Adhesive and Magnetic Properties of Polyvinyl Butyral Composites with Embedded Metallic Nanoparticles

Magnetic metallic nanoparticles (MNPs) of Ni, Ni82Fe18, Ni50Fe50, Ni64Fe36, and Fe were prepared by the technique of the electrical explosion of metal wire. The average size of the MNPs of all types was in the interval of 50 to 100 nm. Magnetic polymeric composites based on polyvinyl butyral with embedded metal MNPs were synthesized and their structural, adhesive, and magnetic properties were comparatively analyzed. The interaction of polyvinyl butyral (supplied as commercial GE cryogenic varnish) with metal MNPs was studied by microcalorimetry. The enthalpy of adhesion was also evaluated. The positive values of the enthalpy of interaction with GE increase in the series Ni82Fe18, Ni64Fe36, Ni50Fe50, and Fe. Interaction of Ni MNPs with GE polymer showed the negative change in the enthalpy. No interfacial adhesion of GE polymer to the surface of Fe and permalloy MNPs in composites was observed. The enthalpy of interaction with GE polymer was close to zero for Ni95Fe5 composite. Structural characterization of the GE/Ni composites with the MNPs with the lowest saturation magnetization confirmed that they tended to be aggregated even for the materials with lowest MNPs concentrations due to magnetic interaction between permalloy MNPs. In the case of GE composites with Ni MNPs, a favorable adhesion of GE polymer to the surface of MNPs was observed.

Effect of Holes in Overlap on the Load Capacity of the Single-Lap Adhesive Joints Made of EN AW-2024-T3 Aluminium Alloy

The paper presents the results of experimental research aimed at determining the possibilities of strengthening structural adhesive joints. Techniques to improve the strength of adhesive joints was to make holes in the front part of the adherends in order to make the joint locally more flexible in the area of stress concentration at the joint edges. The tests were carried out for the lap joints of EN AW-2024-T3 aluminum alloy sheets, which were bonded with Loctite EA3430 epoxy adhesive. Static tests were carried out on the basis of the tensile/shear test. It has been shown that the applied structural modifications allow for an increase in the strength of the joint, in the best variant, an increase in strength of 14.5% was obtained. In addition, it has been shown that making holes in the adherends allows to reduce the spread of strength results.

INVESTIGATION OF MECHANICAL PROPERTIES OF PIPES WITH BUTT CURVED LAP JOINTS SUBJECTED TO TORSION

In this study, the mechanical properties of steel pipe joints bonded with an acrylic adhesive under torsion were investigated by considering different overlap lengths and curvilinear radii. For this purpose, St-37 galvanized steel pipes with ØD = 21.3 mm outer and Ød = 15.9 mm inner diameters were modeled in three dimensions by creating 8, 10, 12 mm overlapping lengths in male and female form and 30, 40 and 50 mm curvilinear radii on the forehead regions. Numerical analyzes of the created models were performed in the ANSYS Workbench program, and samples with an overlap length of 10 mm were prepared on the CNC (Computer Numerical Control) bench to verify the numerical analysis. The prepared male and female specimens were joined using an acrylic-based DP810 structural adhesive resistant to humid environments, curable at room temperature, and validation experiments were carried out. After the study, obtained numerical and experimental data showed that pipe lap joints subjected to torsional moment with the same lap length but different curvilinear radius have been observed to vary significantly in the amount of load they carry. In addition, as the overlap length increased, the amount of load they carried increased. Also, in this study was compared by performing stress analyzes according to the overlap length and radii of curvature.

A Review of Structural Adhesive Joints in Hybrid Joining Processes

Hybrid joining (HJ) is the combination of two or more joining techniques to produce joints with enhanced properties in comparison to those obtained from their parent techniques. Their adoption is widespread (metal to metal joint, composite to composite and composite to metal) and is present in a vast range of applications including all industrial sectors, from automotive to aerospace, including naval, construction, mechanical and utilities. The objective of this literature review is to summarize the existing research on hybrid joining processes incorporating structural adhesives highlighting their field of application and to present the recent development in this field. To achieve this goal, the first part presents an introduction on the main class of adhesives, subdivided by their chemical nature (epoxy, polyurethane, acrylic and cyanoacrylate, anaerobic and high-temperature adhesives) The second part describes the most commonly used Hybrid Joining (HJ) techniques (mechanical fastening and adhesive bonding, welding processes and adhesive bonding) The third part of the review is about the application of adhesives in dependence of performance, advantage and disadvantage in the hybrid joining processes. Finally, conclusions and an outlook on critical challenges, future perspectives and research activities are summarized. It was concluded that the use of hybrid joining technology could be considered as a potential solution in various industries, in order to reduce the mass as well as the manufacturing cost.

Low Viscosity Epoxy Structural Adhesive Cured at Room Temperature for Crack Repair of Subway Tunnel

Epoxy structural adhesive has good mechanical properties, especially high adhesion, low shrinkage rate, and high stability, widely used in steel plate reinforcement, crack repair, bridge splicing, and concrete bonding, etc. However, due to the high cross-linking density and high internal stress after curing, its shortcomings, such as brittleness, the poor performance of fatigue resistance and heat resistance, limit its application in special track engineering. In this work, two kinds of epoxy structural adhesives (EPA-1, EPA-2) with low viscosity and room temperature curing were synthesized by selecting different bisphenol A epoxy resin and active diluent as component A and modified amine curing agent as component B. The results showed that EPA-1 and EPA-2 presented significant toughness compared with the classic construction adhesive (AralditeXH160). The yield strengths of EPA-1 and EPA-2 were 4.88 MPa and 13.13 MPa, and the shear strengths were 11.93 MPa and 13.08 MPa, respectively, showing good adhesive properties. In addition, the viscosities of EPA-1 and EPA-2 were 127 mPa·s and 308 mPa·s, respectively, and their decomposition temperatures were all above ∼280 °C, which indicated that the self-made epoxy structural adhesives could be used for the repair of cracks in the vibration subway tunnel.

Hydrothermal Aging and Bonding Properties of a New Room Temperature Cured Structural Adhesive in Building Components

his paper firstly explores the hydrothermal aging performance of a new room temperature cured structural adhesive at four different levels of relative humidity through dynamic mechanical analysis (DMA). The results show that the strengthening effect of post-curing was stronger than weakening effect of humidity. Then, the Arrhenius equation was introduced to calculate the ratio of the apparent activation energy of this adhesive at the glass transition temperature before and after hydrothermal aging. The little change of the ratio suggests that the adhesive boasts a strong resistance to hydrothermal aging. In addition, the adhesive was tested on concrete structures at room temperature to observe its repairing effect of concrete cracks. The observations reveal that the compressive strength of the cracked concrete block repaired by the adhesive was as high as 90.5% of that of the intact concrete block. Furthermore, the adhesive was used to bond rebars to concrete under three different constant tensile speeds. The results demonstrate that the bonding effect was better under slow constant loading.