https://www.gofundme.com/f/keep-eml-webinar-going

We gratefully acknowledge the financial support for Season 2 of EML Webinar by (as of 18 May 2021):

Denian Zhuang, Jimmy Hsia, Zhigang Suo, Ruobing Bai, Teng Li, Liqing Jiao, Shengqiang Cai, Grace Gu, Xin Wen, Jianyu Li, Jin Yang, Nitesh Arora, and anonymous donors. 

EML Webinar (Season 2) on 19 May 2021 will be given by Eduard Arzt, Saarland University. Designing with gaps – functional surfaces for sustainable gripping. Discussion Leaders: Huajian Gao, Nanyang Technological University

Time: 10 am Boston, 3 pm London, 10 pm Beijing on 19 May 2021

The plant cell wall possesses an unusual combination of strength and ability to expand without weakening or breaking (a quality required for plant growth), but the molecular basis for these traits has long been unclear. In a collaborative study led by Prof. Sulin Zhang and Prof.