Glue Failure Research Articles

Microstructure and properties of WC-reinforced AlCoCrFeNiSi high entropy alloy coatings prepared via high-velocity arc spraying

In this research, (AlCoCrFeNiSi)100-x(WC)x (x=0, 20 and 40 wt%) high entropy alloy (HEA) coatings were successfully deposited on the surface of Q235 steel substrate using high-velocity arc spraying method. The study investigated the presence of WC particles on the phase composition, microstructure, tensile bonding strength, and corrosion behavior of the HEA coatings. X-ray diffraction analysis revealed that without WC particles, the predominant phase in the coating was a face-centered cubic (FCC). However, when 20 wt% and 40 wt% of WC particles were added, the phase composition shifted to include FCC, body-centered cubic (BCC), W3C, Cr7C3, and other carbides. The WC particles also reduced the crystalline grain size of the coatings from 14.75 nm to 10.34 nm. The microhardness value increased from 252.5 HV0.1 to a peak of 529.9 HV0.1, as the content of WC increased representing a microhardness improvement factor ranging from 1.4 to 3 times that of the substrate. The tensile bonding strength of the coatings was also enhanced with WC content. The coating with 40 wt% WC particles demonstrated the highest tensile bonding strength of 40.23 MPa. The cohesion, adhesion, and glue failures occurred after the tensile test, with adhesion failure being more prominent in the coatings without WC particles and glue failure being more prominent in the WC-reinforced coatings. Compared to the Q235 steel substrate, the coated samples showed enhanced resistance against corrosion due to the formation of the passive oxide layers. The effective resistance against corrosion was attained when the proportion of WC particles was 20 wt%, displaying the least values for corrosion current density and corrosion rate in 3.5 wt% NaCl solution. Examination through SEM and XPS analysis indicated that the coatings’ structures and the formation of protective passive layers enhanced the corrosion resistance.

Axial Compression Testing of Bamboo-Laminated Encased Steel Tube Composite Columns

To resolve the problem of premature glue failure in square, thin-walled steel tube/bamboo-laminated composite hollow columns (SBCCs) under compression, a new type of SBCC with transverse binding bars (SBCCB) is proposed. An axial compression test was performed on nine SBCCBs to observe the compressive failure mode and analyse the influence of the net cross-sectional dimension, slenderness ratio and cross-sectional composition on the glue failure and the ultimate bearing load; the results were compared with the known limit stress of SBCCs without transverse binding bars. The experimental results indicate that the compressive damage to SBCCBs is primarily the breaking of the bamboo plywood material and glue failure between the matrix interfaces at the end and middle of the column between the binding bars. The ultimate bearing load is not only related to the dimensions of the cross section and the slenderness ratio but also impacted by the cross-sectional composition. Installing transverse binding bars can effectively reduce glue failure in the test specimens, alter the limit failure mode and significantly increase the ultimate bearing load. Compared to the limiting compressive stress on an SBCC, the limiting compressive stress on an SBCCB is 26% higher on average. A formula for calculating the axial compressive load capacity of an SBCCB was established using nonlinear regression analysis.

Effect of Substrate Surface Roughness on Microstructure and Mechanical Properties of Cold-Sprayed Ti6Al4V Coatings on Ti6Al4V Substrates

Surface condition, especially surface roughness of substrates, critically influences the adhesion of cold-sprayed titanium alloy coatings. To study this, Ti6Al4V (Ti64) coatings were deposited on Ti64 substrates with increasing surface roughness (Ra) from 0.05 µm (polished surface) to 5.4 µm (water-jet cut surface). It was found that the substrate surface roughness did not significantly affect the porosity, hardness and coating surface roughness because these properties were dependent on the deposition parameters such as propellant gas pressure and temperature and nozzle traverse speed. The adhesion test results showed that smoother substrate surfaces improved the coating bond strength of the cold-sprayed Ti64 coatings from about 7.1 MPa (Ra: 5.4 µm, interface failure) to 68.7 MPa (Ra: 0.05 µm, glue failure). The fracture characteristics of the debonded coating/substrate interfaces revealed that there were more adiabatic shear-induced craters observed on the smoother substrate surfaces. Finite element modeling also showed that the substrate surface features (i.e., peaks and valleys) possibly prevented the intimate contact between the particles and substrate and thus induced the non-uniform distributions of temperature, stress and strain at the particle/substrate interface.

Shear Block Test Performance of Melunak and Mengkulang Parallel to Glueline

This experimental research is conducted on shear strength performance of glue laminated timber parallel to glue line using Malaysian tropical hardwood Melunak and Mengkulang. The objective of this research was to determine the shear strength values of Melunak and Mengkulang with the observation and comparison of the wood and glue failure percentage of both species. Total 30 numbers of wood specimens which; 15 numbers of wood for Melunak and 15 numbers of wood Mengkulang. The block specimen dimension was 50x50x50mm, then tested using a shear block fixtures and Universal Testing Machine (UTM). The Malaysian Standard, MS758:2001 was used in conducting shear block test and to obtain the shear strength values for both specimen. Both wood tested specimen results in 9.05% different in its shear strength values, where Melunak average shear strength was higher 0.92N/mm2 than Mengkulang. Test result of shear failure to grain direction in both specimen shows that failure occurred in wood was due to wood surface area. The Melunak average percentage failure of wood and glues area 93.7% and 6.3% respectively. While for Mengkulang average failure percentage for wood and glue area were 89.7% and 10.3% respectively. The difference in result of wood failure of both specimen area directly related to the density of specimens, in which Mengkulang wood has a higher density than Melunak. Both specimens reached to its minimum shear strength capacity that was about 6N/mm2 set by the Malaysian standard MS758:2001. Both Melunak and Mengkulang wood tested specimen results in 9.05% different in its shear strength values, where Melunak average shear strength is higher about 0.92N/mm2 than Mengkulang.

Outcomes of Cyanoacrylate Tissue Adhesive Application in Corneal Thinning and Perforation.

To report the outcomes of cyanoacrylate tissue adhesive (CTA) application in corneal thinning and perforation. A retrospective interventional case series of 137 patients receiving CTA for corneal thinning and perforation in 140 eyes between 2001 and 2018 at a single center was reviewed. Success rate and factors associated with glue failure were analyzed. Median age of the cohort was 63 years and 69 (50%) were women. One hundred fifteen patients (84%) had at least 1 systemic condition, 46 (34%) had autoimmune diseases. Eighty-nine eyes (64%) presented with perforation and 51 (36%) with thinning. The perforation/thinning was central/paracentral in 82 eyes (59%) and peripheral in 57 eyes (41%). Median size of perforation was 3.1 mm. Causes of perforation and thinning were microbial infection in 75 (55%), sterile melt in 49 (35%), laceration in 10, and keratoprosthesis melt in 8 eyes. Median glue retention was 58 days. Success rate of glue application (defined as intact globe without surgical intervention) was 72%, 61%, and 46% at 10, 30, and 90 days after glue application, respectively. Larger size of perforation/thinning, perforation (vs. thinning), and single glue application (vs. multiple) were correlated with higher failure rate. Systemic conditions, use of topical corticosteroid, etiologies, and location of perforation/thinning were not significantly correlated with glue failure. CTA application was moderately effective in stabilizing corneal perforation and thinning in the very short-term. Multiple applications are often required. Maintenance of globe integrity after glue application decreases with time and the need for surgical intervention remains high.

Shear Block Test Performance of Melunak and Mengkulang

This paper presented results of shear block test performance of tropical glued-laminated timber (glulam) from species of melunak and mengkulang. Glulam blocks were manufactured in accordance with MS758:2001. The shear block test for glue lines and the shear strength tests of melunak and mengkulang were conducted and evaluated in accordance with BS EN 14080:2013. Melunak and mengkulang produced average shear strength values of 10.62 N/mm2 and 8.19 N/mm2, respectively. In terms of wood and glue failure percentage, the results showed that melunak and mengkulang were mainly failed due to wood surface area and not due to the glue lamination in which both melunak and mengkulang showed a good bonding performance.

Effects of Traverse Scanning Speed of Spray Nozzle on the Microstructure and Mechanical Properties of Cold-Sprayed Ti6Al4V Coatings

Cold spray has the potential to restore damaged aerospace components made from titanium alloy, Ti6Al4V at low temperature (200-400 °C). Traverse scanning speed during deposition is one of the key factors that affect the quality of the Ti6Al4V coatings as it influences the thermal build-up and coating thickness per pass. As there are fewer reported studies on this, this work investigated the effects of different traverse scanning speeds (100, 300 and 500 mm/s) of cold spray nozzle on the microstructure and mechanical properties of cold-sprayed Ti6Al4V coatings. The cross-sectional analysis showed coating porosities reduces with slower traverse speed, from 3.2 to 0.5%. In addition, the microhardness of the coatings increased from about 361-385 HV due to strain hardening. However, the adhesion strength of the coatings to the substrates significantly decreased with reduced traverse speed from about 60 MPa (glue failure) at 500 mm/s to 2.5 MPa (interface failure) at 100 mm/s. Therefore, this study revealed that the control of heat build-up and thickness per pass during the cold spray deposition of the Ti6Al4V coatings is crucial to attain the desirable properties of the coatings.

Compression tests on square, thin-walled steel tube/bamboo-plywood composite hollow columns

Abstract Thin-walled steel tube/bamboo-plywood composite hollow columns (SBCCs) have excellent physical and mechanical properties. The simple cross section of this composite makes it simple to process and suitable for industrial production. In this paper, axial and eccentric compression tests were conducted on 21 specimens to study the failure characteristics and maximum bearing capacity of this composite. The test results showed that compressive failure in an SBCC is primarily characterized by damage from glue failure at the matrix interface at the end of the column, internal damage of the bamboo-plywood material, damage from glue failure on the tension side in the middle of the column, and buckling damage to the plywood material on the compressive side. The overall adhesive strength between the matrixes primarily determined the failure mode. The maximum bearing capacity of the SBCC generally increased with the net cross-sectional area of the bamboo and decreased with the slenderness ratio and eccentricity. The hollow ratio reduced the slenderness ratio of the test specimens with the same net cross-sectional area of the bamboo and increased the critical compressive load, which significantly improved the compressive load capacity, as was reflected in the slenderness ratio. Finally, a model was formulated based on a non-linear regression analysis of the experimental data. The model was used to determine the allowable compressive capacity of an SBCC to provide guidance for engineering applications.

Improving performance of polyvinyl acetate (PVA) as a binder for wood by combination with melamine based adhesives

In this study blending PVA with MUF and MF was evaluated as an approach to enhance the performance of PVA towards water and elevated temperatures. MF and MUF were added to PVA at different proportions: 15%, 30%, 50%, 70% and 100%. Blends of PVA with MF and MUF were used as adhesives to bond wood joints. The shear strength of wood joints was measured at dry and wet states, and elevated temperatures. Thermogravimetric analysis was used to study thermal stability of PVA and its blends with MF and MUF. The structural changes caused by the inclusions were characterized by Fourier transforms infrared spectroscopy (FT-IR). The results showed that shear strength of wood joints were improved by the addition of MF and MUF to PVA in all conditions. Adding small amounts of MUF or MF (as low as 15%) enhanced the performance of wood joints towards water and elevated temperatures. The extent of improvement was sometimes so high that the strength of glue line surpassed strength of wood in wet conditions leading to wood failure rather than glue failure. MF had more effectiveness in improving shear strength of wood joints than MUF in all conditions. Thermal stability of PVA was increased by MF but the effect of MUF on thermal stability of PVA was dependent on MUF proportions and temperatures. FT-IR analyses showed that there are some chemical bonds between PVA and MF. Considering costs, effectiveness and formaldehyde emission, adding 15% MF to PVA seems the optimal proportion of MF in the PVA blends.

Bonding strength of fluoridated hydroxyapatite coatings: A comparative study on pull-out and scratch analysis

In this study, fluoridated hydroxyapatite coatings are prepared on Ti6Al4V alloy substrate through sol–gel method. The bonding strength is evaluated through two different methods: pull-out method and scanning scratch method. Both results show F incorporation could effectively increase the bonding between coating and substrate. It is found that the pull-out results are actually compounds of adhesion failure, cohesive failure and glue failure; while the critical loads in scanning scratch show only the coating-matrix adhesion strength. It is suggested that scanning scratch test is more suitable to evaluate the bonding strength of bioactive ceramic coatings.

Successful Sphincter-Sparing Surgery for All Anal Fistulas

This study was designed to evaluate the success of a sphincter-sparing treatment algorithm for patients with anal fistulas. All patients with anal fistulas presenting to a single surgeon from 1999 to 2004 were retrospectively reviewed. Patients were treated according to a sphincter-sparing algorithm that utilized three operative approaches: subcutaneous fistulotomy, seton placement followed by fibrin glue, and/or seton placement followed by rectal advancement flap. Data analyzed included: age, gender, type of fistula, operative intervention, treatment success, and functional results. A total of 137 patients with anal fistulas were evaluated (age range, 23-74 years). Fistula etiology was cryptoglandular in 116 (85 percent), inflammatory bowel disease in 9 (7 percent), HIV in 3 (2 percent), and miscellaneous in 9 (7 percent). A subcutaneous fistulotomy was possible in 38 patients (28 percent), and all of these patients healed. The remaining 99 patients (72 percent) with transsphincteric fistulas underwent staged procedures: 89 patients (65 percent) underwent seton placement followed by fibrin glue closure (55 healed, 62 percent success rate), 9 patients had seton placement followed by flap (9 healed, 100 percent success rate), and 1 patient had seton placement alone. Of the 34 patients with fibrin glue failure, retreatment with glue was successful in 8 of 14 (57 percent success rate). The remaining 20 patients who declined glue retreatment and the 6 patients who failed glue retreatment underwent flap (26 healed, 100 percent success rate). All fistulas healed with an average of two operations per patient, and fecal continence was maintained in all patients. By using staged operative procedures without any division of anal sphincter muscle, all fistulas healed with excellent functional results. A sphincter-sparing approach can successfully treat all anal fistulas.

The mechanical properties of composites manufactured from tendon fibres and pearl glue (animal glue)

The mechanical properties of a composite manufactured from bovine tendon and pearl glue (an animal glue containing gelatine and other proteins) are investigated. This composite was traditionally used in the construction of Asiatic re-curve bows for archery and is reputed to be tough yet elastic. Composites were manufactured by hand laying fibres into a mould and then pouring on hot glue. Tensile tests were performed on the specimens with the load being applied along the long axis of the fibres. The composite was found to absorb 18 MJ/m3 of energy to failure, comparable to carbon fibre composites, spring steel and butyl rubber. This energy absorption was achieved through the ductility and strength of the collagen fibres, which were found to be several times larger than the glue (fibre strength was 180 MPa, glue strength was 32 MPa, fibre failure strain was 26%, glue failure strain was 3%). However, the tensile modulus of the fibres and glue were similar. The composite was also found to be extremely damage tolerant, with many micro-cracks developing between strains of 2–20%, and dominated by elastic behaviour to surprisingly large deformations. The reasons for this are discussed.

Influence of Extractives on Bonding Properties of White and Southern Red Oak

Abstract White and southern red oak veneers were subjected to four methods of drying followed by five surface treatments. The four drying methods were mill drying at 350°F, laboratory drying at 350 and 212°F, and air drying. The five surface treatments were no treatment, surface scraping, soaking and dipping in 1% NaOH aqueous solution, and water extraction. Plywood panels were prepared by using a phenol-formaldehyde resin. Even with the best drying-surface treatment combination, wood failure was only 35% for white oak and 39% for southern red oak. Overall, mill drying was the best drying method. Soaking the veneers in 1% NaOH solution significantly increased the bond quality. Mill drying of veneers caused water-soluble extractives to migrate from the interior portions to veneer and lathe check surfaces. SEM examinations of the glue failure surface revealed that gluelines failed to adhere to the cell walls. Difficulties in bonding white and southern red oak veneers may be caused by extractive contamination.