Computational Predictions of the Tensile and Compressive Properties of Rigid-Rod Polymers

1988 ◽  
Vol 134 ◽  
Author(s):  
Scott G. Wierschke
Keyword(s):  
Failure Modes ◽  
Plane Deformation ◽  
Phenyl Group ◽  
Orbital Method ◽  
Tension And Compression ◽  
Ladder Polymers ◽  
Weak Points ◽  
Rigid Rod ◽  
Ladder Polymer ◽  
Bending Failure

ABSTRACTThe Austin Model 1 (AM1) semiempirical molecular orbital method has been used to calculate tensile moduli and molecular tensile and compressive deformation for several rigid-rod polymers and a graphite model. The calculated moduli are an improvement over previous Modified Neglect of Differential Overlap (MNDO) calculations. These are the ultimate moduli or the perfectly aligned bulk systems. By analyzing the deformation of polymer molecules in tension and compression, the failure modes and weak points in the molecules can be determined. In compression, all the heterocyclic rigid-rod polymers exhibit a “bending” failure mode. In tension and compression, the phenyl group in the rods undergoes in-plane deformation more easily than the heterocyclic moiety, thus causing a lowering of the modulus. The hypothetical “ladder” polymer, polyacene, shows higher tensile and compressive resistance than any of the rods, suggesting that further study into the ladder polymers is warranted.

Spectroscopic and morphological studies of highly conducting ion-implanted rigid-rod and ladder polymers

1992 ◽  
Vol 25 (21) ◽  
pp. 5828-5835 ◽  
Author(s):  
John A. Osaheni ◽  
Samson A. Jenekhe ◽  
Andrew Burns ◽  
Gang Du ◽  
Jinsoo Joo ◽  
...  
Keyword(s):  
Morphological Studies ◽  
Ladder Polymers ◽  
Rigid Rod ◽  
Ion Implanted

scholarly journals Tailoring π-conjugation and vibrational modes to steer on-surface synthesis of pentalene-bridged ladder polymers

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Bruno de la Torre ◽  
Adam Matěj ◽  
Ana Sánchez-Grande ◽  
Borja Cirera ◽  
Benjamin Mallada ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Materials Science ◽  
Second Step ◽  
Vibrational Modes ◽  
Force Microscopy ◽  
Synthetic Strategy ◽  
Atomic Force ◽  
Structures And Properties ◽  
Ladder Polymers ◽  
Ladder Polymer

Abstract The development of synthetic strategies to engineer π-conjugated polymers is of paramount importance in modern chemistry and materials science. Here we introduce a synthetic protocol based on the search for specific vibrational modes through an appropriate tailoring of the π-conjugation of the precursors, in order to increase the attempt frequency of a chemical reaction. First, we design a 1D π-conjugated polymer on Au(111), which is based on bisanthene monomers linked by cumulene bridges that tune specific vibrational modes. In a second step, upon further annealing, such vibrational modes steer the twofold cyclization reaction between adjacent bisanthene moieties, which gives rise to a long pentalene-bridged conjugated ladder polymer featuring a low bandgap. In addition, high resolution atomic force microscopy allows us to identify by atomistic insights the resonance form of the polymer, thus confirming the validity of the Glidewell and Lloyd´s rules for aromaticity. This on-surface synthetic strategy may stimulate exploiting previously precluded reactions towards π-conjugated polymers with specific structures and properties.

scholarly journals Thermodynamic synthesis of solution processable ladder polymers

2016 ◽  
Vol 7 (2) ◽  
pp. 881-889 ◽  
Author(s):  
Jongbok Lee ◽  
Bharath Bangalore Rajeeva ◽  
Tianyu Yuan ◽  
Zi-Hao Guo ◽  
Yen-Hao Lin ◽  
...  
Keyword(s):  
Olefin Metathesis ◽  
Thermodynamic Control ◽  
Ladder Polymers ◽  
Ladder Polymer ◽  
Solution Processable

The synthesis of a carbazole-derived, well-defined ladder polymer was achieved under thermodynamic control by employing reversible ring-closing olefin metathesis.

Experimental Research on Four-Tube Concrete-Filled Steel Tubular Laced Columns

2011 ◽  
Vol 311-313 ◽  
pp. 2204-2207 ◽  
Author(s):  
Bo Wang Chen ◽  
Ran He ◽  
Jian Guo Tan ◽  
Yang Oyang
Keyword(s):  
Mechanical Properties ◽  
Yield Point ◽  
Experimental Research ◽  
Failure Modes ◽  
Shear Failure ◽  
Short Columns ◽  
Eccentric Compression ◽  
Bending Failure ◽  
Overall Bending ◽  
Compressive Tests

By means of axial compressive and eccentric compressive tests of four Four-tube Concrete-filled Steel Tubular Laced Columns, to research the mechanical properties and failure modes of this structural without yield point. Research shows that, the failure modes of this model, as well as axial compressive short columns, have the same trend of oblique shear failure, and presenting overall bending failure under eccentric compression. The linear eccentricity takes a biggish influence on mechanical properties of laced columns.

scholarly journals Reliability Analysis of Anchored Geotechnical Structures for the Design Limit States

2020 ◽  
Vol 8 (2) ◽  
pp. 35-47
Author(s):  
Sohaib K Al-Mamoori ◽  
Laheab A. Al-Maliki ◽  
Khaled El-Tawel
Keyword(s):  
Reliability Analysis ◽  
Reliability Index ◽  
Failure Modes ◽  
Limit State ◽  
Tensile Failure ◽  
Limit States ◽  
Geotechnical Parameters ◽  
Retaining Structure ◽  
Geotechnical Structures ◽  
Bending Failure

Reliability has been considered of magnificent importance in engineering design specially in geotechnical engineering due to the unpredictable conditions of soil layers. It is essential to establish well- designed failure modes that could guarantee safety and durability of the proposed structure. This study aims to suggest a reliability analyses procedure for retaining walls by the mean of a reliability index β using the specifications of AASHTO Bridge Design 2002, Eurocode 7, and DIN EN 1993-5 norms. Two failure modes; Tensile failure of tendon (G1) and Failure by bending (G2) were studied and compared by using equation of the Design Limit State (DLS) and by taking some basic geotechnical parameters as Random Variables RV. The analyses demonstrated that the reliability index β and probability of failure Pf are the most important parameter in the reliability analysis. Also, the suitable height (H) for the retaining structure (for all angles ϴ) equals to 6 m and the most critical angle is ϴ= 45º to prevent the failure by tensile of tendon. While the bending failure reliability analysis shows that all heights of retaining structure are suitable. After comparing the two cases it was found that (G1) is more dangerous than (G2).

scholarly journals Categorization of Failures in Polymer Rapid Tools Used for Injection Molding

Processes ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 17 ◽  
Author(s):  
Anurag Bagalkot ◽  
Dirk Pons ◽  
Digby Symons ◽  
Don Clucas
Keyword(s):  
Injection Molding ◽  
Tool Life ◽  
Failure Modes ◽  
Shear Failure ◽  
Cost Effective ◽  
Critical Parameters ◽  
Cost Effective Method ◽  
Edge Failure ◽  
Underlying Mechanisms ◽  
Bending Failure

Background—Polymer rapid tooling (PRT) inserts for injection molding (IM) are a cost-effective method for prototyping and low-volume manufacturing. However, PRT inserts lack the robustness of steel inserts, leading to progressive deterioration and failure. This causes quality issues and reduced part numbers. Approach—Case studies were performed on PRT inserts, and different failures were observed over the life of the tool. Parts molded from the tool were examined to further understand the failures, and root causes were identified. Findings—Critical parameters affecting the tool life, and the effect of these parameters on different areas of tool are identified. A categorization of the different failure modes and the underlying mechanisms are presented. The main failure modes are: surface deterioration; surface scalding; avulsion; shear failure; bending failure; edge failure. The failure modes influence each other, and they may be connected in cascade sequences. Originality—The original contributions of this work are the identification of the failure modes and their relationships with the root causes. Suggestions are given for prolonging tool life via design practices and molding parameters.

scholarly journals Failure mechanism of hollow tree trunks due to cross-sectional flattening

2017 ◽  
Vol 4 (4) ◽  
pp. 160972 ◽  
Author(s):  
Yan-San Huang ◽  
Fu-Lan Hsu ◽  
Chin-Mei Lee ◽  
Jia-Yang Juang
Keyword(s):  
Urban Areas ◽  
Failure Modes ◽  
Shear Failure ◽  
Maximum Shear Stress ◽  
Mode Iii ◽  
Buckling Mode ◽  
Cross Sectional ◽  
Longitudinal Splitting ◽  
Bending Failure ◽  
Hollow Tree

Failure of hollow trees in urban areas is a worldwide concern, and it can be caused by different mechanisms, i.e. bending stresses or flattening-related failures. Here we derive a new analytical expression for predicting the bending moment for tangential cracking, and compare the breaking moment of various failure modes, including Brazier buckling, tangential cracking, shear failure and conventional bending failure, as a function of t / R ratio, where t and R are the trunk wall thickness and trunk radius, respectively, of a hollow tree. We use Taiwan red cypress as an example and show that its failure modes and the corresponding t / R ratios are: Brazier buckling (Mode I), tangential cracking followed by longitudinal splitting (Mode II) and conventional bending failure (Mode III) for 0 <  t / R  < 0.06, 0.06 <  t / R  < 0.27 and 0.27 <  t / R  < 1, respectively. The exact values of those ratios may vary within and among species, but the variation is much smaller than individual mechanical properties. Also, shear failure, another type of cracking due to maximum shear stress near the neutral axis of the tree trunk, is unlikely to occur since it requires much larger bending moments. Hence, we conclude that tangential cracking due to cross-sectional flattening, followed by longitudinal splitting, is dominant for hollow trunks. Our equations are applicable to analyse straight hollow tree trunks and plant stems, but are not applicable to those with side openings or those with only heart decay. Our findings provide insights for those managing trees in urban situations and those managing for conservation of hollow-dependent fauna in both urban and rural settings.

Synthesis of Ladder Polymers Via Soluble Precursor Polymers

1988 ◽  
Vol 134 ◽  
Author(s):  
Larry R. Dalton ◽  
Luping Yu
Keyword(s):  
Thermal Processing ◽  
Elevated Temperatures ◽  
Electrochemical Polymerization ◽  
Van Der Waals Interactions ◽  
Open Chain ◽  
Polymer Backbone ◽  
Langmuir Blodgett ◽  
Poor Solubility ◽  
Ladder Polymers ◽  
Rigid Rod

ABSTRACTAlthough ladder polymers have been known for some time, poor solubility and low molecular weights have prevented processing and have discouraged consideration of these materials for structural and electronic applications. Poor solubility can be associated with strong Van der Waals interactions between delocalized π-electron clouds on adjacent chains. The optimum orbital overlap along the polymer backbone existent for ladder polymers has motivated reexamination of these systems for electronic applications. We have pursued alternatives to the tradiational acid-catalyzed polycondensation of underivatized monomers at elevated temperatures by reacting derivatized (e.g., with alkyl or vinylamine substituents) monomers at reduced temperature in organic solvents (e.g., DMF) to produce open-chain precursors to ladder polymers. These are converted to fully-fused ladder polymers by thermal processing either in solution or as solid state (e.g., thin film) materials. The preparation of precursors of improved solubility greatly enhances processing options and has permitted the utilization of both Langmuir-Blodgett methods and the perparation of optical quality films by casting (including spin casting). By control of thermal processing conditions, both derivatized and underivatized ladder polymers have been prepared. Our approach offers obvious advantages for the investigation of the effect of conformation and of substituents upon electronic properties. The preparation of copolymers with rigid rod and flexible chain segments incorporated in the polymer backbone has also been investigated. For such materials, polymers with fully fused ladder segments can exhibit improved solubility in DMF relative to polymers with open chain segments due to the absence of favorable hydrogen bonding stuctures in the former. Finally, we are investigating the effect of electrochemical polymerization of Langmuir-Blodgett films prepared with derivatized diaminobenzene. Such an approach clearly takes advantage of improved solubility of the derivatized monomer and improved molecular order which can be realized with the Langmuir-Blodgett method. Free radical polymerization may facilitate the realization of improved molecular weight distributions.

Different Force Conditions on Nonlinear Finite Element Analysis of Small Concrete Hollow Block Wall with Failure Modes of Influence

2013 ◽  
Vol 788 ◽  
pp. 602-605
Author(s):  
Hong Yi Chen ◽  
Fu Ma
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Failure Modes ◽  
Failure Pattern ◽  
Displacement Curve ◽  
Relative Deformation ◽  
Element Analysis ◽  
Block Wall ◽  
Load Displacement ◽  
Bending Failure

This paper mainly studies small hollow concrete block wall sets a certain level of reinforcement, vertical bar, core column and high aspect ratio, vertical and horizontal load, changes in load point height wall by shear form and bending failure pattern changes and shear capacity and flexural capacity. Nonlinear analysis simulation using ANSYS finite element analysis software of the specimen, mainly analysis and predict the failure modes of the different loading conditions wall. Obtained by calculating the failure pattern of the specimen, the load-displacement curve, the various stages of the load-displacement values and calculated the relative deformation and ductility factor of the wall under various loading height. Comparative analysis of the load-displacement curve variation of the shear failure and bending failure form, draw the conclusion that bending failure energy consumption better performance.

scholarly journals Washability of E-Textiles: Failure Modes and Influences on Washing Reliability

Textiles ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 37-54
Author(s):  
Sigrid Rotzler ◽  
Martin Schneider-Ramelow
Keyword(s):  
Failure Modes ◽  
Influence Factors ◽  
Integrated Electronics ◽  
Hybrid Products ◽  
Weak Points ◽  
Influencing Parameters ◽  
Targeted Approach

E-textiles, hybrid products that incorporate electronic functionality into textiles, often need to withstand washing procedures to ensure textile typical usability. Yet, the washability—which is essential for many e-textile applications like medical or sports due to hygiene requirements—is often still insufficient. The influence factors for washing damage in textile integrated electronics as well as common weak points are not extensively researched, which makes a targeted approach to improve washability in e-textiles difficult. As a step towards reliably washable e-textiles, this review bundles existing information and findings on the topic: a summary of common failure modes in e-textiles brought about by washing as well as influencing parameters that affect the washability of e-textiles. The findings of this paper can be utilized in the development of e-textile systems with an improved washability.

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