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56 results on '"Yield strain"'

53. Impact of Substrate Characteristics on Stretchable Polymer Semiconductor Behavior.

Author

Sun T, Song R, Balar N, Sen P, Kline RJ, and O'Connor BT

Abstract

Stretchable conductive polymer films are required to survive not only large tensile strain but also stay functional after the reduction in applied strain. In the deformation process, the elastomer substrate that is typically employed plays a critical role in response to the polymer film. In this study, we examine the role of a polydimethylsiloxane (PDMS) elastomer substrate on the ability to achieve stretchable PDPP-4T films. In particular, we consider the adhesion and near-surface modulus of the PDMS tuned through UV/ozone (UVO) treatment on the competition between film wrinkling and plastic deformation. We also consider the role of PDMS tension on the stability of films under cyclic strain. We find that increasing the near-surface modulus of the PDMS and maintaining the PDMS in tension throughout the cyclic strain process promote plastic deformation over film wrinkling. In addition, the UVO treatment increases film adhesion to the PDMS resulting in a significantly reduced film folding and delamination. For a 20 min UVO-treated PDMS, we show that a PDPP-4T film root-mean-square roughness is consistently below 3 nm for up to 100 strain cycles with a strain range of 40%. In addition, although the film is plastically deforming, the microstructural order is largely stable as probed by grazing incidence X-ray scattering and UV-visible spectroscopy. These results highlight the importance of neighboring elastomer characteristics on the ability to achieve stretchable polymer semiconductors.

Published
2019
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55. The effect of braiding parameters on the mechanical properties of braided ropes

Author

Uludağ Üniversitesi/Mühendislik Mimarlık Fakültesi/Tekstil Mühendisliği Bölümü., Ömeroğlu, Sunay, and AAM-7071-2020

Subjects
Rope, Mechanical properties, Polypropylenes, Materials science, Strain, Statistically significant difference, Rope making, strain, Braid pattern, Braided Composites, Braiding, Three Dimensional Composites, Take-up rate, Braided rope, Maximum strains, Tenacity, Materials science, textiles, Polypropylene, Yield strain, Braiding parameters, Mechanical property
Abstract

In this study, the effects of braid pattern and take-up rate on the mechanical properties of the tubular braided ropes of polypropylene were investigated. Strand fineness of 70 tex and 150 tex, braid pattern of 1/1 and 2/2, and high & low take-up rates were selected For both strand finenesses, the highest values for maximum tenacity, modulus and yield tenacity were obtained with the high take-up rate and the 2/2 pattern. However the highest values for maximum strain and yield strain were obtained with the low take-up rate and the 1/1 pattern. There were statistically significant differences between the results of other mechanical properties, except for the maximum strain value for braided ropes produced with a different pattern. There were statistically significant differences among the results of the mechanical properties tested for braided ropes produced with different take-up rates.

Published
2006

56. Tensile properties of segmented block copolymers with monodisperse hard segments

Author

Gerard Jan Eduard Biemond, Reinoud J. Gaymans, Jan Feijen, Faculty of Science and Technology, and Biomaterials Science and Technology

Subjects
Yield Strain, Shearing (physics), Materials science, Yield (engineering), METIS-254523, Fracture Strain, Hard Segment, Mechanical Engineering, Dispersity, Fracture Stress, Modulus, Strain hardening exponent, Article, Stress (mechanics), Materials Science(all), Mechanics of Materials, Ultimate tensile strength, General Materials Science, Crystallite, Composite material, IR-68968, Dynamic Mechanical Thermal Analysis
Abstract

The tensile properties of segmented block copolymers with mono-disperse hard segments were studied with respect to the hard segment content (16–44 wt.%) and the temperature (20–110 °C). The copolymers were comprised of poly(tetramethylene oxide) segments with the molecular weights of 650–2,900 Da and of mono-disperse bisester-tetra-amide segments (T6A6T) based on adipic acid (A), terephthalic acid (T) and hexamethylene diamine (6). An increasing content of T6A6T gave rise to an increased modulus, yield stress and fracture stress. The modulus could be modeled by a composite model. Moreover, a strain-softening was observed well below the yield stress, due to the shearing of the T6A6T crystallites. At strains >200%, a strain-hardening of the PTMO segments took place and this even for PTMO segments that were amorphous in the isotropic state. The strain hardening increased the tensile properties. An increase in temperature had little effect on the modulus of the copolymers, but was found to lower the yield and fracture stresses. At temperatures above the melting temperature of the oriented PTMO, no strain-hardening took place. The yield stress as a function of temperature could be described by the Eyring relationship, but a modulus–yield stress relationship could not be established.

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