Recently resistance welding (RW) technique have emerged as a viable alternative method for the joining of fiber reinforced polymer (FRP) composites. It is more cost-efficient as opposed to the ...conventional adhesive, mechanical and other joining methods. The objective of this paper is to provide a deeper insight into the recent development of the resistance welding technique for FRP composites. The main focus is set on the parameters that govern the welding process and the principal phenomena that affect the joints of the thermoplastic composite. The evaluation methods, the comprehensive failure modes, welding interface behavior and microscopic evaluation of interface are also looked at in detail. And this technology has been further extended to the connection of thermoset composites. In addition, several alternative fresh implants that involve micro-nano carbon materials and offer possibilities for future applications are systematically compared. Continuous resistance welding (CRW) is briefly introduced as one of the most promising methods in the end.
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•Al/Ni reactive multilayer nanofoils are used as a local heat source in the joining of copper foils.•Grain coarsening and grain refining are both occurred in the reactants of Al/Ni ...reactive multilayer nanofoils.•The joints strength of copper foils has been improved with the assistance of Al/Ni reactive multilayer nanofoils.
Interconnected individual battery cells of lithium batteries are unavoidably involved in joining in parallel to improve the battery capacity. Due to the advantage of the small joint area and short process time, micro resistance welding is one of common applied joining techniques of copper foils. However, strength improvement of micro resistance welded copper foils was restricted by the insufficient Joule heat accumulation at the faying interface. Here we used the exothermic reaction of Al/Ni reactive multilayer nanofoils as a local heat source at the faying interface of micro resistance welding of copper foils, designing to increase the heat accumulation and improve the joints strength. Two faying interfaces were formed at the joints of copper foils, one was at the thickness direction of AlNi reactants caused by the diffusion of Cu element based on the high temperature and fracture of coating layer, and another was formed at the surface of AlNi reactants and copper foils. Due to grain boundary relaxation, grain refining of AlNi alloy compound of final product with the average grain size of 27.9 nm at the faying interface attributed to the hardness increase and improvement of joints strength. The joints strength of two-layer copper foils increased to 100 N and the value was 500 N for the joints of multilayer copper foils with the assistance of Al/Ni reactive multilayer nanofoils. These results pave the way for the application of micro resistance welding technique in the battery cells joining of lithium batteries manufacture.
PEI/GF lamination and TI6AL4V alloy are often related to the poor wettability of PEI to TI6AL4V alloy at the interface layer. To overcome these problems, an in situ synthetic candle soot reinforcing ...coating on TI6AL4V alloy was added into the place of the bonding area. The mechanical properties of composite joints were evaluated by single lap shear strength (LSS) tensile test. The mechanism of strengthening TI6AL4V-PEI/GF joint by candle ash was compared.
The paper is devoted to analysis of power losses in a resistance welding machine including supplying system and examination of welding conditions of the welding machine current in a case of ...synchronous (simultaneous) operation of multiple welding machines, i.e., during the conduction of welding current. Analysis of the most important contributors of power losses generated on the current path between a power source and the welded joint is carried out. The analysis is carried out for a DC (direct current) welding machine with power electronics inverter. AC (alternating current) welding machines are also taken into account. The analysis is divided in two parts. The first one is the analysis of single welding machine operation, while in the second part, coexistence (mutual operation) of two synchronous welding machines is considered. The analysis is based on results of numerical and experimental investigations. The first one is focused on calculation of power losses in the energy path (including a Sankey type power loss distribution diagrams), and the second one is based on experimental tests carried out to determine the diameter of the weld nugget and the strength of the joints, for cases of reducing the welding current. An example of simultaneous operation of welding machines was presented and discussed. The percentage voltage drops and power losses in the entire power supply path of the resistance welder are shown. The analysis carried out is extremely important from this point quality of welded joints.
•Thick Al wire was successfully bonded with Au/Cu pad by ultrafast parallel gap micro-resistance method.•Sufficient interfacial reaction was finished within 20 ms.•Cu-based solid solution, (Au, Cu) ...Al2 and (Cu, Au) 9Al4 phase were identified at the bonding interface.
Reliable bonding of thick Al wires and plated Au pad is important for the packaging of power modules. The interfacial phases of the Al/Au/Cu joint after parallel gap micro-resistance welding were observed by transmission electron microscopy (TEM). Obvious Al, Au and Cu elemental interdiffusion can be observed by energy dispersive spectrometer (EDS) mapping, indicating the occurring of sufficient interfacial reaction. Under the effect of current and heat, the core temperature is higher than the melting point of Al. Liquid Al will react with Au and (Au, Cu) Al2 intermetallic compound (IMC) phase was formed rapidly within 20 ms. Besides, excessive Al atoms rapidly diffuse through the Cu-based solid solution, and react with Cu forming (Cu, Au) Al4 IMC phase.
The application of the fusion joining method for composite structures is associated with a nonuniform heat distribution in the heating element, because of which it is difficult to maintain a high ...bonding quality when upscaling this process. To address this issue, two layers of multiwalled carbon nanotube (MWCNT) sheets were interleaved in a carbon fabric heating element to alleviate the low-temperature issue at the edges of the heating element. The temperature at the edges of the heating element increased from 70–80 °C to 160–180 °C. Six different sizes of the heating element were selected to study the effect of the element size on the heat distribution. Lap shear tests were conducted, and the results showed that the lap shear strengths of the carbon fabric heating elements interleaved with MWCNT sheets improved by 49.9%, 71.5%, 84.1%, 110.5%, 118.2%, and 153.6%, respectively. Therefore, the interleaving of the heating element with MWCNT sheets can help improve the bonding quality in the resistance welding of thermoplastic composites.
A hybrid ultrasonic resistance spot welding process is developed, which integrates high-power ultrasonic vibrations into conventional resistance spot welding process. Weldability of galvanized ...transformation induced plasticity (TRIP-780) steel is studied based on this process. Ultrasonic resistance welds showed nugget pullout failure mode and more ductility compared with conventional resistance spot welds. Optical and scanning electron microscopic analysis revealed the refined microstructure in the fusion zone and heat affected zone of ultrasonic resistance welds. Coalesced bainite is present the fusion zone of conventional resistance spot welds while possible tempered martensite and feathery bainite is observed in ultrasonic resistance welds, which accounts for their higher ductile behavior.
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