Shear Strength Research Articles

Development of Double Frame Method to improve the seismic performance of low-rise reinforced concrete buildings

ABSTRACT The current paper proposes a seismic reinforcement method that uses a double frame and is called the Double Frame Method (DFM). Performance tests are conducted to assess the material suitability of a post-installed anchor that directly connects the existing frame to the double frame, while a shear performance test is conducted to examine the vertical connector. The performance of column members with and without DFM reinforcement was compared and evaluated. Ultimately, we have fabricated a two-story, one-span reinforced concrete existing frame test specimen and a DFM reinforced frame test specimen that we can use to examine the effect of improving seismic performance through repeated loading tests. The result of the anchor’s pull-out test show that the average tensile strength is 27.9 kN, exceeding the average design strength of 21.7 kN suggested by the manufacturer. The shear strength test results of the anchor show an average value of 28.7 kN. Meanwhile, the vertical connector test show that the internal force per anchor is 46.83 kN, which is approximately 163% more than the single anchor design shear strength of 28.7 kN. As a result of the DFM-reinforced column test, in the actuator direction, the yield strength is improved by about 120%, while the maximum strength is improved by about 150–180%. As a result of the two-story frame experiment, the double frame reinforced specimen shows a maximum strength of about 4.0 to 4.5 times that of the non-seismic specimen.

Competitive correlation between the interface layers determines the shear strength in Kovar/AgCuTi/Si3N4 joints

AbstractAs a promising high‐thermal‐conductivity ceramics, the direct bonding of Si3N4 with metals remains challenging. Here, we employed active metal brazing of Si3N4 ceramics and Kovar alloys using AgCuTi metal filler, and found that the shear strength in the prepared Kovar/AgCuTi/Si3N4 joints depends on the competitive correlation between the interface layers. The competitive consumption for active element Ti by Kovar/AgCuTi interfacial reactions reduced AgCuTi/Si3N4 interface layer thickness and deteriorated final shear strength, even when using a high‐Ti‐content filler. Surface analysis indicated that interfacial fracture between Ag‐based solid solution and Ti5Si3 was the primary cause of failure. Density functional theory (DFT) revealed that Ag (111)/Fe2Ti (001) interface had higher ideal work of adhesion (Wad) than Ag (111)/Ti5Si3 (001) interface, confirming the importance of AgCuTi/Si3N4 interface layer. Ultimately, by adjusting interface reaction layer thickness, the joints reached a high shear strength of 154.3 MPa.

Study on the characteristics particles of coarse grain material in high bench dump

Particle shape is an important factor affecting the strength and deformation of coarse materials in dumps. However, conducting research on particle shape in current laboratory experiments, and there exists no classification standard for the particle shape of the dump. Considering the project on high-bench dump in Jiangxi Province, based on the random particle construction method, this study determined the characteristic particles of coarse grain material in the dumping site by combining field investigation results, large-scale direct shear tests, and numerical analysis. Further, the influence mechanism of coarse grain content and characteristic particles on the mechanical characteristics of the dump were analyzed. The results showed that the increase in coarse grain content enhanced the irregularity of particle shape, increased the internal friction angle between particles, and reduced the cohesion of the dump. Moreover, with increase in the normal stress, the shear strength changed from insignificant to gradually enhanced, although the increasing trend slowed down. The constructed random particle model can well solve the effects of occlusion, nesting, and friction between particles that is neglected by the standard spherical particle model, and the fitting degree is better. The particle characteristics of coarse-grain materials in the dump were primarily block, strip, and flake. The three types of shape characteristics under low normal stress did not affect the mechanical properties of the dump. Further, with the increase in normal stress, the stress-strain curve reflected the shape characteristics and content of the dominant characteristics in the dump. Specifically, the block sample exhibited the dominant characteristics and the most content under the same normal stress, followed by the strip sample, with the flake sample exerting the least influence. The research results provide a theoretical basis for long-term safe operation, disaster monitoring, and early warning of high bench dump.

Preparation of natural adhesives with high-strength and low temperature fast-curing properties

The development of natural adhesives to substitute petroleum-based products is crucial for sustainable progress. However, the bond strength of most existing natural adhesives still falls short of that of commercially available adhesives and the curing process often demands prolonged high-temperature treatment. Herein, we prepared pure natural adhesives using gelatin (GE), tung oil (TO), and dopamine (DA) as the main raw materials. The shear strength of the adhesive to wood reached up to 6.35 MPa, a significant improvement over most natural wood adhesives reported. Additionally, the tensile strength of the adhesive to wood reached 10.50 MPa, which is comparable to commercially available neoprene-phenolic wood adhesives (9.99 MPa) and cyanoacrylate instant adhesives (9.48 MPa). In addition, the natural adhesive prepared by us exhibits fast curing performance at room temperature and can be fully cured in only 12 min, which is significantly better than the commercially available adhesive. The adhesives prepared in this study also possessed excellent reversible curing properties, antimicrobial properties, low toxicity, and degradability. These characteristics offer new insights for the advancement and dissemination of natural adhesives.

Enhancing Corrosion Resistance and Tribomechanical Characteristics of Powder Coatings via the Integration of Functionalized HF‐Free MXene Reinforcements

AbstractMXene, a new generation of 2D materials, is gaining attention for anti‐corrosion applications due to its large surface area, electrical conductivity, and self‐healing properties. Its low shear strength and self‐lubricating properties enhance wear resistance. Herein, silane functionalized HF‐Free MXene nanosheets “MS‐f_Ti3C2 and MS‐f_Ti3C2@Zn” synthesized through the molten salt method are integrated into the environmentally sustainable powder coating. The electrochemical tests indicate that a powder coating containing a well‐dispersed 1.5 wt.% f_Ti3C2@Zn nanosheets exhibit the highest polarization resistance (1.1 × 106 Ω cm2), lowest Icorr (2.15 × 10−8 A cm−2) and superior anti‐corrosion performance after 42 days of immersion in 3.5 wt.% NaCl. The polarization resistance (Rp) and corrosion current (Icorr) of the untreated coating are measured to be 1.6 × 103 Ω cm2 and 1.6 × 10−5A cm−2, respectively. In addition, the incorporation of MXene material reduces crack development and spalling, and enhances wear resistance during the friction process. The loading of 1.5 wt.% f_Ti3C2@Zn reduces the coefficient of friction (COF) and improves wear rate by 45% and 51%, respectively Analysis of composites via nanoindentation reveals such enhanced mechanical properties. This study presents an effective and sustainable approach to improve the mechanical, tribological, and long‐term corrosion protection of organic coating, thereby exhibiting great potential for using HF‐Free MXene as a multipurpose additive.

Preparation of glass fiber-reinforced polyphenylene sulfide/magnesium hybrid based on micro-arc oxidation by hot pressing molding

ABSTRACT The construction of surface structures and joining technology has become a key technology for the preparation of polymer-metal hybrid(PMH) materials in recent years. The magnesium alloy surface was subjected to micro-arc oxidation(MAO) to create a micro-nanopore structure, and the Glass fiber-reinforced polyphenylene sulfide/magnesium alloy(GFRPPS/Mg) hybrid joints were prepared by hot pressing molding. The joining mechanism of the GFRPPS/Mg hybrid joints was explored, and the interfacial disruption forms, crystalline properties, embedding depths, and interfacial chemistry of the GFRPPS/Mg hybrids were investigated at different hot pressing temperatures. The results demonstrate that the mechanical strength of the GFRPPS/Mg hybrid joints is a consequence of the interplay between micromechanical interlocking and chemical bonding, and the optimal tensile shear strength is 18.51 MPa. The tensile shear failure of the hybrids can be attributed to a combination of cohesive and interfacial failure. The crystalline properties of the failed surface of GFRPPS were also analyzed by X-ray diffraction (XRD), which revealed that the crystallinity also affects the mechanical properties of the GFRPPS/Mg hybrid joints.

Dampak Penggunaan Abu Marmer terhadap Kuat Geser Tanah Lempung

Soil is an important part of the building structure because it has a function as a support for the building. Therefore, soil stability must be considered so that building construction is safe and durable. There are types of clay soils that have high plasticity values and low shear strength. Soils like this require stabilization with the addition of additives such as marble ash. The purpose of this study was to determine whether the addition of marble ash content has an optimal impact on improving the plasticity, density, and shear strength properties. The added material used was marble ash with a content of 3%, 6%, 9%, and 12% by weight of dry soil. The specimens were differentiated based on their curing age before being tested by triaxial. Based on the research results, it was found that the use of marble ash had the maximum impact on improving the plasticity properties and maximum density at an addition of 6%. This was followed by a significant increase in shear strength at the same addition. A good curing age for increasing the angle of internal friction in the soil was obtained at 14 days.

Study on hybrid 3D printing and milling process for customized polyether-ether-ketone components.

Polyether-ether-ketone (PEEK) has been widely applied in various fields due to its excellent mechanical properties and biocompatibility. The efficient and high-quality customized manufacturing of PEEK components are investigated in this study by the hybrid 3D printing and milling process. At first, the alternating hybrid process is selected and verified by comparing two typical hybrid process categories and conducting experiments, respectively. Second, a set of procedures are designed to automate the engineering application of the hybrid process trying to avoid the disadvantages of manual programing. Then, considering the tool length and possible interferences during the hybrid process, a model segmentation algorithm, namely, the exchange principle of avoiding interference (EPAI) is proposed. Based on the introduced EPAI and the programing language Python, the additive and subtractive hybrid manufacturing (ASHM) data processing procedure is proposed and realized by post-processing of the conventional 3D printing codes. Finally, the feasibility experiments have been conducted. The experimental results verify the hybrid manufacturing process in the fabrication of parts with complex internal features. The surface roughness Ra and dimensional error L of the parts have been reduced by 75.5% and 85.2%, respectively, while the shear strength τ has been increased by 14.1%. Compared with conventional milling process, the material consumption is reduced by 48.7%.

Investigating the mechanical and fracture behaviour of Ti-based nanocomposites reinforced with single and bi-crystalline hBN nanosheets

The design and manufacturing of graphene and hBN-based nanocomposites is taking the era of material design to new horizons. The present article employs MD simulations to investigate the mechanical, fracture, and interfacial behaviour of the Ti-based nanocomposites reinforced with pristine as well as defective single and bi-crystalline hBN nanosheets. The nanocomposites exhibited over ∼100 % improvements in the failure strengths as compared to pristine Ti matrices. Reinforcement of the Ti matrices with single and bi-crystalline hBN nanosheets improved the failure strengths of the nanocomposites from 4.06 GPa to 9.74 GPa and 9.80 GPa, respectively. However, an increase in vacancy defect (Single or Di-vacancy) concentration (0–6%) resulted in a successive reduction of the failure strength of the nanocomposites. Moreover, the deformation mechanisms in Ti matrices reinforced with pristine and defective nanosheets were observed to be governed by {101‾1} <101‾2‾ > compression twin and {101‾0} <112‾0 > prismatic slip dislocations, respectively. Furthermore, the pull-out and pull-up velocities models of interfacial shear and cohesive strengths, respectively, were employed to confirm the observed results.

The Influence of Horizontal Reinforcement on Punching Shear Strength

The Influence of Horizontal Reinforcement on Punching Shear Strength

Quasi-static punch shear behavior of glass/epoxy composite: Experimental and numerical study in artificial seawater environment

Enhancing the understanding of how fiber-reinforced polymer composites respond to high-speed impacts is crucial, particularly in comparison to Quasi-Static Punch Shear Test (QS-PST). While researchers have extensively investigated QS-PST in FRP composites through experimental and numerical approaches, there's a notable gap in studies addressing the aging effects through both experimental and numerical methods. In this study, the QS-PST was conducted on S2 glass fiber reinforced epoxy composite materials aged in an artificial seawater environment. Composite plates were fabricated using Vacuum-assisted resin transfer molding (VARTM). Test samples were subjected to aging for durations of 4, 8, and 12 months. Experimental QS-PST were performed on the samples, followed by Finite Element Analysis (FEA) using LS-DYNA and the MAT 162 material model. The mechanical properties of the composite material were incorporated into the FEA and aging effects were simulated with a maximum error of 8.08% by using the proposed material model. The results indicated that the aging process led to a reduction in the punch shear strength of the composite by up to 26.84%. These findings provide valuable insights into the degradation mechanisms of composite materials in marine environments, aiding in the development of strategies for enhanced durability and performance in such conditions.

End-of-life carbon fiber/poly(phenylene sulfide) semipreg scraps from the aerospace industry: Towards a sustainable product

End-of-Life (EoL) carbon fiber (CF)/poly(phenylene sulfide) (PPS) semipreg scraps from the aerospace industry were used for the development of new products. The scraps were cut and placed randomly in aluminum molds, with and without continuous layers of semipreg, to obtain five different laminates processed by hot compression molding. The laminates were inspected by ultrasound, followed by cutting standardized test specimens using a CNC machine. Afterward, the laminates were evaluated for thermal (differential scanning calorimetry, DSC) and mechanical properties (tensile test and interlaminar shear strength, ILSS). The morphological characteristics of fracture surfaces were evaluated by scanning electron microscopy, SEM, and optical microscopy, OM. Ultrasound inspection indicated that four laminates showed the presence of voids, flaws, defects, and internal discontinuities, some very pronounced. However, the five laminates processed did not show differences in thermal stability. The size of the scraps and the direction of the CF contributed unintentionally so that two laminates presented tensile strength values 15 % lower than the reference laminate (822 MPa) and ILSS values (64 MPa) very close to the reference. The micrographs showed the ordering and positioning of the CF/PPS semipreg layers. The results were promising and could be considered as resources for developing new products through recycling processes.

Preparation of Imidazole Compounds as Latent Curing Agents and Their Application in RGB LED Packaging

LED packaging miniaturization has raised more requirements for LED materials. As a material contacting the LED chip directly, the reliability of LED non-conductive adhesive has also garnered increasing attention. This study optimized the formula for non-conductive adhesives for an imidazole curing system. The optimized composition of the adhesive is 25%wt for the curing agent and 30%wt for the silica. The prepared non-conductive adhesive has a 7-day pot life and 9-month storage stability. The shear strength reached 87 g and 72 g at 25 °C and 160 °C, respectively. The reliability of the LED modules packaged with the non-conductive adhesive was researched. The green and blue light intensity change was 4.7%, 43.7%, respectively, indicating good anti-aging properties. The blue light decay was mainly due to adhesive aging. The non-conductive adhesive effectively prevented “caterpillar” growth. This provides useful and practical guidelines for industry for applications of adhesive in different packages.

Performance of Bamboo Bark Fiber Asphalt Mortar Modified with Surface-Grafted Nano-SiO2

In this study, the feasibility of using bamboo bark fibers as modifiers to enhance asphalt mortar performance was investigated. Bamboo bark fibers were modified with NaOH, KH570 silane coupling agent, and nano-SiO2, and their preparation methods were established. The modified fibers were assessed for their oil absorption, thermal stability, and hydrophobicity. The asphalt mortar was evaluated for three key indicators: rutting resistance, deformation resistance, and durability at high temperatures. The microscopic morphology and modification mechanisms of the fibers were also studied. The results showed that modification with NaOH increased fiber porosity and surface roughness, while KH570 and its hydrolysis products enabled nano-SiO2 grafting onto the fibers, improving their adsorption to asphalt. The NaOH-KH570-nano-SiO2 ternary-composite-modified bamboo bark fiber (NKSBF) demonstrated superior hydrophobicity, oil absorption, and thermal stability at the asphalt mixing temperature. Among the modified fibers, asphalt mortar containing 3% NKSBF showed the best performance based on three key indicators, increased the shear strength by 96.4% and the softening point by 7.1% compared to the base asphalt, and increased the ductility by 1% compared to lignin fiber asphalt mortar. The incorporation of 3% bamboo bark fibers improved the rutting resistance, deformation resistance, and durability of short-term-aged asphalt mortar, with NKSBF showing the most significant improvement.

Shear Strength of Conventional and Lightweight Concrete I-Beams with Fibrous Webs

Shear Strength of Conventional and Lightweight Concrete I-Beams with Fibrous Webs

Impact of Shear Strength Degradation on Raft Foundation Performance in Clay Shale

Impact of Shear Strength Degradation on Raft Foundation Performance in Clay Shale

Exploring the effects of fiber content and length on mechanical, free vibration, electrical, and water absorption properties of Phoenix sp. fiber‐reinforced polyester composites

AbstractThis work addresses the experimental investigation of the mechanical, free vibration, electrical resistivity, and moisture uptake characteristics of Phoenix sp. fiber‐reinforced polyester composites (PFRPC) fabricated using the compression molding method. The polyester matrix (PM) was added with Phoenix sp. fibers (PSFs) of different content (5, 10, 15, 20, and 25 wt%) and length (10, 20, and 30 mm) and studied their effect on the aforesaid properties. The results reveal that the composites having 20 wt% of 20 mm length PSFs exhibited optimum mechanical properties. At this loading, the ultimate tensile strength and modulus were 48.36 MPa and 2.86 GPa, respectively, while the flexural strength and modulus were 83.89 MPa and 2.91 GPa, respectively. Furthermore, this composite exhibits an impact strength of 22.04 kJ/m2 and an interlaminar shear strength of 41.88 MPa. The increase in PSF content and length resulted in greater stiffness and decreased mass of the composites, leading to an enhanced natural frequency. The inclusion of PSFs showed a decline in electrical resistivities due to their moisture‐absorbing capability. In contrast, the hydrophilic behavior of PSFs led to a rise in the water absorption rate of the composites due to the increase in fiber variables. Scanning electron microscopy examination shows that short fiber‐reinforced composites have more fiber pull‐outs due to the limited area of contact, whereas long fiber‐added composites possess better bonding with the PM.Highlights Various properties of Phoenix sp. fiber/polyester composites were investigated Increase in fiber content enhanced the mechanical performance of composites Variation in fiber length has only minimal effect on composite properties Phoenix sp. fiber/polyester composites exhibit better insulating property

Microstructure, Mechanical and Fractographic behaviour of the Diffusion Welded Joints of AA2219 and Ti-6Al-4V for Propellant Tank Applications

Diffusion welding is an advanced joining process that assures the feasibility of joining dissimilar metal alloys without producing metallurgical impurities at the joint interface. Two significant aerospace alloys, AA2219 and Ti-6Al-4V, are diffusion welded for the various holding times (30-120 minutes) by keeping the bonding temperature and pressure constant. The effect of holding time on the microstructure of the diffusion welded joints is evaluated using scanning electron microscopy (SEM), and the diffusion behaviour across the joint interface is ensued by the line scan energy dispersive spectroscopy (EDS). The obtained results show that the hardness across the joint interface is increased with increase in holding time. Furthermore, the maximum shear strength of 143.58 MPa is achieved for the joint formed at the holding time of 90 minutes and reduced thereafter. The formation of a thick intermetallic layer at a higher holding time strongly affects the shear strength. It is evident from the resulting fractured surfaces that the joints predominantly failed at the bonding interface, showcasing the brittle kind of failure. The X-ray diffraction (XRD) study on the fractured surfaces substantiates the formation of AlTi, Al2Ti and Al3Ti intermetallic compounds.

Experimental study under thermal shock environment to investigate effect of welding width on properties of ultrasonically welded joints of multiple copper cables

Based on the ultrasonic welding technology, this study uses three different welding widths to weld copper cables with different specifications. The influence of welding width on the mechanical properties and microstructure of each group of welded joints was systematically studied for the first time. The thermal shock test was carried out for each group of welded joints under optimum welding width to simulate the influence of severe temperature change environment on joint performance. It is found that the cross-sectional area of joint is 20 mm2 and optimal welding width of joint composed of two and three cables is 7 mm. The optimal welding temperature of the joint composed of four cables is 5 mm. Under the optimal welding width, the average shear strength of two-cable joint reaches 309.4 N. The four-cable joint is only 232.2 N. Moreover, the welding strength weakens significantly as the number of cables and the peak temperature decreases. The high temperature of bonding interface is the key factor to form a good weld. The peak temperature during welding is negatively correlated with the porosity of joint and positively correlated with peeling strength of joint. In addition, the morphology of ultrasonically welded joints has changed obviously after thermal shock test. With the participation of oxygen, the surface of welded joint is gray and bright brass, while the interior of joint is purple due to lack of oxygen. Moreover, the phenomenon of atomic diffusion and thermal expansion generates joints which were initially in a mechanically interlocked form and welding interface of the metallurgical bond under the action of high temperature. So the maximum joint peel strength is slightly improved.

APPLICATION OF GEOTECHNICAL AND GEOPHYSICAL RESEARCH FOR SOIL CHARACTERIZATION

In the last few decades, modern geotechnical and geophysical in situ researches have been increasingly applied because they represent methods of quickly and instantly obtaining data on the properties and structure of the soil. Exploratory drilling is a research method that only obtains one-dimensional data, and compared to geotechnical and geophysical in situ research, it is relatively expensive and time-consuming. By combining all the research methods mentioned above, the most reliable and high-quality data for soil characterization is obtained. In this paper, examples of the application of geotechnical and geophysical research at two locations, Dugo Selo and Sesvetski Kraljevac, are processed. Applied geotechnical methods include, in addition to exploratory drilling, static cone penetrometer probing (CPTu), dilatometer probing (DMT) and dynamic heavy percussive penetration (DPH). From the geophysical investigations, 2-D geoelectric tomography (ERT) and multichannel analysis of surface waves (MASW) were performed. Also, an analysis of soil parameters obtained by exploratory drilling and in situ geotechnical methods was carried out. Undrained shear strength (cu) and compressibility modulus (M) were selected for comparison. The analysis shows that exploratory drilling results in lower values of the analyzed parameters on average compared to the results of in situ testing.