Tensile Adhesion Strength Research Articles

The compressive strength of concrete retrofitted with wind ash and steel slag pozzolans with a water-cement based polymers

Freeze and thaw phenomena in cold regions are the main cause of severe damage to concrete structures. Alkaliactivated slag repair mortars, which are introduced as a suitable material for the replacement of Portland cement, can be used as the protective coating for these damaged structures. The mechanical properties and durability of this coating layer should be studied. In this study, the mechanical properties and durability of alkali-activated slag repair mortars with silica fume (SF) participation as inorganic additives against freeze-thaw and salt scaling attacks have been investigated. In order to evaluate the effects of alkaline activators type, the ratio of these solutions to Pozzolan (Pozz), and the use of SF as a substitute base material, these three factors were considered as the main variables to produce 12 alkali-activated slag mortar mixtures. To investigate their mechanical properties, compressive strength, tensile adhesion strength, and drying shrinkage tests were conducted. Also, mortar specimen length change, compressive strength loss, weight loss, and dynamic elastic modulus were measured to evaluate the durability features against freeze-thaw and salt scaling attacks. According to the results, in addition to higher compressive strength and adhesion resistance of alkali-activated slag repair mortars, these mortars showed at least 30% better durability against freeze-thaw and salt scaling attacks than cement-based repair mortar. Also, alkali-activated slag mixtures containing potassium hydroxide, alkaline solution (AS) to Pozz ratio of 0.7, and SF had the best mechanical properties and frost resistance among all mixtures.

Mechanical properties and durability of alkali-activated slag repair mortars containing silica fume against freeze-thaw cycles and salt scaling attack

Freeze and thaw phenomena in cold regions are the main cause of severe damage to concrete structures. Alkaliactivated slag repair mortars, which are introduced as a suitable material for the replacement of Portland cement, can be used as the protective coating for these damaged structures. The mechanical properties and durability of this coating layer should be studied. In this study, the mechanical properties and durability of alkali-activated slag repair mortars with silica fume (SF) participation as inorganic additives against freeze-thaw and salt scaling attacks have been investigated. In order to evaluate the effects of alkaline activators type, the ratio of these solutions to Pozzolan (Pozz), and the use of SF as a substitute base material, these three factors were considered as the main variables to produce 12 alkali-activated slag mortar mixtures. To investigate their mechanical properties, compressive strength, tensile adhesion strength, and drying shrinkage tests were conducted. Also, mortar specimen length change, compressive strength loss, weight loss, and dynamic elastic modulus were measured to evaluate the durability features against freeze-thaw and salt scaling attacks. According to the results, in addition to higher compressive strength and adhesion resistance of alkali-activated slag repair mortars, these mortars showed at least 30% better durability against freeze-thaw and salt scaling attacks than cement-based repair mortar. Also, alkali-activated slag mixtures containing potassium hydroxide, alkaline solution (AS) to Pozz ratio of 0.7, and SF had the best mechanical properties and frost resistance among all mixtures.

Stacking of 2D materials containing a thin layer of hexagonal boron nitride using polycaprolactone

To date, even though many transfer methods for 2D materials have been developed, direct transfer of very thin (< 5 nm) hexagonal boron nitride (hBN) and a monolayer of hBN has been elusive. Herein, a novel transfer method for hBN, including monolayer hBN, is introduced that can form various stacks with many 2D materials. Polycaprolactone (PCL) was selected for the method due to its low melting point and softness at room temperature. With PCL, the stacking method was easily controlled, allowing the formation of many stacks with graphene and hBN. When 2D material transfer was attempted using PCL of various molecular weights, higher molecular weight PCL yielded better results. With increasing average molecular weight, the tensile strength, elongation, and adhesion strength of the PCL sample increased. Higher molecular weight and lower molecular weight distribution assisted in the easy and clean transfer of 2D materials.

Обзор методов оценки прочности сцепления газотермических покрытий

The paper presents the comparative analysis of existing methods for accessing the adhesive strength of thermally sprayed coatings on witness samples and products in research and industrial laboratories. The adhesive method of normal separation for cylindrical witness samples with a diameter of 25 mm, a height of 16...45 mm and a coating thickness of at least 0.2 mm is pointed out among the quantitative approaches described in both international and domestic standards. An alternative pin test having no restrictions on the ultimate strength of adhesion was used to evaluate conical witness samples with an end section diameter of 1.5...2.0 mm and a coating thickness of 0.3...0.5 mm. The shear method presents two possible adhesion measurement tests: with cylindrical witness samples having the diameter of 25 mm, the width of the annular coating section of 4 ... 30 mm and the thickness of the working layer not exceeding 0.1 mm and prismatic ones with linear dimensions of shear section of 2.5...5.0 mm and the coating thickness of at least 0.25 mm. During the tests all methods were characterized by irregular loading of the flat section of the coating. Mathematical models for calculating the actual value of the tensile and shear adhesion strength are presented, taking into account the appearance of additional bending and shear forces when loading the coating.

A Compact Icing Research Tunnel for Ice Adhesion Characterization

A compact icing facility is developed to allow the measurement of ice adhesion tensile stress and fracture energy of aerospace impact ice, in coordination with thermal measurements, to ensure a well-characterized thermal environment. The facility was 1.5 m wide, 1.5 m long, and 2.1 m tall, and the tunnel is equipped with a single MOD-1 spray nozzle to produce a cloud of supercooled droplets at the targeted mean volumetric diameter for a liquid water content range from 2 to . The compact icing research tunnel (CIRT) was used to generate ice accretion on an aluminum test specimen, which was then measured to determine the ice tensile adhesion strength for two conditions: impact ice and static ice. The static ice was made by freezing motionless deionized water on the aluminum test specimen, whereas impact ice was obtained as a result of water droplets freezing after impacting the specimen at the velocity of about , with air and surface temperature both at . It was found that the substrate temperature increased significantly through the accretion process, to about 5°C for static ice and 7°C for impact ice (where the latter includes a significant increase in humidity).

Glass‐rigid foam composite for innovative concrete sandwich elements

AbstractIn building envelopes, sandwich elements with facings made of glass currently require either adhesives or mechanical connectors. The avoidance of any connectors seems to be favorable in terms of resource and energy savings both in production and in building envelopes. The present studies are part of the development of a glass‐rigid foam‐concrete sandwich element without additional adhesives and mechanical connectors. This paper reports on the structural bond behavior between polyurethane rigid foam and float glass with different surfaces with or without applying a bonding agent. Tensile bond and shear tests show, that a sandblasted toughened glass surface results in cohesive failure of the insulation layer. The two production‐related surfaces of float glass are defined as atmosphere and tin side. Both surfaces offer an adhesive failure between the insulation layer and glass. Test specimens of glass and insulation layer without bonding agent show no significant differences between the atmosphere and the tin side. Overall, the test specimens with bonding agents achieve higher levels of adhesive tensile bond and shear strength. Light and electron microscopic studies of fractured surfaces show, that the bonding agent has a significant influence on the wetting and pore formation of the liquid polyurethane.

The Mechanical Mechanism and Influencing Factors of Ice Adhesion Strength on Ice-Phobic Coating

Ice accretion can cause problems on polar ships, ocean platforms, and in other marine industries. It is important to understand the interface debonding behavior between ice and the surface of equipment. In this work, we created a mechanical model to analyze the interface debonding behavior between a square-based ice cuboid and an elastic coating base, using contact mechanics and fracture mechanics. Three-dimensional (3D) finite element (FE) simulation was used to simulate the interface debonding for normal and shear separation. A bilinear cohesive zone model (CZM) was used to simulate the interface between the ice cuboid and the elastic coating. We investigated the effect of the elastic modulus E of an elastic film on the critical detachment force Fc for normal and shear separation. The results showed that Fc increases with an increase of the elastic modulus of the elastic film. When E exceeds a certain level, Fc achieves a constant value and then remains stable. Finally, a series of epoxy/polydimethylsiloxane (PDMS) interpenetrating polymer-network (IPN) gel coatings with different elastic moduli were prepared. The ice tensile and shear adhesion strengths (σice and τice) of the coatings were measured. The results were roughly consistent with the results of the numerical simulation when E &lt; 1 MPa.

Application of bromocresol purple dye for plaster drying time determination

This paper verified the efficiency in using the acid-base indicator of bromocresol purple (BCP) dye to determine the moment when gypsum plaster reaches the dry state. For this purpose, the materials used were characterized by X-ray diffraction and by scanning electron microscopy (SEM). We determined the following parameters: workability time, geometric porosity, compressive strength, hardness, and tensile adhesion strength. Two dosages of the indicator, 1.6% and 3.2%, were tested and compared with the reference, and we observed that the addition of the indicator did not change the workability time of the paste. In addition, the values of compressive strength, hardness, and tensile adhesion strength, at the 1.6% dosage, were 6.41 ± 0.59 MPa, 14.19 ± 1.08 N·mm2 and 0.48 ± 0.24 MPa, respectively. At the 3.2% dosage, the values obtained for those properties were 5.55 ± 0.67 MPa, 13.81 ± 0.88 N·mm2 and 0.46 ± 0.23 MPa. Moreover, we verified that the BCP indicator can be used to determine the drying of the gypsum plaster coating, either through the analysis of the color change in the sample surface or by using reflectance spectroscopy.

Tensile Strength and Structure of the Interface between a Room-Curing Epoxy Resin and Thermoplastic Films for the Purpose of Sensor Integration.

The article presents a study on the adhesion of thermoplastic films to a room temperature-hardening epoxy resin, which deals with an important question on sensor integration into fibre composites. By means of a morphological box, a test specimen is developed, which allows to test strength values for the adhesion of thermoplastic films to epoxy resin. Polyimide (PI), which is typically used as a carrier material for flexible sensors, is compared with the thermoplastics polyetherimide (PEI), polyethersulfone (PES) and polyamide 6 (PA6). To evaluate the spatial formation of the interface, images taken with a light microscope, fluorescence microscope and electron microscope and an energy-dispersive X-ray spectroscopy (EDX) analysis are presented. The images show that during the curing process of the epoxy resin the initially expected pronounced interphase does not form. In this respect, it is surprising that PEI achieves such a high adhesion strength even without extended interphase formation, that the failure of the test specimen occurs in the epoxy resin region at a tensile stress of 70 MPa and not at the interface between epoxy and PEI, as might initially be assumed. It is also surprising that PES exhibits the lowest adhesion strength of 5 MPa to room temperature-hardening epoxy resin, although in previous investigations it was often used as a soluble toughness modifier for epoxy resins. The tensile adhesion strength of PI to epoxy resin was found at 27 MPa and the tensile adhesion strength of PA6 to epoxy resin was found at 13 MPa. For sensor integration, the findings mean that flexible sensors on PEI substrates promise a low tendency to delaminate even in the room temperature-hardening epoxy resin used, while the other materials tested indicate an increased tendency to delaminate.

Effect of Powder Particle Size and Spray Parameters on the Ni/Al Reaction During Plasma Spraying of Ni-Al Composite Powders.

It was known for long that Ni-Al composite powders can be used to deposit self-bonding coating as a bond coat for common ceramic coatings due to the exothermic reaction between Ni and Al. However, it was found that with commercial Ni-Al composite powders with a large particle size, it is difficult to ignite the self-propagating reaction between Ni and Al to form Ni-Al intermetallics by plasma spraying. In this study, Ni-Al composite powder particles of different sizes were used to prepare Ni-Al intermetallics-based coatings by plasma spraying. The dependencies of the exothermic reaction between Ni and Al and the coating microstructure on powder particle size and spray parameters were investigated. The phase composition, microstructure, porosity and oxide content of the coatings were characterized by x-ray diffraction, scanning electron microscope and image analyzing. The results show that particle size of Ni-Al composite powders is the dominant factor controlling the exothermic reaction for the formation of Ni-Al intermetallics during plasma spraying. When the powders larger than about 50 μm are used, the reaction forming aluminide cannot complete even by heating of plasma flame generated at high plasma arc power. However, when smaller powders less than 50 μm are used, the exothermic reaction can completely occur rapidly in plasma spraying, contributing to heating of Ni-Al droplets to the highest temperature for development of the self-bonding effect. The positive relationship between molten droplet temperature and tensile adhesive strength of the resultant coatings is recognized to confirm the contribution of high droplet temperature to the adhesive or cohesive strength.

Evaluation of Tensile Adhesion Strength in Simulated Dust Cakes on Fabric Filters

AbstractBased on the results of a 3D simulation of cake formation on characteristic filter models for fabric filters with different surface structure, the tensile adhesion strengths in simulated dust cakes are evaluated on the basis of the resulting inhomogeneous local porosity distribution of the particle packing by calculating fracture points at a balance between adhesion and detaching strengths. Both the evaluation method itself and the evaluation results for a computation example are presented and discussed. A significant proportion of fracture points are found in deeper levels in the filter medium, and the distribution of tensile adhesion strengths there differs strongly from the distributions in top levels of the filter medium. The fracture points in the top layer of the filter medium, where a special surface texture is generated, can contribute a considerable part of the tensile adhesion strengths over the whole filter area.

Influence of the finish-machining by turning and diamond smoothing on the tribological properties of Fe17Cr2Ni0.2C thermally sprayed coatings

In the presented work, cylindrical specimens of aluminium EN AW-5754 are pre-machined by turning to provide fine-structured surfaces before the subsequent coating with Fe17Cr2Ni0.2C by Atmospheric Plasma Spraying (APS). The pre-machining is done with specific MCD-tipped tools that generate helical dovetail structure elements in μm-range and offer high adhesive tensile strength of the applied coating. In this way, finish-machining of the iron based coating is possible. It is carried out at varied tool feed (0.05 mm – 0.15 mm) by turning with CBN-tipped indexable inserts. Depth of cut (0.05 mm) and cutting speed (250 m/min) are kept constant. Specimens are then machined by diamond smoothing with different radial forces (50 N – 200 N), constant tool feed (0.05 mm), and constant machining speed (100 m/min). Properties and geometric features of the machined surfaces are characterised by tactile measurement, 3D laser scanning microscopy, SEM, and tribological analyses. The analyses include the determination of opened pores and pulled-out coating material, that are brought together in the combined surface parameter of the valley void volume. Machining by diamond smoothing after turning generally leads to decreased surface roughness. In addition, the smoothing forces lead to increased absolute values of surface-near compressive residual stresses.The results of this work contribute to the substitution of common honing processes as finish machining steps of thermal spray coatings, especially focussing on the non-homogeneous character of these coatings. In this work, for the specific application and when comparing similar surface finish qualities, it is proven that at diamond smoothing results in less tool wear than finish-machining by turning. As a main result, a material and energy efficient finish-machining process for thermal spray coatings is positively evaluated.

The effect of curing mode of dual-cure resin cements on bonding performance of universal adhesives to enamel, dentin and various restorative materials.

The effect of curing mode of dual-cure resin cements on the tensile bond strength (TBS) of universal adhesives to enamel, dentin, zirconia, lithium disilicate ceramics (LDS), feldspathic porcelain (FP), and a Pd-Au alloy was evaluated. The substrates were bonded using Tokuyama Universal Bond (TUB) or Scotchbond Universal Adhesive (SBU), followed by luting with Estecem II (ECII) or Rely-X Ultimate (RXU), respectively, which were used either in light-curing or self-curing mode. The TBS test was performed after 24 h or 5,000 thermal cycles. Light-curing significantly improved the 24-h TBS of TUB/ECII to enamel, dentin and FP, as well as the TBS of SBU/RXU to all substrates except LDS. After thermal cycling, light-curing significantly increased the TBS of both adhesives/cements to dentin, but significant differences between curing modes were seldom observed for other substrates. This suggested that light-curing is essential for the hydrophilic dentin, but self-curing might be sufficient for other substrates.

Ultrastretchable, self-adhesive, strain-sensitive and self-healing GO@DA/Alginate/P(AAc-co-AAm) multifunctional hydrogels via mussel-inspired chemistry

For conductive hydrogels applied in biosensors, wearable devices and so forth, multifunctionality is an inevitable trend of development to meet various practical requirements and enhance human experience. Herein, inspired by nanocomposite, double-network (DN) and mussel chemistry, a new Graphene oxide@Dopamine/Alginate/Poly(acrylic acid-co-acrylamide) [GO@DA/Alginate/P(AAc-co-AAm)] hydrogel was fabricated through one-pot in-situ radical copolymerization. GO@DA nanofillers, prepared via GO confined DA polymerization, imparted the hydrogel with remarkable adhesiveness. Alginate/P(AAc-co-AAm) DN matrix, physically and chemically crosslinked by Fe3+ and N,N'-Methylenebisacrylamide, made hydrogels ultrastretchable, self-healing and biocompatible. With contents of DA and alginate accurately regulated, the tensile strength, elongation, adhesion strength and conductivity of the optimal hydrogel could reach 320.2 kPa, 1198 %, 36.9 kPa and 3.24 ± 0.12 S/m, respectively. What’s more notable was that the synergistic integration of repeatable adhesiveness, strain sensitivity, use stability, self-healing ability and biocompatibility provided such hydrogels with tremendous possibility of practical application for strain sensors.

Numerical modelling of bond behaviour between steel and CFRP laminates with a ductile adhesive

Ductile adhesives are more appropriate than brittle adhesives for steel structure strengthening by adhesively bonding carbon fibre reinforced polymer (CFRP) due to its greater strain capacity, leading to larger loading and deformation capability. This paper investigated the bond behaviour of CFRP-to-steel joints bonded with a ductile adhesive via numerical studies. Single lap pull tests were also conducted, and the load-displacement relationship at the loaded end and the strain distribution along the CFRP plate were examined. A bond-slip relationship was derived from the test, and based on this, an isosceles trapezoid bond-slip model was proposed. A finite element model was developed for FE analysis of the bond behaviour of the CFRP to steel interface by using the proposed bond-slip model. The finite element model was used to model the experiments, and the good agreement between the experimental results and numerical results demonstrate the effectiveness and accuracy of the finite element model. Finally, a systemically parametric analysis was performed to investigate the effect of FRP modulus, adhesive equivalent strain, adhesive tensile strength and adhesive thickness on initial stiffness, effective bond length and ultimate load. Finally based on the numerical results, a model of effective bond length was proposed.

A high throughput tensile ice adhesion measurement system

A prerequisite for designing materials with low adhesion to ice is to accurately measure the ice adhesion strength of the surface. The majority of studies in this field have typically focused on manipulating and measuring the adhesion strength of different materials under shear stress. Among them, elastomers have proven to be promising ice-phobic surfaces because they enable interfacial cavitation, a tension-driven surface instability. In this work, a high throughput, low cost device is designed to measure the tensile ice adhesion strength of different surfaces. The design and construction of the tensile ice adhesion measurement system is presented, along with the reasoning for the design decisions. The performance of the setup is characterized using experimental trials varying parameters such as temperature, pull-off speed, thickness of the substrate, and ice/substrate interfacial area, to verify the precision of the measurements.

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

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.

Assessment of the Constancy of Performance of Cementitious Adhesives for Ceramic Tiles: Analysis of the Test Results Commissioned by Polish Market Surveillance Authorities

Assessment and verification of constancy of performance (AVCP) is a complex process. Without it, the manufacturer cannot mark the product with the Conformitè Europëenne (CE) marking and place it on the EU market. The verification of the correctness of the AVCP is carried out by market surveillance. In Poland, supervision authorities regularly check manufacturers by collecting construction products that exist on the market for inspection. Among the dry-mix mortars, adhesives for ceramic tiles (CTA) constitute an essential group. The requirements for CTAs are specified in EN 12004. According to the standard, the basic characteristics of cementitious CTAs are tensile adhesion strength and open time. The adhesion measurements are performed after various laboratory conditions tests. The study analyzes the results obtained for 129 samples of cementitious CTAs, collected between the years 2016 and 2019 from the market, and tested in notified laboratories at the request of Polish construction supervision authorities. Many tested products did not meet the threshold values, which resulted in removing them from the market. The paper discusses the complexity of the tensile adhesion strength measurement. The obtained test results are considered in various dimensions, including using the simple acceptance rule method when evaluating the results, which does not consider the measurement uncertainty.

On the role of substrate temperature into bonding mechanism of cold sprayed Titanium Dioxide

Metal oxide, Titanium dioxide, TiO2 draw a huge attention due to its wide range of applications, chemical stability and low cost. TiO2 coatings have potential applications in biomedical implants or as photo-catalytic functional systems. Cold spraying is a process where small particles ranging from 1 to 50µm are stimulated by a stream of supersonic gas at a temperature below material melting point and leading to the coating formed in solid state particles. The aim of the present study was to investigate the influenced of once heated substrate properties on bonding mechanism of cold sprayed Titanium dioxide, TiO2. In this study, tensile adhesion strength, substrate hardness, oxide thickness, oxide composition and interfacial microstructure were evaluated for the coatings. The results of this study indicated that coating adhesion strength reveal a decreased trend from 1.35MPa to 0.49MPa when once heated substrate temperature is increased. Influenced of oxide thickness also will be discussed here as factor that contributed to bonding mechanism between TiO2 and copper substrate.

Study of the incorporation of fabric shavings from the clothing industry in coating mortars

The increase in waste generation in the textile and clothing industry is a reflection of population growth. In Brazil, only 20% of this waste is reused. The construction industry is one of the sectors that are able to absorb solid waste from various industrial activities, seeking alternatives for use and for waste valorization. Correspondingly, in this work, coating mortars were produced with the incorporation of fabric shavings (cement: hydraulic lime: sand at a ratio of 1:1:6 by mass), and evaluated them as reinforcement or thermal insulation materials. The waste was shredded manually to emulate the fibers that exist in the market. To analyze the influence of waste on the coating mortars properties, a 32 factorial design was performed, wherein the yarn content varied (at 1, 2, and 3% in relation to the binder mass) and the length varied at 1, 2, and 3 cm. The mortars that contained the yarns were experimentally evaluated based on flexural tensile strength and tensile adhesion strength tests. The best composition (yarn content of 3% and length of 3 cm) was subjected to a) thermal tests at 40 °C and 60 °C, b) mechanical, and c) physical tests, and their outcomes were compared with those of the reference sample (without waste). When waste was introduced in the mortars, the water/binder ratio increased to maintain the same consistency index. In the adhesion test, the mortars with waste adhered to the substrate and reached the minimum strength value required by the technical standards of 0.30 MPa. The flexural tensile strength was also higher than the established 1.0 MPa. With the exception of tensile adhesion strength, the mechanical strength of the mortar with the fabric yarns was less than that of the reference mortar. The mortar with the added waste yielded a satisfactory performance in thermal tests at 60 °C.