Papers by Keyword: Shear Strength

Abstract: Shear strength probabilistic assessment of concrete members with glass fibre reinforced polymers (GFRP) is performed in the paper. The aim of the analysis performed is to verify the existing code analytical formulas for shear strength calculation using stochastic models, to perform uncertainty propagation, sensitivity analysis and model uncertainty assessment. The study introduces a probabilistic framework that incorporates both model uncertainty and stochastic variability of input parameters into the assessment of shear resistance. The code models of Eurocode 2, ACI 440 and the fib Model Code 2010 are examined with respect to uncertainties involved and the reliability of the design value determination.

Abstract: Glass fiber-reinforced composites (GFRC) are widely used in structural applications due to their high strength-to-weight ratio and excellent fatigue resistance. Nevertheless, the mechanical integrity of adhesive joints remains a critical challenge in composite structural engineering. This study aims to investigate the influence of varying epoxy resin mixing ratios on the lap shear strength of glass fiber-reinforced composite joints. Two experimental schemes were conducted by varying the resin-to-hardener composition in the range of 10:50 to 70:50 (by weight). Single-lap joint specimens were fabricated and tested in accordance with ASTM D5868-95. The results demonstrated that a resin-to-hardener ratio of 50:50 yielded the maximum lap shear strength, reaching 5.71 MPa for resin system A and 5.28 MPa for resin system B. This ratio indicated a stoichiometric balance between epoxy groups and active amine groups, resulting in optimal curing with maximum cross-linking density. Deviations from this optimal ratio, either due to excess or deficiency of one component, led to a significant reduction in joint strength, as indicated by brittle fracture or weak adhesive bonding. These findings highlight the importance of precise control over epoxy adhesive formulations to ensure reliable mechanical performance in composite structures. The implications of this research contribute to the development of more durable and efficient adhesive systems, particularly for GFRC applications in the automotive, aerospace, and marine industries.

Abstract: A 3D Carbon-Carbon (Cf/C) composite with fabric reinforcement is of interest in applications where flexural loads are dominant, such as in the wings and control surfaces of aircraft and missile systems. Investigating the mechanical properties of these composites is crucial for understanding their performance, especially for designing and analysing composite structures used in extreme conditions. In this research paper, the compression and shear responses of the 3D PF Cf/C composite samples have been determined at room temperature. The samples were machined in the directions of XY, XZ, and ZX, respectively. Then, the Iosipescu shear test and the short beam shear test were employed to evaluate the shear strength and shear modulus of the composite samples, respectively. The material exhibits a strain to failure of around 0.15% in the X direction with a modulus of 54 GPa. In the Z direction, it deforms more, with a strain to failure of approximately 20% and a modulus of 6.2 GPa.

Abstract: To improve the reliability of solder joint, Ni–Cu alloy plating films with three-dimensional structures were fabricated on Cu substrates via electroplating. By varying the plating potential, the morphology of the Ni–Cu alloy plating films was controlled, and their effect on solder joint microstructure and mechanical properties was investigated. Sn–5Sb lead-free solder was used to join the plated Cu substrates, followed by aging at 200°C for up to 100 h. Surface observations revealed that more negative plating potentials promoted the formation of larger and more numerous three-dimensional structures. Cross-sectional analysis showed that Cu–Ni–Sn and Cu–Sn reaction layers formed at the solder interface and thickened with aging. Shear test showed that the joint strength decreased after 25 h of aging and remained nearly constant thereafter. In addition, joints with Ni–Cu alloy plating exhibited lower shear strength than those without plating. Fractographic analysis showed that fracture initially occurred within the solder and Cu–Ni–Sn reaction layers, whereas prolonged aging induced fracture propagation through the solder, Cu–Ni–Sn, and Cu–Sn reaction layers.

Abstract: This study examines the influence of low proportions (<2.5%by mass) of 40/63 mm gravel on the shear strength of hardfill used in the Mallegue-Amont Dam (Tunisia). To address the coarse nature of the material, a custom medium-scale direct shear apparatus was developed, despite its non-standard dimensions. Nine mixtures with varying sand-to-gravel ratios were prepared to evaluate the effect of fine content. Experimental testing was supported by statistical analysis and validated through numerical simulations using FLAC3D. Results indicate that the 40/63 mm fraction has a negligible effect on shear strength parameters. Instead, the mechanical response is predominantly controlled by cementation and particles smaller than 40 mm. Numerical modeling confirmed the reliability of the experimental findings and reinforced the validity of the adapted testing approach. The study demonstrates that representative shear strength parameters can be obtained using non-standard equipment, provided mixture preparation and mold dimensions are carefully controlled. These insights contribute to cost-effective hardfill design and improved durability of dam and infrastructure projects.

Abstract: Adhesive bonding is often found for engineering construction technology applications in industries such as aeronautics, automotive, electronics, and aerospace. Single lap joint type connections can be applied to dissimilar materials so that they can reduce the weight of construction. The objective of this study to determine the effects of adding natural latex adhesive to aluminum-cocofiber composites single lap joints. The research material uses two types of adherend, namely aluminum and cocofiber-reinforced composite with an Unsaturated Polyester matrix (UPRs) type Yukalac BQTN with a MEXPO catalyst. Adhesive bonding material uses epoxy resin and the addition of natural latex. The connection is carried out using a single lap joint adhesive bonding method between two different adherend materials. The adhesive material in the single lap joint is 0.2 mm thick using variations in the addition of natural latex adhesive to epoxy with variations of 5%NK: 95%EP, 15%NK: 85%EP, 25%NK: 75%EP, and 35%NK: 65%E.P. The adherend surface treatment was given by roughing the surface with sandpapering grid #150. The single lap joints shear test refers to ASTM D-1002. The test results indicated that the shear strength increases with the addition of 5% natural latex to the epoxy. The roughness treatment applied to the surface provides an irregular effect, thus increasing the bond between the adhesive and the adherend. In addition, it also improves the mechanical interlocking of the single lap joint. The failure modes after the shear stregth test that occur based on macro observations are cohesive, stock-break, thin layer cohesive, and fiber pull-out.

Abstract: A porous nickel (Ni) was brazed to copper (Cu) and stainless steel 304 (SS304) using VZ2250 and MBF67 brazing filler metal with a composition of 77.4Cu-9.3Sn-7.0Ni-6.3P and 64.5Ni-25Cr-6P-1.5Si (Cu: Copper, Sn: Tin, Ni: Nickel, P: Phosphorus, Cr: Chromium, Si: Silicon), respectively for joint microstructure and mechanical properties analysis. Porous Ni with a pore density of 15 pores per inch (PPI) was sandwiched between Cu/VZ2250 and MBF67/SS304. A brazed joint of Cu/Porous Ni/SS304 with VZ2250 and MBF67 brazing filler metal was prepared in a high vacuum furnace at different brazing times of 5, 10, and 15 minutes for 1015 °C with a heating and cooling rate of 10 °C/min, respectively for comparison purpose. The microstructure and mechanical properties of the brazed joint were investigated to identify the joint ability after the brazing process. Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS) confirmed the interfacial microstructure by the formation of the diffusion filler metal (dark grey colour) for the Cu/Porous Ni/SS304 with VZ2250 and MBF67 brazing filler metal. For shear strength tests, the value decreases with an increase in the brazing time. The shear strength tests for the brazed joint of Cu/Porous Ni/SS304 with VZ2250 and MBF67 brazing filler metal show the maximum shear strength test value can be achieved for the brazing time of 5 minutes. The decreasing shear strength value was observed with differences in structural data of porous Ni due to the softening after the brazing process. Keywords: Brazing, Microstructure, Porous Nickel, Shear Strength.

Abstract: In this study, use of adhesive double-sided tape in laser welded ultra-high-strength steel lap joints was evaluated. The test material in the study was abrasion resistant steel (AR400). Optical microscopy was used to investigate macroscopic morphologies of the welds and hardness profiles were measured. Static properties of the joints were evaluated by performing tensile shear strength tests. Fatigue strength of the joints were evaluated by conducting axial fatigue tests. The use of tape resulted in a gap between the welded plates which has several advantages. The gap between the plates markedly increased the width of the weld at the interface of the plates. According to the hardness measurements the hardness of the weld metal was 12% higher compared to the hardness of the AR steel base material. The gap between the plates increased the strength of the joint by up to 20%. The adhesive tape itself did not have a significant effect on the shear strength of the joints. The main advantages of using the tape were a constant air gap and its function as a fastener in welding, so that separate fasteners are not needed.

Abstract: The present study aims to contribute to the knowledge of the mechanical properties of limestone blocks extracted from mines in the Republic of Moldova and used in a new masonry technology. The initial shear strength is examined based on laboratory work carried out on 5 samples from each of the 3 mines in different areas of Moldova. The strength calculation of the proposed masonry technology is carried out based on the standards for load-bearing walls and corresponds to the requirements. The results showed that Moldovan limestone blocks have high mechanical properties. The proposed masonry technology is based on the use of local materials and to increase the strength, instead of steel mesh, fibreglass mesh and epoxy resin will be used, which can be implemented in the Republic of Moldova. This research based on the use of local materials is significant for the development of the construction technology branch in Moldova.

Abstract: In practical engineering applications, it usually gets the expected value of the ultimate side friction of concrete piles by the empirical parameter method. The expected value of the ultimate side friction of concrete piles cannot achieve maximum optimization due to the complexity of formation conditions and the lack of experience of technicians. To accurately obtain the ultimate lateral friction resistance of piles in homogeneous soil layers, optimize the standard value of pile ultimate lateral resistance, ensure construction safety, and save construction costs, the research method combining theoretical derivation and on-site measurement data validation was done in the manuscript. Based on the shear strength of the pile-soil interface of different materials and the shear performance of the soil around the pile, a calculation equation for the standard value of the ultimate lateral friction resistance of concrete piles in different homogeneous soil materials was derived and applied to the equation for calculating the ultimate bearing capacity of foundation pile and the axial force of pile. Finally, based on an engineering example, the calculated results were compared with the measured resultsThe research results show that in thick coarse-grained soil, as the foundation pile is short, the ultimate bearing capacity of a single pile obtained using the calculation equation deduced in this paper is less than that obtained using the empirical equation provided by the national code. In a deep cohesionless homogeneous soil material, the concrete pile shaft axial force calculation using the pile shaft axial force calculation equation deduced in this paper is close to the measured value when the foundation pile bears the ultimate load; the proposed new method has good application value.