scholarly journals Directional Response of Randomly Dispersed Carbon Nanotube Strain Sensors

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2980
Author(s):  
Alfredo Güemes ◽  
Angel Renato Pozo Morales ◽  
Antonio Fernandez-Lopez ◽  
Xoan Xose F. Sanchez-Romate ◽  
Maria Sanchez ◽  
...  
Keyword(s):  
Electrical Response ◽  
Tensile Load ◽  
Epoxy Adhesive ◽  
Resistance Change ◽  
Adhesive Film ◽  
Bonded Joint ◽  
Individual Strain ◽  
Strain Components ◽  
The Individual ◽  
Transverse Strains

Tests on a double lap bonded joint, with transverse strips of randomly oriented carbon nanotubes (CNT) sprayed onto an epoxy adhesive film, showed a positive increment in electrical resistance under tensile load, even though the transverse strains were negative. Other experiments included in this work involved placing longitudinal and transversal CNT sensors in a tensile loaded aluminum plate, and, as reported by other authors, the results confirm that the resistance change is not only dependent on the strains oriented with the electrode line, while the other strain components also influence the response. This behavior is quite different to that of conventional strain gages which have a near zero sensitivity to strains not aligned to the sensor direction. The dependence of the electrical response on all the strain components makes it quite difficult, possibly unfeasible, to experimentally determine the individual strain components with this kind of sensors; however, the manufacturing of aligned CNT sensors could deal with this issue.

scholarly journals Electrical Monitoring as a Novel Route to Understanding the Aging Mechanisms of Carbon Nanotube-Doped Adhesive Film Joints

2020 ◽  
Vol 10 (7) ◽  
pp. 2566 ◽  
Author(s):  
Xoan F. Sánchez-Romate ◽  
Alberto Jiménez-Suárez ◽  
María Sánchez ◽  
Silvia G. Prolongo ◽  
Alfredo Güemes ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Theoretical Calculations ◽  
Electrical Response ◽  
Partial Recovery ◽  
Initial State ◽  
Scanning Calorimetry ◽  
Resistance Change ◽  
Adhesive Film ◽  
Lap Shear ◽  
Aging Conditions

Carbon fiber-reinforced plastic bonded joints with novel carbon nanotube (CNT) adhesive films were manufactured and tested under different aging conditions by varying the surfactant content added to enhance CNT dispersion. Single lap shear (SLS) tests were conducted in their initial state and after 1 and 2 months immersed in distilled water at 60 °C. In addition, their electrical response was measured in terms of the electrical resistance change through thickness. The lap shear strength showed an initial decrease due to plasticization of weak hydrogen bonds, and then a partial recovery due to secondary crosslinking. This plasticization effect was confirmed by differential scanning calorimetry analysis with a decrease in the glass transition temperature. The electrical response varied with aging conditions, showing a higher plasticity region in the 1-month SLS joints, and a sharper increase in the case of the non-aged and 2-month-aged samples; these changes were more prevalent with increasing surfactant content. By adjusting the measured electrical data to simple theoretical calculations, it was possible to establish the first estimation of damage accumulation, which was higher in the case of non-aged and 2-month-aged samples, due to the presence of more prevalent brittle mechanisms for the CNT-doped joints.

Fatigue Behavior of Adhesive Joints Under Biaxial Loading Conditions

1993 ◽  
Author(s):  
Erol Sancaktar
Keyword(s):  
Biaxial Loading ◽  
Fatigue Behavior ◽  
Epoxy Adhesive ◽  
Steel Beams ◽  
Loading Conditions ◽  
Adhesively Bonded Joints ◽  
Shear Loads ◽  
Bonded Joint ◽  
Solid Film ◽  
Static Shear

Abstract Fatigue data obtained under biaxial loading conditions for adhesively bonded joints are used to plot S-N type diagrams to assess the effects of biaxiality in loading. Independently Loaded Mixed-Mode Specimens (ILM MS) are used for data collection purposes. These specimens are basically two (steel) beams bonded to be fatigue loaded under cantilever (opening) mode while a simultaneous but physically separate in-plane (static) shear load is also induced with the aid of a small hydraulic piston embedded in the specimen. Application of such static shear loads results in different S-N behavior for the bonded joint. The model adhesives used are Metlbond 1113-2 and Metlbond 1113 solid film thermosetting adhesives similar to those commonly used in aircraft and aerospace industries. The former is an elastomer-modified epoxy adhesive and the latter is identical except that it containes a synthetic earner cloth. Thus, the effects of carrier cloth in adhesive’s S-N behavior is also assessed. Analytically, the classical linear log-log representation of the adhesive S-N data is explored and modifications necessary to reflect the effects of biaxiality in loading and also the presence of a carrier cloth are assessed. The fatigue failure results are also compared with results obtained under monotonic biaxial loading conditions.

Electro-flexure response of multi-functional natural fiber hybrid composites

2020 ◽  
pp. 073168442095739
Author(s):  
Christopher Meninno ◽  
Vijaya Chalivendra ◽  
Yong Kim
Keyword(s):  
Carbon Fiber ◽  
Carbon Fibers ◽  
Fiber Length ◽  
Natural Fiber ◽  
Hybrid Composites ◽  
Electrical Response ◽  
Linear Increase ◽  
Resistance Change ◽  
Flax Fibers ◽  
Flexural Loading

An experimental study was conducted to investigate the electro-flexure response of conductive natural fiber hybrid laminate composites. The composites were composed of laminates of jute and flax fibers, and the composites were subjected to flexural loading for the electrical and bending response. Multi-walled carbon nanotubes were shear mixed and ultrasonicated into the epoxy matrix. Short carbon fibers were reinforced in-between the laminates using “wet flocking” technique. To measure the electrical response under flexural loading, a four-point circumferential probe method was used. A parametric study was conducted to investigate flexural performance and damage sensing by varying carbon fiber lengths (150 and 350 µm) and the carbon fiber densities (500, 1000, 1500, and 2000 fibers/mm2). The addition of carbon fibers decreased the flexural strength for most of the cases, however increased the flexural strain at break for all composites of carbon fiber length of 150 µm. During the nonlinear deformation, the composites of carbon fiber length of 150 µm demonstrated a linear increase in resistance; however, that of carbon fiber length of 350 µm showed increasing slope of resistance. Overall, the composites of carbon fiber length of 350 µm showed lower resistance change at break compared to that of carbon fiber length of 150 µm.

scholarly journals Steroidogenesis in the NCI-H295 Cell Line Model is Strongly Affected By Culture Conditions and Substrain

2020 ◽  
Vol 128 (10) ◽  
pp. 672-680
Author(s):  
Max Kurlbaum ◽  
Silviu Sbiera ◽  
Sabine Kendl ◽  
M. Martin Fassnacht ◽  
Matthias Kroiss
Keyword(s):  
Culture Media ◽  
Hormone Secretion ◽  
Culture Conditions ◽  
Cell Culture Supernatant ◽  
Aldosterone Secretion ◽  
Liquid Chromatography Tandem Mass ◽  
Individual Strain ◽  
Growing Conditions ◽  
The Individual ◽  
Cell Banks

Abstract Context NCI-H295 cells are the most widely used model for adrenal steroidogenesis and adrenocortical carcinoma and have been used for decades in laboratories worldwide. However, reported steroidogenic properties differ considerably. Objective To evaluate heterogeneity of steroidogenesis among NCI-H295 cell strains, clarify the influence of culture media and test response to inhibitors of steroidogenesis by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Methods NCI-H295 cells were obtained from two cell banks and cultivated in different media. An LC-MS/MS-based panel analysis of thirteen steroids was adapted for cell culture supernatant. Cells were treated with metyrapone, abiraterone and mitotane. Results Mineralocorticoid synthesis was strongly affected by passaging as reflected by reduction of aldosterone secretion from 0.158±0.006 to 0.017±0.001 µg/106 cells (p<0.05). Relevant differences were also found for cells from two vendors in terms of aldosterone secretion (0.180±0.001 vs. 0.09±0.002 µg/106 cells, p<0.05). Selection of medium strongly impacted on cortisol secretion with>4-fold difference (40.6±5.5 vs. 182.1±23 µg/106 cells) and reflected differential activation of the glucocorticoid pathway. Exposure to abiraterone, metyrapone and mitotane resulted in characteristic steroidogenic profiles consistent with known mechanism of drug action with considerable differences in metabolites upstream of the blocked enzyme. Conclusion We demonstrate that steroid hormone secretion in NCI-H295 cells is strongly affected by the individual strain, passage and growing conditions. These factors should be taken into account in the evaluation of experiments analyzing steroid parameters directly or as surrogate parameters of cell viability.

scholarly journals Analysis of production parameters of single-lap bonds adhesive bonded with composites based on aluminium filler 

2017 ◽  
Vol 63 (No. 1) ◽  
pp. 36-44 ◽  
Author(s):  
Müller Miroslav
Keyword(s):  
Adhesive Bonding ◽  
Epoxy Adhesive ◽  
Polymer Particle ◽  
Material Strength ◽  
Adhesively Bonded ◽  
Metal Sheets ◽  
Bonded Joint ◽  
Negative Effect ◽  
Adhesively Bonded Joint ◽  
Agricultural Machines

In the area of bonding of sheets of metals, mainly in construction of transport and agricultural machines, single-lap bonds are used. In manufacturing corporations focused on bonding of the metal sheets the technologies such as riveting, welding and adhesive bonding are particularly used. These methods are frequently combined. The aim of the research was the evaluation of lap length of alloy AlCu4Mg adhesively bonded using two component epoxy adhesive, which is commonly used in construction of machines and its modification based in addition of filler in form of aluminium microparticles. The secondary aim of the research was to ascertain the influence of microparticle volume of aluminium filler on mechanical properties of polymer particle composite. Strength of adhesively bonded joint depends on the thickness of the bonded material. Strength of the adhesively bonded joint is dependent on the lapping length of adhesively bonded material. The highest values of strength of adhesively bonded joint were reached with the coefficient of the proportional length 0.27 ± 0.01. The assumption about negative effect of filler on tensile strength during the experiments was not confirmed. 

Fracture mechanisms of softwood under longitudinal tensile load at the cell wall scale

Holzforschung ◽  
2020 ◽  
Vol 74 (7) ◽  
pp. 715-724 ◽  
Author(s):  
Dong Wang ◽  
Lanying Lin ◽  
Feng Fu ◽  
Mizi Fan
Keyword(s):  
Cell Wall ◽  
Growth Ring ◽  
Middle Lamella ◽  
Tensile Load ◽  
Initial Crack ◽  
Tensile Fracture ◽  
Fracture Mechanisms ◽  
Wood Grain ◽  
Fracture Types ◽  
Transverse Strains

AbstractThis study was undertaken to elucidate the longitudinal tensile fracture behaviors of softwood at the cell wall scale by means of microscopic analyses. The fracture types of the tracheids at the different fracture surfaces were also distinguished. The results indicated that the main tracheid fracture of the earlywood (EW) sample was transverse transwall breakage. The tracheid fracture process of the transverse transwall breakage was initiated as a fracture in the S2 layer, with the crack propagating into the S1/S2 interface. For the EW/latewood (LW) sample, the strain concentration and initial crack under longitudinal tensile load generally occurred in wood rays in the EW part, which caused the tracheids to experience transverse transwall breakage. The differences in longitudinal and transverse strains between EW and LW under longitudinal tensile load led to shear stress and parallel-to-grain cracks occurring at the growth ring border. When the crack propagated along the wood grain in the EW tissue or growth ring boundary, this resulted in EW longitudinal transwall breakage. However, when the crack propagates along the wood grain in the LW tissue, it could cause the LW tracheid to undergo intrawall breakage, with the crack occurring predominantly at the compound middle lamella (CML)/S1 interface region.

Assessment of Homogeneity of Extruded Alumina-SiC Composite Rods Used in Microwave Heating Applications by Impedance Spectroscopy

2013 ◽  
Vol 1538 ◽  
pp. 323-328
Author(s):  
Justin R. Brandt ◽  
Rosario A. Gerhardt
Keyword(s):  
Electrical Conductivity ◽  
Electrical Response ◽  
Percolation Model ◽  
Homogeneous Distribution ◽  
Impedance Response ◽  
Silicon Carbide Whiskers ◽  
Percolation Behavior ◽  
Sic Whiskers ◽  
The Individual

ABSTRACTComposite rods consisting of Alumina (Al2O3) and Silicon Carbide whiskers (SiCw) are used to fabricate microwave cooking racks because they effectively act as a microwave intensification system that allows cooking at much faster rates than conventional microwave ovens. The percolation behavior, electrical conductivity and dielectric properties of these materials have been reported previously. However, it has been observed that the electrical response of the extruded bars is a function of the rod length and that long rods show substantially different behavior than thinner disks cut from them. A percolation model has been proposed that describes the effect of the alignment of the semiconducting SiC whiskers and the quality of the interfaces present in the composite rods: SiC-SiC and SiC-Al2O3-SiC for example. This study was undertaken with the goal of testing out whether the response of the individual sections could be used to generate the response of the full length rods and to assess the importance of the homogeneous distribution of the SiC fillers on the resultant impedance response.

Tensile Strength Prediction of Woven Composite Bonded Joint

2010 ◽  
Vol 139-141 ◽  
pp. 59-62 ◽  
Author(s):  
Jian Yu Zhang ◽  
Yue Fu ◽  
Li Bin Zhao ◽  
Hai Feng Chang ◽  
Bin Jun Fei
Keyword(s):  
Damage Model ◽  
Tensile Load ◽  
Numerical Prediction ◽  
Progressive Damage ◽  
Woven Composite ◽  
Damage Propagation ◽  
Three Samples ◽  
Final Failure ◽  
Bonded Joint ◽  
Out Of Plane

A progressive damage method is adopted to predict the structural strength of a woven out-of plane composite bonded π joint. A 3D progressive damage model is established and analyzed via a user defined subroutine embedded into the general FEA package. The numerical prediction gives the information of damage onset, damage propagation and final failure pattern, initial and final failure strength. Three samples of woven composite π joint under tensile load are tested to verify the numerical results. The numerical prediction agrees well with the experimental outcomes. All the numerical and experimental results provide insight into the basic understanding of static strength of woven composite bonded π joint.

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