Effects of Lap Configuration on Mechanical Properties and Composition Distribution of Three-layer Overlapped Laser Weldments on Al/Cu Dissimilar Materials

Battery cells are connected via bus-bars to meet performance requirements, such as power and capacity, and multiple layers of dissimilar materials functioning as anodes, cathodes, or bus-bars are overlapped and welded together. In laser welding, the formation of brittle intermetallic phases in the weld joint is inevitable and, in turn, deteriorates the mechanical properties. To obtain the desirable joint performance, appropriate welding parameters to avoid intermetallic phase formations and joint designs to release stress concentrations must be obtained. This study investigates the effects of lap configurations and process parameters on the tensile-shear load, T-peel load, and composition distribution when multi-layered joints of dissimilar materials are produced by laser welding. Two layers of 0.4 mm Al sheets were welded with a single 0.2 mm Cu sheet, which was emulated using electric vehicle battery interconnects. The results show that the penetration depth varied in accordance with the lap configuration even under the same heat input condition. The lap configuration and welding parameters influenced the composition distribution of the welds, as they altered the solidification rate, number of Cu/Al contact interfaces, and location of the high-density material. The failure load of the T-peel specimens was always lower than that of the tensile-shear specimens except for the Cu−Al−Al lap configuration. The T-peel load of the Cu−Al−Al lap configuration was similar to that of the tensile-shear load. When the stress-concentrated joint was homogeneous, it was more robust.

Enzymatic Conversion of Lignosulfonate into Wood Adhesives: A Next Step towards Fully Biobased Composite Materials

This study investigates the effect of the enzymatic polymerization of lignosulfonate for the formulation of a lignosulfonate-based adhesive. For this, beech lamellas were glued together and tested according to the EN 302-1 standard. The results showed that the laccase-polymerized lignosulfonate-based wood adhesives (LS-p) had similar mechanical properties as a standard carpenter’s glue (PVAc-based D3 class white glue), as no significant difference in tensile shear strength between these two adhesive types was found. However, carpenter’s glue showed almost 100% wood failure, while with the lignosulfonate-based wood glue, the samples failed, mainly in the glueline. Pre-polymerization of LS-p is the most critical factor to achieve the required viscosity, which is also connected to the wetting properties and the resulting tensile shear strength. The longer the pre-polymerization, the higher the viscosity of the LS-p adhesive, with the tensile shear strength reaching a plateau. The presented data show the potential of using enzymatically pre-polymerized lignosulfonate as a well-performing wood adhesive. Further development and optimization of the pre-polymerization process is required, which is also important to push towards upscaling and practical applications.

Study on the Effect of Bond Strength on the Failure Mode of Coarse-Grained Sandstone in Weakly Cemented Stratum

Bond strength is one of the most important parameters and can affect the macroscopic mechanical properties and the damage state of rock to some degree. Coarse-grained sandstone was studied using the controlled variable method. The influence of parallel bond strength on the peak strength and failure mode of coarse-grained sandstone was simulated, and the evolution law of peak strength and the failure mode of bond strength were comprehensively analyzed. The results show that the peak strength of the rock was positively correlated with the bond strength; the difference in quantity between the tensile and shear cracks was negatively correlated with tensile bond strength and positively correlated with shear bond strength. With a tensile-shear bond strength ratio of less than 0.5, the peak strength of the rock was usually stable at the certain extreme value under a constant tensile bond strength. The tensile cracks were negatively correlated with the tensile-shear bond strength ratio, and the shear cracks were positively correlated with the tensile-shear bond strength ratio. The main failure mode of the coarse-grained sandstone in the weakly cemented stratum of the Hongqinghe coal mine is shear failure. The research results can be used to guide the ground control of other mine stopes or roadways with weak cementation lithology.

Hybrid Carbon/Glass Fiber Reinforced Polymer; A Frontier Material for Aerospace Industry : A Review on Mechanical Properties Enhancement

Composite is the combination of two or more materials that differ in properties and composition to form unique properties. This paper reported in the literature on the field of deformation of hybrid composite under tensile, shear and flexural loading are presented in this chapter. This article review provides insight and state of the art for mechanics of composites that provides underlying theory for understanding the deformation and behaviour for the hybrid composite under various loading conditions. This paper also discusses mechanical behaviour of hybrid composites under static loading (Tensile, Shear, Flexural). It is essential to understand the principle that governs the mechanics of composites of laminate under loading which also applicable to hybrid composites C/GFRP.The high modulus fibre, such as Carbon fibre offers stiffness and load bearing capabilities, whereas the low modulus fibre, such as glass fibre makes the composite more durable and low in cost

Strength of three-sheet spot welds with critical nugget sizes in tensile shear, cross tension, peel and fatigue tests

Plug failures have been observed in three-sheet spot welds, where the weld nugget did not penetrate into the outer sheet. Such solid-state bonds were found to be formed as a result of high contact pressure and temperature during welding. The strength of single spot welds was studied in a three-sheet combination (0.61 mm DX54 on two 1.21 mm DP600) with nugget penetrations into the thin sheet below 40%. The static strength was evaluated by tensile shear, cross tension and mechanized peel testing, and fatigue tests were carried out in tensile shear configuration at 30 Hz and mean load of 2 kN. It was found that loading of the specimens in tensile shear, mechanized peel and cross tension tests leads to a plug failure and a ductile fracture of the thin sheet. The weld strength is not correlated with the nugget penetration into the thin sheet but is determined by the area of the bonded interface, instead, as shown by peel and cross tension tests. Fatigue tests revealed that the specimens break by a plug failure. The failure mechanism was found to be ductile for the highest load range after approximately 33 000 cycles. At lower load ranges, evidence of a crack was found in the DX54 sheet, leading to higher stress concentration and subsequent ductile fracture. It was estimated that a load range of 940 N leads to failure after approximately 106 cycles.

Characterization of Macro Mechanical Properties and Microstructures of Cement-Based Composites Prepared from Fly Ash, Gypsum and Steel Slag

Using solid wastes (SWs) as backfilling material to fill underground mined-out areas (UMOAs) solved the environmental problems caused by SWs and reduced the backfilling cost. In this study, fly ash (FA), gypsum and steel slag (SS) were used to prepare cement-based composites (CBC). The uniaxial compression, computed tomography (CT) and scanning electron microscope (SEM) laboratory experiments were conducted to explore the macro and micromechanical properties of CBC. The findings showed that the uniaxial compressive strength (UCS) of CBC with a curing time of 7 d could reach 6.54 MPa. The increase of SS content reduced the UCS of CBC, while the gypsum and FA content could increase the UCS of CBC. Microscopic studies have shown that the SS particles in CBC have noticeable sedimentation, and the increase of SS content causes the failure mode of CBC from tensile to tensile-shear. These research results can provide a scientific reference for the preparation of backfilling materials.

Influence of Veneer Density on Plywood Thickness and Some Mechanical Properties

It has been common knowledge that as the density of wood increases, the mechanical properties also improve. In turn, the density of wood depends on many factors, including the wood moisture content, location and cross-section in the trunk, the type of treatment and the parameters of technological processes. There is a great deal of research reported in the scientific literature on the effect of solid wood density on mechanical properties for different wood species as well as for structural timber. However, no research data can be found related investigation of the influence of veneer density on the properties of the birch plywood. In the present study, researching the properties of 7-ply birch plywood (thickness 9 mm), it was concluded that as the density of veneers increases, the bending properties of plywood in the direction of wood fibers (covered veneers) increases. When determining the plywood gluing quality, similar tendencies have been observed. For plywood with a lower density in all veneer plies the gluing quality (tensile-shear test) for perpendicular wood fiber veneers increases in the direction from the symmetry axis or middle veneer to the plywood outer plies, which can be explained by the fact that the outer plies become denser at the time of the hot pressing process. The results of the study will allow birch plywood manufacturers in direct production, sort veneers by density, to produce plywood with very predictable gluing quality, plywood thickness and mechanical properties in bending.

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.