scholarly journals Piezoresistive bond lines for timber construction monitoring—experimental scale-up

2021 ◽  
Author(s):  
Christoph Winkler ◽  
Stefan Haase ◽  
Ulrich Schwarz ◽  
Markus Jahreis
Keyword(s):  
Electrical Contact ◽  
Scale Up ◽  
Strain Analysis ◽  
Conductive Filler ◽  
Bond Line ◽  
Wood Products ◽  
Image Correlation ◽  
Test Sequence ◽  
Strain Sensing ◽  
Electrically Conductive

AbstractSeveral laboratory studies and experiments have demonstrated the usability of polymer films filled with electrically conductive filler as piezoresistive material. Applied to adhesives, the glue lines of wood products can achieve multifunctional—thus bonding and piezoresistive/strain sensing—properties. Based on critical load areas in timber constructions, upscaled test setups for simplified load situations were designed, especially with regard to a stress-free electrical contact. In a second step, another upscaling was done to small glulam beams. Based on an experimental test sequence, the piezoresistive reactions as well as the behaviour until failure were analysed. The results show in all cases that a piezoresistive reaction of the multifunctionally bonded specimens was measurable, giving a difference in the extent of relative change. Additionally, measured phenomena like inverse piezoresistive reactions, electrical resistance drift and the absence of a piezoresistive reaction were discussed, based on additional strain analysis by digital image correlation. A model of macroscopic and microscopic strains influencing the piezoresistive reaction of the electrically conductive bond line in wood was used to explain all experimental results. Finally, a first scale-up of piezoresistive bond lines from laboratory samples to glulam beams was possible and successful.

scholarly journals Mechanical and Electrical Performance of Flexible Polymer Film Designed for a Textile Electrically-Conductive Path

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2169
Author(s):  
Agnieszka Tabaczyńska ◽  
Anna Dąbrowska ◽  
Marcin Masłowski ◽  
Anna Strąkowska
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Surface Resistance ◽  
Conductive Filler ◽  
Extrusion Process ◽  
Electrical Performance ◽  
Electrically Conductive ◽  
Non Invasive ◽  
Flexible Polymer ◽  
The Stability

Electro-conductive paths that are mechanically resistant and stable during simulated aging cycles are promising, in relation to the non-invasive application in e-textiles in our everyday surroundings. In the paper, an analysis of the influence of electro-conductive filler, as well as ionic liquid on surface resistance is provided. Authors proved that depending on the tested variant, obtained surface resistance may vary from 50 kΩ (when 50 phr of Ag and [bmim][PF6] ionic liquid applied) to 26 GΩ (when 25 phr of Ag and [bmim][PF6] ionic liquid applied). The samples were also evaluated after simulated aging cycles and the stability of electric properties was confirmed. Moreover, it was proved that the addition of ionic liquids reduced the resistance of vulcanizates, while no significant influence of the extrusion process on conductivity was observed.

Experimental Characterization and Finite Element Modeling of Film Capacitors for Automotive Applications

2016 ◽  
Author(s):  
D. Croccolo ◽  
T. M. Brugo ◽  
M. De Agostinis ◽  
S. Fini ◽  
G. Olmi
Keyword(s):  
Finite Element ◽  
Mechanical Response ◽  
High Reliability ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Life Time ◽  
Element Model ◽  
Image Correlation ◽  
Thermal Loads ◽  
Mechanical Shock

As electronics keeps on its trend towards miniaturization, increased functionality and connectivity, the need for improved reliability capacitors is growing rapidly in several industrial compartments, such as automotive, medical, aerospace and military. Particularly, recent developments of the automotive compartment, mostly due to changes in standards and regulations, are challenging the capabilities of capacitors in general, and especially film capacitors. Among the required features for a modern capacitor are the following: (i) high reliability under mechanical shock, (ii) wide working temperature range, (iii) high insulation resistance, (iv) small dimensions, (v) long expected life time and (vi) high peak withstanding voltage. This work aims at analyzing the key features that characterize the mechanical response of the capacitor towards temperature changes. Firstly, all the key components of the capacitor have been characterized, in terms of strength and stiffness, as a function of temperature. These objectives have been accomplished by means of several strain analysis methods, such as strain gauges, digital image correlation (DIC) or dynamic mechanical analysis (DMA). All the materials used to manufacture the capacitor, have been characterized, at least, with respect to their Young’s modulus and Poisson’s ratio. Then, a three-dimensional finite element model of the whole capacitor has been set up using the ANSYS code. Based on all the previously collected rehological data, the numerical model allowed to simulate the response in terms of stress and strain of each of the capacitor components when a steady state thermal load is applied. Due to noticeable differences between the thermal expansion coefficients of the capacitor components, stresses and strains build up, especially at the interface between different components, when thermal loads are applied to the assembly. Therefore, the final aim of these numerical analyses is to allow the design engineer to define structural optimization strategies, aimed at reducing the mechanical stresses on the capacitor components when thermal loads are applied.

Bridge transition monitoring: Interpretation of track defects using digital image correlation and distributed fiber optic strain sensing

2019 ◽  
Vol 234 (6) ◽  
pp. 616-637
Author(s):  
Eric M Pannese ◽  
W Andy Take ◽  
Neil A Hoult ◽  
Ruobing Yan ◽  
Hoat Le
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Fiber Optic ◽  
Current Knowledge ◽  
Image Correlation ◽  
Order Estimate ◽  
Monitoring Site ◽  
Railway Bridge ◽  
Strain Sensing ◽  
Vertical Stiffness

Railway bridge transitions represent locations of vertical stiffness variations that are believed to amplify the dynamic wheel loads which contribute to the development of both differential track settlement and hanging sleeper issues that are difficult to resolve despite the current knowledge of bridge transition behaviour. This paper presents a field monitoring study of a railway bridge transition in which track defects – including both gaps between the rail and sleeper plates, i.e. “rail–sleeper gaps,” and rail flange scrape marks exposing bare steel – were observed during a visual inspection of the transition. Trains were monitored by measuring both track displacements using Digital Image Correlation and distributed rail strains using a Rayleigh-based fiber optic analyzer. Through analysis and interpretation of the collected monitoring data, it was found that measurements of rail–sleeper gaps could be used to obtain a first-order estimate of the shape of the differential track settlement profile. Additionally, it was found that measurements of scrape marks on the rail flange could be used to estimate the extent of longitudinal rail movement that could occur during train passage, and that the loads applied to the bridge structure were influenced by the nature of the rail–sleeper gaps at the monitoring site.

The Nanomechanics of Tetrahedral Amorphous Diamond-Like Carbon (ta-C) MEMS

2003 ◽  
Author(s):  
I. Chasiotis ◽  
S. W. Cho ◽  
T. A. Friedmann ◽  
J. P. Sullivan
Keyword(s):  
Strain Analysis ◽  
Film Surface ◽  
Image Correlation ◽  
Diamond Like Carbon ◽  
Tensile Stresses ◽  
Notched Specimens ◽  
Failure Properties ◽  
First Time ◽  
Very High

The mechanics of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) MEMS structures have been investigated in connection with their elastic and failure properties. For this purpose, micro-tension specimens of thicknesses between 1.2 μm and 1.8 μm and gage widths of 10 μm or 50 μm have been fabricated by the Sandia National Laboratories (SNL). The mechanical characterization has been conducted via in situ AFM measurements and Digital Image Correlation (DIC) data strain analysis and the deformation fields of uniform tension specimens and internally notched specimens with acute notches (K=27) have been experimentally obtained. The elastic modulus and Poisson’s ratio were measured for the first time directly from the specimens averaging 750 GPa and ν=0.16 respectively, while the tensile strength was found to be very consistent averaging 7.0 GPa. Stressed material domains with smaller dimensions in the vicinity of micronotches exhibited even higher failure strength reaching an average of 11.5 GPa with about 10% scatter. AFM images of specimens under high tensile stresses have also indicated the possibility of an sp3 to sp2 phase transformation on the film surface at very high tensile stresses (>6 GPa).

Strain Sensing Behavior and Its Mechanisms of Electrically Conductive PPy-Coated Fabric

2013 ◽  
Vol 16 (5) ◽  
pp. 565-570 ◽  
Author(s):  
Junpu Wang ◽  
Pu Xue ◽  
Xiaoming Tao ◽  
Tongxi Yu
Keyword(s):  
Strain Sensing ◽  
Electrically Conductive ◽  
Coated Fabric

A Novel Method for Optical High Spatiotemporal Strain Analysis for Transcatheter Aortic Valves In Vitro

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Simon Heide-Jørgensen ◽  
Sellaswasmy Kumaran Krishna ◽  
Jonas Taborsky ◽  
Tommy Bechsgaard ◽  
Rachid Zegdi ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Image Correlation ◽  
Deformation Analysis ◽  
Flow Loop ◽  
Transcatheter Aortic Valve ◽  
Wear And Tear ◽  
Valve Implantation

The transcatheter aortic valve implantation (TAVI) valve is a bioprosthetic valve within a metal stent frame. Like traditional surgical bioprosthetic valves, the TAVI valve leaflet tissue is expected to calcify and degrade over time. However, clinical studies of TAVI valve longevity are still limited. In order to indirectly assess the longevity of TAVI valves, an estimate of the mechanical wear and tear in terms of valvular deformation and strain of the leaflets under various conditions is warranted. The aim of this study was, therefore, to develop a platform for noncontact TAVI valve deformation analysis with both high temporal and spatial resolutions based on stereophotogrammetry and digital image correlation (DIC). A left-heart pulsatile in vitro flow loop system for mounting of TAVI valves was designed. The system enabled high-resolution imaging of all three TAVI valve leaflets simultaneously for up to 2000 frames per second through two high-speed cameras allowing three-dimensional analyses. A coating technique for applying a stochastic pattern on the leaflets of the TAVI valve was developed. The technique allowed a pattern recognition software to apply frame-by-frame cross correlation based deformation measurements from which the leaflet motions and the strain fields were derived. The spatiotemporal development of a very detailed strain field was obtained with a 0.5 ms time resolution and a spatial resolution of 72 μm/pixel. Hence, a platform offering a new and enhanced supplementary experimental evaluation of tissue valves during various conditions in vitro is presented.

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