Improvement In Shear Strength Research Articles

Shear Strength of Soft Soil Reinforced with Singular Bottom Ash Column

Structures construct on soft clays are often affected by stability and settlement problems due to high compressibility, low shear strength and low permeability of soft clay which will lead to bearing capacity failure and excessive settlement. The soft clay samples had the dimensions of 50 mm diameter and 100 mm in height. The bottom ash column had two (2) different area replacement ratios which were 4% and 9% (10 mm and 15 mm diameters respectively) with the bottom ash column penetration ratio of 0.3, 0.7 and 1.0. The results of the unconfined compression test show that there is an improvement in shear strength of soft kaolin clay when reinforced with bottom ash column. For samples with area replacement ratio 4%, the results show the increment of 25%, 37.5% and 50% at height penetrating ratio of 0.3, 0.7 and 1.0, respectively in shear strength. Meanwhile, for samples of 9% area replacement ratio, the shear strength of the soft kaolin clay increased about 14.29, 28.57 and 57.14%, respectively. It can be concluded that by reinforcing the soft clay using singular bottom ash column, the shear strength of the soils increases and become more significant as the area replacement ratios and the column penetration ratios increase.

Study on Pile Bearing Capacity Improvement in Soft Soil After Vacuum Consolidation

The main problem in developing property over soft soil is significant settlement due to the consolidation process. The soil settlement, which will occur gradually throughout the years, will disrupt existing infrastructures, in this case bridges. To mitigate this issue, the common method is by speeding up the consolidation. The consolidation process must be sped up to avoid the differential settlement problem at the bridge abutments. Due to the limited supply of fill material, a vacuum consolidation method is adopted. In this method, a Prefabricated Vertical Drain (PVD) is installed, and a vacuum is applied to impose pressure as preloading. Because of the consolidation process, theoretically, the effective stress of the consolidated soil increases, and the soil shear strength does as well. Increasing the shear strength of the soils will increases the pile capacity. However, the interesting question is how much the shear strength of the soil can increase and impacts the pile capacity. In this paper, the shear strength improvement of the consolidated soil and the effect on pile bearing capacity is evaluated. This study used a series of in-situ tests that were carried out before and after the vacuum consolidation. A pile loading test using the Pile Dynamic Analyzer (PDA) method was carried out to verify the pile bearing capacity improvements. From the comparison result, it is shown that the theoretical capacity of the piles after consolidation were close to the pile test results.

Shear Strength and Durability of Expansive Soil Treated with Recycled Gypsum and Rice Husk Ash

Expansive soil underlying structures pose a significant risk to the integrity of superstructures. Chemical soil stabilization can be used to strengthen soils due to the cost and impracticality of mechanical approaches. Waste materials such as recycled gypsum and rice husk ash have been considered alternatives because of their sustainable and economic advantages. A combination of these additives was used to address the high absorption of gypsum and the lack of cohesion of the pozzolan. The study assessed the short-term and long-term performance of expansive soil treated with recycled gypsum and rice husk ash under normal and fluctuating moisture conditions. Direct shear tests indicated ductile and compressive soil behavior with improved shear strength. A good approximation of stress–strain response was made with a modified hyperbolic model for treated soils that exhibited strain hardening and compressive volumetric strain. Durability and water immersion tests were performed for samples after varying curing periods and cycles of capillary soaking to assess the behavior when exposed to varied environmental conditions. Samples under the modified durability test experienced significant strength loss, with decreasing compressive strength as curing durations increased. Specimens in the modified water immersion test experienced significant strength loss; however, it was determined that curing durations did not contribute to the change in the strength of the sample. Expansion index tests also determined that the treatment effectively mitigated expansivity and collapsibility in all samples. Despite improvement in shear strength and expansion potential, further investigation is needed to enhance the durability of soil treated with gypsum and rice husk ash.

Experimental Study on the Effect of Soil Reinforcement and Slip Resistance on Shallow Slopes by Herbaceous Plant Root System

In this study, Setaria viridis was selected as the research object, the soil reinforcement mode of roots was analyzed, and the general mechanical model of soil reinforcement was proposed. The direct shear tests of root–soil composite and root tensile tests were carried out, and the relationship between the root additional cohesion and root depth was studied. Furthermore, numerical simulations were established to explore the variation law of shallow displacement and slope stability as a function of the root ratio. The results show that the effect of herbaceous plant roots on the soil was composed of material modification and root binding force on the soil. The shear strength improvement of the root–soil composite was mainly reflected by the increase in cohesion. Furthermore, the composite cohesion was positively correlated with the root content but negatively correlated with the water content. With the increase in root diameter, the tensile strength of the Setaria viridis root increased linearly, but its tensile strength decreased and showed a power relation. The greater the total cohesion of the root–soil composite layer, the smaller the total displacement and the higher the slope stability. Thus, the slope’s herbaceous vegetation could effectively control the deformation and slip of the shallow soil, which has good application value for reducing soil erosion in mining areas.

Thermal response of encapsulated nanoscale phase change materials with crosslink: A molecular dynamics study

Crosslink plays a key role in improving the thermal and mechanical stability of encapsulated phase change materials (EPCM). In this paper, molecular models of EPCM with different crosslinked density (non-crosslinked, 20 %, 40 %, 60 %, and 80 %) were constructed and then the molecular dynamics method was employed to investigate the thermal response characteristics. Specifically, the local structural characteristics, overall morphology, kinetic properties, and thermo-mechanical properties were analyzed. The results indicate that establishing crosslinked structures effectively enhances the structural steadiness of the EPCM under thermal and mechanical effects, and restricts the radial thermal diffusion of the core substance. More precisely, the presence of crosslinked structure (80 % crosslinked density) led to a 26.61 % improvement in tensile strength, a 5.59 % increase in compression resistance, and a 14.4 % improvement in shear strength than non-crosslinked structure. It is worth mentioning that, the results indicate a remarkable turning point in the occupancy volume change and mechanical properties of the system around the crosslinked density of 40 %.

Reinforced ECC-UHPC-SCC composite modular framed shear wall systems under lateral cyclic loading

The shear strength and deformability of high performance reinforced composite framed shear wall systems made of Engineered Cementitious Composite (ECC), Ultra-High-Performance Concrete (UHPC) and Self-Consolidating Concrete (SCC) subjected to lateral cyclic shear loading to failure were investigated. A total of seven framed shear wall specimens were constructed using combinations of ECC or SCC wall, SCC frame and ECC or UHPC frame joints. The performance of such novel modular forms of walling systems were compared based on experimental results in terms of cracking, failure mode, hysteretic shear load-deformation response, shear load capacity, ductility, bearing capacity degradation, stiffness degradation, dissipated energy, viscous damping capacity, induced wall shear stresses and strain development characteristics. ECC walling system exhibited better structural performance compared to their SCC counterparts showing up to 40% higher load capacity forming significantly higher number of closely spaced diagonal cracks with up to 72% lower crack shear stress, 14% to 21% higher ductility, up to 2 times higher energy dissipation capacity and lower rate of stiffness/bearing capacity degradation through both hysteretic and damping actions. The incorporation of ECC and ECC or UHPC joint in frame significantly improved shear strength capacity of infill wall and overall framed shear wall system. ECC incorporated framed shear walls even with frames made of SCC and UHPC joints also exhibited superior performance. This study confirmed the superior performance of ECC material for the construction of reinforced framed shear wall with boundary frame made of ECC/SCC/UHPC combinations for better seismic resistance.

Shear strength of soil by using rice husk ash waste for sustainable ground improvement

In the global construction industry, areas characterized by weak and expansive soils are on the rise, necessitating effective solutions for strength enhancement. Addressing this concern, sustainable soil amendments have gained attention, with rice husk ash (RHA) from rice milling industries being a notable focus. Our experimental study aimed to assess the shear strength of this innovative construction material, introducing a unique approach that considers subgrade layers with minimal cement dosage, including upper, bottom, and double layers a novel contribution yet unexplored in existing literature. In addition to conventional mechanical testing, we employed SEM (Scanning Electron Microscopy) and EDS (Energy-Dispersive X-ray Spectroscopy) analyses to comprehensively explore the treated soils' microstructural and elemental composition aspects. Examining sixteen specimen combinations of weak expansive soil-RHA-cement, varying proportions of RHA (2%, 4%, 6%) and cement (2%, 4%, 6%) were mixed to understand their effects on shear strength parameters. Our findings revealed significant shear strength improvement in each subgrade layer, with specimen 6%RHA6%C in the lower subgrade layer exhibiting the highest cohesive strength at 143 kN/m2. Notably, the double layer configuration, specimen 2%RHA6%C, achieved maximum deviatoric stresses of 383 kN/m2. This novel construction material contributes to effective waste management and presents an innovative engineering solution for sustainable ground improvement, offering promising prospects for future geotechnical advancements.

Strengthening non-engineered building using vegetal FRCM retrofitting: A numerical modeling approach for seismic assessment

The concept of developing alternative rehabilitation techniques to enhance the performance of structures with low seismic resistance has come to light in recent years. Substantial research and methods have been devoted to evolving strengthening techniques worldwide for structures with economic value, with the ultimate goal of enhancing seismic resilience in them. Among these, Fiber Reinforced Cementitious Matrix (FRCM) stands out as a reliable alternative to conventional retrofitting approaches due to its high strength-to-density ratio and negligible mass increment. However, the inadequacy of full-scale modeling and the application of FRCM in building components persist in the research domain. Therefore, this paper aims to develop a numerical model for the full-scale application of vegetal FRCM composites in retrofitting a representative non-engineered building. The full-scale application of the four vegetal FRCM materials (hemp, cotton, flax, and sisal) in 1-ply and 2-ply configurations was undertaken to strengthen a non-engineered building. The results of pushover analysis show that buildings retrofitted with 2-ply hemp and 2-ply flax FRCM exhibited the most significant improvement in base shear strength, with increments of about 30% and 28.5% respectively, compared to the peak base shear of the bare frame. Additionally, the retrofitted models demonstrated an increase in their ductility. A subsequent fragility analysis highlighted a reduction in the seismic hazard vulnerability of the building for the relevant earthquake spectrums. Finally, the results from the numerical analysis confirm that the use of vegetal fibers as cementitious matrix can have significant potential to be an effective and sustainable strengthening technique for seismically deficient buildings.

Fabrication of glass to PLA joints with an intermediate aluminum layer by using low-cost industrial nanosecond IR fiber lasers

We present an adhesive free, low-cost and effective solution for joining of thermoplastic additive manufactured parts to glass using an industrial nanosecond IR pulsed fiber laser. We demonstrate the potential of the method by means of laser joints of glass to Polylactic Acid (PLA). The glass to PLA joints are realized via Laser Transmission Welding (LTW) and Laser Direct Welding (LDW) using an intermediate sacrificial thin layer of aluminum. The laser joints are compared with adhesive glass to PLA joints. The mechanical testing involves a thorough strength evaluation by using block shear test method, demonstrating the superior performance of laser-welded joints over conventional adhesive alternatives. The results of these shear tests reveal a remarkable 565 % improvement in shear strength in comparison to the adhesive joints (maximum shear strength of laser bonds: 9.57 MPa). Furthermore, a Weibull statistical analysis is applied to assess the reliability of the joints, disclosing a very high survival probability of the samples under a loading of 4.5 MPa as well as a σ0 (stress for which the 1/e (37 %) of the samples survive) of 8.15 MPa.

Superior mechanical and ballistic performance of carbon nanotube‐reinforced phenolic/aramid fabric composites via a two‐roll pressing process

AbstractIn this study, aramid fiber (AF)/phenolic resin prepreg was fabricated by impregnating low content carbon nanotube (CNT)‐reinforced phenolic resin with aramid fabric through a two‐roll pressing process. Both non‐functionalized and carboxylic‐functionalized CNTs (CNTs and CNTs‐COOH) were used for comparison study. For each of the formulations, composite laminate was made by a hot‐pressing process with a number of the prepregs stacked together. Mechanical properties and ballistic performance of the laminates and material failure mechanisms were evaluated and analyzed. Both non‐functionalized and CNTs‐COOH can effectively improve the mechanical and ballistic performance of the laminates. With CNTs‐COOH reinforcement, better results were achieved. As compared with the laminate without CNT reinforcement, 1.0 wt% CNTs‐COOH‐reinforced laminate showed 19.41%, 22.29%, and 45.83% improvement in tensile, flexural, and adhesion shear strength, respectively. The ballistic test results showed that the V50 and the specific energy absorption (SEA) were increased by 5.77% and 13.44%, respectively. The correlation between mechanical and ballistic performance of the composites was analyzed and conducted.

Acrylonitrile‐butadiene‐lignin thermoplastic rubber adhesive for enhanced metal‐to‐metal joining

AbstractWith the growing requirement for lightweight structural materials in automotive, aerospace, and infrastructure applications, multi‐material joints made with adhesive have attracted intense research interest. Commercial thermoset adhesives are one‐time cures, and difficult to disassemble the bonded components for repair and recycling. Our prior work with a thermoplastic acrylonitrile‐butadiene‐lignin rubber (ABL) addresses this sustainability/recycling challenge, but the adhesive exhibits deficient joining strength compared to standard thermosets. Here, we modify the ABL matrix by loading particulate fillers to enhance its modulus and toughness. The goal is to manufacture a cure‐free thermoplastic adhesive system with a simple dispensing protocol and characteristic ductility combined with a high yield stress for improved shear strength of a bonded joint. Fumed silica (FS) and epoxidized glass spheres (EGS) were used as fillers in the ABL to promote the dispersion of lignin particles that tailored the functionalities and free energy components of the adhesive surface. With optimal loading of FS (5 wt%) and EGS (30 wt%) in the ABL adhesive matrix, the lap‐shear strength of the bonded aluminum joint was elevated by 128%, compared to the neat ABL, reaching 21 MPa, which is 90% of the performance of a commercial epoxy‐based adhesive.Highlights A partly renewable filler‐toughened thermoplastic adhesive has been developed. This thermoplastic gives nearly equivalent performance of adhesively bonded aluminum joint compared to standard thermosets. Experimental and simulation data help understand the adhesive reinforcing mechanism by the fillers.

Experimental study of ground improvement techniques of soft Kaolin soil using sand drain and jute wrapped with polyamide polyester vertical drain”

Thick alluvial deposits of soft clayey soils are characterized by low shear strength, high compressibility and low hydraulic conductivity. In recent years, soil improvement is required to provide adequate bearing capacity and improve shear strength of the soft cohesive soils to satisfy the need for various type of construction on sites underlain by such soft soils. Amongst various ground improvement techniques like vibroflotation, compaction with explosive, electro-osmosis, heavy tamping, stone column etc., the technique of preloading or pre-compression used in combination with vertical drains is one of the oldest and most widely used techniques to preconsolidate and strengthen weak compressible soils in situ. To accelerate the time of Primary consolidation, Prefabricated Vertical drains are used in soft clays as they decrease the drainage path. In this paper, we investigate the consolidation rate of soft soil with Sand drain and jute wrapped with polyamide polyester drain as PVD. The present paper focuses on Study of pore water dissipation, effect on consolidation due to radial drainage flow and gain in strength using 254 mm diameter Rowe Type Oedometer for both the drain materials. The load in increment of ΔP/P = 1 is applied and measurement of settlement by conventional method is done. It is observed that Jute wrapped with polyamide polyester drain as PVD performs better in comparison to Sand Drain.

Shear Performance of the Interface of Sandwich Specimens with Fabric-Reinforced Cementitious Matrix Vegetal Fabric Skins

The utilization of the vegetal fabric-reinforced cementitious matrix (FRCM) represents an innovative approach to composite materials, offering distinct sustainable advantages when compared to traditional steel-reinforced concrete and conventional FRCM composites employing synthetic fibers. This article introduces a design for sandwich solutions based on a core of extruded polystyrene and composite skins combining mortar as a matrix and diverse vegetal fabrics as fabrics such as hemp and sisal. The structural behavior of the resulting sandwich panel is predominantly driven by the interaction between materials (mortar and polyurethane) and the influence of shear connectors penetrating the insulation layer. This study encompasses an experimental campaign involving double-shear tests, accompanied by heuristic bond-slip models for the potential design of sandwich solutions. The analysis extends to the examination of various connector types, including hemp, sisal, and steel, and their impact on the shear performance of the sandwich specimens. The results obtained emphasize the competitiveness of vegetal fabrics in achieving an effective composite strength comparable to other synthetic fabrics like glass fiber. Nevertheless, this study reveals that the stiffness of steel connectors outperforms vegetal connectors, contributing to an enhanced improvement in both stiffness and shear strength of the sandwich solutions.

Hydrochar-based facile and greenwood bio-adhesives production from distilled spent grain

The use of urea-, melamine-, and phenol–formaldehyde resin adhesives is endangering human health and damaging the environment. Developing formaldehyde-free plywood bio-adhesive is becoming a hot spot, and this study, for the first time, reports the preparation of facile and green wood bio-adhesives using hydrochar derived from distilled spent grain (DSG) by hydrothermal carbonization (HTC), which is promising for treating and valorizing high-moisture bio-waste such as DSG. HTC contributed to the dewatering, screening, and activation of active components in DSG, benefiting their interactions with cross-linkers and wood panels. The results show that the HTC temperature can significantly affect the reaction activity of hydrochar, thus influencing bonding strength. BD-180 bio-adhesive (mixture of cross-linkers glycerol triglycidyl ether/polyvinyl alcohol and hydrochar from HTC of DSG at 180 °C) had an excellent wet shear strength (1.24 MP), meeting the Chinese national standard GB/T 9846–2015 (≥0.7 MPa). Maillard reaction was a key reaction during HTC to destroy the secondary structure of proteins, resulting in the release of abundant –OH and –NH2. These functional groups in hydrochar were the major active sites available for the formation of covalent bonds (e.g., C–N and C–O–C) between bio-adhesive and wood panels, promoting the improvement in wet shear strength of bio-adhesives. This work provides a new method for the valorization of DSG and contributes to the development of green wood bio-adhesives without formaldehyde problems.

Influence of width-to-depth and effective length-to-depth ratio on shear strength of reinforced concrete slender beams without shear reinforcement: comparative analysis

PurposeFrom the factors that affect shear strength of reinforced concrete (RC) beams, the study examines the effect of controversial parameters, width-to-depth (b/d) and effective length-to-depth (leff/d) ratio on shear strength of RC slender beams.Design/methodology/approachThe researchers utilized a database of 676 experimental test results from ACI-DAfStb database, Conducted regression analysis to examine relationship between b/d and leff/d ratios and shear strength, compare and analyze sensitivity to changes in b/d and leff/d ratios for the selected 12 shear models for RC beams.FindingsIncreasing b/d ratio enhanced shear strength until b/d ˜ 3, but further increases had limited impact and increasing leff/d ratio resulted in decreased shear strength. From comparative analysis, the models provided by various design standards were found to be safe, with EC-2 and JSCE models being conservative. From considered research models, Campione and Arslan models were conservative, while Kim and White model were observed to be unsafe. Sensitivity analysis indicated ACI318-19, JSCE, CEB-FIP-90 and Arslan models were sensitive to changes in b/d and leff/d ratios. National code models generally captured shear strength characteristics well. Certain models suggested a constant/decreasing b/d effect despite observed shear strength enhancement. Most models indicated improved shear strength with an increasing leff/d ratio, contrary to experimental findings while TS500 and Hwang models aligned with experimental results.Research limitations/implicationsThe study's limitations include the dependence on the available database, which may not encompass all possible experimental scenarios. Further research should aim to expand the database and investigate additional parameters that may influence shear strength in RC beams.Practical implicationsThe findings of this study have practical implications for the design and analysis of RC beams by suggesting that the width-to-depth and length-to-depth ratios should be carefully considered to optimize shear strength. The identified models can assist engineers in selecting appropriate shear strength prediction models based on specific design scenarios.Social implicationsThe study contributes to the advancement of knowledge in the field of reinforced concrete beam design, which has implications for the safety and reliability of structural systems. By understanding the factors influencing shear strength, engineers can design more efficient and robust structures, ensuring the safety of buildings and infrastructure.Originality/valueThis study provides valuable insights into the influence of the width-to-depth and effective length-to-depth ratios on shear strength in reinforced concrete beams. It contributes to the understanding of these factors and their impact on shear strength, addressing the lack of consensus among researchers. The comparative analysis of shear models and the sensitivity analyses add value by identifying the models that align better with experimental observations. The study emphasizes the need for accurate models that account for these factors and highlights the importance of further research to refine and develop improved predictive models.

Review of Subgrade Soil Stabilised with Natural and Synthetic Fibres

Subgrade soil is an essential component in the design of road structures as it provides lateral support to the roadway. One of the main reasons for pavement failure is subgrade settlement, which leads to a loss of subgrade strength. If the mechanical properties of subsoils are lower than required, a soil stabilisation method may be an option to improve the soil properties of the weak subsoil. Soil stabilisation is one of the techniques for improving poor subsoil, which results in significant improvement in tensile strength, shear strength and bearing capacity of subsoil. Soil stabilisation can be broadly divided into four types: thermal, electrical, mechanical, and chemical. The most common method of improving the physical and mechanical properties of soils is stabilisation with binders such as cement and lime. However, soil stabilisation with conventional methods using cement and lime has become uneconomical in recent years, so an alternative such as fibres may be sought. This review provides a comprehensive comparison of the effectiveness of natural fibres and synthetic fibres in stabilising subgrade soils.

Microstructural and mechanical characterizations of SiC–304SS joints brazed with Cu–10TiH2 filler

A high-quality brazed joint of SiC ceramic and 304 stainless steel (SiC–304SS) was achieved by Cu–10TiH2 brazing alloy. The effects of brazing temperature on the interfacial microstructure and mechanical properties of SiC–304SS were analyzed. The typical interfacial microstructure of joints brazed at 1030 °C for 10 min was 304SS/σ-phase/(Fe, Cr) Ti/Fe2Ti/Cu(s,s) + Fe2Ti + TiC/SiC ceramic. With the brazing temperature increasing, the element Fe continued diffusing into the brazing seam and reacted with the element Ti. Then the width of σ-phase and the amount of Fe2Ti phase became increasing, and Fe2Ti phase became continuous. While, due to the reaction between Fe and Si, a buffer layer formed in SiC–304SS joints brazed at 1040 °C and 1050 °C. The main component of the buffer layer was FeSi2, TiC phases and carbon particles. In addition, the buffer layer contributed to forming a good gradient transition of coefficient of thermal expansion (CTE), releasing residual stress and improving shear strength of the joints. When brazing at 1050 °C for 10 min, the maximum shear strength of the joint was 100 MPa at room temperature and 53 MPa at 600 °C.

Sustainable design framework for enhancing shear capacity in beams using recycled steel fiber-reinforced high-strength concrete

According to a recent estimate, over 1.5 billion wasted tyres which containing over 40% of vulcanised rubber and 15% of steel fibre are discarded yearly, which posing a serious threat to circular economy implementation and transition to net zero. To minimise the greenhouse gas(GHG) emission and the environmental side effect caused by burning and burying these waste tyres, recycling and reusing these materials for sustainable structural designs has become the centre of attention. This paper focuses on applying recycled bead steel fibre to improve the shear capacity of fibre-reinforced concrete beams. Moreover, the existing national standard known as Eurocode 2 and TR63 can hardly illustrate the relationship between fibre and high-strength concrete. This study is the first to investigate shear behaviours of high-strength industrial and recycled steel fibre reinforced concrete beams with consideration of different shear span ratios. Therefore, twenty real-scale beams are constructed to examine the shear capacity of high-strength industrial and recycled steel-fibre reinforced concrete beams, which aims to compare the improvement of shear strength through experiments and identify different shear strength improvements of the two categories of steel fibre. Besides, comprehensive data of 164 beams from previous studies have been collected to benchmark with the experimental results for the formula design. This study proves the feasibility of replacing industrial steel with recycled steel fibre to improve the shear capacity of fibre-reintroduced concrete beams. Moreover, there are six novel equations designed developed using Eurocode 2 and TR63 as a basis in this study. Based on the findings of the paper, the proposed formulas demonstrate remarkable accuracy, with an average value of 0.982 and standard deviation of 0.213, respectively. Following an exhaustive comparison of RSF and ISF reinforced concrete beams, with a focus on economic expenditure and GHG emissions, it can be concluded that RSF offers superior economic and environmental benefits, which reduce the emissions up to 25.39% and price up to 28.04% when replacing ISF 0.8% RSF, respectively.

Microstructural effects of copper deposits on direct bonding for 3D IC integration

Cu-to-Cu direct bonding has been regarded as an important approach to achieve three-dimensional integrated circuit integration. This study aims to investigate the effects of microstructure and Xenon flash exposure on the direct bonding of copper deposits. Copper electrodeposits, along with a sputtered deposit, with various grain sizes, preferred orientations, as well as surface hardnesses, were prepared to clarify the influence of individual factors quantitatively. Experimental results show that joint strength and grain boundary density followed a positively linear relationship regardless of other microstructural differences, suggesting the dominating role of grain boundary diffusion. Grain refinement can effectively enhance bonding strength, even only one side of the directly bonded joints possessed fine grains. Considering the portable device applications which may suffer from drop shocks, drop testing of the packages comprising sputtered copper on Si chips joined with electroplated copper on Al2O3 substrates assembled by thermal compression bonding was performed for the first time. Noticeably, a proper flash irradiaiton prior to bonding brought about not only remarkable improvement in shear strength by up to 60 % but also drop resistance for direct-copper bonds. The resistance against drop shock for directly-bonded daisy chains subjected to an appropriate light exposure prior to bonding was superior than the joints bonded using impact-resistant solders.

Slurry infiltration and sintering cycle‐dependent mechanical properties of 3D oxide/oxide ceramic matrix composites

AbstractIn this study, oxide/oxide ceramic matrix composites reinforced with three‐dimensional fiber preform were fabricated by a slurry infiltration and sintering (SIS) process. The influence of the SIS cycle on microstructures and mechanical properties of the 3D oxide/oxide composite was investigated. Results showed that the porous matrix was densified due to the SIS effect. The elastic modulus of the weak matrix and interfacial shear strength increased with the increasing SIS cycle. This led to an obvious improvement in flexural strength and interlaminar shear strength of the composite. The fracture toughness and work of fracture of the composite slightly decreased. A good balance between fracture strength and damage tolerance was achieved on the sixth SIS fabricated oxide/oxide composite, which had a high flexural strength of 295.1 ± 14.9 MPa, a high interlaminar shear strength of 18.2 ± .5 MPa, and a high fracture 11.5 ± .8 MPa m1/2. The SIS process is a promising way to fabricate the 3D oxide/oxide composite.