Softening Of Matrix Research Articles

Hardening overwhelming softening in Ti-based metallic glass composites upon cold rolling

For in-situ Ti48Zr20Nb12Cu5Be15 metallic glass matrix composites (MGMCs) upon cold rolling, the yield strength is obviously enhanced, and the plasticity instability is effectively alleviated. The increase in yield strength in such kinds of composites is due to the fact that the work hardening of dendrites overwhelms the softening of the amorphous matrix. A quantitative model of predicting yield strengths with rolling straining in MGMCs is successfully established. This provides useful guidances for structural applications of ductile MGMCs.

Matrix stiffness epigenetically regulates the oncogenic activation of the Yes-associated protein in gastric cancer.

In many cancers, tumour progression is associated with increased tissue stiffness. Yet, the mechanisms associating tissue stiffness with tumorigenesis and malignant transformation are unclear. Here we show that in gastric cancer cells, the stiffness of the extracellular matrix reversibly regulates the DNA methylation of the promoter region of the mechanosensitive Yes-associated protein (YAP). Reciprocal interactions between YAP and the DNA methylation inhibitors GRHL2, TET2 and KMT2A can cause hypomethylation of the YAP promoter and stiffness-induced oncogenic activation of YAP. Direct alteration of extracellular cues via in situ matrix softening reversed YAP activity and the epigenetic program. Our findings suggest that epigenetic reprogramming of the mechanophysical properties of the extracellular microenvironment of solid tumours may represent a therapeutic strategy for the inhibition of cancer progression.

Modeling on mechanical behavior and damage evolution of single-lap bolted composite interference-fit joints under thermal effects

This paper reports the modeling method and outcomes of mechanical performance and damage evolution of single-lap bolted composite interference-fit joints under extreme temperatures. The anisotropic continuum damage model involving thermal effects is established on continuum damage mechanics which integrates the shear nonlinearity constitutive relations characterized by Romberg-Osgood equation. The temperature-induced modification of thermal strains and material properties is incorporated in stress-strain analysis, extended 3D failure criteria and exponential damage evolution rules. The proposed model is calibrated and employed to simulate behavior of composite joints in interference fitting, bolt preloading, thermal and bearing loading processes, during which the influence of interference-fit sizes, preload levels, laminate layups and service temperatures is thoroughly investigated. The predicated interfacial behavior, bearing response and failure modes are in good agreement with experimental tests. The numerical model is even capable of reflecting some non-intuitive experimental findings such as residual stress relaxation and matrix softening at elevated temperatures.

ILC1 drive intestinal epithelial and matrix remodelling.

Organoids can shed light on the dynamic interplay between complex tissues and rare cell types within a controlled microenvironment. Here, we developed gut organoid co-cultures with type-1 innate lymphoid cells (ILC1) to dissect the impact of their accumulation in inflamed intestines. We demonstrate that murine and human ILC1 secrete TGFβ1, driving expansion of CD44v6+ epithelial crypts. ILC1 additionally express MMP9 and drive gene signatures indicative of extracellular matrix remodelling. We therefore encapsulated human epithelial-mesenchymal intestinal organoids in MMP-sensitive, synthetic hydrogels designed to form efficient networks at low polymer concentrations. Harnessing this defined system, we demonstrate that ILC1 drive matrix softening and stiffening, which we suggest occurs through balanced matrix degradation and deposition. Our platform enabled us to elucidate previously undescribed interactions between ILC1 and their microenvironment, which suggest that they may exacerbate fibrosis and tumour growth when enriched in inflamed patient tissues.

Effect of heat treatment on SLM-fabricated TiN/AlSi10Mg composites: Microstructural evolution and mechanical properties

This paper systematically investigates the effect of artificial aging (AA), solution (SHT), and T6-like (solution followed by artificial aging (SHA)) heat treatments on the microstructural evolution and mechanical properties of selective laser melted TiN/AlSi10Mg composites. Results show that the microstructure and mechanical properties reveal inconspicuous changes after AA where the eutectic fibrous Si networks remain. However, SHT vanishes the Si networks, precipitates and coarsens Si particles, and eventually softens the Al matrix, leading to a significant decrease in tensile strength and hardness of heat-treated composites and an increase in ductility. The addition of TiN nanoparticles plays a significant role in microstructural evolution during heat treatment. By increasing solution temperature from 460 °C to 540 °C, Mg2Si phase precipitates out of the Al matrix, followed by AlFeSi intermetallic at 500 °C and AlSiTi intermetallic at 540 °C, respectively. Interestingly, unexpected enhancements of hardness (from 91.5 ± 2.3 HV to 105.9 ± 2.1 HV) and tensile strength (from 268.7 ± 2.5 MPa to 336.8 ± 1.5 MPa) are achieved as the solution temperature increases. This abnormal phenomenon is attributed to the precipitation hardening by the Mg2Si precipitate and needle-like intermetallics, which overcomes the effects of microstructural coarsening and matrix softening. This paper sheds light on how the mechanical properties of as-built TiN/AlSi10Mg composites can be tailored using different heat treatment techniques.

Multiscale study of CO[formula omitted] impact on fluid transport and carbonate dissolution in Utica and Eagle Ford shale

In this work, we study the impact of CO2 on carbonate-rich Utica and Eagle Ford shale with respect to mineralogical alteration, fluid transport, and enhanced oil recovery. The study encompasses diagnostic tools that include Computed Tomography (CT), pulse decay techniques for core or centimeter scale investigations, Scanning Electron Microscopy (SEM), and μ-CT for micro-scale evaluations. The core-scale findings did not show any significant contributions to matrix flow or oil recovery in the presence of the water saturated (wet) sc-CO2 or carbonated water. Computed Tomography was able to capture aperture reduction during pure carbonated water injection. This effect is likely a result of matrix softening near the fracture surface and reduction in aperture due to effective stress. These results made it apparent that finer diagnostics such as SEM and μ-CT are essential in capturing any interaction between the CO2-water fluids and the carbonate-rich shale. The micron scale investigations showed that indeed carbonated water dissolves calcite but not dolomite over the time scale of observations; however, the depth of dissolution was limited to 100’s of microns. Additionally, Energy Dispersive Spectroscopy (EDS) and μ-CT images reveal that the water moisture residing in the wet sc-CO2 phase does not cause any measurable carbonate dissolution in rocks in contact with that phase. Finally, our analysis proves that the gold-coating used in sample preparation for SEM imaging does not affect the outcome of dissolution observed in our experiments.

Study on rolling of a new near-α titanium alloy: Microstructure refinement and dual-scale silicides evolution

In this study, a novel near-α titanium alloy sheet with dual-scale silicides was successfully fabricated by rolling in α+β two phase field. The microstructure refinement, dual-scale silicides evolution and their influence on the tensile properties were systematically investigated. The results indicate that the preheating before rolling and the reheating between rolling passes play vital roles in the process of microstructure refinement. Thus, a new microstructure refinement mechanism was proposed considering the heat treatment besides the rolling deformation. The dual-scale silicides exhibit obvious differences in size, shape and distribution. The mean size of large-scale silicides is about 1.58 μm while the one of small-scale silicides is only 152 nm. The sheet with dual-scale silicides shows an outstanding room temperature tensile strength (1370 MPa) but an ordinary 650 °C tensile strength (513 MPa). This is because the strengthening mechanisms can be attributed to the microstructure refinement, dual-scale silicides and the residual substructures at room temperature. At 650 °C, however, the matrix softening is dominant due to the directionally arranged α/β microstructure has a low flow resistance at high temperature.

High-temperature mechanical behavior of boron nitride nanosheets/fused silica composites

Boron nitride nanosheets (BNNSs) with relatively low dielectric constant and excellent mechanical strength were employed for fabrication of BNNSs/fused silica (FS) composites. High-temperature mechanical behavior and microstructural evolution of the composites were investigated. The addition of BNNSs can improve the mechanical properties of FS efficiently, and the reinforcement from BNNSs can be preserved during the high temperature service. The flexural strength of BNNSs/FS composites exhibited anomalous gains at certain high temperature range, which can be explained by the softening of FS matrix, the heal of defect tips, and the reinforcement from BNNSs.

Epoxy‐Polypyrrole‐Cotton Tertiary Composite with Electro‐Tunable Stiffness

AbstractIn this work, a tertiary epoxy composite reinforced with polypyrrole (PPy) coated cotton fabric layers exhibiting electrical voltage induced thermally tunable stiffness is reported. The thin coating of PPy over cotton fabric is accomplished via oxidative vapor phase polymerization that allows creation of an active thin layer over the fibers without affecting their mechanical properties. Six such functional layers are stacked within an epoxy matrix to prepare the composite that shows in‐plane electrical insulator behavior (volume resistivity > 109 Ω cm) but considerably reduced resistivity by an order of 103 across the cross‐sections. The presence of conductive layers enables the composite to heat via Joule's effect when an electrical voltage is applied across two ends. This causes softening of matrix near the matrix‐reinforcement interface and thereby changing composite's stiffness. On application of variable voltage, a non‐linear decrease of 91% in composite stiffness is observed (6371.2 N m−1 at 0 V to 566.4 N m−1 at 63 V). A stable and tunable mechanical performance of the composite is further demonstrated by cyclic changes in stiffness due to voltage change with recovery up to 95% of original stiffness after 14 continuous cycles.

Microstructure evolution and mechanical properties at high temperature of selective laser melted AlSi10Mg

In this study, the microstructure and tensile properties of selective laser melted AlSi10Mg at elevated temperature were investigated with focus on the interfacial region. In-situ SEM and in-situ EBSD analysis were proposed to characterize the microstructural evolution with temperature. The as-fabricated AlSi10Mg sample presents high tensile strength with the ultimate tensile strength (UTS) of ∼450 MPa and yield strength (YS) of ∼300 MPa, which results from the mixed strengthening mechanism among grain boundary, solid solution, dislocation and Orowan looping mechanism. When holding at the temperature below 200 °C for 30 min, the microstructure presents little change, and only a slight decrement of yield strength appears due to the relief of the residual stress. However, when the holding temperature further increases to 300 °C and 400 °C, the coarsening and precipitation of Si particles in α-Al matrix occur obviously, which leads to an obvious decrease of solid solution strength. At the same time, matrix softening and the weakness of dislocation strengthening also play important roles. When the holding temperature reaches to 400 °C, the yield strength decreases significantly to about 25 MPa which is very similar to the as-cast Al alloy. This might be concluded that the YS is dominated by the matrix materials. Because the softening mechanism counteracts work hardening, the extremely high elongation occurs.

Effects of Extracellular Matrix Softening on Vascular Smooth Muscle Cell Dysfunction.

Vascular smooth muscle cells (VSMCs) shift from a physiological contractile phenotype to an adverse proliferative or synthetic state, which is a major event leading to aortic disease. VSMCs are exposed to multiple mechanical signals from their microenvironment including vascular extracellular matrix (ECM) stiffness and stretch which regulate VSMC contraction. How ECM stiffness regulates the function and phenotype of VSMCs is not well understood. In this study, we introduce in vitro and in vivo models to evaluate the impact of ECM stiffnesses on VSMC function. Through unbiased transcriptome sequencing analysis, we detected upregulation of synthetic phenotype-related genes including osteopontin, matrix metalloproteinases, and inflammatory cytokines in VSMCs cultured using soft matrix hydrogels in vitro, suggesting VSMC dedifferentiation toward a synthetic phenotype upon ECM softening. For the in vivo model, the lysyl oxidase inhibitor β-aminopropionitrile monofumarate (BAPN) was administrated to disrupt the cross-linking of collagen to induce ECM softening. Consistently, decreased ECM stiffnesses promoted VSMC phenotypic switching to a synthetic phenotype as evidenced by upregulation of synthetic phenotype-related genes in the aortas of mice following BAPN treatment. Finally, BAPN-treated mice showed severe expansion and developed aortic dissection. Our study reveals the pivotal role of ECM softening in regulating the VSMC phenotype switch and provides a potential target for treating VSMC dysfunction and aortic dissection disease.

Strength degradation of 42CrMo steel in a thermal field and its characterization method

The effect of thermal temperature on microstructures and mechanical properties of 42CrMo steel was reported in this paper. A sharp strength degradation in this material occurs as the thermal aged temperature rise to 600 °C, and the lath microstructure turned into a fine and granular tempered sorbite. The mechanism of the strength degradation due to C and Cr element precipitating that caused the matrix softening. Besides, the magnetic parameters were sensitive to the microstructure change of 42CrMo steel, which showed good regularity as compared with its strength variation. The results manifested that the electromagnetic technique is an effective method to assess the thermal degradation of 42CrMo steel.

Temperature dependent strengthening mechanisms and yield strength for CNT/metal composites

Strengthening mechanisms in CNT/metal composites are significant guidelines on composites design. However, the strengthening mechanisms at high temperatures have few been reported. In this work, the evolution of four common strengthening mechanisms in CNT/metal composites, including load transfer strengthening, grain refinement strengthening, enhanced dislocation density strengthening and Orowan strengthening, with temperature was investigated by our developed theoretical models. Then by considering those temperature dependent strengthening mechanisms, a temperature dependent yield strength model for CNT/metal composites was established. Further, the effects of residual thermal stress and quicker softening of matrix on the temperature dependent yield strength of composites were also taken into account. Good agreement is obtained between the model predictions and available experimental results. This study contributes a simple method to predict the yield strength for CNT/metal composites over a wide range of temperatures. In addition, the contribution of each strengthening mechanism to the yield strength of composites at different temperatures was extensively discussed. Some useful suggestions for the design of new CNT/metal composites with high yield strength at elevated temperatures were provided.

Substance evolution and wear mechanism on friction contact area of brake disc for high-speed railway trains at high temperature

The high temperature induced by the increased braking speed of high-speed railway train leads to the variation of structure and composition of tribo-film on the wear region of brake disc. The tribo-film was characterized in detail after the pin-on-disc experiments at 400–800 ℃. The results indicate with the increase of temperature, the tribo-film changes from single layer structure (mechanical mixing layer (MML)) to double layer structure (MML at the bottom and oxide layer at the top). In addition, the wear mechanism also changes from abrasive wear on the surface of disc to adhesive wear on the tribo-film. Those are related to the increased substance transfer rate between the friction interfaces with the softening of copper matrix.

High‐temperature properties and failure mechanism of 3D six‐directional braided composites under out‐of‐plane compression

AbstractThree‐dimensional (3D) six‐directional braided carbon/epoxy composites with different braiding angles were fabricated successfully. The effect of braiding angles and temperature on mechanical properties and failure mechanism were analyzed. The results show that the braiding angle and temperature both have a significant effect. As braiding angle increases, out‐of‐plane compression stress vs strain curve increases and the compression properties improve. At high temperatures, the stress vs strain curves are non‐linear up and the compression properties reduce. Besides, the out‐of‐plane performances of 3D six‐directional braided composite at room and high temperatures are more excellent than 3D four‐directional and five‐directional braided composites. Under out‐of‐plane compression, at room temperature, the materials appear 45° shear fracture; the phenomenon of fibers shear fracture and extraction is more distinct with larger braiding angle; the main failure is the fiber bundles expand outward and the matrix cracks. At high temperatures, the materials exhibit ±45° shear cracks; composites are compressed flat and expand along the transverse direction; the main failure is the matrix softening and exfoliation from the fiber bundles, the fiber/matrix interface debonds seriously.

Heat partition in edge trimming of fiber reinforced polymer composites

Thermal loading of fiber reinforced composites during traditional machining is inevitable. This is due to the fact that most of the mechanical energy utilized in material removal is converted into heat, which is subsequently dissipated into the workpiece and the cutter, and is carried away by the chips. Heat conduction into the workpiece during machining might cause thermal damage due to matrix softening and decomposition if the generated temperatures exceeded the glass transition temperature of the epoxy resin. In this work, the amount of heat flux applied to the machined edge and the temperature distribution in multidirectional CFRP and GFRP composite laminates was determined using an iterative inverse heat conduction method. The transient heat conduction problems in the laminate and cutter were simulated independently using the finite element method and the amount of heat flux applied to each was determined. It was also found that the heat flux conducted to the workpiece represented only a small fraction of the total heat and is more influenced by the feed speed than the spindle speed. The temperature of the machined surface was estimated and correlations with the resulting machined surface texture were made.

Relaxation of Extracellular Matrix Forces Directs Crypt Formation and Architecture in Intestinal Organoids.

Intestinal organoid protocols rely on the use of extracellular scaffolds, typically Matrigel, and upon switching from growth to differentiation promoting media, a symmetry breaking event takes place. During this stage, the first bud like structures analogous to crypts protrude from the central body and differentiation ensues. While organoids provide unparalleled architectural and functional complexity, this sophistication is also responsible for the high variability and lack of reproducibility of uniform crypt-villus structures. If function follows form in organoids, such structural variability carries potential limitations for translational applications (e.g., drug screening). Consequently, there is interest in developing synthetic biomaterials to direct organoid growth and differentiation. It has been hypothesized that synthetic scaffold softening is necessary for crypt development, and these mechanical requirements raise the question, what compressive forces and subsequent relaxation are necessary for organoid maturation? To that end, allyl sulfide hydrogels are employed as a synthetic extracellular matrix mimic, but with photocleavable bonds that temporally regulate the material's bulk modulus. By varying the extent of matrix softening, it is demonstrated that crypt formation, size, and number per colony are functions of matrix softening. An understanding of the mechanical dependence of crypt architecture is necessary to instruct homogenous, reproducible organoids for clinical applications.

Mechanical properties and failure mechanisms of 3D six-directional braided composites at elevated and liquid nitrogen temperatures

3D six-directional braided carbon/epoxy composites are fabricated successfully, and their mechanical properties and failure mechanisms at room, elevated and liquid nitrogen temperatures are reported. The results show the temperature has an important influence on load-deflection curves and bending properties. All the curves are divided into three stages: initial linear elastic, nonlinear and final fracture stage. At room temperature, the linear characteristic is obvious and properties are excellent. The failure is a gradual process from external to internal due to good reinforcement of transverse yarns, and fibers are sheared and pulled out. At elevated temperatures, the curves decline successively and nonlinear features increase, with decrease of bending properties. The damage is matrix softening and plasticization, interface debonding. At liquid nitrogen temperature, zigzagged fluctuation feature increases and linear elastic characteristic strengthens. Bending properties have been improved significantly and failure is fibers shear fracture and formation of shear bands among fiber/matrix interface.

Two stress rupture modes observed in Alloy 617–9%Cr dissimilar welded joint

The fracture transition behavior during the stress rupture test for Alloy 617–9%Cr dissimilar welded joint was investigated in the present study. The results showed that the specimen with applied stress of 240 MPa at 566 °C ruptured at the heat-affected zone of 9%Cr steel (9%Cr-HAZ), while the rupture location transferred to the interface between the weld metal (WM) and 9%Cr-HAZ with the decreased applied stress. The rupture behavior occurred in the 9%Cr-HAZ was caused by type IV crack due to the matrix softening. The notch was primarily formed in the interface due to the difference of oxidation resistance and mismatch of mechanical properties between the WM and 9%Cr-HAZ, and therefore the cracks initiated and propagated along the interface with the continuous load, eventually leading to the interface failure.

Enhanced high-temperature compressive strength of TiC reinforced stainless steel matrix composites fabricated by liquid pressing infiltration process

High-temperature compressive strengths of titanium carbide (TiC) reinforced stainless steel composites fabricated by liquid pressing infiltration process were investigated at various temperatures. Effect of TiC on compressive strength of SUS431 was found to increase with increasing testing temperature. TiC reinforcement successfully suppressed softening of SUS431 matrix, resulting in about 5 times higher strength than that of SUS431 at 1050 °C. The novel SUS431 composites reinforced with uniformly dispersed, high volume fraction TiC show great promise for applications in high-temperature environments.