Experimential Study on Failure Mode and Ultimate Shear Bonding Force of CFRP Plate-Steel Interface under Anchor Compression

In order to study the paste failure mode and ultimate shear bonding force of CFRP plate-steel interface anchor bonding, a single-sided shear test was carried out on a total of 15 carbon fiberboard (CFRP)-steel composite beam structure specimens in five groups. The test results show that for organic adhesives, the uniform anchoring method can improve the bearing capacity of the construction; for organic adhesives, the ultimate shearing when the specimen is peeled with inorganic glue is used. The bonding capacity is greater than that of specimens with organic adhesives.

Preparation of tin coating on the surface of copper-coated carbon fiber and its effect on the microstructures and properties of the composite coating

In order to prevent the copper coating on the carbon fiber surface from oxidizing and falling off, the tin coating is plated on the surface of copper-coated carbon fiber. In this paper, the copper-tin composite coating with different thicknesses of tin coatings were successfully prepared by electroless plating. The results show that with the increasing of electroless tin plating time, the thickness of the copper-tin composite coating increases. The test results of the bonding force between the composite coating and the carbon fiber show that the coating bonding force is the best when the thickness of composite coating is between 1.31 μm and 1.55 μm. This is due to the formation of copper-tin intermetallic compounds preventes direct contact between the copper coating and oxygen, which can effectively inhibit the oxidation of the copper plating layer, thereby making the plating layer less likely to fall off. However, the excessively thick tin coating would increase the internal stress of the coating, and promote the generation of cracks on the surface of the composite coating, which would cause the composite coating to fall off. This research will provide new ideas for the preparation of high-performance copper plating on the surface of carbon fiber, and provide an important theoretical and practical basis for the application of copper coatings.

Preparation of Modified PVA Copolymer by DAAM/ADH and Cross-Linking Mechanism for Paper

Herein, a novel modified polyvinyl alcohol(DA-IPVA) used as sizing agent was prepared by using diacetone acrylamide(DAAM) as graft monomer and N-(isobutoxymethyl)acrylamide(IBMA) as self-cross-linking monomer. The effect of the amount of DAAM on the properties of emulsion, film and sizing paper was discussed. The surface micro-structure of the sizing paper was characterized by SEM and AFM. The addition of DAAM/ADH and IBMA endowed DA-IPVA with cross-linked active group and increased cross-linking density and hydrophobicity after ADH was added into the emulsion and the cross-linking structure was formed. The enhancing mechanism of surface sizing agent for paper was revealed. The DA-IPVA can be cross-linked on the surface and inside of the paper to form a dense network structure, which improves the bonding force between the fibers. When the mole fraction of DAAM of the cross-linking monomer is 8%, the surface sizing performance of the paper is obviously improved compared with the base paper. The dry and wet strength is increased by 266.5% and 334.3% respectively, and the folding resistance is increased 2946.67%. This study can have a profound impact on the development of the technology of cross-linking surface sizing agent for paper.

Stochastic Damage Constitutive Relationship of Steel-Reinforced Concrete Bond-Slip

The bond-slip damage of the interface between profile steel and concrete is the key point of steel-reinforced concrete structure. This paper is based on the statistical analysis of a large amount of experimental data and the distribution characteristics of bonding stress on the bonding surface of the profile steel and concrete, and the conversion rules between the three parts (chemical bonding force, frictional resistance, and mechanical interaction) of the bond force are obtained. According to the mutual conversion rules of the three parts of the bonding force on the steel-reinforced concrete bonding surface, a mesomechanical model based on the spring-friction block element is established. Taking into account the discreteness of concrete performance on the bonding surface and the randomness of defects, using the stochastic damage theory, a constitutive model of stochastic bonding damage on the steel-reinforced concrete bonding surface is established. The comparative analysis with the results of a large number of steel-reinforced concrete pull-out tests shows that the model can reasonably reflect the damage characteristics of the steel-reinforced concrete bonding surface.

Discrete Element Simulation Based on Elastic–Plastic Damping Model of Corn Kernel–Cob Bonding Force for Rotation Speed Optimization of Threshing Component

Current corn kernel-cob bonding mechanics models (LSD models) uniformly consider the bonding force changes during the maize threshing operation as an elastic change, resulting in computational errors of up to 10% or more in discrete element simulations. Due to the inability to perform high-precision discrete element simulation of the mechanics characteristics during the corn threshing operation, the core operating parameters of the corn thresher (rotation speed of the threshing component) rely mainly on empirical settings, resulting in a consistent difficulty in exceeding 85% of the corn ear threshing rate. In this paper, by testing the mechanics characteristics of corn kernels, the bonding force is found to have both elastic and plastic changes during the threshing process. An elastic–plastic (EP) damping model of the corn kernel–cob bonding force was established by introducing a bonding restitution coefficient e to achieve an integrated consideration of the two changes. By testing the relationship between the properties of the corn ear itself and the model parameters, the pattern of the effect of the corn ear moisture content and the loading direction of the ear by force on the EP model parameters was found. By establishing a model of the relationship between the corn cob’s own properties and the model parameters, the EP model parameter values can be determined by simply determining the moisture content of the ear. In this paper, the EP model was established and the high-precision simulation and analysis of the process of bonding force variation between corn kernel and cob is realized on the self-developed AgriDEM software. At the meantime, the optimal values of the threshing component rotation speed under different conditions of moisture content of corn ear were obtained by establishing an optimization model of threshing component rotation speed. The test results showed that the corn ear threshing rate could reach more than 92.40% after adopting the optimized speed value of the threshing component in this paper. Meanwhile, the test results showed that the discrete element simulation results based on the EP model did not significantly differ from the measured results of the thresher. Compared with the most widely used LSD model, the EP model can reduce the computational error by 3.35% to 6.05%.

Hydrophilicity Control of Ag-Paste Electrodes by UV/Ozone Treatment

Ag-paste is used as an electrode material in various fields as a manufacturing advantage that enables solution processing. However, when a subsequent thin film is formed on the solidified Ag-paste electrode, there is a fear that the bonding force between the Ag-paste electrode and the subsequent thin film is weakened and peeled off due to the low surface energy of the Agpaste electrode. It is necessary to increase the surface energy of the Ag-paste electrode surface since it ultimately directly affects the yield of the device or product. In this study, the UV/ozone treatment process was introduced to increase the Ag-paste surface energy, thereby making the surface hydrophilic. Additionally, it was confirmed that the UV/ozone treatment process affected only the surface of the Ag-paste electrode by extracting the contact resistance.

Addressing the Broken Wire Issue during the Assembly Manufacturing of QFN Leadframe Device

The integrity of the assembly wirebond process’ 2nd bond poses a big challenge for semiconductor manufacturing of quad-flat no-leads (QFN) devices, particularly on multiple wires on a lead. These devices are vulnerable to induce or obtain broken wire at heel defect. This type of defect is an abnormality in the formation of the stitch, mostly a crack or fracture seen on the facade of the stitch. Normally, it happens when there is too much vibration or transfer of ultrasonic generator (USG) power combined with high bonding force on 2nd bond. In the case of leads with common wires, broken wire at heel could also happen through excessive USG application resulting to transfer of resonance on adjacent wires. This paper presents a better understanding and analysis done to provide an adequate and appropriate solution to broken wire at heel issue.