Modelling of the electromechanical impedance technique for prediction of elastic modulus of structural adhesives

2020 ◽  
pp. 147592172091692
Author(s):  
Zi Sheng Tang ◽  
Yee Yan Lim ◽  
Scott T Smith ◽  
Ricardo Vasquez Padilla
Keyword(s):  
Tensile Strength ◽  
Elastic Modulus ◽  
Model Updating ◽  
Dynamic Elastic Modulus ◽  
Curing Process ◽  
Electromechanical Impedance ◽  
Structural Adhesives ◽  
Reinforced Polymer ◽  
Impedance Technique ◽  
Fibre Reinforced Polymer

In order to strengthen and repair existing concrete structural elements, fibre-reinforced polymer composites are often externally bonded using structural adhesives. It is thus desirable to monitor the in situ performance of the sandwiched adhesive layer in such fibre-reinforced polymer–strengthened systems via its stiffness and strength gain throughout the curing process. The electromechanical impedance technique, which relies upon the utilisation of piezoelectric sensors, offers this capability. Although the technique has been verified experimentally in the laboratory, no known electromechanical impedance–based modelling study has been reported. This study, therefore, proposes the first electromechanical impedance–based finite element and analytical models to monitor the curing of structural adhesives. The dynamic elastic modulus of structural adhesives during curing can be determined from the developed models via a model updating process. Semi-empirical relationships were then developed to determine the tensile strength of structural adhesives from the resonance frequency obtained from the electromechanical impedance technique. This was made possible by correlation between static tensile tests on structural adhesives and the dynamic elastic modulus. These electromechanical impedance–based models were found to perform equally well when compared to the previously developed wave propagation–based models. This study shows the robustness of the electromechanical impedance technique for non-destructively predicting the dynamic elastic modulus and tensile strength of adhesives throughout the curing process.

Fabrication and Mechanical Characterization of Carbon Nanotubes-Enhanced Epoxy

2010 ◽  
Vol 168-170 ◽  
pp. 1102-1106
Author(s):  
Haydar Faleh ◽  
Lu Ming Shen ◽  
Riadh Al Mahaidi
Keyword(s):  
Carbon Nanotubes ◽  
Elastic Modulus ◽  
Bonding Performance ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Multi Walled Carbon Nanotubes ◽  
Fibre Reinforced Polymer ◽  
Walled Carbon Nanotubes ◽  
Strength And Ductility

Owing to its outstanding characteristics in good affinity to heterogeneous materials, corrosion resistance and on-the-spot processing capability, epoxy has been widely used as adhesives in retrofitting structures with carbon fibre reinforced polymer (CFRP). In this study, different weight fractions of multi-walled carbon nanotubes (MWCNTs) will be dispersed into epoxy to produce toughened adhesives that can improve the CFRP/structure bonding performance. The preliminary results indicate that adding 2% MWCNTs to Araldite-420 increase its ultimate strength by 17% and its elastic modulus by 14%. Ultrasonic mixing may increase Sikadur-30’s elastic modulus but reduce its strength and ductility regardless of the MWCNTs concentration. The mechanism of MWCNTs infusion effects on the mechanical properties of epoxy is also examined using SEM.

Preliminary Results of the Use of Hydroxyapatite as a Consolidant for Carbonate Stones

2011 ◽  
Vol 1319 ◽  
Author(s):  
Enrico Sassoni ◽  
Sonia Naidu ◽  
George W. Scherer
Keyword(s):  
Tensile Strength ◽  
Elastic Modulus ◽  
Dynamic Elastic Modulus ◽  
Capillary Absorption ◽  
Treatment Technique ◽  
Constant Weight ◽  
Lattice Match ◽  
Partial Immersion ◽  
Phase Characterization ◽  
Indiana Limestone

ABSTRACTThe effectiveness of using hydroxyapatite (HAP) as a consolidant for carbonate stones was evaluated. HAP was chosen as a consolidating agent since it is notably less soluble than calcite and has a similar crystal structure and a close lattice match to it. Among possible methods for forming HAP, the reaction between the calcite of the stone and a solution of diammonium hydrogen phosphate (DAP) in mild conditions was chosen. Indiana Limestone samples, artificially damaged by heating to 300°C for 1 hour, were treated with a 1 molar DAP solution by partial immersion and capillary absorption for 48 hours or by brushing until apparent refusal and wrapping with a plastic film for 48 hours. After washing in deionized water for 3 days and drying under a fan at room temperature until constant weight, the improvements in dynamic elastic modulus and tensile strength were evaluated. The formation of calcium phosphate phases was observed by scanning electron microscopy (SEM) and the phase characterization performed by energy dispersive X-ray spectroscopy (EDS) and electron back-scattered diffraction (EBSD). The water absorption modification after the consolidating treatment was then assessed. Results show that treated samples experienced significant increases in dynamic elastic modulus and tensile strength, as a consequence of crack reduction and pore filling consequent to HAP deposition at grain boundaries. The sorptivity of the treated samples is reduced by 26-44% (based on treatment technique), so that water and water vapor exchanges with the environment are not blocked.

scholarly journals Combined Effects of Sustained Loads and Wet-Dry Cycles on Durability of Glass Fiber Reinforced Polymer Composites

2017 ◽  
Vol 2017 ◽  
pp. 1-14
Author(s):  
Mengting Li ◽  
Jun Wang ◽  
Weiqing Liu ◽  
Ruifeng Liang ◽  
Hota GangaRao ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Elastic Modulus ◽  
Fiber Reinforced Polymer ◽  
Distilled Water ◽  
Combined Effects ◽  
Gfrp Composites ◽  
Glass Fiber Reinforced Polymer ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Sustained Loads

This paper deals with durability of glass fiber reinforced polymer (GFRP) composites under the combined effects of sustained tensile loads and wet-dry (WD) cycles. Two different solutions (distilled water and saltwater) were used to imitate the freshwater and marine environments, respectively. Tensile properties of the unconditioned and conditioned specimens were measured to study the durability of GFRP composites under these 2 effects. The response indicated that both tensile strength and elastic modulus increased initially upon WD cycles, which was attributed to both the postcuring of resin and the sustained tensile stress allowing for fastec cure. Further exposure to WD cycles in distilled water or saltwater led to a steady decrease in tensile strength and modulus. WD cycles of saltwater and distilled water have similar effects on the degradation of the tensile properties for unstressed specimens. However, the elastic modulus and elongation at rupture of stressed specimens under WD cycles of saltwater decreased more than those specimens under WD cycles of distilled water. Moreover, increase of sustained loads led to a decrease in tensile strength. Based on Arrhenius method, a prediction model which accounted for the effects of postcure processes was developed. The predicted results of tensile strength and elastic modulus agree well with those obtained from the experiments.

Temperature and damage influence on electromechanical impedance method used for carbon fibre–reinforced polymer panels

2016 ◽  
Vol 28 (6) ◽  
pp. 782-798 ◽  
Author(s):  
Tomasz Wandowski ◽  
Pawel H Malinowski ◽  
Wieslaw M Ostachowicz
Keyword(s):  
Carbon Fibre ◽  
Damage Detection ◽  
Low Frequency ◽  
Guided Wave ◽  
Impedance Method ◽  
Electromechanical Impedance ◽  
Reinforced Polymer ◽  
Guided Wave Propagation ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This article deals with damage detection process under varying temperature. Carbon fibre–reinforced polymer samples are investigated using electromechanical impedance method. In the article, influence of changing temperature on resistance in electromechanical impedance is investigated. Authors propose new approach for compensation of temperature influence on damage detection. Damage detection is based on root mean square deviation index. Due to strong damping of utilized composite material, low-frequency range is utilized in this research. Real part of electromechanical impedance is measured for frequency band 1–20 kHz. Damage is in the form of artificially made delamination with different sizes. Authors also discuss the problem of influence of structure’s boundary condition on low-frequency measurements. In the research, scanning laser vibrometry for guided wave propagation method is utilized for visualization of the introduced delamination.

Durability Performances of Aramid Fiber Reinforced Polymer as Reinforcement Material for Concrete Structures in Cold Regions

2020 ◽  
Vol 853 ◽  
pp. 171-176
Author(s):  
Shuo Zhang ◽  
Chun Lin Liu ◽  
Wen Zhu ◽  
Meng Xiong Tang ◽  
He Song Hu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Elastic Modulus ◽  
Epoxy Resin ◽  
Aramid Fiber ◽  
Fiber Reinforced Polymer ◽  
Resin Matrix ◽  
Fiber Reinforced ◽  
Freeze Thaw ◽  
Dry Air ◽  
Reinforced Polymer

A series of tests were conducted to investigate the mechanical performances of aramid fiber reinforced polymer (AFRP) and its epoxy resin matrix after 0, 20, 40, 60 and 80 freeze-thaw cycles in the dry air, respectively. After a given number of freeze-thaw cycles, the residual tensile strength and elastic modulus of AFRP specimens were measured, and the lap-shear strength of epoxy resin adhesive specimens was gained. Test results show that: (1) Variation of the elastic modulus of AFRP with the increasing of the freeze-thaw cycles exhibits the same tendency as the tensile strength did. They increase in the first 20 to 40 cycles and then decrease till the end of 80 cycles; (2) The tensile strength and elastic modulus of AFRP decreases by 5.1% and 8.2%, respectively, after 80 cycles as compared with that kept in the laboratory environments. However, the effect of the freeze-thaw cycling in the dry air on the tensile properties of CFRP is very limited within 80 cycles; (3) The freeze-thaw cycling in the dry air of this study has an adverse effect on the adhesive property of the epoxy resin, which could be regarded as the evidence for the degradation of the interface between aramid/carbon fiber and matrix.

scholarly journals Basalt reinforced concrete structures for retrofitting concrete surfaces

2018 ◽  
Vol 199 ◽  
pp. 09014
Author(s):  
Benjamin Wolf ◽  
Andrea Kustermann ◽  
Christian Schuler ◽  
Christoph Dauberschmidt ◽  
Ömer Bucak
Keyword(s):  
Tensile Strength ◽  
Reinforced Concrete ◽  
Load Capacity ◽  
Weather Conditions ◽  
Bending Test ◽  
Basalt Fibre ◽  
Bending Tests ◽  
Three Point Bending ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer

Reinforced concrete facades exist since decades exposed to natural weather conditions. Thus nowadays lot of them are damaged by carbonation induced corrosion and therefor require repairing and retrofitting. The aim of this research project is to investigate the possibilities of basalt fibre reinforced concrete as repairing material and also basalt rebars as additional strengthening reinforcement. Investigations with basalt fibre reinforced mortar prisms showed best results in 3 point bending tests, tensile strength and also compressive strength using 0.3 Vol.-% basalt fibres in mixture. The mechanical properties of basalt rebars made of basalt fibre reinforced polymer were tested, showing higher values in tensile strength and Young´s Modulus than comparable steel reinforcement samples. The basalt rebar reinforced concrete samples achieved higher ultimate loads in three-point bending test compared to SRC samples. But after failure in the bonding area no residual load capacity remained. Finally basalt reinforcement bars seems to be well suited for use as retrofitting material for facade elements, but numerous properties have to be examined in further investigations.

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