Increase In Shear Strength Research Articles

Preparation and Evaluation of a Novel Branched Polymer as Thickener for Calcium Chloride-Based Drilling and Completion Fluids

Preparation and Evaluation of a Novel Branched Polymer as Thickener for Calcium Chloride-Based Drilling and Completion Fluids

The effect of post-bond heat treatment on microstructure and mechanical properties of a two-step heating transient liquid-phase bonding IN738LC

ABSTRACT This study evaluated the bonding of a Ni-based superalloy, Inconel 738LC, using two-step heating and conventional TLP bonding techniques using a foil of BNi-2 filler alloy with a thickness of 70 μm. The bonds were processed. The first step at 1160 °C for 1 min and the second step at 1120 °C for different isothermal solidification times (50, 65, 80, and 95 minutes), and the conventional TLP process at 1120 °C for 80 min. It was inferred from the results of microstructural examinations that the joints contained eutectic product constituents that formed an athermal solidified zone (ASZ) during the bonding time of 50 min. It was also found that 80 min was required to complete isothermal solidification in the two-step TLP bonding employed in this study, whereas isothermal solidification was incomplete in conventional TLP for 80 min. The time necessary to complete the isothermal solidification was lowered using two-step TLP bonding. The microstructure after being subjected to a two-stage postbond heat treatment, becomes close to the base metals. As a result, homogenizing microstructure forms throughout the joint. The heat-treated sample contained a much greater amount of the γ′ phase generated at the bond location, resulting in increased shear strength and hardness of the bond.

Use of bore-epoxy anchorage system with CFRP laminates for shear strengthening of RC beams: An experimental and analytical investigation

Shear strengthening of reinforced concrete (RC) beams with externally bonded reinforcement (EBR) using carbon fiber reinforced polymer (CFRP) plates and sheets have become a widely accepted practice. To avoid the associated premature debonding failure, this study presents an experimental and analytical investigation on the use of bore-epoxy as an anchorage system for CFRP plates and sheets bonded on both sides of shear deficient RC beams of rectangular cross-sections. Nine (9) RC beams were prepared and strengthened with CFRP plates and sheets as EBR with bore-epoxy anchorage system considering different bore diameters and tested under four point bending. The results indicate that RC beams strengthened with bore-epoxy anchorage system have high shear strength as compared with the unstrengthened control beam and those strenghtended with the conventional EBR approach (without boring). The increase in the shear strength over the control beam was found to be up to 67 % and 121 % for cases of CFRP plates and sheets, respectively. Moreover, the increase of shear strength in comparison with the conventional EBR method ranged from 9.33 % to 20.36 % for CFRP plates and from 12.97 % to 36.10 % for CFRP sheets. Consistently, the contribution of bore-epoxy on the shear strength increased with the increase of bore diameter. Consequently, the existing formulas in the ACI440.2 R for predicting the shear strength of FRP strengthened RC beams were modified to incorporate the improvement made by the proposed bore-epoxy approach. The revised models predicted the experimental shear strength of RC beams, strengthened with bore-epoxy, with a good level of accuracy with average mean absolute percentage error (MAPE) = 6.07 %, 14.71 %, normalized mean square error (NMSE) = 0.097, 0.16, and coefficient of determination R2 = 0.912, 0.974 for plates and sheets, respectively.

Dynamic shear strength of precast connection with UHPC-based and traditional grouted sleeves: Test, simulation, and analytical formulas

Dynamic shear strength is critical for ensuring the integrity of prefabricated structures with grouted sleeve connections under dynamic loads such as impacts and earthquakes. However, studies have yet to be conducted to clarify the dynamic shear strength of grouted sleeve connections for designs. To this end, this study systematically investigated the dynamic shear behavior of precast connection with grouted sleeves through physical experiments, numerical simulations, and theoretical analysis. Drop hammer impact tests were performed on nine precast connection specimens that differ in amounts of impact energy, axial loads, rebar ratios, and grouting materials. Experimental data indicated that the dynamic shear performance of the ultra-high-performance concrete (UHPC)-based connections is superior to that of traditional grouted sleeve connections. The impact-induced displacement of a grouted sleeve connection is very sensitive to the amount of impact energy. Detailed finite element (FE) models were further developed to examine the dynamic shear strength of precast connections. Good agreements are observed between the numerical results and experimental data, demonstrating the rationality of the developed FE modeling method. It was found that the dynamic shear strengths of grouted sleeve connections are more sensitive to axial load levels and concrete strength grades than rebar ratios. Based on extensive simulation results obtained from the validated modeling method, the analytical formulas were proposed to predict the dynamic increase factor (DIF) and shear strength of precast connections. The analytical results predicted by the proposed formulas agree well with the FE results, demonstrating the applicability of the proposed formulas.

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.

Shear mechanical behavior and fracturing path of red sandstone treated by joninted effect of water-fractures

Water content and primary fractures can change the mechanical characteristics of rock, making it easy to induce geological disasters. Therefore, direct shear tests of red sandstone under the action of water-fracture were carried out in this paper. The results show that shear strength of rock samples with fractures is less than that of intact rock samples. With the increase of primary fracture dip angle, shear strength and macroscopic crushing area of the rock sample increases first and then decreases with 20° as the boundary. It shows that the primary fractures weaken the shear mechanical properties and change the macroscopic failure mode. The shear performance of water-bearing rock samples is weaker than that of intact rock samples, and the weakening degree of water-saturated on shear performance of rock samples is lower than that of unsaturated water state. The fracture surfaces of rock samples are divided into 'shortest path single through type', 'longest path single through type' and 'cross path through type'. The failured rock samples are divided into 'single through type' and 'cross through type'. The research results can provide reference for geological disaster management under relevant conditions.

Effect of polypropylene fibres on the shear strength of fine-grained soil

This paper presents the results of shear strength tests of fine-grained soil reinforced by randomly oriented fibres. The tests were carried out in a direct shear apparatus on samples with a diameter of 100 mm and a height of 20 mm. The samples were formed directly in the apparatus box at a natural moisture content and two values of the degree of compaction (IS = 0:79 and 0.90). The studies were carried out for samples of natural moisture content and for soaked ones. The two types of polypropylene fibres were used: monofilament and fibrillated (of traded names Fibermesh 300-e3 and SikaCem Fiber-12, respectively). The fibre content was 0.25; 0.50 and 1.00% by the weight of the dry soil. The results showed that the presence of fibre within the soil increased its the shear strength. The improvement of the shear strength was related to the type of reinforcement, its content and the soil parameters. The maximum increase in shear strength was 47% compared to the shear strength of the unreinforced soil. The increase in shear strength values were related mainly to the increase in the angle of internal friction of the soil. It was found that as the degree of compaction of the soil increases, the higher enhance of the shear strength of reinforced soil occurs. It was also found that the improvement of shear strength of reinforced soaked samples was more significant than for un-soaked ones.

INVESTIGATION OF THE SHEAR STRENGTH OF REINFORCED SILTY SAND

Introduction: This paper presents an experimental investigation that aims to study the influence of silt content, glass fiber content, and their combined effect on the shear behavior of silty sand. For this purpose, a series of tests using direct shear apparatus (as methods) were carried out on sand mixed with various silt and fiber contents. Samples were prepared with a relative density of 50 %, and each mixture was tested at three different normal stresses. The experimental results indicated an increase in shear strength at 10 % silt content, followed by a decrease in shear strength with increasing silt content from 10 % to 30 %. It was also found that 0.5 % is the optimal content that can be added to sand-silt mixtures to enhance their shear strength and friction angle, although the mixtures become more contractive.

Tensile Properties and Weibull Modulus of Polymeric-Fiber-Reinforced Epoxy-Impregnated Bundle Composites

The tensile properties and the Weibull statistical distributions of the tensile strength of poly-(para-phenylene-2,6-benzobisoxazole) (PBO), poly-(para-phenylene terephthalamide) (PPTA), copoly-(para-phenylene-3,4′-oxydiphenylene terephthalamide (PPODTA), polyarylate (PAR), and polyethylene (PE) polymeric fiber epoxy-impregnated bundle composites have been investigated. The results show that the Weibull modulus decreases as the tensile modulus, strength, and inverse of the failure strain increase. The interfacial shear properties were also examined using the microdroplet composite. For the lower interfacial shear strength of polymeric fibers, the Weibull modulus decreases as interfacial shear strength increases. Conversely, for the higher interfacial shear strength of polymeric fibers, the Weibull modulus increases as interfacial shear strength increases. Interestingly, these inflection points were also observed for the 20–30 MPa interfacial shear strength.

Experimental Investigation on Shear Strength at the Permeable Concrete–Fine-Grained Soil Interface for Slope Stabilization Using Deep Socket Counterfort Drains

In slopes where high pore water pressure exists, deep counterfort drains (also called drainage trenches or trench drains) represent one of the most effective methods for improving stability or mitigating landslide risks. In the cases of deep or very deep slip surfaces, this method represents the only possible intervention. Trench drains can be realized by using panels or secant piles filled with coarse granular material or permeable concrete. If the trenches are adequately “socket” into the stable ground (for example sufficiently below the sliding surface of a landslide or below the critical slip surface of marginally stable slopes) and the filling material has sufficient shear strength and stiffness, like porous concrete, there is a further increase in shear strength due to the “shear keys” effect. The increase in shear strength is due both to the intrinsic resistance of the concrete on the sliding surface and the resistance at the concrete–soil interface (on the lateral surface of the trench). The latter can be very significant in relation to the thickness of the sliding mass, the “socket depth”, and the spacing between the trenches. The increase in shear strength linked to the “shear keys effect” depends on the state of the porous concrete–soil interface. For silty–clayey base soils, it is very significant and is of the same order of magnitude as the increase in shear resistance linked to the permanent reduction on the slip surface in pore water pressure (draining effect). This paper presents the results of an experimental investigation on the shear strength at the porous interface of concrete and fine-grained soils and demonstrates the high significance and effectiveness of the “shear keys” effect.

Unveiling the reinforcement benefits of innovative textured geogrids

The smooth surface texture of the commercially available geogrids limits the shear strength mobilization at the interfaces. This study presents the design, manufacturing, and interface performance evaluation of innovative textured geogrids. Geogrids with square, triangular, and hexagonal apertures with and without inherent surface texture were manufactured through additive manufacturing (3D printing) technique, using PLA (Poly Lactic Acid) filament. The texture includes elevated pins of 3 mm height at the junctions and inherent diamond pattern of 1 mm height on the ribs. The individual and combined effects of surface texture and aperture shape on the stress–displacement relationship, dilation angle, and the thickness of shear zone are quantified using large-scale direct shear tests and Particle Image Velocimetry (PIV) analysis. Results showed that the textured geogrid with hexagonal aperture has exhibited the maximum interface coefficient of 0.96 with sand followed by the geogrids with triangular and square apertures. Irrespective of the aperture shape, provision of the surface texture resulted in an overall increase of interface shear strength by more than 13%. Further, PIV analysis revealed that the shear zone is 25% thicker for textured geogrids of different aperture shapes, suggesting higher interlocking and passive resistance offered by their textured surfaces.

Research on the shear stress and microscopic deformation mechanism of deep sea sediments under the action of tracked miner

The traction force of the tracked miner is primarily determined by the shear characteristics of deep-sea sediments. The influence of different parameters on the shear characteristics of deep-sea sediments and the particles change law of the soil–track interface are discussed. By constructing the relationship between the particles horizontal displacement and residual shear strength, a novel shear rheological damage model of deep-sea sediments considering the influence of grounding pressure is proposed, and the microscopic mechanism of shear displacement of deep-sea sediments is explained. The results show that the peak shear strength and residual shear strength increase significantly with the increase of grounding pressure, track length, grouser height and shear speed. Moreover, the particles within the soil–track interface move along the lower right of the vehicle operating direction during the shearing process under different working conditions, the change of particle spacing shows a non-linear trend, and a quantitative equation for the horizontal deformation of soil–track interface under the experimental conditions is constructed. Additionally, the new shear model has a high level of accuracy in fitting with the experimental data, the internal particle migration changes on the soil–track interface can be divided into four characteristics: compaction, failure, deformation and translation.

Experimental study on the mechanical properties of desert sand improved by the combination of additives and bio-cement.

Bio-cement is a green and energy-saving building material that has attracted much attention in the field of ecological environment and geotechnical engineering in recent years. The aim of this study is to investigate the use of bio-cement (enzyme-induced calcium carbonate precipitation-EICP) in combination with admixtures for the improvement of desert sands, which can effectively improve the mechanical properties of desert sands and is particularly suitable for sand-rich countries. In addition, the suitability of tap water in bio-cement was elucidated and the optimum ratio of each influencing factor when tap water is used as a solvent was derived. The results showed that peak values of unconfined compressive strength (maximum increase of about 130 times), shear strength (increase of 27.09%), calcium carbonate precipitation value (increase of about 4.39 times), and permeability (decrease of about 93.72 times) were obtained in the specimens modified by EICP combined with admixture as compared to the specimens modified by EICP only. The incorporation of skimmed milk powder, though significantly increasing the strength, is not conducive to cost control. The microscopic tests show that the incorporation of admixtures can provide nucleation sites for EICP, thus improving the properties of desert sand. This work can provide new research ideas for cross-fertilization between the disciplines of bio-engineering, ecology, and civil engineering.

Strengthening and repair of RC beams using natural sisal Fabric-Reinforced Cementitious Matrix composite

The present work reports the results of an experimental program on the mechanical characterization of Reinforced Concrete (RC) beams externally strengthened/repaired by natural sisal Fabric-Reinforced Cementitious Matrix (FRCM) composite. For such, undamaged and pre-cracked RC beams were U-wrapped with a sisal FRCM composite and then tested under bending load. The results showed significant increases in shear strength, up to 25 % for beams with stirrups and 75 % for beams without them. The strengthened/repaired beams also presented stirrups yielding delay during the tests. When compared with other synthetic FRCM strengthening systems from the literature, the enhanced mechanical results of the present work were mechanically equivalent. The cracking pattern and debonding of the sisal FRCM wrap system were measured by the Digital Image Correlation (DIC) technique. The wrap application reduced the crack propagation and debonding behavior was not detected. Finally, the experimental results were confronted with an analytical approach guided by ACI 549.4R-20 and considered sufficiently accurate.

Dodging reality, striking the virtual: An undulating strategy for effectively enhancing CF/PEEK interfacial adhesion!

The design of carbon fiber (CF)-reinforced polyetheretherketone (PEEK) composite materials with suitable interfaces has consistently been challenging. In this study, we sulfonated poly (phthalazinone ether sulfone ketone) (PPESK) and PEEK to prepare water-soluble SPPESK and SPEEK. Subsequently, we prepared a water-soluble sizing agent (SPPESK/SPEEK) via a straightforward blending process. This sizing agent tended to accumulate randomly on the surfaces of CFs, forming a thin film with a heterogeneous structure in the nanoscale. At the molding temperature of the composite material, the two components on the fiber surface exhibited different rheological behaviors, with PEEK preferentially infiltrating the SPEEK region, forming strong molecular entanglements. Meanwhile, the SPPESK region provided a rigid supportive structure, offering the potential for the mechanical interlocking of PEEK in the interface layer. The performance of the prepared composite materials was significantly enhanced, with their interlaminar shear strength and flexural strength reaching 87.1 MPa and 975.8 MPa, respectively. With respect to those of commercial fiber-reinforced PEEK composites, an 89.8 % increase in interlaminar shear strength and a 79.39 % increase in flexural strength were observed. This interface reinforcement mechanism presents a universally applicable strategy for the future development of fiber-reinforced composite materials.

High performance Cu/SAC305 solder low temperature bonding using Ti3C2 MXene interlayer

Ti3C2 MXene (MX) was introduced as the interlayer between the Cu film and Sn-3.0Ag-0.5Cu (SAC) solder to inhibit the overgrowth of intermetallic compounds (IMCs) at the bonding interface of Cu and SAC solder. The Cu-MX-SAC bonding was fabricated at 160 °C for 6 mins under a load of 10 MPa. Compared with Cu-SAC bonding, after 72 h aging, the average thickness of the IMCs layer in the Cu-MX-SAC structure is about 47 % thinner. As aging time increases, the diffusion rate of Cu atoms is limited due to the introduction of MXene interlayer, and the growth of IMCs in the Cu-MX-SAC structure is controlled by volume diffusion. For the Cu-MX-SAC solder bonding, after prolonged aging, the shear strength increases, and contact resistance at the bonding interface is almost no change compared with Cu-SAC solder bonding.

Co-enhancement of toughness and strength of room-temperature curing epoxy adhesive derived from hydroxyl-terminated polybutadiene based polyurethane resin

Incorporation of flexible chains into epoxy adhesives facilitates toughening but usually poses an opposite effect on strengthening. Herein, by combining hydroxyl-terminated polybutadiene (HTPB) with polyether diol as soft chains, epoxy-terminated polyurethane (EHTPU) is synthesized, a strategy balancing strengthening and toughening is developed. The use of polyolefin soft chains substantially contributes to sea-island phase separation for maintaining low glass transition temperature (Tg) and high strength and toughness simultaneously. Specifically, the modified epoxy adhesive has seen a significant increase in shear strength to 19.75 MPa, tensile strength to 48.25 MPa and fracture toughness to 3.63 MPa·m1/2, with increment of 914 %, 268 %, and 149 %, respectively, compared to neat epoxy. Moreover, even under low temperatures of -45 °C, the modified epoxy resin can still maintain a high shear strength, demonstrating excellent low-temperature adhesion performance. At the same time, the incorporation of EHTPU does not significantly affect the overall thermal stability of the epoxy resin, meeting the requirements for stability in practical applications. It is worth mentioning that the adhesive exhibit excellent bonding performance under different environments and substrates, indicating that this composite material has broad application prospects in various industrial fields. These findings provide valuable insights into optimizing the performance of epoxy resins by controlling the introduction of specific modifiers and offer new ideas and methods for the development of room temperature curing epoxy resin adhesives.

Mechanical characterization and puncture resistance of 3D‐printed PLA lattice structures

AbstractThe increasing application of additively manufactured (AM) materials in engineering and biomedical fields highlights the necessity of understanding their mechanical behavior, particularly with complex lattice structures. Polylactic acid (PLA), a popular biopolymer in additive manufacturing, exhibits mechanical characteristics highly dependent on its structural design. This research investigates the quasi‐static puncture failure analysis and mechanical characteristics of additively manufactured (AM) polylactic acid (PLA) materials with various lattice structures. The mechanical behavior, including tensile strength, flexural properties, interlaminar shear strength (ILSS), Izod impact resistance, and quasi‐static punch shear strength (QS‐PSS), was investigated following the respective ASTM protocols. Results indicate a 6% increase in tensile strength, to ca. 28 MPa, for the triangular PLA lattice structure compared with plain lattice structures. In the flexural test, the hexagonal structure showed a 13% increase in bending strength, to ca. 45 MPa, compared with the plain structure. Additionally, the hexagonal PLA lattice structure exhibited a 24% increase in shear strength, to approximately 8 MPa, over the plain lattice structure in the interlaminar shear strength analysis. In the Izod impact analysis, the plain lattice structure demonstrated a 17% increase in impact strength, to ca. 278 J/m, compared with the circular structure. A stainless‐steel hemispherical indenter was employed to investigate the quasi‐static punch shear behavior (QS‐PSS) of different lattice structures. The triangular structure displayed increased total energy absorption capacity and specific energy absorption of ca. 19 J and 0.529 J/g, respectively, compared with other lattice structures. These results are important for the creation of additively manufactured PLA lattice structures, improving the puncture resistance of advanced composites.Highlights Polylactic acid (PLA) lattice structures were fabricated. Plain, circular, triangular, and hexagonal lattice structures were investigated. Lattice structures were used as reinforcements. The triangular structure demonstrated improved strength. The triangular structure reduced crack formation and propagation.

Experimental Study of Soil Compaction with Proctor Standard Test Equipment

Soil is the surface layer of the earth which consists of minerals, organic materials, air, living things. Clay soil is one type of soil that is important in determining the bearing capacity of subgrade required for construction. The bearing capacity of the soil is obtained by compacting it, using the TS-365 Automatic Standard Proctor. Soil compaction is the process of removing air from the pores of the soil, and is effective for improving soil properties in order to increase the density (density) of the soil so that shear strength increases, soil settlement decreases, and soil permeability decreases. The standard proctor test uses 5 separate soil samples weighing 2 kg, with a mixture of 16%, 19%, 22%, 25% and 28% air respectively. The test results show that the soil obtained from the Pojok sub-district area. Mojoroto, East Java obtained the results of soil compaction data using a standard proctor test, it was obtained that the optimum dry volume weight of the soil was 1,630 gr/cm3 and the optimum water content was 32%. So that the results of soil testing in the laboratory can be used as a reference for controlling soil compaction in construction.

Effects of spraying parameters and heat treatment temperature on microstructure and properties of single-pass and single-layer cold-sprayed Cu coatings on Al alloy substrate

Exploring the deposition of single-pass and single-layer pure Cu coatings on Al alloy substrate through high-pressure cold spray technology is a crucial endeavor with significant implications for advancing the utilization of such coatings. Regrettably, research in this specific area remains scarce, highlighting the need for further investigation and understanding. This study examined the characteristics of cold-sprayed Cu coatings deposited on a 6061 T6 aluminum alloy substrate under varying gas temperatures and pressures, and explored the effects of subsequent heat treatment on the microstructure and mechanical properties of the Cu coatings. The morphology, phase composition, surface roughness, thickness, porosity, microstructure, shear strength, and microhardness of the cold-sprayed Cu coatings were systematically analyzed. The findings indicated that the spraying parameters had a substantial impact on the properties of the Cu coatings. Specifically, increased gas pressure led to rougher surfaces and lower porosity, whereas higher gas temperature produced smoother surfaces and also reduced porosity. At 800 °C and 4.0 MPa, the Cu coatings exhibited the lowest surface roughness, measuring 8.03 μm. Conversely, at 800 °C and 5.5 MPa, the Cu coatings demonstrated the lowest porosity, at 0.26 %. Moreover, the microstructure analysis showed evidence of dynamic recrystallization in the deposited Cu particles, contributing to enhanced mechanical properties. Following this, the influence of heat treatment on the microstructure and properties of the cold-sprayed Cu coatings was examined. The results demonstrated that annealing at different temperatures induced changes in the interfacial microstructure, with the formation of intermetallic compounds between the Cu coating and Al alloy substrate. This interdiffusion phenomenon led to improved bonding strength and mechanical properties of the Cu coatings, as evidenced by increased shear strength. After undergoing heat treatment at 400 °C, the Cu coatings exhibited the highest shear strength, measuring 49.89 MPa. However, excessive heat treatment temperatures resulted in the formation of cracks and a decrease in mechanical properties.