Bending Behavior of Hybrid Timber-Steel Beams

Driven by climate change and the need for a more sustainable construction sector, policy is increasingly demanding and promoting timber hybrid construction methods. In the German state of Baden-Württemberg, every new public building has to be of timber or timber hybrid construction (Holzbauoffensive BW). The objective of multi-story buildings with large floor spans can only be achieved in a resource-efficient way by hybrid constructions combining timber and steel components. A research project recently completed at the Karlsruhe Institute of Technology was aimed at the development and systematic investigation of hybrid bending beams in which an advantageous combination of the materials steel and timber is used. For this purpose, steel profiles are integrated into timber cross-sections in a shear-resistant manner by adhesive bonding. As part of the experimental, numerical and analytical investigations, different cross-sections of steel and timber, as well as different construction materials, were considered (GL24h, LVL48p, LVL80p, S355 and S420). The results of large-scale four-point bending tests illustrate the potential of this new hybrid construction method. Depending on the geometry and material combinations tested, the bending stiffness could be increased by up to 250%, and the load-carrying capacity by up to 120%, compared to a glulam beam with identical dimensions.

Durability of Resin Bonding to Dental 3Y-TZP Zirconia Using Different Adhesive Systems

This laboratory study was conducted to evaluate and compare the resin bond strength of different adhesive resin systems in different combinations and the durability of their bonds with zirconia ceramic.

MATERIALS AND METHODS

One hundred and twenty-eight specimens were milled from 3Y-TZP zirconia ceramic. The bonding surfaces of all disks were wet polished, steam cleaned, airborne-particle abraded and ultrasonically cleaned in 99% isopropanol. The specimens were randomly divided into four main groups according to the applied resin system; two conventional and two self-adhesive systems were used. Each group was further subdivided into two subgroups; the first was conditioned with the specified primer for conventional luting resins or not conditioned for the self-adhesive systems, whereas the second subgroup of each was conditioned with the same phosphate monomer-containing primer (Alloy Primer). The zirconia specimens were adhesively bonded, using the allocated luting resin, to plexiglass tubes filled with self-curing composite resin (Clearfil FII). Half of the specimens of each subgroup were stored in distilled water at 37 °C for 3 days, whereas the other half were subjected to artificial aging, 150 days of storage and additional thermal cycling. Thereafter, all specimens were subjected to TBS testing using a universal testing machine. Statistical analysis was conducted using two-way ANOVA followed by separate one-way ANOVAs. The Games-Howell post-hoc test was applied for pairwise comparisons.

RESULTS

All specimens survived storage with thermal cycling. The mean TBS values ranged from a minimum of 43.4 ± 5.0 MPa to a maximum of 66.4 ± 3.5 after 3 days and from a minimum of 13.6 ± 2.5 MPa to a maximum of 50.1 ± 9.4 MPa after 150 days.

CONCLUSIONS

Artificial aging had a significantly negative effect on all test groups. The chosen adhesive-resin system had a significant effect on the resulting TBS values. The highest TBS values were achieved for the self-adhesive luting resin G-Cem One but were statistically comparable to the results obtained for the dual-cure luting resin G-Cem LinkForce.

Ultrasonic Features for Evaluation of Adhesive Joints: A Comparative Study of Interface Defects

Ultrasonic non-destructive evaluation in pulse-echo mode is used for the inspection of single-lap aluminum adhesive joints, which contain interface defects in bonding area. The aim of the research is to increase the probability of defect detection in addition to ensuring that the defect sizes are accurately estimated. To achieve this, this study explores additional ultrasonic features (not only amplitude) that could provide more accurate information about the quality of the structure and the presence of interface defects. In this work, two types of interface defects, namely inclusions and delaminations, were studied based on the extracted ultrasonic features in order to evaluate the expected feasibility of defect detection and the evaluation of its performance. In addition, an analysis of multiple interface reflections, which have been proved to improve detection in our previous works, was applied along with the extraction of various ultrasonic features, since it can increase the probability of defect detection. The ultrasonic features with the best performance for each defect type were identified and a comparative analysis was carried out, showing that it is more challenging to size inclusion-type defects compared to delaminations. The best performance is observed for the features such as peak-to-peak amplitude, ratio coefficients, absolute energy, absolute time of flight, mean value of the amplitude, standard deviation value, and variation coefficient for both types of defects. The maximum relative error of the defect size compared to the real one for these features is 16.9% for inclusions and 3.6% for delaminations, with minimum errors of 11.4% and 2.2%, respectively. In addition, it was determined that analysis of the data from repetitive reflections from the sample interface, namely, the aluminum-adhesive second and third reflections, that these contribute to an increase in the probability of defect detection.

Mechanical Performance of Adhesive Connections in Structural Applications

Adhesive bonding is an excellent candidate for realising connections for secondary structures in structural applications such as offshore wind turbines and installations, avoiding the risk and associated welding problems. The strength of the adhesive layer is an important parameter to consider in the design process it being lower than the strength capacity of the bonding material. The presence of defects in the adhesive materials undoubtedly influences the mechanical behaviour of bonded composite structures. More specifically, the reduction in strength is more pronounced as the presence of defects (voids) increases. For this reason, a correct evaluation of the presence of defects, which can be translated into damage parameters, has become essential in predicting the actual behaviour of the bonded joints under different external loading conditions. In this paper, an extensive experimental programme has been carried out on adhesively bonded connections subjected to Mode I and Mode II loading conditions in order to characterise the mechanical properties of a commercial epoxy resin and to define the damage parameters. The initial damage parameters of the adhesive layer have been identified according to the Kachanov-Sevostianov material definition, which is able to take into account the presence of diffuse initial cracking.

Rheological and Mechanical Properties of an Acrylic PSA

The adhesion of pressure-sensitive adhesives (PSAs) is a complex phenomenon that can be understood through the characterization of different properties, including viscoelastic, mechanical, and fracture properties. The aim of the present paper is to determine the viscoelastic behaviour of an acrylic PSA and place it in the viscoelastic window, as well as to determine the tensile strength of the material. Additionally, different numbers of stacked adhesive layers and two crosshead speeds were applied to characterize the tensile strength of the adhesive in the different conditions. Adding a new interface between layers showed a negative influence in the tensile strength, while a higher crosshead speed implied a considerable increase in the same value. Finally, double cantilever beam (DCB) fracture tests were performed, and the J-integral approach was used to evaluate the fracture energy throughout the tests. The substrate roughness, the number of stacked layers, and the thickness of the PSA proved to decrease the performance of the PSA in fracture tests. While tensile bulk tests in viscoelastic materials are not easily found in the literature, as well as DCB tests, for fracture characterization, the obtained results allowed for the characterization of those properties in an acrylic PSA.

The Influence of MSR-B Mg Alloy Surface Preparation on Bonding Properties

Nowadays, industrial adhesives are replacing conventional bonding methods in many industries, including the automotive, aviation, and power industries, among others. The continuous development of joining technology has promoted adhesive bonding as one of the basic methods of joining metal materials. This article presents the influence of surface preparation of magnesium alloys on the strength properties of a single-lap adhesive joint using a one-component epoxy adhesive. The samples were subjected to shear strength tests and metallographic observations. The lowest properties of the adhesive joint were obtained on samples degreased with isopropyl alcohol. The lack of surface treatment before joining led to destruction by adhesive and mixed mechanisms. Higher properties were obtained for samples ground with sandpaper. The depressions created as a result of grinding increased the contact area of the adhesive with the magnesium alloys. The highest properties were noticed for samples after sandblasting. This proved that the development of the surface layer and the formation of larger grooves increased both the shear strength and the resistance of the adhesive bonding to fracture toughness. It was found that the method of surface preparation had a significant influence on the resulting failure mechanism, and the adhesive bonding of the casting of magnesium alloy QE22 can be used successfully.

Reducing Interface Defects and Porosity of Adhesive Bonded Aluminum Alloy Joints via Ultrasonic Vibration

The surface microstructure formed by physical or chemical modification is essential for the desired joint strength. However, defects in the bonding interface and adhesive can be found. Such defects decrease shear strength and durability. In this study, ultrasonic vibration was applied to liquid adhesive on the sandblasted aluminum alloy plates. With ultrasonic treatment, the joints obtained the compact bonding interfaces and lower porosity of the adhesive layer. The treatment improved the shear strength by 9.1%. After two weeks of hydrothermal aging, the shear strength of joints only sandblasted decreased drastically by 48.9%, while it was 14% for the joints with ultrasonic vibration. The cavitation effect in the adhesive was detected by the aluminum foil erosion method. The result showed that a great number of micro-jets generated by the cavitation effect have intensive impact on the bonding interface which provide the adhesive with powerful force to fill the micro-grooves. Another finding in this work is that bubbles were gathered in the adhesive away from the vibration area. This mechanism was successfully used to reduce the porosity of the adhesive layer of joints.

Flexural Behaviour of GFRP-Softwood Sandwich Panels for Prefabricated Building Construction

Studies have shown that the proper selection of core materials in sandwich structures improves the overall structural performance in terms of bending stiffness and strength. The core materials used in such systems, such as foam, corrugated, and honeycomb, are frequently applied in aerospace engineering. However, they are a costly option for civil engineering applications. This paper investigates the bending performance of the proposed GFRP softwood sandwich beams assembled using pultruded GFRP with adhesive connection methods for potential applications in prefabricated building construction. The ultimate load capacity, load-deflection responses, failure modes, bending stiffness, load-axial-strain behaviour, and degree of composite action were experimentally evaluated. The effects of varying shear-span-to-depth ratios a/d between 2 and 6.5, as well as different timber fibre directions of the softwood core, on the overall structural performance were clarified. The results showed that changing the timber fibres' orientation from vertical to longitudinal shifted the failure mode from a brittle to progressive process. Moreover, the adhesive bonding was able to provide full composite action until the failure occurred. Finally, numerical modelling was developed to understand failure loads, deformation, failure modes, and strain responses, and to evaluate bending stiffness and composite action. The results showed satisfactory agreement with the experiments.

Molecular Understanding of the Interfacial Interaction and Corrosion Resistance between Epoxy Adhesive and Metallic Oxides on Galvanized Steel

The epoxy adhesive-galvanized steel adhesive structure has been widely used in various industrial fields, but achieving high bonding strength and corrosion resistance is a challenge. This study examined the impact of surface oxides on the interfacial bonding performance of two types of galvanized steel with Zn-Al or Zn-Al-Mg coatings. Scanning electron microscopy and X-ray photoelectron spectroscopy analysis showed that the Zn-Al coating was covered by ZnO and Al₂O₃, while MgO was additionally found on the Zn-Al-Mg coating. Both coatings exhibited excellent adhesion in dry environments, but after 21 days of water soaking, the Zn-Al-Mg joint demonstrated better corrosion resistance than the Zn-Al joint. Numerical simulations revealed that metallic oxides of ZnO, Al₂O₃, and MgO had different adsorption preferences for the main components of the adhesive. The adhesion stress at the coating-adhesive interface was mainly due to hydrogen bonds and ionic interactions, and the theoretical adhesion stress of MgO adhesive system was higher than that of ZnO and Al₂O₃. The corrosion resistance of the Zn-Al-Mg adhesive interface was mainly due to the stronger corrosion resistance of the coating itself, and the lower water-related hydrogen bond content at the MgO adhesive interface. Understanding these bonding mechanisms can lead to the development of improved adhesive-galvanized steel structures with enhanced corrosion resistance.

Surface Modification Using MAPLE Technique for Improving the Mechanical Performance of Adhesive Joints

The adhesive bonds that ensure the appropriate mechanical properties for metal joining imply the surface chemical and wetting modification characteristics of the substrates. In this work, matrix-assisted pulsed laser evaporation (MAPLE) was used for the surface modification of Al via the deposition of two chemical compounds, polyvinyl alcohol (PVA) and triethanolamine (TEA), from frozen aqueous solutions. The deposition of the TEA and PVA layers was evidenced by FT-IR, SEM, and AFM analysis. The contact angle measurements evidenced the change in the hydrophilicity of the surface and surface free energies. The performance of the commercial silyl-based polymer adhesive Bison Max Repair Extreme Adhesive^® was evaluated by tensile strength measurements. This method led to a change in tensile strength of 54.22% in the case of Al-TEA and 36.34% for Al-PVA compared with the control. This study gives preliminary insights into using MAPLE, for the first time in adhesive applications, as a pretreatment method for Al plates for adhesive bonding reinforcement.

An Exploratory Study on Determining and Modeling the Creep Behavior of an Acrylic Pressure-Sensitive Adhesive

In the present paper, an exploratory study on the creep behavior of a pressure sensitive adhesive (PSA) is performed. After the determination of the quasi-static behavior of the adhesive for bulk specimens and single lap joints (SLJ), SLJs were subjected to creep tests at 80%, 60%, and 30% of their respective failure load. It was verified that the durability of the joints increases under static creep conditions as the load level decreases, with the second phase of the creep curve becoming more pronounced, where the strain rate is close to zero. In addition, cyclic creep tests were performed for the 30% load level at a frequency of 0.04 Hz. Finally, an analytical model was applied to the experimental results in order to reproduce the values obtained for both static and cyclic tests. The model was found to be effective, reproducing the three phases of the curves which allowed for the characterization of the full creep curve, something not commonly found in the literature, especially for PSAs.

Experimental Study of Steel-Aluminum Joints Made by RSW with Insert Element and Adhesive Bonding

This work focuses on joining steel to aluminum alloy using a novel method of joining by resistance spot welding with an insert element based on anticorrosive steel in combination with adhesive bonding. The method aims to reduce the formation of brittle intermetallic compounds by using short welding times and a different chemical composition of the insert element. In the experiment, deep-drawing low-carbon steel, HSLA zinc-coated steel and precipitation-hardened aluminum alloy 6082 T6 were used. Two types of adhesives-one based on rubber and the other based on epoxy resin-were used for adhesive bonding, while the surfaces of the materials joined were treated with a unique adhesion-improving agent based on organosilanes. The surface treatment improved the chemical bonding between the substrate and adhesive. It was proved, that the use of an insert element in combination with adhesive bonding is only relevant for those adhesives that have a load capacity just below the yield strength of the substrates. For bonded joints with higher load capacities, plastic deformation of the substrates occurs, which is unacceptable, and thus, the overall contribution of the insert element to the load capacity of the joint becomes negligible. The results also show that the combination of the resistance spot welding of the insert element and adhesive bonding facilitates the joining process of galvanized and nongalvanized steels with aluminum alloys and suppresses the effect of brittle intermetallic phases by minimizing the joining area and welding time. It is possible to use the synergistic effect of insert element welding and adhesive bonding to achieve increased energy absorption of the joint under stress.

Creep Crack Growth Behavior during Hot Water Immersion of an Epoxy Adhesive Using a Spring-Loaded Double Cantilever Beam Test Method

Double cantilever beam (DCB) tests were conducted by immersing the specimens in temperature-controlled water while applying a creep load using a spring. By introducing a data reduction scheme to the spring-loaded DCB test method, it was confirmed that only a single parameter measurement was sufficient to calculate the energy release rate (ERR). Aluminum alloy substrates bonded with an epoxy adhesive were used, and DCB tests were performed by changing the initial load values, spring constants, and immersion temperatures for two types of surface treatment. The initial applied load and spring constant had no effect on the ERR threshold. In contrast, the threshold decreased with the increasing immersion temperature, but even in the worst case, it was 15% of the critical ERR in the static tests. Using the creep crack growth relationship, it was revealed that there were three phases of creep immersion crack growth in the adhesive joints, and each phase was affected by the temperature. The spring-loaded DCB test method has great potential for investigating the combined effects of creep, moisture, and temperature, and this study has demonstrated the validity of the test method. The long-term durability of adhesive joints becomes increasingly important, and this test method is expected to become widespread.

A Response Surface Methodology Approach to Improve Adhesive Bonding of Pulsed Laser Treated CFRP Composites

In this work, a response surface-designed experiment approach was used to determine the optimal settings of laser treatment as a method of surface preparation for CFRP prior to bonding. A nanosecond pulsed Ytterbium-doped-fiber laser source was used in combination with a scanning system. A Face-centered Central Composite Design was used to model the tensile shear strength (TSS) of adhesive bonded joints and investigate the effects of varying three parameters, namely, power, pitch, and lateral overlap. The analysis was carried out considering different focal distances. For each set of joints, shear strength values were modeled using Response Surface Methodology (RSM) to identify the set-up parameters that gave the best performance, determining any equivalent conditions from a statistical point of view. The regression models also allow the prediction of the behavior of the joints for not experimentally tested parameter settings, within the operating domain of investigation. This aspect is particularly important in consideration of the process optimization of the manufacturing cycle since it allows the maximization of joint efficiency by limiting the energy consumption for treatment.

Experimental and Numerical Study of Thermal Residual Stresses on Multimaterial Adherends in Single-Lap Joints

The presence of residual stresses in composite materials can significantly affect material performance, especially when integrated in bonded joints. These stresses, often generated during the cure process, can cause cracking and distortion of the material, and are caused by differences in the coefficients of thermal expansion or cure shrinkage. In the current research, multimaterial adherends combining carbon-fibre-reinforced polymer (CFRP) and aluminium in a single-lap joint (SLJ) configuration are analysed, allowing us to understand the effect of the thermal residual stresses, developed during the curing process, in the overall performance of the joints. A numerical model resorting to a finite element analysis (FEA) is developed to assess and predict the behaviour of the joints. The use of FML (fibre metal laminates) was found to significantly improve the strength of the joints, as well as the failure mode. The proposed geometry performed similarly to the comparable FML geometry, in addition to a decrease in the joint weight.

Apparent Young's Modulus of Epoxy Adhesives

This article presents the results of a study of the properties of epoxy adhesives in an adhesive joint. The study analysed changes in Young's modulus values as a function of the rigidity of the adhesive and the type of joined material. The values of Young's modulus values were determined on the thickness of the adhesive joint using the nanoindentation method and in a tensile test of dumbbell shape sample for the adhesive material. The obtained results were analysed in terms of changes to the values of Young's modulus of the adhesive as a function of the distance from the joined material-adhesive phase boundary and compared to the adhesive material. Zones were distinguished in the layer of the adhesive joint-adjacent to the wall and the core, with different values of Young's modulus. Conclusions were drawn, indicating the relationship between the adhesive joint thickness and the increase in the value of Young's modulus. Significant differences were found in the values of Young's modulus of the adhesive joint compared to Young's modulus of the adhesive in the form of plastic.

Development and Characterisation of Joints with Novel Densified and Wood/Cork Composite Substrates

The automotive industry, driven by the desire to decrease the environmental impact of vehicles, is permanently seeking to develop lightweight structural components, which lead to lower gas emissions and energy consumption, reducing their carbon footprint. In parallel, adopting innovative, constructive solutions, which dispense non-recyclable and energy-intensive materials, can increase the footprint reduction. Thus, an increase in the use of renewable materials for structural applications, including wood and its by-products, has been observed over the last few decades. Furthermore, composite materials are often joined by using petroleum-based synthetic adhesives, which should be progressively replaced by eco-friendly bio-adhesives. In this study, novel densified wood and wood/cork composites, joined with a bio-adhesive, are proposed and characterised. The densification of the wood aims to enhance the mechanical properties of the natural material, with the purpose of improving the energy absorption of the wood/bio-adhesive joint. To mitigate delamination and the brittle behaviour of wood/cork agglomerates were introduced between the wood substrate and the bio-adhesive. Different configurations of single lap joints (SLJ) were manufactured to study the effect of the overlap length and loading rate on the performance of the joints, both in terms of failure load and energy absorption. Afterward, the joints were numerically simulated. The densification process was successful, although it represents an additional challenge in terms of surface flatness, because the bio-adhesive requires zero bondline thickness. The increase of the overlap had a positive impact on the energy absorption of the joint, and the addition of cork resulted in a more consistent failure mode and higher strain to failure. The numerical models developed had a good correlation with the experimental results.

Influence of Pre-Treatment and Artificial Aging on the Retention of 3D-Printed Permanent Composite Crowns

The aim of this in vitro study is to investigate the bonding properties of a 3D-printable permanent composite material in comparison to milled composite materials. The tested materials are 3D-printed BEGO VarseoSmile Crown plus (VA1_ab, VA1_nt, VA2_ab, VA2_nt), Vita Enamic (EN1, EN2), and 3M Lava Ultimate (UL1, UL2) (N = 64; n = 8). For this purpose, all crowns are luted to polymer tooth stumps #46 (FDI) using dual-curing luting composite, strictly according to the manufacturer’s instructions. VA1_ab and VA2_ab are additionally airborne-particle abraded. 4 groups (VA2_ab, VA2_nt, EN2, UL2) are artificially aged (1,200,000 cycles, 50 N, 10,000 thermocycles), whereby no specimen has failed. All 64 specimens undergo pull-off testing until retention loss. The mean forces of retention-loss is 786.6 ± 137.6 N (VA1_nt, *), 988.6 ± 212.1 N (VA2_nt, *, Ɨ), 1223.8 ± 119.2 N (VA1_ab, Ɨ, ǂ), 1051.9 ± 107.2 N (VA2_ab, *, Ɨ), 1185.9 ± 211.8 N (EN1, Ɨ, ǂ), 1485.0 ± 198.2 N EN2, ǂ), 1533.8 ± 42.4 N (UL1, ǂ), and 1521.8 ± 343.4 N (UL2, ǂ) (one-way ANOVA (Scheffé method); p < 0.05; *, Ɨ, ǂ: group distribution). No characteristic failure modes can be detected. In conclusion, all of the pull-off forces reflect retention values that seem to be sufficiently high for clinical use. Additional airborne-particle abrasion of VA does not result in significantly better retention but can be recommended.

Study on the Effect of Salt Solution on Durability of Basalt-Fiber-Reinforced Polymer Joints in High-Temperature Environment

Due to the low price and good comprehensive properties, FRP composite material has become a new type of civil application material in recent years. In this paper, Araldite^® 2012 adhesive was used to bond basalt-fiber-reinforced polymer (BFRP), and the durability of its bonded joints was investigated. Experiments were carried out at 80 °C/DI water (deionized water), 80 °C/3.5% NaCl solution (3.5% SS), and 80 °C/5.0% NaCl solution (5.0% SS) at 0- (unaged), 10-, 20-, and 30-day aging. The specimen and BFRP in the environment of 80 °C/DI water, 80 °C/3.5% SS, and 80 °C/5.0% SS found salt solution under the condition of all sample water absorption decreases, and the activity of salt solution chemistry was weaker compared with deionized water. The load–displacement curve of the joint failure was obtained through quasi-static tensile experiments, and it was found that the adhesive would undergo a post-curing reaction that had a positive impact on the stiffness of the joint in a high-temperature environment. At the same time, it was found that the joint failure strength decreased less in the salt solution environment, and deionized water was more destructive than the salt solution. Referring to the change in water absorption, it was found that the change in the mechanical properties of the joint was mainly related to the permeation effect of the polymer. The change in the T_g of adhesive was measured by differential scanning calorimetry (DSC). It was found that T_g would decrease after aging, and the change in T_g was mainly related to the mobility of the molecular chain. Thermogravimetric analysis (TGA) was used to analyze the thermal behavior of the epoxy resin and some organic matter, and the main weight loss stage was 340–450 °C, which was the complete degradation of epoxy resin and some organic matter. Macro visual and microscopic scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to analyze the failure section, and it can be concluded that the failure mode of joint tear failure transitioned to cohesion in the late–mixed interface failure, at the visible interface between the fiber and the resin matrix.

Wafer-Level 3D Integration Based on Poly (Diallyl Phthalate) Adhesive Bonding

Three-dimensional integration technology provides a promising total solution that can be used to achieve system-level integration with high function density and low cost. In this study, a wafer-level 3D integration technology using PDAP as an intermediate bonding polymer was applied effectively for integration with an SOI wafer and dummy a CMOS wafer. The influences of the procedure parameters on the adhesive bonding effects were determined by Si–Glass adhesive bonding tests. It was found that the bonding pressure, pre-curing conditions, spin coating conditions, and cleanliness have a significant influence on the bonding results. The optimal procedure parameters for PDAP adhesive bonding were obtained through analysis and comparison. The 3D integration tests were conducted according to these optimal parameters. In the tests, process optimization was focused on Si handle-layer etching, PDAP layer etching, and Au pillar electroplating. After that, the optimal process conditions for the 3D integration process were achieved. The 3D integration applications of the micro-bolometer array and the micro-bridge resistor array were presented. It was confirmed that 3D integration based on PDAP adhesive bonding is suitable for the fabrication of system-on-chip when using MEMS and IC integration and that it is especially useful for the fabrication of low-cost suspended-microstructure on-CMOS-chip systems.

SiGe/Si Multi-Quantum-Well Micro-Bolometer Array Design and Fabrication with Heterogeneous Integration

The micro-bolometer is important in the field of infrared imaging, although improvements in its performance have been limited by traditional materials. SiGe/Si multi-quantum-well materials (SiGe/Si MQWs) are novelty thermal-sensitive materials with a significantly high TCR and a comparably low 1/f noise. The application of such high-performance monocrystalline films in a micro-bolometer has been limited by film integration technology. This paper reports a SiGe/Si MQWs micro-bolometer fabrication with heterogeneous integration. The integration with the SiGe/Si MQWs handle wafer and dummy read-out circuit wafer was achieved based on adhesive wafer bonding. The SiGe/Si MQWs infrared-absorption structure and thermal bridge were calculated and designed. The SiGe/Si MQWs wafer and a 320 × 240 micro-bolometer array of 40 µm pitch L-type pixels were fabricated. The test results for the average absorption efficiency were more than 90% at the wavelength of 8-14 µm. The test pixel was measured to have a thermal capacity of 1.043 × 10^-9 J/K, a thermal conductivity of 1.645 × 10^-7 W/K, and a thermal time constant of 7.25 ms. Furthermore, the total TCR value of the text pixel was measured as 2.91%/K with a bias voltage of 0.3 V. The SiGe/Si MQWs micro-bolometer can be widely applied in commercial fields, especially in early medical diagnosis and biological detection.

Experimental Study of the Impact of Glass Beads on Adhesive Joint Strength and Its Failure Mechanism

The use of modern structural adhesives provides a lightweight, practical, and high strength joining methodology, which is increasingly being adopted in the automotive and aeronautical sectors, among many others. However, the strict mechanical performance standards that must be met in these applications require a constant search for ways of improving the adhesives’ behavior, which has led to the growing use of reinforcements as a way of improving the capabilities of bonded joints. The aim of this work was, thus, to analyze how the addition of inorganic fillers to the adhesive layer affects a joint’s strength and its failure mechanism. To this end, single lap joint specimens with mild steel and high strength steel substrates were tested, at quasi-static speeds, and with different amounts of glass microspheres reinforcing two different structural adhesives. The experimental results indicated that the addition of glass particles reduced the joint performance for both substrates under study. Furthermore, the failure pattern was found to evolve from adhesive failure to a cohesive type of failure as the amount of glass particles present in the adhesive was increased.

Enhanced Long-Term Reliability of Seal DeltaSpot Welded Dissimilar Joint between 6061 Aluminum Alloy and Galvannealed Steel via Excimer Laser Irradiation

Structural-adhesive-assisted DeltaSpot welding was used to improve the weldability and mechanical properties of dissimilar joints between 6061 aluminum alloy and galvannealed HSLA steel. Evaluation of the spot-weld-bonded surfaces from lap shear tests after long-term exposure to chloride and a humid atmosphere (5% NaCl, 35 °C) indicated that the long-term mechanical reliability of the dissimilar weld in a corrosive environment depends strongly on the adhesive-Al6061 alloy bond strength. Corrosive electrolyte infiltrated the epoxy-based adhesive/Al alloy interface, disrupting the chemical interactions and decreasing the adhesion via anodic undercutting of the Al alloy. Due to localized electrochemical galvanic reactions, the surrounding nugget matrix suffered accelerated anodic dissolution, resulting in an Al6061-T6 alloy plate with degraded adhesive strength and mechanical properties. KrF excimer laser irradiation of the Al alloy before adhesive bonding removed the weakly bonded native oxidic overlayers and altered the substrate topography. This afforded a low electrolyte permeability and prevented adhesive delamination, thereby enhancing the long-term stability of the chemical interactions between the adhesive and Al alloy substrate. The results demonstrate the application of excimer laser irradiation as a simple and environmentally friendly processing technology for robust adhesion and reliable bonding between 6061 aluminum alloy and galvannealed steel.

Predictable 3D guided adhesive bonding of porcelain veneers using 3D printed trays

OBJECTIVE

This clinical report describes a novel digital technique to facilitate and improve the porcelain laminate veneers adhesive bonding procedure using a customized 3D printed guide.

CLINICAL CONSIDERATIONS

Porcelain veneers can be stabilized in their fully seated position with a digitally design 3D printed guide before the resin cement is polymerized. The excess cement can be carefully and predictably removed without the risk of dislodgement, rotation or misfit, allowing the clinician to light cure them under controlled pressure in the correct seating position without the risk of fracturing the ceramic material.

CONCLUSIONS

Fabricating a custom 3D printed guide for veneer bonding provides significant assistance to an otherwise cumbersome and daunting clinical procedure.

CLINICAL SIGNIFICANCE

Adhesive bonding of multiple ceramic veneers is a challenging and technique sensitive procedure. The use of a custom 3D printed guide presented in this article offers a practical aid to achieve a more predictable and precise outcome.

Novel Processing Algorithm to Improve Detectability of Disbonds in Adhesive Dissimilar Material Joints

Adhesively bonded dissimilar materials have attracted high interest in the aerospace and automotive industries due to their ability to provide superior structural characteristics and reduce the weight for energy savings. This work focuses on the improvement of disbond-type defect detectability using the immersion pulse-echo ultrasonic technique and an advanced post-processing algorithm. Despite the extensive work done for investigation, it is still challenging to locate such defects in dissimilar material joints due to the large differences in the properties of metals and composites as well as the multi-layered structure of the component. The objective of this work is to improve the detectability of defects in adhesively bonded aluminum and carbon fiber-reinforced plastic (CFRP) by the development of an advanced post-processing algorithm. It was determined that an analysis of multiple reflections has a high potential to improve detectability according to results received by inspection simulations and the evaluation of boundary characteristics. The impact of a highly influential parameter such as the sample curvature can be eliminated by the alignment of arrival time of signals reflected from the sample. The processing algorithm for the improvement of disbond detectability was developed based on time alignment followed by selection of the time intervals with a significant amplitude change of the signals reflected from defective and defect-free areas and shows significant improvement of disbond detectability.

Effect of Sanding and Plasma Treatment of 3D-Printed Parts on Bonding to Wood with PVAc Adhesive

Additive manufacturing is becoming increasingly important for manufacturing end products, not just prototyping. However, the size of 3D-printed products is limited due to available printer sizes and other technological limitations. For example, making furniture from 3D-printed parts and wooden elements requires adequate adhesive joints. Since materials for 3D printing usually do not bond very well with adhesives designed for woodworking, they require special surface preparation to improve adhesion. In this study, fused deposition modelling (FDM) 3D-printed parts made of polylactic acid (PLA), polylactic acid with wood flour additive (Wood-PLA), and acrylonitrile-butadiene-styrene (ABS) polymers were bonded to wood with polyvinyl acetate (PVAc) adhesive. The surfaces of the samples were bonded as either non-treated, sanded, plasma treated, or sanded and plasma treated to evaluate the effect of each surface preparation on the bondability of the 3D-printed surfaces. Different surface preparations affected the bond shear strength in different ways. The plasma treatment significantly reduced water contact angles on all tested printing materials and increased the bond tensile shear strength of the adhesive used. The increase in bond strength was highest for the surfaces that had been both sanded and plasma treated. The highest increase was found for the ABS material (untreated 0.05 MPa; sanded and plasma treated 4.83 MPa) followed by Wood-PLA (from 0.45 MPa to 3.96 MPa) and PLA (from 0.55 MPa to 3.72 MPa). Analysis with a scanning electron microscope showed the smooth surfaces of the 3D-printed parts, which became rougher with sanding with more protruded particles, but plasma treatment partially melted the surface structures on the thermoplastic polymer surfaces.

Effect of Mechanical Pretreatments on Damage Mechanisms and Fracture Toughness in CFRP/Epoxy Joints

Adhesive bonding of carbon-fiber-reinforced polymers (CFRPs) is a key enabling technology for the assembly of lightweight structures. Surface pretreatment is necessary to remove contaminants related to material manufacturing and ensure bond reliability. The present experimental study focuses on the effect of mechanical abrasion on the damage mechanisms and fracture toughness of CFRP/epoxy joints. The analyzed CFRP plates were provided with a thin layer of surface epoxy matrix and featured enhanced sensitivity to surface preparation. Various degrees of morphological modification and fairly controllable carbon fiber exposure were obtained using sanding with emery paper and grit-blasting with glass particles. In the sanding process, different grit sizes of SiC paper were used, while the grit blasting treatment was carried by varying the sample-to-gun distance and the number of passes. Detailed surveys of surface topography and wettability were carried out using various methods, including scanning electron microscopy (SEM), contact profilometry, and wettability measurements. Mechanical tests were performed using double cantilever beam (DCB) adhesive joints. Two surface conditions were selected for the experiments: sanded interfaces mostly made of a polymer matrix and grit-blasted interfaces featuring a significant degree of exposed carbon fibers. Despite the different topographies, the selected surfaces displayed similar wettability. Besides, the adhesive joints with sanded interfaces had a smooth fracture response (steady-state crack growth). In contrast, the exposed fibers at grit-blasted interfaces enabled large-scale bridging and a significant R-curve behavior. While it is often predicated that quality composite joints require surfaces with a high percentage of the polymer matrix, our mechanical tests show that the exposure of carbon fibers can facilitate a remarkable toughening effect. These results open up for additional interesting prospects for future works concerning toughening of composite joints in automotive and aerospace applications.

Secure and precise insertion of minimally invasive resin-bonded fixed dental prostheses after ridge augmentation by means of a positioning splint

OBJECTIVE

Single-retainer resin-bonded fixed dental prostheses (RBFDPs) are described as an excellent minimally invasive treatment modality for the replacement of a single missing incisor even in cases of congenitally missing teeth that are often associated with hard and soft tissue defects that need to be properly managed to optimize the esthetic outcome. The lack of a retentive form due to the minimally invasive preparation form makes the adhesive bonding procedure for RBFDPs relatively technique-sensitive and might discourage practitioners from offering this treatment modality.

CLINICAL CONSIDERATIONS

A patient with both maxillary lateral incisors congenitally missing was assessed for eligibility for treatment with RBFDPs. Bilateral horizontal ridge defects were present and treated through ridge augmentation to ensure an ovate pontic design and enhance the esthetic outcome. A minimally invasive preparation within enamel was conducted; the restorations were digitally designed and milled out of (3Y-TZP) zirconia ceramic with labial veneering with feldspathic ceramic for enhanced esthetics. An improved design of positioning splints was used for the adhesive bonding procedure to ensure exact, secure, and flawless insertion of the restorations.

CONCLUSIONS

RBFDPs offer a highly esthetic treatment modality for missing teeth in the anterior area. Tissue defects could be overcome be means of a minor oral surgery, while using improved positioning splints might ensure flawless adhesive bonding and promote the usage of RBFDPs.

CLINICAL SIGNIFICANCE

Hard and soft tissue defects can be remarkably optimized through a minor ridge augmentation. Improved positioning splints allow an easy and secure positioning as well as visual inspection of the seating in end-position and complete removal of resin cement excess. Implementing the concept of insertion splints might promote RBFDPs for anterior tooth replacement as it helps preventing bonding errors.

Effect of Ultrasonic Vibration on Adhesive Bonding of CFRP/Al Alloy Joints Grafted with Silane Coupling Agent

Adhesive bonding is widely used in the joining of metals and carbon fiber-reinforced plastics (CFRPs). Ultrasonic vibration was used to improve adhesive bonding of CFRP/Al alloy joints grafted with silane coupling agent, and the effect of the ultrasound on the bonding was studied. The surface of Al alloy was treated with a silane coupling agent, and then the ultrasonic vibration was applied on the adherend during the adhesive bonding process. The shear strength was tested, and the mechanism was analyzed by scanning electron microscope (SEM) and Fourier transform infrared spectrometer (FTIR). It is found that the ultrasonic assisting can further promote the bonding of the Al alloy and the adhesive. For the test joins, the shear strength was increased by 267.50% using the silanization treatment plus the ultrasonic assisting. The ultrasonic assisting promoted the grafted epoxy group to react with the adhesive more sufficiently at the Al/adhesive interface by causing micro-mixing and intensified molecule collision, and thus more chemical bond was formed. Under the ultrasonic action, the interface and the adhesive layer became tighter owing to the impact contact at the interface and the oscillating flow in the adhesive layer. The ultrasonic vibration assisting increased the bonding strength by promoting the chemical bond and improving physical morphology.

Metallization of Organically Modified Ceramics for Microfluidic Electrochemical Assays

Organically modified ceramic polymers (ORMOCERs) have attracted substantial interest in biomicrofluidic applications owing to their inherent biocompatibility and high optical transparency even in the near-ultraviolet (UV) range. However, the processes for metallization of ORMOCERs as well as for sealing of metallized surfaces have not been fully developed. In this study, we developed metallization processes for a commercial ORMOCER formulation, Ormocomp, covering several commonly used metals, including aluminum, silver, gold, and platinum. The obtained metallizations were systematically characterized with respect to adhesion (with and without adhesion layers), resistivity, and stability during use (in electrochemical assays). In addition to metal adhesion, the possibility for Ormocomp bonding over each metal as well as sufficient step coverage to guarantee conductivity over topographical features (e.g., over microchannel edges) was addressed with a view to the implementation of not only planar, but also three-dimensional on-chip sensing elements. The feasibility of the developed metallization for implementation of microfluidic electrochemical assays was demonstrated by fabricating an electrophoresis separation chip, compatible with a commercial bipotentiostat, and incorporating integrated working, reference, and auxiliary electrodes for amperometric detection of an electrochemically active pharmaceutical, acetaminophen.

Influence of Adhesive in FSW: Investigation on Fatigue Behavior of Welded, Weld-Bonded, and Adhesive-Bonded Joints in Aluminum AA 6082 T6

Friction stir welding (FSW) is a solid-state technique, which has assumed an increasingly important role in automotive, naval, and aeronautical industry over the years. Nowadays, thanks to its several benefits, FSW is used to weld any type of metallic, polymeric, or composite material. In recent decades, adhesive bonding has also enhanced relevance due to a request for much lighter structures to increase performance without increasing fuel consumption. From a mechanical perspective, welding has a high tensile strength despite a low fatigue resistance through the lack of joint elasticity. Therefore, the aim of this study is to investigate and compare static and dynamic behavior of welded, weld-bonded, and adhesive-bonded joints. After choosing the most suitable adhesive, surface preparation, consisting of sandblasting, was carried out. First of all, on the basis of previous experience in FSW, the process parameters of hybrid welding were determined. Both quasi-static and dynamic behavior of welded, adhesive-bonded, and weld-bonded joints, made in overlapped configuration, were then compared. Experimental tests showed that the adhesive limits the negative effect, due to the presence of the structural notch of FSW overlapped joints.

Functionalization of Neutral Polypropylene by Using Low Pressure Plasma Treatment: Effects on Surface Characteristics and Adhesion Properties

Polyolefins are considered among the most difficult polymeric materials to treat because they have poor adhesive properties and high chemical barrier responses. In this paper, an in-depth study is reported for the low pressure plasma (LPP) treatment of neutral polypropylene to improve adhesion properties. Changes in wettability, chemical species, surface morphology and roughness of the polypropylene surfaces were evaluated by water contact angle measurement, X-ray photoelectron spectroscopy and, furthermore, atomic force microscopy (AFM). Finally, the bonded joints were subjected to tensile tests, in order to evaluate the practical effect of changes in adhesion properties. The results indicate that plasma is an effective treatment for the surface preparation of polypropylene for the creation of bonded joints: contact angles decreased significantly depending on the plasma-parameter setup, surface morphology was also found to vary with plasma power, exposure time and working gas.

Preparation of Textured Surfaces on Aluminum-Alloy Substrates

The ways of producing porous-like textured surfaces with chemical etching on aluminum-alloy substrates were studied. The most appropriate etchants, their combination, temperature, and etching time period were explored. The influence of a specifically textured surface on adhesive joints' strength or superhydrophobic properties was evaluated. The samples were examined with scanning electron microscopy, profilometry, atomic force microscopy, goniometry, and tensile testing. It was found that, with the multistep etching process, the substrate can be effectively modified and textured to the same morphology, regardless of the initial surface roughness. By selecting proper etchants and their sequence one can prepare new types of highly adhesive or even superhydrophobic surfaces.

Silicon Carbide Nanoparticles as an Effective Bioadhesive to Bond Collagen Containing Composite Gel Layers for Tissue Engineering Applications

Additive manufacturing via layer-by-layer adhesive bonding holds much promise for scalable manufacturing of tissue-like constructs, specifically scaffolds with integrated vascular networks for tissue engineering applications. However, there remains a lack of effective adhesives capable of composite layer fusion without affecting the integrity of patterned features. Here, the use of silicon carbide is introduced as an effective adhesive to achieve strong bonding (0.39 ± 0.03 kPa) between hybrid hydrogel films composed of alginate and collagen. The techniques have allowed us to fabricate multilayered, heterogeneous constructs with embedded high-resolution microchannels (150 µm-1 mm) that are precisely interspaced (500-600 µm). Hydrogel layers are effectively bonded with silicon carbide nanoparticles without blocking the hollow microchannels and high cell viability (90.61 ± 3.28%) is maintained within the scaffold. Nanosilica is also tested and found to cause clogging of smaller microchannels when used for interlayer bonding, but is successfully used to attach synthetic polymers (e.g., Tygon) to the hydrogels (32.5 ± 2.12 mN bond strength). This allows us to form inlet and outlet interconnections to the gel constructs. This ability to integrate hollow channel networks into bulk soft material structures for perfusion can be useful in 3D tissue engineering applications.

Wafer-Level Packaging Method for RF MEMS Applications Using Pre-Patterned BCB Polymer

A radio-frequency micro-electro-mechanical system (RF MEMS) wafer-level packaging (WLP) method using pre-patterned benzo-cyclo-butene (BCB) polymers with a high-resistivity silicon cap is proposed to achieve high bonding quality and excellent RF performance. In this process, the BCB polymer was pre-defined to form the sealing ring and bonding layer by the spin-coating and patterning of photosensitive BCB before the cavity formation. During anisotropic wet etching of the silicon wafer to generate the housing cavity, the BCB sealing ring was protected by a sputtered Cr/Au (chromium/gold) layer. The average measured thickness of the BCB layer was 5.9 μm. In contrast to the conventional methods of spin-coating BCB after fabricating cavities, the pre-patterned BCB method presented BCB bonding layers with better quality on severe topography surfaces in terms of increased uniformity of thickness and better surface flatness. The observation of the bonded layer showed that no void or gap formed on the protruding coplanar waveguide (CPW) lines. A shear strength test was experimentally implemented as a function of the BCB widths in the range of 100⁻400 μm. The average shear strength of the packaged device was higher than 21.58 MPa. A RF MEMS switch was successfully packaged using this process with a negligible impact on the microwave characteristics and a significant improvement in the lifetime from below 10 million to over 1 billion. The measured insertion loss of the packaged RF MEMS switch was 0.779 dB and the insertion loss deterioration caused by the package structure was less than 0.2 dB at 30 GHz.

Adhesive Defect Monitoring of Glass Fiber Epoxy Plate Using an Impedance-Based Non-Destructive Testing Method for Multiple Structures

The emergence of composite materials has revolutionized the approach to building engineering structures. With the number of applications for composites increasing every day, maintaining structural integrity is of utmost importance. For composites, adhesive bonding is usually the preferred choice over the mechanical fastening method, and monitoring for delamination is an essential factor in the field of composite materials. In this study, a non-destructive method known as the electromechanical impedance method is used with an approach of monitoring multiple areas by specifying certain frequency ranges to correspond to a certain test specimen. Experiments are conducted using various numbers of stacks created by attaching glass fiber epoxy composite plates onto one another, and two different debonding damage types are introduced to evaluate the performance of the multiple monitoring electromechanical impedance method.

Rethinking the traditional full-mouth rehabilitation by applying minimal prosthetic dentistry for maximum patient benefit

The field of dentistry is an ever-evolving discipline. A marked rise in the use of endosseous implants, adhesive ceramic bonding, and composite resins, as well as continued patient desire for minimally invasive procedures, has created a new conservative era in the practices of many restorative dentists. These trends, coupled with the significant financial impact associated with the reconstruction of failing, worn, and esthetically compromised dentitions, have facilitated a paradigm shift in the way that individual patient cases are being treatment planned today. Applying restraint to conventional practices involving the unnecessary gross removal of hard tooth structure is both a skill that needs to be cultivated as well as an evident obligation to the patient. A case report demonstrates the utilization of multiple restorative materials to provide a minimally invasive definitive treatment that was biomechanically, esthetically, and financially satisfactory for the patient.

Shear Strength and Interfacial Toughness Characterization of Sapphire-Epoxy Interfaces for Nacre-Inspired Composites

The common tensile lap-shear test for adhesive joints is inappropriate for brittle substrates such as glasses or ceramics where stress intensifications due to clamping and additional bending moments invalidate results. Nevertheless, bonding of glasses and ceramics is still important in display applications for electronics, in safety glass and ballistic armor, for dental braces and restoratives, or in recently developed bioinspired composites. To mechanically characterize adhesive bondings in these fields nonetheless, a novel approach based on the so-called Schwickerath test for dental sintered joints is used. This new method not only matches data from conventional analysis but also uniquely combines the accurate determination of interfacial shear strength and toughness in one simple test. The approach is verified for sapphire-epoxy joints that are of interest for bioinspired composites. For these, the procedure not only provides quantitative interfacial properties for the first time, it also exemplarily suggests annealing of sapphire at 1000 °C for 10 h for mechanically and economically effective improvements of the interfacial bond strength and toughness. With increases of strength and toughness from approximately 8 to 29 MPa and from 2.6 to 35 J/m², respectively, this thermal modification drastically enhances the properties of unmodified sapphire-epoxy interfaces. At the same time, it is much more convenient than wet-chemical approaches such as silanization. Hence, besides the introduction of a new testing procedure for adhesive joints of brittle or expensive substrates, a new and facile annealing process for improvements of the adhesive properties of sapphire is suggested and quantitative data for the mechanical properties of sapphire-epoxy interfaces that are common in synthetic nacre-inspired composites are provided for the first time.

Intentional replantation of adhesively reattached vertically fractured maxillary single-rooted teeth

AIM

To evaluate the clinical outcomes of intentionally replanted maxillary single-rooted teeth with vertical root fractures (VRFs) after being repaired extraorally using 4-methacryloxyethyl trimellitate anhydride/methacrylate-tri-n-butyl borane (4-META/MMA-TBB) resin cement.

METHODOLOGY

Twenty-one root filled maxillary single-rooted teeth with VRFs were evaluated. After atraumatic extraction, fractured fragments were adhesively cemented. The teeth were then replanted and splinted to the neighbouring teeth for 2 weeks. Plaque index (PI), gingival index (GI), probing depth (PD) and clinical attachment level (CAL) were assessed at baseline, 6 and 12 months, and radiographic evaluations were made using PAI scores at baseline and 12 months. Mobility was evaluated using periotest values (PTV) at baseline, 1, 3, 6 and 12 months. Replanted teeth, contralateral teeth (control teeth) and adjacent teeth were analysed statistically using repeated measures one-way anova, unpaired t-tests and Wilcoxon matched-pairs signed-rank tests.

RESULTS

Two teeth were extracted in the first month after surgery. PI, GI, CAL and PD scores of the replanted teeth were significantly lower at 6 month (P < 0.0001 for all) and 12 month (P < 0.0001 for all) postoperatively when compared to baseline, but the values were not significantly different from those of the control and adjacent teeth. PTV of the test teeth increased significantly (P < 0.0001) after the intervention and decreased to baseline levels by month 12. PTVs were significantly higher (P < 0.05) at baseline, 1, 3 and 6 months in the test teeth when compared with the control teeth, but were not significantly different at month 12. PAI scores of teeth with VRF were significantly lower (P < 0.05) at 12 months compared with baseline.

CONCLUSIONS

Adhesive cementation and intentional replantation were an effective treatment modality for this group of vertically fractured maxillary single-rooted teeth. The clinical periodontal parameters decrease by month 6, and the mobility returned to the physiological limits of natural teeth 12 months after replantation.

Surface modification with alumina blasting and H2SO4-HCl etching for bonding two resin-composite veneers to titanium

The purpose of this study was to investigate the effect of an experimental surface treatment with alumina blasting and acid etching on the bond strengths between each of two resin composites and commercially pure titanium. The titanium surface was blasted with alumina and then etched with 45wt% H2SO4 and 15wt% HCl (H2SO4-HCl). A light- and heat-curing resin composite (Estenia) and a light-curing resin composite (Ceramage) were used with adjunctive metal primers. Veneered specimens were subjected to thermal cycling between 4 and 60°C for 50,000 cycles, and the shear bond strengths were determined. The highest bond strengths were obtained for Blasting/H2SO4-HCl/Estenia (30.2 ± 4.5 MPa) and Blasting/Etching/Ceramage (26.0 ± 4.5 MPa), the values of which were not statistically different, followed by Blasting/No etching/Estenia (20.4 ± 2.4 MPa) and Blasting/No etching/Ceramage (0.8 ± 0.3 MPa). Scanning electron microscopy observations revealed that alumina blasting and H2SO4-HCl etching creates a number of micro- and nanoscale cavities on the titanium surface, which contribute to adhesive bonding.

Effect of interface structure on mechanical properties of advanced composite materials

This paper deals with the effect of interface structures on the mechanical properties of fiber reinforced composite materials. First, the background of research, development and applications on hybrid composite materials is introduced. Second, metal/polymer composite bonded structures are discussed. Then, the rationale is given for nanostructuring the interface in composite materials and structures by introducing nanoscale features such as nanopores and nanofibers. The effects of modifying matrices and nano-architecturing interfaces on the mechanical properties of nanocomposite materials are examined. A nonlinear damage model for characterizing the deformation behavior of polymeric nanocomposites is presented and the application of this model to carbon nanotube-reinforced and reactive graphite nanotube-reinforced epoxy composite materials is shown.