Interfacial Shear Bond Strength Research Articles

Preparation process and mechanical properties of laser cladding gradient molybdenum coating on copper alloy

Different types of Mo coatings were prepared on the surface of a copper alloy via laser cladding technology in this study to address the problem of low hardness of copper alloy current-carrying friction subsets. Meanwhile, the problems of high reflectivity of copper alloy materials to infrared laser light and mutual insolubility of Cu and Mo were solved by introducing an intermediate layer structure, and the coating process was optimized to obtain a coating with excellent formation. The microstructure, hardness, and interfacial shear bond strength of coatings were tested. Results showed that the Mo coating prepared using a plasma-spheroidized powder had a lower dilution rate and finer and tighter grain growth compared with the Mo coating prepared by crushing agglomerated powder. The coating phase mainly consisted of Mo, Ni3Mo, MoO2, and Cu0.81Ni0.19. The unfused particles present in the plasma-spheroidized powder coating acted as a second hard reinforcing phase, which could significantly increase the hardness of the coating. Three kinds of coatings exhibited strong bond strength, and coatings prepared from different powders fractured in diverse ways. In sum, the plasma-spheroidized Mo coating prepared using the three-way powder feeding method not only had good formation but also possessed the most excellent mechanical properties.

Interfacial bond strength of coloured SCC repair layers: an experimental and optimisation study

ABSTRACT This study investigates experimentally and analytically the interfacial bond strength of coloured SCC repair layers. Ten SCC mixes with 5%, 10% and 15% of blue, green or red pigments were produced to examine their fresh properties. Subsequently, 60 coloured SCC specimens were tested to assess interfacial bond strength using pull-off and push-out tests. The results confirm that pigments reduce the mechanical properties of SCC and its bond strength to concrete substrates, with red pigment reducing (by up to 41%) interfacial bond strength. It is shown that the push-out test is effective to determine the interfacial shear bond strength between the SCC repair layers and substrates. A GNNC-Modified PSO algorithm is proposed to calculate accurately (R2 = 0.95) the interfacial bond strength of coloured SCC repair layers. This study contributes towards developing more effective test methods and more accurate models to calculate interfacial bond strength of the SCC repair layers used in this study.

Effect of Resin Cement at Different Thicknesses on the Fatigue Shear Bond Strength to Leucite Ceramic.

This in vitro study was performed to evaluate fatigue survival by shear test in the union of leucite-reinforced feldspathic ceramic using different cement thicknesses. Leucite-reinforced glass ceramics blocks were sectioned in 2-mm thick slices where resin cylinders were cemented. The samples were distributed in two experimental groups (n = 20) according to the cement thickness (60 and 300 μm). The specimens of each group were submitted to the stepwise fatigue test in the mechanical cycling machine under shear stress state, with a frequency of 2 Hz, a step-size of 0.16 bar, starting with a load of 31 N (1.0 bar) and a lifetime of 20,000 cycles at each load step. The samples were analyzed in a stereomicroscope and scanning electron microscopy to determine the failure type. There is no significant difference between the mean values of shear bond strength according to both groups. Log-rank (p = 0.925) and Wilcoxon (p = 0.520) tests revealed a similar survival probability in both cement layer thicknesses according to the confidence interval (95%). The fracture analysis showed that the mixed failure was the most common failure type in the 300-μm thickness group (80%), while adhesive failure was predominant in the 60-μm thickness group (67%). The different cement thicknesses did not influence the leucite ceramic bonding in fatigue shear testing; however, the thicker cement layer increased the predominance of the ceramic material failure. The resin cement thicknesses bonded to leucite ceramic did not influence the long-term interfacial shear bond strength, although thicker cement layer increased the ceramic material cohesive failure. Regardless the cement layer thickness, the shear bond strength lifetime decreases under fatigue.

Development of an analytical framework for evaluation of critical fiber length in asphalt concrete with a fiber pullout test

The interfacial shear bond strength (τ) between fibers and matrix is typically measured by fiber pullout test to determine the critical fiber length (Lc) in fiber reinforced composites. In fiber reinforced asphalt concrete (FRAC), the τ is a time-dependent property and it is affected by asphalt modulus. The main objective of this study was to establish a relationship between the τ and modulus of asphalt mastic and asphalt concrete (AC), from which the Lc in AC was determined. Results from direct tension test, performed to validate the analytical framework, suggested that the use of longer fibers (38-mm vs 19-mm) showed higher reinforcement efficiency in FRAC.

An experimental study on interfacial bond strength between hybrid engineered cementitious composite and concrete

In this research, an experimental study was conducted to investigate the interfacial bond strength of polyvinyl-alcohol fibre reinforced engineered cementitious composite (PVA-ECC) and steel-polyvinyl alcohol hybrid fibre reinforced engineered cementitious composite (SPH-ECC) to compare the effects of using hybrid fibre ECC against mono-fibre ECC and aiming to promising and effective retrofitting material for reinforced concrete structures. Slant shear tests and splitting tensile tests were performed to study the shear bonding and splitting tensile bonding behaviours, respectively. The effect of surface roughness of the concrete surface on bond strength was also studied by measuring the bond strength of surfaces with different roughness under the As-Cast (AC) and Sandblasted (SB) surface treatment conditions. Interfacial surface roughness was measured using both quantitative and qualitative assessment methods. Experimental results obtained shown that sandblasting could greatly increase the roughness of concrete surfaces and lead to bond strength enhancement for both types of ECC-concrete interfaces. In addition, it was also found that for sandblasted surface, more significant increase was observed for the SPH-ECC interface due to dowel actions of the steel fibre. This indicated that SPH-ECC is a more suitable repairing/retrofitting material than PVA-ECC when sandblasting is applied. Finally, by using logarithmic regression, empirical relationships were proposed to predict the relationships of interfacial shear bond strength with the surface roughness of concrete.

CNT toughened aluminium and CFRP interface for strong adhesive bonding

This study presents a simple technique for strengthening the adhesive-bond strength between aluminium (Al) substrate and carbon fibre reinforced polymer (CFRP) utilising resin pre-coating (RPC) with carbon nanotubes (CNTs). The CNT-containing RPC solution with 90 ​wt% acetone and 10 ​wt% resin (without hardener) was applied onto Al substrates, where micro-/nano-vertical channels had been created by chemical or mechanical surface treatments to accommodate CNTs. RPC was able to fill all micro-/nano-cavities over the Al substrate surface, then CNTs were pulled into those vertical micro-channels by the capillary action generated from acetone evaporation. Normal epoxy adhesive (resin ​+ ​hardener) was applied after the CNT-containing RPC treatment. CNTs bridging across the interface between the adhesive joint and Al substrate and sealing of micro-/nano-cavities by RPC effectively enhanced the interfacial shear bond strength between the Al substrate and CFRP by 30–100% depending on the Al substrate surface profiles. Al substrates with two different chemical treatments were compared in this study for the effectiveness of CNT interfacial reinforcement. Results from a steel substrate after sandblasting were also included for comparison.

Influence of nano-TiO2 on the wellbore shear bond strength at cement-formation interface

Abstract This research investigates the wellbore shear bond strength of nano-TiO2-containing oil-well cement pastes with particle sizes of 20 and 40 nm. The nanoparticles were picked by the weight of cement at proportions corresponding to 1, 2, 3 and 4%. Test results indicated that nano-TiO2 significantly enhanced the interfacial shear bond strength. The results also revealed that the strength enhancement was reliant on the nano-TiO2 particle sizes. The specimens containing nano-TiO2 40 nm provided greater strength compared to 20 nm, due to effective pozzolanic activity. By fluctuating the nano-TiO2 dosages, the optimal replacement content was 3% for all particle sizes. The particle size did not affect the appropriate dosage of nano-TiO2, it only impacted the bonding strength of the interfaces. With 3% (40 nm) nano-TiO2, the 3, 7, 14 and 28 days strength increased by 557.38, 504.17, 528.57 and 412.04% respectively. The scanning electron microscope, X-ray diffraction and thermogravimetric technique were used to examine the influence of nano-TiO2 on the cement-formation bonding.

Interfacial Shear Bond Strength between Steel H-Piles and Polymer Concrete Jackets

Steel H-piles have been used widely in bridge construction throughout the U.S. because of their relatively large load-carrying capacity while occupying a small area. However, many H-piles suffer from corrosion, which may lead to abrupt collapse. A cost-effective repair technique, including encasing the corroded region of the steel pile into a concrete jacket, which acts as an alternative load path for the applied axial load, has been used by several state Departments of Transportation. Methyl methacrylate polymer concrete (MMA-PC) is a type of concrete that is commonly used as a repair material. However, there is limited research on the assessment of bond strength between MMA-PC and steel elements. This paper investigates experimentally the bond behavior of seven full-scale steel H-piles encased in concrete jackets. The jackets were cast using either MMA-PC or Portland cement concrete (CC). Different embedment lengths of 63.5 mm (2.5 in.), 127 mm (5 in.), and 190.5 mm (7.5 in.) were used for the MMA-PC and one embedment length of 254 mm (10 in.) was used for the CC jacket. Cylindrical and prismatic jacket configurations were used and tested using push-out. The experimental results revealed that using the MMA-PC jacket was more effective compared with the CC jacket in relation to the load-carrying capacity. For design purposes, a shear bond stress of 2.96 MPa [0.43 kips per square inch (ksi)] can be used for MMA-PC jackets having an embedment length of at least 127 mm (5 in.) whereas a value of 0.83 MPa (0.12 ksi) can be used for CC.

Determining Interfacial Shear Bond Strength in Thin Laminated Metal Composites

The interfacial shear bond strength is a key factor determining the ultimate mechanical properties and performances of laminated metallic composites. Conventional test method is hard to accurately obtain the interfacial shear bond strength of the thin laminated metallic composites (TLMCs) because of the thin thickness and low rigidity. In this paper, an improved uniaxial tensile testing specimen to overcome the difficulty is designed by removing a portion of the cladding of the tensile specimen. The delaminated fracture strain of the cladding peeling off from the substrate can be obtained accurately during a uniaxial tensile test. The relationships among interfacial microstructures, delaminated fracture strain and the interfacial shear bond strength were studied. The research revealed that the delaminated fracture strain and the interfacial shear bond strength are all increased with increasing the thickness of interfacial diffusion layer. A formula available for calculating the shear bond strength was derived by analyzing the relationship of shear stress and delamination. As examples, the interfacial shear bond strengths of Al/Mg/Al TLMCs fabricated by different rolling reduction ratios were tested and investigated.

An Improved Cross-Bonded Method for Measuring Interfacial Bond Strength of Adhesives

Interfacial bond strength is one of the vital mechanical properties of adhesives. The cross-bonded method, which is widely used to measure the interfacial tensile and shear bond strength simultaneously, has attracted extensive attention. An improved cross-bonded method is presented in this study in order to promote the accuracy and reliability of the testing results. The ergo 9900 glue, E-7 glue, AB glue and 502 glue were measured in this study. Compared with the original method, the results of the improved cross-bonded method show that: (i) the coefficient of variation of the interfacial bond strength decreased significantly; (ii) the interfacial shear bond strength of the adhesives is closer to its true value.

Interfacial shear bond strength between different base metal alloys and five low fusing feldspathic ceramic systems

This study compared the bond strength between metal alloys and 5 ceramic systems. Ceramic systems (Vita VMK68, Ivoclar IPSd. SIGN, Ceramco II, Matchmaker and Finesse) were fired onto either Ni-Cr or Co-Cr base metal alloy. Metal-ceramic interfaces were subjected to shear loading until failure. The ceramic type significantly affected the bond strength results (p<0.05). For Ni-Cr alloy, the results ranged between 15.4-25.3 MPa and for Co-Cr alloy between 13.3-19.0 MPa. The highest mean bond strength value was obtained with the combination of Ni-Cr alloy-Ceramco II (25.3 MPa), the lowest bond strength was received from the combination of Co-Cr alloy-Ivoclar IPS d.SIGN ceramic (13.3 MPa). Adhesive failures between metal and ceramic were significantly more frequent with Ni-Cr alloy (31 out of 50) than with Co-Cr (20 out of 50) (p<0.05). Ceramco II presented the highest bond strength with both Ni-Cr and Co-Cr being significantly different from one another.

Evaluation of interfacial bond strength of repaired composite resins.

Background: Repair of composite restorationsis a choice if absence of caries is guaranteed. The purpose of this study was to evaluate the interfacial shear bond strength of the immediately repaired composite specimens. Materials and methods: Sixty specimens from 2 types of composite were made in a special mold and polymerized with light. Three methods of surface treatment of the initial layer were done prior to the application of the repair layer including the use of matrix strip or not and abrasion. The specimens were subjected to shear force from the testing machine and mean for each group was calculated. Results: The non–air inhibited specimens showed the highest values of shear bond strength (mean =13.1 Mpa) which was significantly different from the bur abraded specimens (p 0.05) for both types of composite. Conclusion: The absence of air inhibited layer by using matrix strip increase the interfacial bond strength of the immediately repaired composite with inferior interfacial bonding for the bur abrasion method.

Shear bond strength of repaired composite resin restorations

This study was peformed to evaluate the interfacial shear bond strength of base (direct and indirect) and repair composites with aging and surface treatment methods. Direct composite resin specimens (, Heraeus Kulzer, Germany) were aged for 5 min, 1 hour, 24 hours, and 1 week in distilled water before surface treatment, and then divided into five groups Group 1, grinding; Group 2, grinding and application of bonding agent, Group 3, grinding, etching with 37% phosphoric acid for 30sec, and application of bonding agent, Group 4, grinding, etching with 37% phosphoric acid for 30sec, silane treatment, and application of bonding agent ; Group 5, grinding, etching with 4% hydrofluoric acid for 30sec. silane treatment, and application of bonding agent. Indirect composite resin specimens (, Heraeus Kulzer, Germany) were aged for 1 week in distilled water and divided into seven groups Group 1 - Group 5, equal to Charisma specimens; Group 6, grinding, etching with 37% phosphoric acid for 60sec, silane treatment, and application of bonding agent; Group7, grinding, etching with 4% hydrofluoric acid for 60 sec, silane treatment, and application of bond-ing agent. The repair material() was then added on the center of the surface (5 mm in diameter. 5 mm in height). The shear bond strength was tested and the data was analyzed using one-way ANOVA and the Student- Newman-Keuls test. The following conclusions were drawn. 1 The shear bond strength of specimens aged for 1 hour was significantly higher in Group 2 and Group 5 than in Group 1 (p specimens aged for 1 week was signifi-cantly higher in Group 3 and Group 5 than in Group 1 (p specimens, there was significant difference between the bond strength of 24 hours and that of 1 week (p specimens, the shear bond strength of specimens aged for 24 hours was significantly higher than the others(p specimens, 5. Most of the specimens showed cohesive fractures. Artglass^{\circledR}$ specimens that were etched with acid (phosphoric or hydrofluoric) for 30 sec showed more cohesive fractures.

Stress transfer in the fibre fragmentation test

An improved micromechanics model has been developed of the stress transfer for a single fibre embedded in a matrix subjected to uniaxial loading. Debond crack growth is analysed based on the shear strength criterion such that when the interfacial shear stress reaches the shear bond strength, debonding occurs; and the average strength concept based on Weibull statistics is considered for fibre fragmentation. The influences of the interfacial shear bond strength and the fibre strength on the stress distributions in the composite constituents are evaluated (...)

Theory and Analysis of Fracture Energy in Fiber Reinforced Composites

Abstract A micro-mechanics model is developed to analyze the stress distributions and fracture energies associated with crack propagation and fiber pull-out in reinforced composites. The stress and work mechanisms of interfacial debonding, fiber deformation, and the frictional work of fiber pull-out are considered as semi-independent contributions to fracture toughness. The theoretical expressions of Cottrell for frictional work WF and Outwater and Murphy for fiber deformational work WD are obtained as special relations in a general relation for the total work WT [dbnd] Ws + WF + WD where Ws defines the matrix shear work for interfacial debonding of fiber and matrix. Three dimensional diagrams of fracture energies WT , Ws , or Wr versus interfacial shear bond strength λ0 and frictional shear stress λf identify regions of optimized fracture energy. The influence of environmental degradation of bond strength upon fracture energy is analyzed in terms of the theory.