Adhesive Curing Research Articles

Volumetric effective cure shrinkage measurement of dual curable adhesives by fiber Bragg grating sensor

A robust optical strain sensor, called fiber Bragg grating, is employed to measure the effective cure shrinkage—a part of cure shrinkage that is accumulated only after the gel point—of a dual cure adhesive during each stage of curing—(1) UV-curing stage and (2) thermal-curing stage. Unique experimental setups and procedures are developed and implemented to cope with the technical challenges associated with each stage of curing, including gel point detection and uniform curing. The effective cure shrinkage is measured to be 2.1% and 0.78% for acrylate compound (UV-curing) and two epoxy compounds (thermal-curing), respectively. The measurement accuracy of the proposed approach is corroborated by an additional measurement under the identical curing conditions. The results can be used to predict the cure-induced residual stresses of dual curable adhesives.

Insights into the Synthesis, Secretion and Curing of Barnacle Cyprid Adhesive via Transcriptomic and Proteomic Analyses of the Cement Gland

Barnacles represent one of the model organisms used for antifouling research, however, knowledge regarding the molecular mechanisms underlying barnacle cyprid cementation is relatively scarce. Here, RNA-seq was used to obtain the transcriptomes of the cement glands where adhesive is generated and the remaining carcasses of Megabalanus volcano cyprids. Comparative transcriptomic analysis identified 9060 differentially expressed genes, with 4383 upregulated in the cement glands. Four cement proteins, named Mvcp113k, Mvcp130k, Mvcp52k and Mvlcp1-122k, were detected in the cement glands. The salivary secretion pathway was significantly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the differentially expressed genes, implying that the secretion of cyprid adhesive might be analogous to that of saliva. Lysyl oxidase had a higher expression level in the cement glands and was speculated to function in the curing of cyprid adhesive. Furthermore, the KEGG enrichment analysis of the 352 proteins identified in the cement gland proteome partially confirmed the comparative transcriptomic results. These results present insights into the molecular mechanisms underlying the synthesis, secretion and curing of barnacle cyprid adhesive and provide potential molecular targets for the development of environmentally friendly antifouling compounds.

Preparation, Characterization and Incorporation of Ascorbic Acid Coated Superparamagnetic Fe3O4 Nanoparticles into Universal Dental Adhesives to Enhance their Dentin Bond Strength and Stability

Aims (Purpose): The study aims were to prepare, characterize, and incorporate colloidal suspension containing Ascorbic Acid Coated Superparamagnetic Nanoparticles (AA-SPN) into two universal adhesives to increase the dentin Shear Bond Strength (SBS) and stability by subjecting them to external magnetic field. Settings and Design: An invitro study. Methods and Material: A colloidal suspension of AA-SPN was prepared, characterized, and incorporated into All Bond universal (Bisco, USA) and Prime&Bond universal (Dentsply, Sirona) at 2% by mass. Sixty-four freshly extracted third-molars were divided randomly into four groups, i.e., GI: All Bond Universal (control), GII: All Bond Universal (2%-incorporated), GIII: Prime&Bond universal (control), and GIV: Prime&Bond universal (2%-incorporated). GII and GIV are subjected to 1min magnetic force before adhesive curing. The teeth were restored with Filtek Z350 composite (3M ESPE, USA). Each group was subdivided into two subgroups of 8 teeth each. The first subgroup subjected to thermocycling followed by 1-day water storage, and the second subgroup subjected to thermocycling followed by 6- months water aging before testing the SBS. Statistical analysis used: Statistical analysis was conducted by independent variable t-test performed by using IBM-SPSS program version 22. Results: GII and GIV showed significantly higher (p<0.05) immediate SBS after thermocycling, and maintained a significantly higher bond strength after 6 months water aging in comparison to their control groups. GIV showed significantly higher SBS in comparison to the GII. Groups I, II showed the lowest SBS after 6 months of water aging. Conclusions: Universal adhesives containing 2% AA-SPN subjected to external magnetic field significantly improved the immediate and delayed shear bond strength values compared to their corresponding control adhesives. Significance: The synergistic actions of superparamagnetism of the magnetite nanoparticles in response to magnetic field, and the medicinal values of vitamin C including collagen cross linking and MMPs inhibition, significantly increased and maintained the bond strength of universal adhesive to sound dentin when subjected to external magnetic field in comparison to the non-incorporated adhesives

Use of confocal Raman microscopy to characterise ethyl cyanoacrylate adhesive depth curing.

In situ spatial temporal measurement of monomer conversion during adhesive bondline curing remains a challenging area. The aim of this work was to demonstrate the effectiveness of using confocal Raman microscopy in a specially configured experimental set-up, as a versatile tool for measuring monomer concentration changes as a function of both time and adhesive bond depth during ethyl cyanoacrylate polymerisation. This also allowed monitoring of the extent of polymerisation at the adhesive substrate interface independently of the bulk bondline polymerisation region. Key kinetic parameters such as inhibition time tlag, rate of reaction Rmax and extent of reaction [αt]max were obtained by fitting the experimental data to sigmoidal growth curves using simple piecewise regression models. A systematic characterisation of a polymerisation reaction was conducted using different sample substrate types (copper alloy (red brass), aluminium, aluminium alloy, stainless steel and borosilicate glass) and at various reaction temperatures. Reaction rates were found to decrease further away from the substrate interface in the bulk volume region. The fastest kinetics occurred in the vicinity of nucleophilic hydroxyl rich surfaces such as at the copper alloy (red brass). In addition to substrate surface chemistry, surface roughness was also a factor, with the highest reaction rates occurring with a grit blasted (roughened) aluminium alloy (2024 T3) surface. An approximately linear dependence of the ln Rmaxvs. 1/T (Arrhenius) plot was recorded within the temperature range of 291-328 K. A better fit was obtained however through the use of two separate linear slopes, possibly indicative of a change of polymerisation reaction mechanism taking place at elevated temperatures with two distinct activation energies. Further work conducted using a larger number of temperatures would be useful to verify this finding. This work confirmed that differences in the rates of interfacial and bulk polymerisation processes could be readily measured in situ using confocal Raman microscopy which is a powerful technique for investigating such surface-confined and bulk polymerisation reactions.

Microscale pH and Dissolved Oxygen Fluctuations within Mussel Aggregations and Their Implications for Mussel Attachment and Raft Aquaculture

Mussel mariculture uses the natural attachment strategy of marine mussels by allowing them to aggregate on submerged rope lines that are then pulled to the surface and harvested. Mussels attach to ropes using a network of byssal threads, proteinaceous fibers that adhere to surfaces underwater using a powerful biological glue (adhesive plaque). Plaques use the surrounding seawater as a molecular trigger during adhesive curing, a process that requires a pH greater than 7.0 and an abundance of dissolved oxygen to progress. To ascertain whether mussels experience seawater conditions that are potentially harmful to mussel attachment, this study measured the conditions within mussel aggregations at a mussel farm in Washington state and, then, applied those conditions to plaques to determine whether such conditions are sufficient to weaken attachment. Seawater monitoring demonstrated that mussels infrequently experience acidic (pH <5.0) and hypoxic excursions (O2 <2 mg L–1) in the summer, especially near the seafloor. When reproduced in laboratory assays, the most extreme pH excursions observed delayed plaque strengthening when applied early in the plaque-curing process, whereas extreme excursions in hypoxia decreased adhesion strength after the adhesive had fully matured. In either case, adhesion strength was rescued after reimmersion in open-ocean seawater conditions, highlighting the resilience of the mussel holdfast to stresses other than mechanical strain. The window of susceptibility to changes in environmental conditions during and after curing could contribute to fall-off events at mussel farms, especially in the late summer months.

Characterization and mechanism of accelerated curing of adhesives by in situ ultrasonic vibration for bonded joints

Abstract Ultrasonic vibration can accelerate the curing of epoxy compounds. Previous studies have not explored the nonthermal effects of ultrasound. In this article, we show the accelerated curing process using in situ ultrasonic vibration that removes the thermal effect. The acceleration mechanism of nonthermal effects is clarified. Bisphenol A epoxy resin/low molecular weight polyamide 650 system was used as the adhesive of the joint, and carbon-fiber-reinforced plastic (CFRP)/aluminum alloy joint was used as the bonding object. Ultrasonic vibration was applied in situ to the CFRP laminate in the joint through an ultrasonic tool head. Fourier transform infrared spectroscopy and differential scanning calorimetry were used to characterize the process of conventional curing and ultrasonic curing of adhesives. Results show that the curing rate of the adhesive can be increased by 2500%. By improving the Kamal model, we describe a new model that can describe the ultrasonic curing process very well. The model shows that ultrasound can reduce the activation energy. Temperature monitoring confirmed that pulsed ultrasound can maintain the temperature of the adhesive stable during the curing process. Dynamic thermomechanical analysis showed that pulsed ultrasound accelerates the curing process and improves the mechanical properties of the adhesive. Ultrasound promotes mass transfer between the resin and the curing agent and increases the collision probability between the reactants, thus increasing the reaction rate.

Glass Optical Connector Ferrule for Solder-Reflow-Compatible Photonic IC Edge Interconnections

A glass-tube-based MT-style fiber array ferrule is presented that provides a compact interface to PIC (Photonic Integrated Circuit) edge waveguides. The approach aligns and attaches a glass ferrule on the PIC substrate top surface using solder-reflow-resistant UV curable adhesives. A mating fiber array connector ferrule is attached to the PIC after solder reflow. Mate/demate experiments on pairs of matching glass-based connector ferrules demonstrated IL (insertion loss) values across eight single mode fiber array channels of less than 1.5 dB without using index matching fluid between coupled arrays. A compact connector packaging housing compatible with glass tube-based ferrules is also presented.

A Method for Manufacturing Glued Plywood Based on Furan Resins

A method for the production of plywood, which prevents percolation of the adhesive based on furan resins through the outer layers of veneer, is proposed. The method consists in hot pressing of the assembled plywood packages with the adhesive applied to the corresponding veneer layers in two stages: first, without creating pressure, and then at working specific pressure until the adhesive cures in the central layer. It is shown that this method, despite its technological simplicity, provides proper quality of the products.

Hybrid joining: Numerical process development of flat-clinch-bonding

Abstract Clinching is one of the most commonly used mechanical joining processes in the automotive industry. In it, two or more overlapping metal sheets are locally formed so that a form- and force-closed joint with a die-side protrusion is established. Because of this protrusion, conventional clinching technology cannot be used for visible areas (e.g., automotive body shells) or functional surfaces (e.g., sliding surfaces). Flat-clinching is a special type of clinching for producing one-sided planar joints. Using this technology, it is possible to join the same or different kinds of materials (e.g., metal and metal, metal and plastic, or metal and wood). The flat-clinch-bonding process combines flat-clinching and adhesive bonding. After applying the adhesive, metal sheets are mechanically fixed by flat-clinching, thus guaranteeing the assembly handling strength. This allows continuous processing and shortens process time. The final operational strength of the assembly is achieved after complete adhesive curing. This paper describes the development of flat-clinch-bonding using numerical simulations. Special attention is paid to material characterization and implementation of material data in the simulation model. After calibrating the simulation model using reference experiments, the process of flat-clinch-bonding is investigated. The focus is on minimizing the size of adhesive pockets, as they prevent interlocking. The knowledge gained from the simulations is subsequently experimentally proven. Also, the joint strength of the novel process variant is experimentally determined and compared to the strength of an elementary adhesive bond.

Sensitivity-Enhanced Extrinsic Fabry-Perot Interferometric Fiber-Optic Microcavity Strain Sensor.

This study presents an extrinsic Fabry–Perot interferometric (EFPI) fiber-optic strain sensor with a very short cavity. The sensor consists of two vertically cut standard single-mode fibers (SMFs) and a glass capillary with a length of several centimeters. The two SMFs penetrate into the glass capillary and are fixed at its two ends with the use of ultraviolet (UV) curable adhesives. Based on the use of the lengthy glass capillary sensitive element, the strain sensitivity can be greatly enhanced. Experiments showed that the microcavity EPFI strain sensor with initial cavity lengths of 20 μm, 30 μm, and 40 μm, and a capillary length of 40 mm, can yield respective cavity length–strain sensitivities of 15.928 nm/με, 25.281 nm/με, and 40.178 nm/με, while its linearity was very close to unity for strain measurements spanning a range in excess of 3500 με. Furthermore, the strain–temperature cross-sensitivity was extremely low.

Volumetric polymerization shrinkage and its comparison to internal adaptation in bulk fill and conventional composites: A μCT and OCT in vitro analysis

ObjectiveTo quantify the volumetric polymerization shrinkage (VPS) of different conventional and bulk fill resin composites, through micro-computed tomography (μCT), and qualitative comparison of gap formation through optical coherence tomography (OCT). MethodsBox-shaped class I cavities were prepared in 30 third-molars and divided into 5 groups (n=6): G1- Filtek Z100 (Z100); G2- Tetric Evoceram Bulk Fill (TEC); G3- Tetric EvoFlow Bulk fill (TEF); G4- Filtek Bulk fill (FBU); and G5- Filtek Bulk fill Flowable (FBF). All groups were treated with Adper Single Bond Plus adhesive and light cured (Bluephase 20i). Each tooth was scanned three times using a μCT apparatus: after cavity preparation (empty scan); after cavity filling (uncured scan) and after light curing of the restorations (cured scan). The μCT images were imported into a three-dimensional rendering software, and volumetric polymerization shrinkage percentage was calculated (%) for each sample. In the same images, interfacial gaps in the pulpal floor were qualitatively evaluated. After μCT evaluation, the pulpal floor from each tooth was polished until a thin tooth structure was obtained and OCT images were obtained by scanning the pulpal portion. Gap formation was observed and qualitatively compared to the μCT images. ResultsVPS means ranged from 2.31 to 3.96% for the studied resin composites. The bulk fill materials, either high viscosity or flowable, were not statistically different from each other (p>0.05). The conventional resin composite Z100 presented statistically higher VPS than both high viscosity bulk fill materials studied (p<0.05), although it was statistically similar to the flowable bulk fill materials studied (p>0.05). Both μCT and OCT methodologies enabled gap formation visualization, and images from both technologies could be associated. Gap formation was mostly observed for G1-Z100, G4-FBU, and G5-FBF. VPS% and pulpal gap formation could not be completely associated with each other for all groups and samples. Voids were observed in most of the resin composite fillings, and most VPS were observed in the occlusal area of the samples. SignificanceVolumetric polymerization shrinkage was material-dependent, although bulk fill materials did not differ from each other. Both μCT and OCT enabled interfacial pulpal gap formation visualization. VPS and gap formation cannot be completely associated with one another.

Adhesive-related warping of thin wooden bi-layers

Warping of layered wood-based panels is still a challenging problem in the development of thin engineered wood products. Wood as an anisotropic and hydrophilic material tends to change its volume and mechanical properties with changing moisture content. Besides the wood components, also the mechanical properties of certain adhesives are sensitive to moisture changes. A moisture load onto the adhered wood is resulting in different stress and strain states between the adherends. It is expected that adhesives with different moisture-related properties participate differently to this interaction. To observe an adhesive-related warping, thin spruce/HDF (Picea abies and high-density fibreboard) bi-layers with identical material geometries were manufactured under laboratory conditions, using different wood adhesive systems, which are currently used in furniture and flooring industry [polyurethane (PUR), emulsion polymer isocyanate (EPI), polyvinyl acetate (PVAc), urea formaldehyde (UF) and ultra-low emitting formaldehyde amino adhesive (ULEF)]. The bi-layers were exposed to certain relative humidity conditions, and the resulting deformation was measured with a high-precision laser distance detector. Moisture-dependent warping of the bi-layers was obtained in relation to the used adhesive systems. As a result of the study, it can be shown that initial warping after panel manufacturing strongly depends on the adhesive curing characteristics and, especially, on the amount of water that is released into the wood adherend. For the post-setting panel warping, a differentiation into two adhesive groups became visible: rigid and flexible adhesives. Rigid adhesives (UF and ULEF) showed a higher degree of warping compared to the group of flexible adhesives (PUR, EPI and PVAc).

Functionalized polyester-based materials as UV curable adhesives

UV curable adhesives offer major advantages in comparison to other polymeric based adhesive systems, such as fast-curing rate and control of the polymerization heat evolution, being ideal for application on damaged tissues.Herein, functionalized polymers were prepared by modifying polycaprolactone diol (PCL) with an isocyanate-functional unsaturated acrylic ester, Laromer® 9000, using two different proportions. These functionalized materials were chemically/physically characterized and, after the addition of a biocompatible photoinitiator (Irgacure® 2959), were crosslinked by UV light irradiation. Such procedure allows the obtention of flexible transparent films. Films’ properties such as swelling, hydrolytic degradation, thermal stability, surface energy and adhesive capacity were evaluated. Furthermore, to assess the applicability of the films in biomedical applications, their haemocompatibility and biocompatibility were determined using human dermal fibroblasts as model.

Accelerated curing of glued-in threaded rods by means of inductive heating – part II: modelling

ABSTRACT The curing behaviour of inductively heated glued-in rods (GiR) experimentally tested in Part I of this work was further investigated with regard to the kinetics of adhesive curing, and evolution of strength with time. For that, dynamic DSC measurements were performed, and appropriate kinetic models were derived. These investigations were complemented with rheological experiments in which the adhesive were subjected to the same thermal regime as in the inductive heating of the GiR. Curing kinetics of the GiR were then compared to the increase of strength with time. The comparison showed that curing progress, defined by conversion degree, does not result in proportional strength increase. It was then attempted to estimate the influence of potential residual stresses from the induction curing on joint capacity. A relatively simple FE model was thus derived, which considered two different loading cases: a tensile force acting on the rod, and a shrinkage resulting from the induction process. Their superposition allowed for a general description of the fact that joint capacities increased with time elapsed since induction heating. Depending upon the adhesive considered, fair to very good quality of prediction were achieved.

Modification of urea- and phenol-formaldehyde adhesives by natural fillers for the production of plywood

For the manufacture of plywood and chipboard are used urea-formaldehyde and phenol-formaldehyde hot curing adhesives. When it is necessary to reduce the content of toxic substances, to increase the strength and reliability of gluing, other properties of adhesive bonding heat urea and phenol-formaldehyde resins are modified. Urea-formaldehyde and phenol-formaldehyde resins were used for research. Urea-formaldehyde resin was modified with technical lignosulfonates with particle sizes of 0.01-0.2 mm, shungites with particle sizes of 0.2-0.8 mm, black shales with particle sizes of 0.005-0.2 mm and aluminosilicates with particle sizes of 0.2 - 0.8 mm. Phenol-formaldehyde resin was modified with pectol, black shales with particle sizes of 0.005-0.2, technical lignosulfonates with particle sizes of 0.01-0.2, and cold sludge from aluminum production with particle sizes of 0.01-0.2. A comparative analysis revealed that all the modifiers under study improve the physicochemical parameters of urea-formaldehyde and phenol-formaldehyde resins, increase the performance properties of glued materials from wood. Plywood was tested for shear strength over the adhesive layer and for the content of free formaldehyde in accordance with Russian standards. Modification of urea and phenol-formaldehyde resins with the proposed substances increases the strength of plywood, at the same time reducing the free formaldehyde content in products.

On the Effect of Heat Treatments on the Adhesion, Finishing and Decay Resistance of Japanese cedar (Cryptomeria japonica D. Don) and Formosa acacia (Acacia confuse Merr.(Leguminosae))

In Taiwan, it is important to maintain sustainable development of the forestry industry in order to raise the self-sufficiency of domestic timber. Japanese cedar (Cryptomeria D. Don and Formosa acacia (Acacia confusa Merr.(Leguminosae)) have abundant storage options and are the potential candidates for this purpose. Heat treatment is a new environment-friendly method used to enhance the dimensional stability and durability of wood. On treatment, a surface with new characteristics is produced because of wood component changes. Consequently, an inactivated surface and a weak boundary layer are generated, and the wettability for adhesives and coatings is reduced. Furthermore, it decreases the pH value of the wood surface, and results in delay or acceleration during the curing of adhesives. This phenomenon must be paid attention to for practical applications of heat-treated wood. Ideal heat-treated conditions of C. japonica and A. confusa woods with productive parameters such as temperature, holding time, heating rate, and thicknesses of wood were identified in our previous study. In this research work, we focus on the normal shear strength of heat-treated wood with adhesives such as urea-formaldehyde resin (UF) and polyvinyl acetate (PVAc), and the finishing performances of heat-treated wood with polyurethane (PU) and nitrocellulose lacquer (NC) coatings as well as assessing the decay-resistance of heat-treated wood. The results show that heat-treated wood had a better decay resistance than untreated wood. The mass decrease of heat-treated wood was only 1/3 or even less than the untreated wood. The normal shear strength of heat-treated wood with UF and PVAc decreased from 99% to 72% compared to the untreated wood, but the wood failure of heat-treated wood was higher than that of the untreated one. Furthermore, the adhesion and impact resistance of wood finished by PU and NC coatings showed no difference between the heat-treated wood and untreated wood. The finished heat-treated wood had a superior durability and better gloss retention and lightfastness than that of the untreated wood.

Simulational and experimental investigation on the print-through high-frequency aberration of the shear-joint NIF deformable mirror.

A shear-joint deformable mirror (DM) is important in the high-power laser systems such as the National Ignition Facility (NIF). In this paper, the print-through high-frequency aberration (PT-HIFA) that arises from adhesive curing and is corresponding to the actuator array is reported to exist in the initial surface shape of a lab-made shear-joint NIF DM. Meanwhile, experimental results show that the PT-HIFA has a great modulation on the laser intensity. This PT-HIFA could not be corrected effectively by the DM and may result in dangerous damage in the high power laser systems. In order to eliminate the PT-HIFA, we investigate the influence of the structural parameters on the PT-HIFA in a shear-joint DM through simulation and experiment. Simulational results show that the structural parameters have different influences on the PT-HIFA. In the experiment, by optimizing the structural parameters, the PT-HIFA could be eliminated in the shear-joint NIF DM and the modulation effect on the laser intensity could be removed. This investigation could help other researchers to determine appropriate structural parameters and to achieve a fine surface shape in their own shear-joint DMs.

Strength improvement in single lap adhesive joints by notching the adherends

In this study, an easy procedure is proposed to improve the strength of Single Lap Joints (SLJs) by introducing a notch in the adherends right after the overlap length. At first, the effect of different notch parameters on the peel, shear and von Mises stress distributions of the adhesive mid-plane layer is investigated by using the Finite Element (FE) method. The considered parameters are the notch angle, the notch width, the notch depth, and the notch distance from the overlap length. Afterwards, a simple 90-degree notch angle which can be easily manufactured is selected for adherend notching based on the numerical results. In addition, in order to experimentally investigate the effects of different notch parameters on the failure load of adhesive joints, five various notch depths with two different adhesive curing methods are considered. Finally, the experimentally obtained fracture loads are compared with the theoretical ones which are based on the predictions of von Mises stress and peel. The results show that using the adherend notching can significantly improve the load bearing capacity of SLJs. For instance, a simple notch with 20% notch depth ratio can improve the load bearing capacity of the SLJ about 60%.

Corrosion protection and thermal and mechanical properties for epoxy–thiol–imidazole systems of improved performance

Epoxy–thiol–imidazole system is promising for microelectronic packaging areas, such as underfills and low-temperature fast curing adhesives, but there is little knowledge on the corrosion resistance of this system. In this article, the anticorrosion and thermal and mechanical properties were characterized by theoretical and experimental methods and were understood from a fundamental perspective of structure. The cure behaviors were evaluated by differential scanning calorimeter. The mechanical and thermal properties were characterized by dynamic mechanical, thermomechanical, and thermos-gravimetric methods. The water absorption process was monitored using gravimetric measurement. Results show that among compositions of variable thiol–epoxy molar ratios, the one with ratio 0.25 has the best anticorrosion property and improved mechanical property, as well as good water resistance at room temperature. Both the average tensile strength and modulus increased initially and then declined with the addition of thiol part, while the average peel strength increased to above thrice the value of that of neat epoxy–imidazole system for thiol–epoxy 1:1 system.

Influence of a wollastonite microfiller and a halloysite nanofiller on properties of thermally curable pressure-sensitive structural adhesives

A thermally curable pressure-sensitive structural tape (SAT-0) was prepared using an epoxy acrylate copolymer and an epoxy resin and modified with a wollastonite microfiller (SAT-W) and a halloysite nanofiller (SAT-H). Influence of the minerals on self-adhesive features and curing behavior of the tapes as well as on shear strength of aluminum/SAT/aluminum joints has been investigated. Thermally uncured SATs containing the fillers exhibited higher Tg (+5 °C for SAT-H), adhesion (+64% for SAT-H) and tack (+10% for SAT-W) while their cohesion was lower (−22% for SAT-W and −86% for SAT-H) in relation to SAT-0. Moreover, filler addition reduced the shear strength of the Al/SAT/Al overlap joints (−6% for Al/SAT-H/Al and −22% for Al/SAT-W/Al), however, the microfiller-based systems exhibited better crack and fatigue resistance, and higher shear strength after ageing tests than SAT-0 and SAT-H (+100% after thermal ageing, +85% after exposure in a climatic chamber, and +27% after immersion in a fuel).