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Epoxy vitrimers immerged as an appealing alternative to traditional plastics. However, high loading of catalyst and harsh processing conditions are prerequisites to fully exploit the vitrimer properties. In this work, stoichiometric ratio, an often neglected factor, was utilized to further accelerate the rate of dynamic transesterification. Epoxy vitrimers with four epoxy/acid stoichiometries (60:30, 40:30, 30:30, and 24:30) were prepared to comparatively analyze their network structures, thermomechanical properties, and reprocessing properties. It was found that the off‐stoichiometry epoxy vitrimers have almost the similar excellent thermal stability as epoxy thermosets. Vitrimers with excess epoxy showed increased tensile strength (from 26.3 to 42.7 MPa) and decreased elongation at the break (from 5.5% to 1.7%). Meanwhile, excess epoxy induced abundant of hydroxy groups in the vitrimers, imparting satisfactory repairability, reformability, and recyclability. Specifically, epoxy/acid (60:30) repaired 94% in 10 min at 180°C, and maintained over 93% mechanical properties after reforming and recycling. However, simply increasing the epoxy content will compromise the structural integrity of the network, simultaneously resulting in reduced toughness of epoxy vitrimers. These findings demonstrated that epoxy/acid stoichiometry can be a powerful tool to develop epoxy vitrimers with both excellent thermomechanical and reprocessing properties. [ABSTRACT FROM AUTHOR]

Fatigue failure is one of the main reasons for the failure of engineering application components. It is then necessary to propose a novel model for predicting fatigue strength expensive and time-consuming, fatigue strength could be predicted by the tensile strength based on the proposed novel model. In the present study, four intensity levels 304 stainless steel (SS) were prepared by rolling, in order to explore the relationship between tensile strength and fatigue strength, which, increase gradually with grain refinement. A novel model for fatigue strength prediction is established based on that fatigue strength is affected by tensile strength and work-hardening strength. Comparing the proposed model with the other two fatigue strength calculation methods, the model can greatly reduce the experimental cost with almost no reduction in accuracy. [ABSTRACT FROM AUTHOR]

Recently, much research has been reported on the fabrication of carbon-nanofiller (e.g., carbon nanotube (CNT), carbon nanosheet (CNS), and graphene)-reinforced copper matrix composites due to their wide potential applications. However, the preparation processes are generally complicated and difficult for commercial applications. Here, we propose a facile method to fabricate CNS-reinforced copper matrix composites by directly pyrolyzing copper formate powder at high temperature and then consolidating by spark plasma sintering. Interestingly, a complex interface consisting of CNSs, Cu nanoparticles, and CuO nanoparticles is found in the composite. The as-sintered CNS/Cu composite containing 0.27 vol% CNSs has a tensile yield strength of 498 ± 2 MPa and an electrical conductivity of 80.8 ± 0.1% International Annealed Copper Standard. The analysis of strengthening mechanism indicates that 51% of the tensile yield strength is contributed by the complex interface. The introduction of H 2 during the pyrolyzing copper formate process results in an increase on the elongation and conductivity of CNS/Cu composite. After rolling, the elongation of CNS/Cu composite is as high as 8.5% and the friction coefficient is 0.25. This work provides a new guideline to the facile fabrication and interfacial design of advanced carbon-nanofiller-reinforced metal matrix composites with high performance. Image 1 [ABSTRACT FROM AUTHOR]

Fluorine-free cellulosic paper was successfully obtained by coating the glassine base paper with eco-friendly cellulosic coating, which was made from dissolving cellulose in 8 wt% NaOH/12 wt% urea aqueous solution. Then the coated paper was severally immersed into CH3COOH, Na2SO4, and H2O solution to coagulate and regenerate. Benefiting from the compact matrix and fully covered surface, the resultant cellulosic paper exhibited favorable barrier properties and mechanical performance. Notably, the paper coagulated with CH3COOH displayed the reduction in water–vapor transmission rate, air permeability, and uptake of organic solvents due to its low porosity (26.8%) and narrow pore size distribution (0.1–0.36 µm). The tensile strength and elongation at break of papers treated by CH3COOH at coating weight of 5 g/m2 were increased by 72.1% and 34.0%, respectively. In summary, the fluorine-free cellulosic paper with high oil and grease resistance is attractive for the development of high-performance materials for food packing applications. Fluorine-free paper was obtained from the glassine base paper coated with eco-friendly, non-fluorinated, and degradable cellulosic coating, then coagulated with CH3COOH, Na2SO4, and H2O solution, respectively. The resultant functional papers displayed enhanced barrier properties (oil, organic solvent, vapor, and gas) and mechanical performance. [ABSTRACT FROM AUTHOR]

The cellulose microfibril-precipitated calcium carbonate (CMF–PCC) composite filler has been studied in improving the printing and optical properties of ordinary paper. However, the effect of CMF–PCC composite filler on the properties of Xuan paper, especially the ink diffusion properties, has rarely been investigated. In this study, the CMF–PCC composite filler was prepared by double-exchange reaction. The effects of CMF–PCC composite filler on the physical properties and ink diffusion properties of Xuan paper were detailedly studied. The results showed that the PCC particles in the CMF–PCC composite filler were rhombohedral calcite, with a uniform particle size and high adhesion rate, under the optimum reaction conditions. The Xuan paper filled with the CMF–PCC composite filler had higher tensile strengths and opacity than the conventional PCC or GCC loading. Notably, the CMF–PCC composite filler can effectively improve and regulate the Chinese ink diffusion properties of Xuan paper. [ABSTRACT FROM AUTHOR]

The effect of rolling parameters on microstructure and tensile properties of nanocrystalline/microcrystalline 304 stainless steel (SS) casted by the aluminothermic reaction was investigated in this work. It was found that majority of the nanocrystalline austenite of the 304 SS rolled at 700 ∘ C and 900 ∘ C grew up and transformed to sub-microcrystalline. While the nanocrystalline/microcrystalline structure still retained rolled at 900 ∘ C with 40% deformation followed 600 ∘ C with 70% thickness reduction, and microcrystalline austenite grains distributed evenly. The strength and ductility of the various rolled 304 SS were improved compared with the as-casted 304 SS steel. The steel rolled at 900 ∘ C with 80% deformation exhibited a uniform elongation as large as 31.3%, which is almost the same ductility level of counterpart coarse-grained steel. The rolled steel at 700 ∘ C with 80% deformation achieved the maximum tensile strength but the smallest elongation. The sample, two-step rolled at 900 ∘ C with 40% thickness reduction and then 600 ∘ C with 70% thickness reduction, yielded the satisfactory combination of strength and ductility. The yield strength and elongation were appropriate 767 MPa and 22.8%, respectively, which resulted from the optimized nanocrystalline/microcrystalline structure and distribution. [ABSTRACT FROM AUTHOR]

The tensile fracture behavior of the annealed 316L austenitic stainless steel at room temperature was studied by in-situ tensile platform loaded on the field emission scanning electron microscope with 4.2e−4 s−1 of initial strain rate. The results showed that tensile strength and yield strength of annealed specimens of 316L for annealing treatment for 28 h at 800 °C were higher than those of as-cast specimens. After annealing, microstructures of the specimens were mainly micron crystals. When the applied loading was 162 MPa, initiation source appeared. Loading reached 380 MPa, main cracks continued to expand and became deeply, and specimen yielded at this time. When loading reached up to 533 MPa, specimens reached the maximum stress value. After breaking completely, included angle was approximately 70° between fracture surface and direction of tensile axis. The composition of the fracture was more pure and continuity of the matrix was good. This showed that micro/nanostructure stainless steel prepared by aluminothermic reaction casting, which could improve the mechanical properties through controlling size of nanocrystalline and microcrystalline austenite grains and their volume fraction. [ABSTRACT FROM AUTHOR]

As the stress-strain data of the fusion-brazed filler material AA4047 could not be easily or directly measured, an isotropic strain-hardening model of the fusion zone material AA4047 was estimated by an inverse method to quantify the tensile behavior of AA6111-T4 coach-peel joints. The Hill’s 1948 quadratic anisotropic yield stress function for the base sheet metal AA6111-T4 was first determined by conducting uniaxial tensile tests on the sheet metal in the rolling, diagonal, and transverse directions. Based on the yield stress function and isotropic strain hardening behavior determined for the base sheet metal, the linear-exponential strain hardening model was used to identify the fusion zone material AA4047 by an iterative correction and image-based finite element analysis of the welded joint. Modeling of joints with and without flawed brazing interface showed that the load-carrying capacity of coach-peel joints was insensitive to the existence of the brazing zone metal AA4047. When the fusion zone model was also applied to the brazing zone, the predicted and measured force-displacement curves of the coach-peel joint matched well. The failure stress of the coach-peel joint was identified as the von Mises fracture stress of 100 MPa at the brazing interface. [ABSTRACT FROM AUTHOR]

The nanostructural evolution and mechanical properties during rolling with 30, 50, and 70% deformation of exceptional nano/microcrystalline 304 stainless steel prepared by the aluminothermic reaction casting method are investigated in this paper. The results of the microstructural evolution show that the grain size of the nano/sub‐micrograins have minor changes in which the volume fraction decrease dramatically, but the distribution of the nanograins become uniform with increased rolling deformation. The results of mechanical tests show that the increase in rolling deformation causes great increase in hardness and in yield strength from 274 to 364 HV and from 616 to 743 MPa, respectively. However, the tensile strength increases slightly from 925 to 995 MPa, and elongation decreases slightly from 24.5 to 21.9%. Conclusively, this work proves that an increase in rolling deformation causes a significant improvement in the hardness and strength and no considerable loss of the ductility in nano/microcrystalline 304 stainless steel. [ABSTRACT FROM AUTHOR]

Large dimensional bulk 1045 carbon steel with nanolaminate pearlite is prepared by aluminothermic reaction casting method. The steel is rolled at 873 K with different thickness reduction. Microstructures evolution and mechanical properties are characterized in detail. The results show that the nanolaminate cementites are crushed with the increase of thickness reduction, the dislocation density increases, meanwhile the tensile strength is improved greatly. The rolled steels possess the key combination of three characteristics, namely, high density dislocation, nanolamination, and second‐phase particles. When the thickness reduction is 60%, most of the lamellar cementites are crushed to globular particles, the tensile strength reaches 719 MPa, and the elongation is 14%. It provides a guidance for all high strength alloy design efforts by this route. [ABSTRACT FROM AUTHOR]

Welded joints made of 6061-T6 Al alloy were studied to evaluate warm laser shock peening (WLSP) and laser shock peening (LSP) processes. The estimation model of laser-induced surface residual stress was examined by means of experiments and numerical analysis. The high-cycle fatigue lives of welded joint specimens treated with WLSP and LSP were estimated by conducting tensile fatigue tests. The fatigue fracture mechanisms of these specimens are studied by surface integrity and fracture surface tests. Experimental results and analysis indicated that the fatigue life of the specimens processed by WLSP was higher than that with LSP. The large increase in fatigue life appeared to be the result of the larger residual stress, more uniform microstructure refinement and the lower surface roughness of the WLSP specimens. [ABSTRACT FROM AUTHOR]

The buildings including steel-structured bridges, plants and ocean platforms which take steel as the main material are prone to fall into pitting corrosion. Mechanical properties are greatly affected by pitting corrosion and hence the security of buildings can hardly be guaranteed. The mechanical drilling and milling method is employed to form conical blind holes and then to simulate corrosion pits in present work, after which the effects of the shape, depth and distribution of corrosion pits on the tensile properties of steel have been systematically investigated. The results indicate that the fracture location of steels with corrosion pits occurred at the cross section with larger pitting corrosion factor. The load-displacement curves of the steels were changed due to the existence of corrosion pits, the yield platform got shorter and even disappeared, accompanied with poorer ductility and brittle fracture. Pit shape, depth and distribution impacted little on the ultimate load of tensile samples, the ultimate strength almost correlated only with the maximum cross-sectional area. However, the yield load of steels was affected by both pit shape and distribution. The elongation was mainly affected by pit denseness and depth, denser and deeper pits per unit area would give rise to smaller elongation. Finally, multivariate regression analysis was performed to acquire the prediction model of elongation. [ABSTRACT FROM AUTHOR]

High electrolyte wettability, thermal dimensional stability, and tensile strength are prerequisites for implementing separators in practical applications. In this study, we report on the discovery of nanofibril membranes derived from various plant fibers commonly used in the papermaking industry, for low cost and higher performances than the commercially available Celgard2325 in regard to the application of separators for lithium-ion batteries. Nanofibril membranes showed water contact angles as low as 18°, negligible size change at a heating temperature of 160 °C for 120 min, and tensile strength up to 137.6 MPa. The homogenization was found to strongly contribute to these improved performances. These findings suggest that the plant fiber-derived nanofibril membranes are anticipated to be promising candidates as separators for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

To combat the emergence of drug-resistant bacteria, a locally isolated bacteriophage (HZJ) targeting H5α Escherichia coli was used as an antibacterial agent to make wound dressing samples in this study. The phages were physically embedded within an alginate hydrogel sample so that they could later be released with their tails being free during the infection process, which preserves their lytic activity. The HZJ phage isolated in the study have a 20 min latent period and are stable between pH 6 and pH 9 and at temperatures below 45 °C. The addition of phage to an E. coli culture suppressed over 99% of bacterial growth in 2-h (p < 0.001). Phage-embedded hydrogel fibers were used to create porous wound dressing material using three-dimensional (3D) printing. The majority of phage lytic activity (85%–90%) was preserved after encapsulation. After they were embedded in samples, HZJ lysed 57% to 67% of bacteria (p < 0.001) within 2 h and the antibacterial effects lasted at least 24 h. The small amount of phage released in 2 h was able to quickly replicate and effectively lysed the majority of the bacterial hosts. Phage-embedded alginate samples released 10% of its incorporated phage particles in 24 h. The SEM micrographs show that, compared to phage-free samples, fewer E.coli cells were observed on phage-embedded samples 2 h after bacteria were exposed to the samples. The phage-embedded sample was not cytotoxic to L929 cells. The presence of HZJ in alginate hydrogel promoted cell growth (p < 0.01) and adhesion to the samples. Further, the existence of phage did not alter the tensile strength and modulus of samples (p > 0.05). An antibacterial dressing capable of slowly releasing lytic phages and effectively suppressing bacterial growth for up to 24 h was produced in this study. This model represents an attractive means to reduce use of antibiotics and other additives in conventional dressings. Unlabelled Image • Bacteriophage-embedded hydrogel wound dressing successfully created by 3D plotting. • Purified phages lysed 99% bacteria in 2 h and stable under physiological conditions. • 0.03% bacteriophages released from dressing reduced 57% of bacteria in 2 h. • Lytic phages released from dressing exhibited antibacterial activity for up to 24 h. • Phage-embedded dressings are compatible with fibroblast cells. [ABSTRACT FROM AUTHOR]

Slow strain rate tensile test in a hydrogen-rich environment was performed to study the effects of laser peening (LP) on the tensile properties and martensitic transformation of AISI 316L stainless steel. Underlying physio-chemical processes involved in hydrogen embrittlement of 316L steel in the hydrogen-rich environment has been proposed. Results show that the grain refinement, mechanical twins and high-density dislocations were found in the laser peened specimens. The movement of hydrogen-carrying dislocations and martensite transformation were prevented by complex grain boundaries and high-density dislocations during tensile process. The ultimate tensile strength of the laser peened specimen were increased by 7.73% and 8.45% in air and hydrogen-rich environment respectively compared with that of non-laser peened specimen. What's more, the elongation loss of laser peened sample was far less than that of non-LP sample in a hydrogen-rich environment. LP induced compressive residual stress (CRS), grain refinement, high-density dislocations and a dense surface layer on the treated surface are beneficial for suppressing hydrogen penetration. • Tensile properties of 316L steel were improved by LP in the hydrogen-rich environment. • LP was effective for preventing martensitic transformation in 316L steel. • A dynamic hydrogen charging device was developed for tensile test in the hydrogen-rich environment. • Underlying physio-chemical processes involved in HE of 316L steel in the hydrogen-rich environment has been proposed. [ABSTRACT FROM AUTHOR]

Abstract Tensile strength is one of the most important mechanical parameters controlling the development of cracks in soil. However, it is frequently neglected in conventional geotechnical practice, because its magnitude is small and difficult to measure relative to other soil strength parameters. In this paper, a newly designed direct tensile test apparatus was employed to measure the tensile strength of an unsaturated clayey soil. A digital image acquisition and analysis system was developed for tensile strain analysis with the help of Particle Image Velocimetry (PIV) and Digital Image Correlation (DIC) techniques. Six groups of samples were compacted at a dry density of 1.7 Mg/m3 and different water contents (6.5%, 8.5%, 10.5%, 12.5%, 16.5% and 20.5%). Test results show that the tensile strength characteristic curve (tensile strength versus water content) of the compacted unsaturated soil exhibits mono-peak feature. When water content is relatively low, the tensile strength increases with increasing water content and reaches the maximum value at a critical water content of about 9.3%. Then, it declines with further increase in water content. The evolution of tensile strength with water content depends on both suction and microstructure. Based on plotted tensile load-displacement curves, the tensile failure process can be divided into three typical stages which are: stress increasing stage (I), failure developing stage (II) and post-failure stage (III). It is found that the overall tensile failure process presents different patterns controlled by water content. Generally, the failure developing stage (II) lasts longer and the failure ductility is more pronounced when the sample is compacted at higher water content. Using PIV and DIC techniques, the development of displacement direction and strain concentration during tension can be well captured for appreciation of the soil failure mechanism. Based on the strain concentration information, the tensile fracture location and direction can be pre-determined for soil samples. Graphical abstract Unlabelled Image Highlights • New direct tensile test apparatus with image capture system is designed. • Tensile curve shows three typical stages which strongly depend on water content. • TSCC of compacted soil shows mono-peak feature related to both suction and fabric. • Tensile stiffness and failure brittleness decrease with increasing water content. • PIV/DIC is valuable to get deformation and strain concentration characteristics. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of Cryogenic Treatment (CT) and Laser Peening (LP) on the fatigue properties of 2024-T351 aluminum alloy. The measurements of tensile properties and microhardness were carried out, and the residual stress tests were also conducted through x-ray diffraction (XRD) technology. Examination of microstructure was executed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) observations. Fatigue tests were conducted and the fatigue fracture morphologies were also analyzed by SEM. Experimental results found that both CT and LP could enhance the fatigue properties of 2024-T351 aluminum alloy. The process of CT prior to LP could provide a higher fatigue life compared with single CT or LP process. After CT prior to LP, the fatigue life of the treated specimen was 28,077 cycles under gradient loading, which obtained an increase of 4640 cycles compared to the untreated specimen. Meanwhile, compared with single CT and LP, CT prior to LP could produce finer grains, more precipitated second phases, higher density dislocation and compressive residual stresses. Beneficial microstructure evolution and compressive residual stress induced by CT prior to LP were considered to be the main factors that contribute to the improvement of the fatigue properties. [ABSTRACT FROM AUTHOR]

Highlights • A heterogeneous composite structure of 1045 steel was formed. • Both strength and ductility of steel was found to increase simultaneously. • The strength increase is believed to result from cementite nanostructuring. • A relationship between the strength and microstructure was established. Abstract The effects of low temperature annealing on the microstructure and mechanical properties of cold rolled 1045 steel were investigated. It was found that the isothermal annealing at 673 K could transform cementite in the rolled steel from lamella to nano-crystalline state. Against the conventional theory, the low temperature annealing treatment could simultaneously enhance the tensile strength and ductility of the cold rolled steel. The underlying mechanisms of enhancing mechanical properties were analyzed, with a focus on the heterogeneous composite structure of a soft fine-grained matrix embedded with hard nano-scale cementite particles. [ABSTRACT FROM AUTHOR]

Graphene/copper composite using graphene oxide sheets with three kinds of lateral sizes (~0.92 μm, ~5.49 μm and ~13.73 μm) were prepared via molecular level mixing method and spark plasma sintering process. The lateral size effects of graphene on the structure, mechanical performance, thermal and electrical conductivities of the composites were investigated while the volume fraction of graphene remained 2.5 vol%. For microstructure, small-sized graphene sheets (denoted as SRGO) tend to distribute randomly in the composites while middle-sized (denoted as MRGO) and large-sized graphene sheets (denoted as LRGO) are prone to form the carbon-rich aggregate with micro-layered structure. MRGO/Cu composite has the highest tensile yield strength (663 MPa) while SRGO/Cu composite exhibits the most excellent thermal and electrical conductivities (334 W/(m × K), 82 %IACS) among the three composites. This work provides a better understanding the formation mechanism of hierarchical layered graphene/Cu composite and can further promote the development of architectural design of graphene based composites. [ABSTRACT FROM AUTHOR]