A5016101458- Polymer crystallization and properties
- Polymer Nanocomposites and Properties
- High-Velocity Impact and Material Behavior
- Polymer composites and self-healing
- Mechanical Behavior of Composites
- Structural Response to Dynamic Loads
- Metal and Thin Film Mechanics
- Diamond and Carbon-based Materials Research
- Silicone and Siloxane Chemistry
- Energetic Materials and Combustion
- Synthesis and properties of polymers
- Force Microscopy Techniques and Applications
- biodegradable polymer synthesis and properties
- Electrospun Nanofibers in Biomedical Applications
- Planetary Science and Exploration
- Advanced Sensor and Energy Harvesting Materials
- Ion-surface interactions and analysis
- Particle Dynamics in Fluid Flows
- Building materials and conservation
- Advanced NMR Techniques and Applications
- Elasticity and Material Modeling
- Tribology and Wear Analysis
- Engineering and Material Science Research
- Cellular and Composite Structures
- Optical measurement and interference techniques
Institute for Soldier Nanotechnologies
2010-2023
DEVCOM Army Research Laboratory
2014-2023
United States Army Combat Capabilities Development Command
2019-2023
Massachusetts Institute of Technology
1985-2023
Siliconware Precision Industries (Taiwan)
2020
United States Army
1991-1993
United States Department of the Army
1990
Understanding high-velocity microparticle impact is essential for many fields, from space exploration to medicine and biology. Investigations of microscale have hitherto been limited post-mortem analysis impacted specimens, which does not provide direct information on the dynamics. Here we report real-time multi-frame imaging studies 7 μm diameter glass spheres traveling at 700-900 m/s elastomer polymers. With a poly(urethane urea) (PUU) sample, observe hyperelastic phenomenon seen...
Hydrogels have been proposed for sensing, drug delivery, and soft robotics applications, yet most of these materials suffer from low mechanical robustness high permeability to small molecules, limiting their widespread use. This study reports a general strategy versatile method fabricate robust, highly stretchable, impermeable hydrogel laminates via hybrid lamination an elastomer layer bonded between layers. By controlling the layers' composition thickness, it is possible tune stiffness...
Abstract The effect of clay loading on the mechanical behavior and melt state linear viscoelastic properties intercalated polycarbonate (PC) nanocomposites was investigated. At low frequencies, dynamic oscillatory moduli data revealed diminished frequency dependence with increasing nanoclay loading. 3.5 5 wt% exhibited dramatically altered relaxation behavior, from liquid‐like to pseudo‐solid–like, compared pure PC 1.5 nanocomposite. Thermal degradation resulted compounding organo‐modified...
This study investigates the molecular dependencies of dynamic stiffening and strengthening through comparison high strain rate impact responses various polyurethanes polyureas. We use an in-house designed tabletop microimpact experimental platform—the laser-induced particle test—to perform impacts measure corresponding material response. Dynamic mechanical analysis differential scanning calorimetry are used to show that glass transition temperature is a useful predictor response at ambient...
Abstract Transparent poly(urethane urea) (TPUU) materials offer an avenue to enable material designs with potential achieve simultaneous enhancements in both physical and mechanical properties. To optimize the performance required for each application, molecular features that influence microstructure, glass transition temperature ( T g ), deformation mechanisms, behavior must be understood exploited. In this work, a comprehensive characterization of select model PUUs tunable microstructures...
Microlayers of polycarbonate (PC) with poly(methylmethacrylate) (PMMA) or poly(styrene-co-acrylonitrile) (SAN) were processed varying layer thicknesses. Adhesion between PC and PMMA was found to be an order magnitude higher than SAN, as determined the T-peel method. To probe effect adhesion difference on yielding deformation PC/PMMA PC/SAN microlayers, macroscopic stress–strain behavior examined a function thickness strain rate, results interpreted in terms microdeformation behavior. During...
Abstract The dynamic mechanical behavior of molecularly oriented semicrystalline polyethylene terephthalate (PET) induced via the equal‐channel angular extrusion (ECAE) process was investigated. Dynamic analyses in both torsional mode and bending were utilized. results indicate that ECAE‐oriented PET has a higher storage modulus above glass‐transition temperature than reference (control sample). combined effect molecular orientation crystallinity is responsible for changes primary secondary...
Equal-channel angular-extrusion (ECAE) may greatly alter polymer properties because it creates anisotropy in the microstructure. Tensile, fracture toughness, flexure, and ballistic impact tests were performed to quantify ECAE effects on polymethylmethacrylate (PMMA). Young's modulus increased by 5% for one process condition, while strength elongation failure remained same or decreased. Fracture toughness improved 178% under a one-pass condition. Ballistic resistance changes after molecular...
Deformation-induced glass transition in segmented elastomers has been proposed to allow highly desirable enhanced energy dissipation. In this study, we investigate the temperature-dependent microscale impact response of polyurea at a fixed velocity. We observe local elevated absorption around 115 °C, which is attributed glass-to-rubber temperature under present high-rate dynamic loading. Dielectric spectroscopy was performed, and soft-segmental α2-relaxation extracted fit with...
The 5G revolution have brought about the huge impact for communication industry which produces a series of innovative technologies, such as Sub 6Ghz and millimmeter wave (mmWave) 28Ghz spectrum, beam forming, multiconnectivity edge computing are widely applied in generation high speed data transmission low latency purpose. Furthermore, system package (SiP) module design assembly technology plays an key role IOT, antenna (AiP) RF applicatons, compare to tranditional SiP design,...
The impact fracture behavior of molecularly orientated polycarbonate (PC) sheets was investigated. molecular orientation achieved via a newly developed equal channel angular extrusion (ECAE) process. Improvement in propagation resistance observed the ECAE processed PC sheets. improved found to be directly related changes because ECAE. unique characteristics process for polymer are described. potential benefits enhancing physical and mechanical properties extruded discussed. © 2001 John Wiley...