Search Results (476)

Oral diseases, such as periodontitis, remain a major global concern due to their high incidence and significant morbidity. The principal drivers are bacterial overgrowth and associated inflammation. Bioactive glass of the 45S5 Bioglass^® composition (BG) is known for its remineralising, osteogenic and antibacterial effects via ion release, but its application has been limited in oral environments. In this study, a photocurable GelMA hydrogel was developed as a carrier matrix for BG (1–15% w/v) to obtain synergy between the adhesive properties of the GelMA and the bioactivity of the glass. Incorporation of 10% w/v BG improved ultimate tensile strength (97 kPa) compared to pure GelMA (58 kPa) and reduced swelling by 18%. The composites showed ~60% higher adhesive strength on collagen sheets than GelMA alone. Tensile bonding strengths reached 54 kPa on collagen sheets and 23 kPa on tooth sections. Lap-shear adhesive strengths were 44 kPa on collagen and 18 kPa on implant metal. In vitro studies confirmed the composite’s biocompatibility with dental pulp stem cells and antibacterial activity against Escherichia coli and methicillin-resistant Staphylococcus aureus. Overall, the GelMA/BG composite presents a multifunctional platform for dental remineralisation with promising mechanical, adhesive and antibacterial performance. Full article

Silicone gel for high-voltage power module packaging is prone to interfacial failure due to poor intrinsic adhesion, which seriously threatens the reliability of devices. This study explores ways to improve the adhesion performance of silicone gel from the two aspects of crosslink network structure and interfacial connection. The crosslink structure is regulated by adjusting the ratio of side-hydrogen-containing silicone oil to terminal-hydrogen-containing silicone oil, and interface adhesion is improved by adding three different contents of silane coupling agents (KH560, KH570, A171). The adhesion strength is evaluated by lap shear experiments. The results show that when the ratio of side-hydrogen to terminal-hydrogen is 16:24, the adhesion strength reaches a peak value of 0.0921 MPa. Among the coupling agents, KH560 shows the most significant enhancement, with the adhesion strength reaching 0.1356 MPa at 4% addition and a 47% improvement over the baseline, KH570 is only effective at low addition levels, and A171 shows the weakest effect due to vinyl interference in the crosslink network. Breakdown tests confirm that all three modification schemes do not seriously damage insulation performance. This study provides a feasible strategy and basis for the adhesion reliability design of silicone gel for power module packaging. Full article

The aim of the presented study is to verify the possibility of forming hybrid adhesive-mechanical joints between aluminum sheet and PP matrix composites reinforced with carbon and glass fibers using thermal drilling technology. The research responds to weight reduction trends in the automotive and aerospace industries, seeking joining methods that preserve the continuity of reinforcing fibers. The methodology included applying an experimental organosilicate agent to the aluminum, sequential thermal drilling, and an innovative modification of bushing geometry using a 9.3 mm diameter tool. Joint quality was evaluated via tensile shear testing and non-destructive analysis using computed tomography (CT). Results showed that the organosilicate layer significantly increased the load-bearing capacity and adhesion of glass fiber joints. Hybrid joints exhibited higher energy absorption than purely adhesive joints. The proposed bushing geometry modification led to a statistically significant increase in total dissipated energy (by 28% to 37%) and a desired change in the failure mechanism from composite pull-out to bushing shear. CT analysis confirmed the preservation of fiber integrity through radial deflection. Consequently, hybrid joining via thermal drilling with modified geometry effectively utilizes the mechanical properties of metallic materials in multi-material structures. Full article

Externally bonded reinforcement (EBR) using fiber reinforced polymer (FRP) is one of the most widely used techniques for strengthening reinforced concrete (RC) structures. However, early debonding of the concrete surface layer in the EBR method limits its structural performance. Recently, the externally bonded reinforcement on grooves (EBROG) method has emerged as a promising alternative. This study experimentally investigates the bond behavior between CFRP plates and concrete strengthened using the EBROG method. A total of 78 specimens were fabricated and evaluated using single-lap shear tests. The investigated parameters include groove dimensions, number of grooves, and concrete compressive strength. A digital image correlation (DIC) system was used to measure displacement. Unlike the EBR method, no debonding of the concrete surface layer occurred in the EBROG specimens, and the bond strength improved by 49.56–154.48% without additional surface treatment. Increased groove dimensions and a greater number of grooves significantly enhanced the bond performance. Higher concrete compressive strength and larger groove dimensions also delayed the onset of debonding. Based on the experimental results, a new effective strain model was proposed, and flexural capacity predictions using this model showed higher accuracy than those obtained from existing models. Full article

This paper investigates the seismic performance of precast concrete shear-wall subassemblies connected by post-cast ultra-high performance concrete (UHPC) zones and short lap-spliced reinforcement with a lap length of $10d$, where d denotes the diameter of the reinforcement bar. Seven quasi-static cyclic tests were conducted, including one cast-in-place control specimen, five specimens with horizontal UHPC back-cast joints at the wall base, and one exploratory specimen with both horizontal and vertical UHPC back-cast joints. The variables considered were the joint arrangement and the axial compression ratio. The specimens with horizontal joints generally exhibited compression-flexure-dominated damage, and the crushing zone shifted from the wall-footing interface to the ordinary concrete immediately above the UHPC back-cast zone. The specimen with the vertical joint (TW6) exhibited bending-shear damage, accompanied by limited in-plane lateral slip at the beam–wall joint and shear damage of several vertical bars. Specimen TW2, with an axial compression ratio of 0.30, was identified as a construction-quality-sensitive case because an insufficient local UHPC cover caused splitting damage and reduced hysteretic stability. The strain measurements indicate that, within the limits of the present instrumentation, the 10d lap in the UHPC zone provided effective stress transfer in the tested specimens; however, direct interface-slip and bond-slip tests are still required for generalized design verification. Under an axial compression ratio of 0.20, TW1 and TW6 showed comparable seismic indices to the cast-in-place specimen, but the conclusions are limited to the tested configurations. All specimens reached ultimate drift ratios greater than 1/100, and their seismic performance is discussed together with failure mode, stiffness degradation, energy dissipation, and connection reliability. Full article

Aluminum alloys are attractive for oil production, refining, and hydrocarbon-processing equipment because of their low density, high specific strength, and heat-transfer properties; however, their use is limited by localized corrosion in chloride-, sulfur-, and water-containing environments. This review analyzes combined anodic oxide/polymer and anodic oxide/fluoropolymer coating systems as surface-engineering approaches for improving corrosion resistance, adhesion, and durability of aluminum alloys under such conditions. The reviewed data show that coating performance is governed by anodic oxide morphology, pore sealing or polymer impregnation, and oxide/polymer interfacial stability. Quantitative results indicate that anodizing and pore widening can increase aluminum/polyamide lap-shear strength from 5.0 to 17.4 MPa, while optimized interfacial treatment can provide 22.5 ± 0.5 MPa before aging and 18.1 ± 0.2 MPa after humid aging. Corrosion data show that anodizing can increase the polarization resistance of aluminum alloy 6061 in seawater from 17.2 kΩ·cm² to 2.24 MΩ·cm². For wear-related durability, optimized anodizing can increase the critical scratch load from 37.3 to 118.9 N. These values provide practical benchmarks for designing anodic oxide/polymer systems for complex oilfield and hydrocarbon-processing environments. Full article

The adhesive bonding of aluminum with other materials is widely used in the aerospace, marine, automotive and railroad industries that require lightweight materials. Adhesive bonding has the advantages of reduced corrosion, stress concentration, and cost effectiveness. To improve bonding strength and performance, we examined the use of ascorbic acid (vitamin C), which is a water-soluble compound and a natural reducing agent. Owing to its reducing power and acidity, ascorbic acid allows the Al etching process to proceed efficiently to increase the surface roughness and prevent Al oxidation. In addition, this study used an eco-friendly technique of simply immersing aluminum substrates in an ascorbic acid solution with sodium chloride. The surface free energy was evaluated using the sessile drop method and calculated using the Owens–Wendt–Rabel and Kaelble method. Confocal microscope was used to investigate the roughness of the surface, and the functional groups of Al surface were analyzed by X-ray photoelectron spectroscopy. The bonding strength was measured using the single-lap joint shear test. Compared to aluminum without treatment, the bonding strength of a treated AA 6061 was enhanced by 58.6%. Full article

This study investigates the effect of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) passivation time on the adhesive bonding performance of aluminum substrates using an epoxy adhesive. Alkaline etching was used to generate a chemically active surface prior to silane treatment. GPTMS passivation led to the formation of silane-derived species on the aluminum surface. SEM/EDS indicated the presence of silicon-containing species. ATR-FTIR analysis showed the progressive development of siloxane (Si–O–Si) bonding with increasing passivation time. The mechanical performance of the bonded joints was evaluated using single-lap shear (SLS) testing. The SLS strength increased from 4.3 ± 1.0 MPa in the as-received substrate to 5.5 ± 1.2 MPa after etching. After GPTMS passivation, the strength reached a plateau beginning at 3 min, with a value of 13.5 ± 1.8 MPa. This corresponds to increases of 28% after etching and 223% after GPTMS passivation. This plateau behavior indicates a self-limiting interfacial process. The improved adhesion is attributed to siloxane formation within the silane layer and the chemical compatibility between GPTMS and the epoxy adhesive. A first-order conceptual semi-quantitative model was developed to relate silane surface coverage to adhesion strength. The results demonstrate that adhesion depends on both surface coverage and the development of siloxane bonding within the silane layer. This study highlights the importance of controlled passivation time in improving adhesion performance under the present experimental conditions. Full article

Adhesive joints typically require high safety factors, as their mechanical performance is highly sensitive to environmental and manufacturing variations. Health monitoring can reduce these safety factors by continuously assessing the condition of the joint. While intrinsic and extrinsic sensing approaches exist, they are often based on periodic inspection or manual sensor integration, which limits their suitability for continuous in-service monitoring. This study investigates a novel sensor placement using additively manufactured strain sensors deposited by jet dispensing across the adhesive gap. Tensile lap-shear specimens were fabricated using CFRP (carbon-fiber-reinforced plastic) laminate, an epoxy adhesive, and silver-ink strain sensors placed internally within the joint and externally across the adhesive gap. Mechanical testing revealed that externally printed sensors produced an average resistance change of 65.3% near the failure stress of the adhesive joint, an order of magnitude higher than sensors embedded within the adhesive layer with 6.6% average resistance change. However, the average coefficient of variation increased as well, from 7.6% for internal to 32.6% for external. This sensor response exceeds reported environmentally induced variations in printed sensors and thus represents a promising candidate for condition monitoring. Further work is required to demonstrate actual damage detection capabilities and assess long-term stability under environmental and cyclic loading conditions. Full article

To ensure safety in structural design, a method to quantify the damage in thermoplastic ultrasonic single-spot-welded Single-Lap Shear (SLS) joints is needed. This paper investigates whether detailed knowledge regarding the shape of the weld is required when using the global compliance to quantify damage. A finite element model using cohesive zone elements is developed in Abaqus to simulate single-spot SLS specimens with varying weld areas, aspect ratios, and damage growth directions, covering damage levels from 0 to 90% of the initial weld area. For each configuration, the relationship between intact weld area and global compliance is evaluated, and the numerical trends are compared to previously published experimental data from similar joints. The results show that weld size and damage growth direction have negligible influence on the relationship between global compliance and weld area, and that weld shape is also insignificant as long as the aspect ratio remains within a practical range; only very elongated welds with an aspect ratio over 4.4, which are unlikely in production, deviate significantly. Global compliance can be used as a reliable indicator of damage in single-spot ultrasonic welds that is insensitive to weld shape. This enables simplified in situ damage monitoring and reduces the need for detailed geometric characterisation during mechanical testing. Full article

Single-lap shear joints made from fabric T300/polyphenylene sulfide (T300/PPS) and unidirectional T700/low-melt polyaryletherketone (T700/LM-PAEK) laminates are joined via induction and conduction welding at different processing temperatures. The joints are tested experimentally to investigate the influence of the processing temperature on the damage evolution in the specimens which is tracked using digital image correlation. Cracks grow rapidly in the unwelded parts of the joint interface but assume a stable steady-state propagation rate when reaching the fully welded overlap region. It is found that higher welding temperatures lead to longer weld lengths, which improve the strength and stiffness of the specimens and delay damage initiation. An accelerated crack growth rate indicates that the structure is close to its ultimate load after which the joint fails abruptly as the crack growth becomes unstable. Induction welding temperatures at the upper end of the recommended processing window (330 °C for T300/PPS and 385 °C for T700/LM-PAEK) result in the joints with the highest load-carrying capacity and slowest crack propagation, but also the least damage tolerance. Full article

The growing need for lightweight, multifunctional, and high-performance structures in the automotive, aerospace, electronics, and medical industries has driven the development of advanced joining technologies for polymers and metal-polymer combinations. Among these, ultrasonic welding (USW) and friction stir spot welding (FSSW) have emerged as promising solid-state techniques capable of producing reliable joints with minimal thermal degradation and enhanced interfacial bonding. This review focuses on recent developments in USW and FSSW of thermoplastics, fiber-reinforced composites, and hybrid metal–polymer systems, with a particular emphasis on process mechanics, microstructural evolution, and joint performance. The mechanisms of heat generation, material flow behavior, and consolidation are discussed in relation to key process parameters, including applied pressure, rotational speed, vibration amplitude, plunge depth, and dwell time. Microstructural transformations such as polymer chain orientation, recrystallization, interfacial diffusion, and defect formation are analyzed to establish process–structure–property relationships. Mechanical performance metrics, including lap shear strength, fatigue resistance, impact behavior, and environmental durability, are critically compared across different materials and welding methods. Furthermore, recent advances in numerical and thermo-mechanical modeling, in situ process monitoring, and data-driven optimization are discussed to highlight pathways toward predictive and scalable manufacturing. Current industrial applications and existing limitations such as challenges in automation, thickness constraints, and hybrid material compatibility are also evaluated. Finally, key research gaps and future directions are identified to improve joint reliability, sustainability, and broader industrial adoption of advanced solid-state welding technologies. Full article

Concrete structures are highly vulnerable to fire exposure, which accelerates the degradation of mechanical properties and may lead to partial or total structural failure. Externally bonded carbon fiber-reinforced polymer (CFRP) systems are widely used for post-fire strengthening; however, the bond behavior at the interfaces between CFRP and fire-damaged concrete, particularly under different cooling conditions, is not yet fully understood. In this study, the bond behavior was investigated experimentally and theoretically. Double-lap joint tests of thirty-nine specimens were conducted, including three unheated control specimens and thirty-six specimens exposed to temperatures of 200 °C, 400 °C, and 600 °C for durations of one and two hours. Two cooling methods, natural air cooling and water cooling, were applied prior to CFRP bonding. The results indicated that bond strength increased under exposure conditions of no more than 400 °C, whereas a significant reduction was observed at 600 °C. Water cooling resulted in lower bond strength compared with air cooling, while longer exposure durations improved bond performance under certain thermal conditions. The reasons behind the phenomena were analyzed in detail. Based on the experimental results, an analytical model for predicting the bond strength at the interfaces between fire-damaged concrete and CFRP sheets was developed. The model can account for the effects of peak temperatures, exposure durations, and cooling methods, and demonstrated high predictive accuracy (R² = 0.94). The findings provide valuable insight into CFRP–concrete interaction after fire exposure and offer practical guidance for the assessment and rehabilitation of fire-damaged concrete structures. Full article

One promising innovative joining process for non-oriented electrical sheets is based on an electro-insulating layer combined with a self-bonding varnish. The aim of this study was to investigate the adhesion of the self-bonding varnish as evaluated by a lap-shear test. During the experiments, non-oriented electrical steels with low to high silicon content were analyzed and tested. The Si content, the bond thickness, and the surface roughness Ra, as well as the selected steel production parameters—such as the radiation tube furnace temperature (RTF), the grain growth temperature (i.e., heating temperature (HF)), the peak metal temperature (PMT), and the annealing atmosphere (dry or humid, controlled by dew point)—were considered as the variables. The results showed that the lap-shear strength was independent of the surface roughness within the investigated range. In contrast, the bond thickness exhibited a weak positive effect on the lap-shear strength, while the Si content showed condition-dependent behavior. The RTF and the HF resulted in a relatively stable mechanical performance, whereas the PMT and the humid annealing atmosphere were identified as critical factors influencing adhesion. Full article

Bioadhesive materials capable of operating under aqueous conditions are of considerable interest for biomedical and materials science applications. Peptide-based systems represent an attractive platform for such materials due to their structural tunability, inherent biocompatibility, and ability to form supramolecular networks through noncovalent interactions. In this work, a focused library of tyrosine-containing dehydropeptides was designed and synthesized to investigate how molecular architectures influence self-assembly, hydrogel formation and adhesive properties. The peptides were synthesized using a solution-phase Boc strategy and systematically varied with respect to N-terminal protection and C-terminal functionality. The N-protected dehydropeptides formed supramolecular hydrogels through multiple gelation triggers, including pH reduction and heating–cooling cycles. Rheological characterization confirmed the formation of viscoelastic networks with tunable mechanical properties, with storage moduli reaching tens of kilopascals depending on peptide structure. Scanning electron microscopy revealed dense fibrous nanostructures consistent with supramolecular hydrogel formation. The N,C-deprotected dehydropeptides displayed reduced gelation propensity but formed cohesive films with measurable adhesive performance toward hydrophilic substrates. Lap-shear tests demonstrated high shear strengths for the hydrophilic films, highlighting their structural robustness under stress. Overall, this study provides insights into the structure–property relationships governing tyrosine-containing dehydropeptide assemblies and demonstrates their potential as minimalistic building blocks for supramolecular adhesive materials. Full article