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1. Enhancement of Relative Permittivity of Material with Metallic Inclusions – Experimental Verification

   https://doi.org/10.1109/SoutheastCon51012.2023.10115156  

   Saha, Arun Kumar; Pendleton, Walker (April 2023, IEEE)

   In this project, it was shown by simulation that the permittivity of a material could be enhanced by embedding metal inclusions in the host material. Later, a series of systematic experiments were carried out with free space material measurement equipment/system to demonstrate the enhancement of permittivity with circular metal patches printed periodically on a host material to validate the simulation results. 

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2. Toward an accommodation account of deaccenting under nonidentity

   https://doi.org/10.3765/elm.1.4875  

   Geiger, Jeffrey; Xiang, Ming (July 2021, Experiments in Linguistic Meaning)

   Beltrama, Andrea; Schwarz, Florian; Papagragou, Anna (Ed.)

   Two competing models attempt to explain the deaccentuation of antecedent nonidentical discourse-inferable material (e.g., Bach wrote many pieces for viola. He must have LOVED string instruments). One uses a single grammatical constraint to license deaccenting for identical and nonidentical material. The second licenses deaccenting grammatically only for identical constituents, whereas deaccented nonidentical material requires accommodation of an alternative antecedent. In three experiments, we tested listeners’ preferences for accentuation or deaccentuation on nonidentical inferable material in out-of-the-blue contexts, supportive discourse contexts, and in the presence of the presupposition trigger too. The results indicate that listeners by default prefer for inferable material to be accented, but that this preference can be mitigated or even reversed with the help of manipulations in the broader discourse context. By contrast, listeners reliably preferred for repeated material to be deaccented. We argue that these results are more compatible with the accommodation model of deaccenting licensing, which allows for differential licensing of deaccentuation on inferable versus repeated constituents and provides a principled account of the sensitivity of accentuation preferences on inferable material to broader contextual manipulations. 

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3. 3-D PRINTING OF DIELECTRIC ELECTROACTIVE POLYMER ACTUATORS AND CHARACTERIZATION OF DIELECTRIC FLEXIBLE MATERIALS

   Gonzalez, David; Newell, Brittany; Garcia, Jose; Noble, Lucas; Mamer, Trevor (October 2018, ASME Conference on Smart Materials, Adaptive Structures, and Intelligent Systems (SMASIS))

   Dielectric electroactive polymers are materials capable of mechanically adjusting their volume in response to an electrical stimulus. However, currently these materials require multi-step manufacturing processes which are not additive. This paper presents a novel 3D printed flexible dielectric material and characterizes its use as a dielectric electroactive polymer (DEAP) actuator. The 3D printed material was characterized electrically and mechanically and its functionality as a dielectric electroactive polymer actuator was demonstrated. The flexible 3-D printed material demonstrated a high dielectric constant and ideal stress-strain performance in tensile testing making the 3-D printed material ideal for use as a DEAP actuator. The tensile stress- strain properties were measured on samples printed under three different conditions (three printing angles 0°, 45° and 90°). The results demonstrated the flexible material presents different responses depending on the printing angle. Based on these results, it was possible to determine that the active structure needs low pre-strain to perform a visible contractive displacement when voltage is applied to the electrodes. The actuator produced an area expansion of 5.48% in response to a 4.3 kV applied voltage, with an initial pre-strain of 63.21% applied to the dielectric material. 

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4. Additive Manufacturing of Polymer Matrix Composite Materials with Aligned or Organized Filler Material: A Review

   https://doi.org/10.1002/adem.202001002  

   Niendorf, Karl; Raeymaekers, Bart (January 2021, Advanced Engineering Materials)

   The ability to fabricate polymer matrix composite materials with continuous or discontinuous filler material, oriented in a user‐specified direction, enables implementing designer material properties, such as anisotropic mechanical, thermal, and electrical properties. Conventional fabrication methods rely on a mold, which limits specimen geometry and is difficult to implement. In contrast, additive manufacturing, including fused filament fabrication or fused deposition modeling, direct ink writing, or stereolithography, combined with a method to align filler material such as a mechanical force or an electric, magnetic, shear force, or ultrasound wave field, enables 3D printing polymer matrix composite material specimens with complex geometry and aligned filler material, without the need for a mold. Herein, we review the combinations of fabrication and filler material alignment methods used to fabricate polymer matrix composite materials, in terms of operating and design parameters including size, resolution, print speed, filler material alignment time, polymer matrix and filler material requirements, and filler manipulation requirements. The operating envelope of each fabrication method is described and their advantages, disadvantages, and limitations are discussed. Finally, different combinations of 3D printing and filler material alignment methods in the context of important engineering applications, such as structural materials, flexible electronics, and shape‐changing materials, are illustrated. 

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5. Frictional Ignition of Metals in High Pressure Oxygen: A Critical Reassessment of NASA Test Data

   https://doi.org/10.2514/6.2023-1489  

   Garcia Jimenez, Andres; Cordero, Zachary C. (January 2023, AIAA Scitech 2023)

   In this paper we develop a material index for selecting alloys resistant to frictional ignition in high pressure oxygen environments. A previous ignition-resistance metric proposed by NASA WSTF varies strongly and unpredictably with test conditions, thus limiting its usefulness. The material index developed here incorporates key material properties that strongly influence ignition behaviors, including friction coefficient, ignition temperature, and thermal effusivity. Finite element simulations were used to compute ignition temperatures for 15 alloys based on published frictional ignition data from NASA White Sands Testing Facility (WSTF). These values were used with the material index to construct property diagrams for ranking the materials based on their intrinsic frictional ignition resistance. The results demonstrate that nickel-based superalloys with low iron content are less likely to ignite under frictional heating than ferrous alloys and nickel-based superalloys with high content iron. The material index is then used to predict material performance outside of the test conditions, highlighting the effect of ambient temperature on nominal ignition resistance. We conclude by developing an empirical relation between ignition temperature and enthalpy of oxidation which can guide design of new ignition-resistant alloys. 

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