International Journal of Adhesion and Adhesives最新文献

Laser-etching technology can perform micro-nano processing on the sub-surface of composite, thereby enhancing its mechanical interlocking to improve the adhesive performance. However, it can easily cause surface fiber damage and destroy the integrity of composite. Hence, the influences of surface micro-texturing and laser-etching effect on the adhesive property and failure behaviors of basalt fiber reinforced polymer (BFRP) composite single-lap-joint are investigated. Here, different surface micro-texturing of BFRP with different laser-etching power and line space are processed by laser-etching. The surface morphology and wetting property of experimental samples are characterized, and single lap tests are conducted to evaluate the adhesive properties. Results show that the adhesive property firstly increases and then decreases with the laser power increase, where the samples etched with 10 W and line space of 0.1 mm perform the best. It is found that the epoxy on the surface is removed by laser-etching to improve the contact area, but the fiber damage is formed to affect the adhesive property. When the laser-etching reaches a certain depth in spite of fiber damage, it can achieve the best bonding performance with the balance of performance and structural integrity. Finally, the multi-scale simulations are conducted to effectively demonstrate the laser-etched interface bonding behavior and damage evolution process of BFRP single lap joints.

This study presents experimental and numerical investigations on the effects of composite ply angle, thickness and number of layers on energy absorption behavior of adhesively bonded carbon fiber-reinforced plastic/aluminum hybrid structure under quasi-static axial loading. This paper aims to use the advantages of adhesive bonding for the local strengthening of a square shaped aluminum energy absorber by composite and as a result achieving desirable energy absorption behavior prior to failure in the connection and without heterogeneous deformation of the structure while reducing the weight of the structure and usage of material and at the same time obtaining favorable results compared to the traditional ways like reinforcing the aluminum structure with composite globally. For this purpose, two models were made and analyzed; one reinforced with four L-shaped composites adhesively bonded using Araldite 2015 to four outside corners of the aluminum square and the other reinforced locally to four corners from within the square. Finite element model was developed for analysis of these hybrid structures. Five different ply angles for composite and multiple number of composite layers varied from 2 to 8 layers under the same and different thicknesses were investigated. Moreover an alpha factor has been determined to measure the importance of local reinforement of the square shape aluminum energy absorber by L-shaped composites. The results showed that compared to aluminum and aluminum with global composite reinforcement energy absorbers, due to the adhesive connection between aluminum and composite in the locally reinforced CFRP/aluminum specimen, the composite had better energy absorption by following the collapse pattern of aluminum and creating a continuous collapse and failure modes. The results indicated good coordination and agreement between the simulated models and the experimental tests. The findings from this experiment demonstrates significant potential for local reinforcement of structures employing adhesives. Utilizing such connections and the ability to strengthen specific areas based on arbitrary geometry and strengthening location could offer substantial opportunities in constructing lightweight structures with high energy absorption across diverse applications.

This research aimed to analyze the low-velocity impact on jute/epoxy polymer samples and used their fractured samples for computer tomographic (CT) analysis for predicting the impact damage areas developed on jute/epoxy polymer by using its impact images. The computer tomography analysis was performed with two different thicknesses of natural fabric composites. Initially, this developed the jute/epoxy polymer composites using Compression molding techniques with different thickness and these fabricated samples undergoes to analyzed the low-velocity impact strength with an automated data acquisition system on different thicknesses of jute fabric-reinforced polymer composite materials. The fabricated composite plates were tested under the low-velocity impact testing method with different loading conditions. The higher impact strength was observed on the 6 mm thickness of the plate. The impact analysis on laminate materials is performed with different energy levels on the same thickness of the plate individually. Among various energy absorption tests, the 10 J created more damage on the 3 mm thick plate and 15 J created more damage on the 6 mm thick plate. After the impact testing, the samples were analyzed in the damaged areas using CT scanning systems. Based on this analysis, the fabricated materials were best-suited for lightweight application areas.

The increasing demand for lightweight vehicles to improve fuel efficiency and performance has driven the adoption of thin-walled tubes made from lightweight hybrid materials as key energy-absorbing components in automotive structures. However, joining these hybrid materials presents a challenge, as traditional methods like welding are unsuitable. This study examines the axial crushing behavior of multi-cell, thin-walled energy-absorbing tubes with square cross-sections, joined using adhesive bonding. A two-cell square aluminum tube was experimentally constructed and tested to evaluate its energy absorption characteristics and failure modes. Additionally, the tube was modeled in ABAQUS software, incorporating elastoplastic deformation of the aluminum and cohesive contact properties for the adhesive layer. After validating the model with experimental data, a parametric study was conducted to assess the impact of different plate material combinations and wall thicknesses on crashworthiness and failure modes. The findings revealed that the effectiveness of material combinations (Al/St) with varying wall thicknesses depends on the adhesive bond's ability to maintain plate integrity during axial loading. In some cases, specific Al/St combinations with particular wall thicknesses resulted in a loss of structural integrity, leading to global cohesive failure. Finally, an analytical equation was developed to predict the axial mean crush force, which demonstrated strong agreement with both experimental and numerical results.

Carbon fiber reinforced polymer (CFRP) is an engineering composite material with excellent performance. After metallization, the CFRP composite exhibits unique properties such as electromagnetic shielding and high electrical conductivity. In this study, we utilized laser treatment process to enhance the adhesion strength of the copper layer electrolessed on CFRP composite. The surface microstructure of CFRP and the copper layer was determined using an optical microscope, and the adhesion force of the copper layer on CFRP composite was measured through 3M tape and pull-out tests. The results indicate that with an increase in the number of laser treatment cycles, the trenches depth on the surface of CFRP composite also increases, leading to high surface roughness and thus enhancing the adhesion strength between the copper layer and the composite. The adhesion state of the copper layer on laser-treated CFRP composite can be qualitatively classified as grade 5B. Additionally, both mechanical cutting and laser treatment can improve the adhesion strength of the samples. The samples treated by mechanical cutting and the laser scan with ±45° exhibit the highest adhesion strength of 5.48 MPa. This is 415 % higher than that of the untreated sample, with a minimum damage area after pull-out testing, approximately 10 %. Compared to the sandblasting pretreatment process, the adhesion strength of the sample by laser treatment increased by 119 %.

As the medium between the reinforcement and the matrix, the interface plays a critical role in the mechanical properties of silicon carbide particle reinforced aluminum matrix composites. This study used first-principles calculation methods to systematically analyze 14 different 6H-SiC/Al low-index interfaces, including atomic configuration, interface bonding strength, and electronic structure and bonding principles between interfaces. The adhesion work calculations reveal that the C-top-SiC(0001)/Al (111) and SiC(0001)/Al (100) interfaces have larger adhesion work values, specifically 5.09 J/m² and 5.021 J/m², respectively. Additionally, the rigid tensile testing confirms that the tensile stress values at the interfaces of C-top-SiC(0001)/Al (111) and SiC(0001)/Al (100) are higher, measuring 36.4 GPa and 32.5 GPa, respectively. The above results show that the interface bonding strength of these two configurations is the highest, the most stable, and most likely to appear in the 6H-SiC/Al interface configuration. The results of the analysis on charge density difference and partial density of states indicate that the interfaces of C-top-SiC (0001)/Al (111) and SiC (0001)/Al (100) are primarily composed of strong ionic and covalent bonds.

Objective

To evaluate the shelf-life effect of a silane-containing universal adhesive (UA) on its shear bond strength (SBS) to lithium disilicate glass-ceramic (LiSi₂).

Methods

SBS to mirror-polished (‘MP’) and hydrofluoric acid-etched ground (‘HF’) lithium disilicate glass-ceramic (Initial LiSi, GC) with/without prior separate ceramic primer application (G-Multi Primer, GC: ‘G-MP’) was measured. Scotchbond Universal Plus (‘SBUp’) (3M Oral Care) was used 33 (‘fresh’) and 6 (‘expiring’) months before the expiration date. ‘MP’ specimen preparation involved (1) ‘G-MP’ priming (or not), (2) ‘SBUp’ application, (3) composite (Clearfil AP-X, Kuraray Noritake) placement, and (4) 20 s light-curing (SmartLite Pro, Dentsply Sirona). ‘HF’ specimen preparation involved (1) HF (Porcelain Etch, Ultradent) etching, (2) phosphoric acid (K-Etchant, Kuraray Noritake) post-etching, with (3) and (4) being the same as for ‘MP’. Upon light-curing, all specimens were stored in 37 °C water for either 1 week (‘immediate’) or 3 months (‘aged’) prior to SBS measurement. Statistics involved Linear Mixed-Effects modelling (α = 0.05).

Results

SBS was not significantly affected by SBUp's shelf life, except for a significantly higher SBS recorded for ‘fresh’ SBUp applied on HF-etched and separately silane-primed LiSi₂. Aging did not significantly decrease SBS. In fact, a significant increase in SBS upon aging was recorded for HF-etched LiSi₂ that was not separately silane-primed. The significantly highest bond strength was measured when LiSi₂ was HF-etched followed by separate silane-priming.

Significance

Despite the UA investigated has silane in its formulation, the most effective and durable bonding to LiSi₂ was achieved by HF-etching followed by separate silane-priming, irrespective of the UA's shelf life.

Objective

To evaluate microtensile bond strengths (μTBS), nanoleakage (NL), and degree of conversion (DC) of two universal adhesives, using etch-and-rinse (ER) or self-etch (SE) strategies on eroded dentin submitted to in vitro and in situ erosive challenges.

Methods

Dentin blocks were prepared from 120 human molars and categorized based on dentin condition (sound, in vitro eroded, and in situ eroded), adhesive system (Scotchbond Universal [SBU] and Zip bond Universal [ZIP]), and adhesive strategy (ER and SE). In the in situ erosive challenge, 20 volunteers wore acrylic resin palatal devices with dentin blocks, immersing them in cola soft drink for 90 s, six times daily for 15 days. The same erosive protocol was used in vitro, followed by rinsing and remineralization. Sound dentin blocks served as controls. Afterward, all dentin blocks were restored with composite resin and sectioned into resin-dentin bonded sticks for μTBS, NL, and DC assessments. Data were analyzed using three-way ANOVA and Tukey's test (α = 0.05).

Results

Sound dentin exhibited the highest μTBS and DC values and the lowest NL values, while in situ eroded dentin showed the lowest μTBS and DC values and the highest NL values (p = 0.000001). While some differences in the μTBS values were observed between universal adhesives when evaluated on sound dentin (p = 0.0001), no significant differences between adhesives were observed when tested on in vitro and in situ eroded dentin. Regarding NL and DC, no significant differences were found between SBU and ZIP, as well as among adhesive strategies (p > 0.05).

Conclusion

Erosion in dentin, especially under in situ conditions, presents significant challenges to the adhesion of restorative materials. The choice of an effective adhesive system is crucial, as dentin eroded in situ showed lower adhesion strength and greater nanoleakage. These results highlight the need for specific clinical strategies to improve the durability and effectiveness of restorations.

Soybean-based adhesive has been commercialized in the wood industry owing to its several advantages, such as no formaldehyde, good bonding properties, and renewability. However, the large-scale application of soybean-based adhesive is greatly limited by its significantly higher cost than urea-formaldehyde resin. Thus, in this study, a cost-effective polyamidoamine-epichlorohydrin (PAE) resin with improved crosslinking efficiency to soybean meal was prepared from branched polyamidoamine (PAA) with reduced dehydration time at high temperatures. Test results from GPC, FTIR and NMR analyses showed that traditional PAA synthesis involving 3-h dehydration time at 180 °C resulted in over-branching of PAA resin and poor crosslinking efficiency of PAE resin and decreased water resistance of obtained soybean-based adhesive. PAA resin synthesized at appropriate dehydration time (1 h) remained sufficient secondary amine groups for being grafted by epichlorohydrin to form effective PAE resin with more azetidinium groups. As a result, the water resistance of soybean-based adhesive crosslinked by the optimal PAE-1 resin prepared from 1 h-dehydrated PAA-1 significantly improved by 42.9 % compared with that of soybean-based adhesive crosslinked by traditional PAE resin, attributing to forming denser and stronger crosslinking networks after thermally cured. Consequently, this optimal PAE-1 could reduce the cost of soybean-based adhesive due to decreasing 16.7 wt% of PAE dosage without compromising bonding property and the energy consumption of PAA/PAE synthesis. Therefore, an appropriate decrease in the dehydration time of PAA resin at a high temperature provides an effective, economical, and energy-saving strategy to improve the bonding property of soybean-based adhesives.

Nowadays, bonded joints have increasingly become the most used joining process in many industrial fields and even in civil engineering due to their simple geometry and structural efficiency and especially with the development of structural adhesives. Several solutions have been proposed in order to improve the mechanical strength of bonded joints by taking into consideration modifications to the adhesive edges and adherends to attenuate as much as possible the high stress concentration at the level of the adhesive. In this study, a 3D numerical model was developed in Abaqus to evaluate the influence of geometric changes in the adherends’ and adhesive edges on the mechanical strength of a single-lap joint under uniaxial tensile stress. Two modified geometric configurations of the bonded joint were proposed, taking into account on the one hand the presence of an adhesive fillet as the first modification and on the other hand, a removal of material at the level of the free edges of the adherends (adherends notching) as the second modification. The objective is to analyze the impact of these geometric modifications on the reduction of stress concentration in the adhesive and to explore how this new joint design can contribute to improve the strength of bonded joints. The results clearly show that a geometric modification at the level of the two free edges of the two substrates improves the strength of the joint and reduces the high stress concentrations in the adhesive. The joint strength is greatly improved if these modifications are optimized in relation to the overlap length and especially in relation to the thickness of the adherends and the adhesive. Adherend notching or applying an adhesive fillet resulted in a considerable reduction in peel stresses.