Matt Pharr's blog

On behalf of Texas A&M University & Texas A&M Engineering Experiment Station, we are excited to announce that over 80 symposia in 10 thematic areas have been accepted for the 2022 Society of Engineering Science (SES) Annual Technical Meeting that will be held on our campus in College Station, Texas, from October 16-19, 2022.

On behalf of Texas A&M University & Texas A&M Engineering Experiment Station, we are excited to announce the 2022 Annual Technical Meeting of the Society of Engineering Science that will be held on our campus in College Station, Texas, from October 16-19, 2022.

On behalf of Texas A&M University & Texas A&M Engineering Experiment Station, we are excited to announce the 2022 Annual Technical Meeting of the Society of Engineering Science that will be held on our campus in College Station, Texas, from October 16-19, 2022.

Mechanics of High-capacity Rechargeable Batteries

Cole Fincher, Yuwei Zhang, Matt Pharr

Department of Mechanical Engineering, Texas A&M University

1. Introduction

Colleagues,

The technical meeting of the Society of Engineering Science (SES) will be held at the Hyatt Regency in Minneapolis on September 28-30, 2020. As part of this meeting we are organizing a symposium in Track 5: Frontiers in Mechanics of Materials with a minisymposium title of “Mechanics Of Electrochemically Active and Ferroelastic Materials”. The deadline for abstract submission is March 17th. We encourage you to submit an abstract or to forward to any interested parties, e.g., your students or colleagues.

We have discovered a peculiar form of fracture that occurs in a highly stretchable silicone elastomer (Smooth-On Ecoflex 00–30). Under certain conditions, cracks propagate in a direction perpendicular to the initial pre-cut and in the direction of the applied load. In other words, the crack deviates from the standard trajectory and instead propagates perpendicular to that trajectory. The crack arrests stably, and thus the material ahead of the crack front continues to sustain load, thereby enabling enormous stretchabilities. We call this phenomenon 'sideways' and stable cracking.

Colleagues:

The technical meeting of the Society of Engineering Science (SES) will be held at Washington University in St. Louis on October 13-15, 2019. As part of this meeting we are organizing Symposium 7.4 on “Mechanics of Electrochemically Active Materials”. The deadline for abstract submission is April 30

Owing to their enormous capacities, Li-S batteries have emerged as a prime candidate for economic and sustainable energy storage. Still, potential mechanics-based issues exist that must be addressed: lithiation of sulfur produces an enormous volume expansion (~80%). In other high capacity electrodes, large expansions generate considerable stresses that can lead to mechanical damage and capacity fading.

Skin is the largest organ of the human body, and it offers a diagnostic interface rich with vital biological signals from the inner organs, blood vessels, muscles, and dermis/epidermis. Soft, flexible, and stretchable electronic devices provide a novel platform to interface with soft tissues for robotic feedback and control, regenerative medicine, and continuous health monitoring.

Dear Colleagues,

We invite you to submit an abstract to "Symposium VI-B: Energy Materials" at the 54rd Annual Technical Meeting of the Society of Engineering Science: SES2017.  More information on the symposium can be found at this link or at the bottom of this message.

Dear Colleagues,

We invite you to submit an abstract to "Symposium VI-B: Energy Materials" at the 54rd Annual Technical Meeting of the Society of Engineering Science: SES2017.  More information on the symposium can be found at this link or at the bottom of this message.

We measure stresses that develop in sputter-deposited amorphous Ge thin films during electrochemical lithiation and delithiation. Amorphous LixGe electrodes are found to flow plastically at stresses that are significantly smaller than those of their amorphous LixSi counterparts. The stress measurements allow for quantification of the elastic modulus of amorphous LixGe as a function of lithium concentration, indicating a much-reduced stiffness compared to pure Ge.

Silicon is a promising anode material for lithium-ion batteries due to its enormous theoretical energy density. Fracture during electrochemical cycling has limited the practical viability of silicon electrodes, but recent studies indicate that fracture can be prevented by taking advantage of lithiation-induced plasticity. In this paper, we provide experimental insight into the nature of plasticity in amorphous LixSi thin films. To do so, we vary the rate of lithiation of amorphous silicon thin films and simultaneously measure stresses.

Dielectric elastomer transducers are often subject to large tensile stretches and are susceptible to rupture. Here we carry out an experimental study of the rupture behavior of membranes of an acrylic dielectric elastomer (VHB 4905). Pure-shear test specimens are used to measure force-displacement curves, using samples with and without pre-cracks. We find that introducing a pre-crack into a membrane drastically reduces the stretch at rupture. Furthermore, we measure the stretch at rupture and fracture energy using samples of different heights at various stretch-rates. The stretch at rupture is found to decrease with sample height, and the fracture energy is found to increase with stretch-rate.
This paper has appeared in the Journal of Applied Physics and can be downloaded from:

The following message is from Dr. Frans Spaepen at Harvard University:

Dear colleague,

  I am writing to draw your attention to our annual solicitation for
applications to Rowland Junior Fellows Program, which may be of interest to
your graduate students and postdoctoral fellows.

Here is a paper that I wrote my freshman year of college.  It discusses some observations about fracture toughness in a form of silicon carbide that had potential use in nuclear fission and fusion reactors.  It was published in the Department of Energy's Journal of Undergraduate Research.