Low Elastic Modulus Research Articles

Study on isotropic design of triply periodic minimal surface structures under an elastic modulus compensation mechanism

The energy absorption characteristics of the triply periodic minimal surfaces (TPMS) structure may vary significantly due to the anisotropy under multi-directional loading conditions. To address this issue effectively, an isotropic design strategy based on a precise elastic modulus compensation mechanism for different TPMS lattices is proposed. This strategy involves combining a TPMS lattice with a high elastic modulus in the axial direction with another TPMS lattice featuring a low elastic modulus in the same direction, leveraging the complementary effects of elastic modulus to achieve isotropy. The relationship between the relative density and the elastic modulus of six types of TPMS lattices is analyzed through homogenization simulation and finite element analysis. Mathematical expressions are then fitted using the Gibson-Ashby model. Additionally, a Kriging model is employed to establish the relationship between the Zener anisotropy values of hybrid TPMS structures and the relative density of their component lattices. This enables the precise complementary effect of elastic modulus in different TPMS lattice structures, providing a widely applicable selection rule for achieving isotropy. Using the Primitive-Diamond hybrid lattice as an example, the Zener anisotropy index after hybridization is reduced by 65.2 % and 31.37 % compared to single Primitive and Diamond lattices, respectively.

Mechanical Characteristics Of Composite Materials Made From Polyester Resin Mixed With Cocopeat On Static Loads

Cocopeat is a binder between coconut fibers in coconut fiber. Cocopeat has high lignin and cellulose content and is resistant to bacteria and fungi. The aim of the research was to determine the mechanical characteristics of cocopeat mixtures with various dosage ratios of 20%, 40%, 60% to 80%. Mechanical characteristic testing is carried out by applying a load to specimens that have been made in accordance with ASTM D 638-03 standards. The maximum load given is 980N. The test results show that the highest stress value is found in the 40% cocopeat mixture composition, which is 8.1902 Mpa and the highest elastic modulus is found in the 20% cocopeat mixture composition, which is 13.8x10-3 Gpa, while the lowest tensile stress value is found in the 60% cocopeat mixture. and the lowest modulus of elasticity was found in a composition of 80% cocopeat mixture, namely 5.12 x 10-4 Gpa. Thus, more and more cocopeat powder is added to composite materials made from polyester resin. This causes a decrease in the value of stress and modulus of elasticity.

3D Printed Carbon Nanotubes Reinforced Polydimethylsiloxane Flexible Sensors for Tactile Sensing

Technology is constantly evolving, and chronic health issues are on the rise. It is essential to have affordable and easy access to remote biomedical measurements. This makes flexible sensors a more attractive choice owing to their high sensitivity and flexibility along with low cost and ease of use. As an additional advantage, 3D printing has become increasingly popular in areas such as biomedicine, environment, and industry. This study demonstrates 3D-printed flexible sensors for tactile sensing. A biocompatible silicone elastomer such as polydimethylsiloxane (PDMS) with low elastic modulus and high stretchability makes an excellent wearable sensor material. Incorporating CNTs at varying concentrations (0.5, 1, 2)wt% enhances the sensor’s mechanical strength, conductivity, and responsiveness to mechanical strain. In addition to enhancing the thermal stability of the composite by 44%, multi-walled carbon nanotubes (MWCNTs) also enhanced the breaking strength by 57% with a 2 wt% CNT loading. Moreover, the contact angle values improved by 15%, making it a biomedical-grade hydrophobic surface. The electrical characteristics of these sensors reveal excellent strain sensitivity, making them perfect for monitoring finger movements and biomedical measurements. Overall, 2 wt% CNT-PDMS sensors exhibit optimal performance, paving the way for advanced tactile sensing in biomedical and industrial settings.

Changes in the material properties of spider glue droplet proteins accompanied shifts in prey capture biomechanics as cobweb spiders diverged from their orb weaving ancestors

Although descended from orb weavers, spiders in the family Theridiidae spin cobwebs whose sticky prey capture gumfoot lines extend from a silk tangle to a surface below. When a crawling insect contacts glue droplets at the bottom of a gumfoot line, the line's weak pyriform anchor releases, causing the taut line to contract, pulling the insect from the surface and making its struggles to escape ineffective. To determine if this change in prey capture biomechanics was accompanied by a change in the material properties of theridiid glue, we characterized the elastic modulus and toughness of the glue droplet proteins of four theridiid species at 20–90 % relative humidity and compared their properties with those of 13 orb weaving species in the families Tetragnathidae and Araneidae. Compared to orb weavers, theridiid glue proteins had low extensions per protein volume and low elastic modulus and toughness values. These differences are likely explained by the loss of tension on a gumfoot line when its anchor fails, which may prioritize glue droplet adhesion rather than extension. Similarities in theridiid glue droplet properties did not reflect these species’ evolutionary relationships. Instead, they appear associated with differences in web architecture. Two species that had stiffer gumfoot support lines and longer and more closely spaced gumfoot lines also had stiffer glue proteins. These lines may store more energy, and, when their anchors release, require stiffer glue to resist the more forceful upward thrust of a prey. Statement of significanceWhen a crawling insect contacts glue droplets on a theridiid cobweb's gumfoot line, this taut line's anchor fails and the insect is hoisted upward, rendering its struggles to escape ineffective. This strategy contrasts with that of orb weaving ancestors, which rely on more closely spaced prey capture threads to intercept and retain flying insects. A comparison of the elastic modulus and toughness of gumfoot and orb web glue proteins shows that this change in prey capture biomechanics is associated with reductions in the stiffness and toughness of cobweb glue. Unlike orb web capture threads, whose droplets extend in a coordinated fashion to sum adhesive forces, gumfoot lines become untethered, which prioritizes glue droplet adhesive contact over glue droplet extension.

Mechanical and Electrochemical Corrosion Behaviors of Porous Ti-6Al-4V Alloys Prepared by an Electrochemical Sintering Approach

Titanium alloys have been widely used in bone implants, but the mechanical properties, elastic modulus mismatch between bone and metal, and stress shielding effects can occur. However, porous materials can effectively overcome this problem. In recent years, porous structures have attracted enough attention from researchers. Adjustment of the porous structure may make the titanium alloys better able to meet the requirements of the implant. In this study, we have successfully prepared Ti-6Al-4V alloys by combining powder metallurgy with electrolysis in molten salt. At the same time, CaCl2 was used as a sacrificial space holder to adjust the porosity and porous structure. The Ti-6Al-4V alloys prepared by this method contain 29%–60% porosity and elastic modulus has been controlled between 1.8 GPa to 7.8 GPa, which is suitable for cancellous bone, trabecular, and other parts with low elastic modulus. In addition, the higher porosity also showed better corrosion resistance in the Hank’s solution. The potentiodynamic polarization curves show that the corrosion resistance increases significantly with an increase in porosity.

Ionic Liquid Enabled Transparent Heterogeneous Elastomers for Soft Electronics

AbstractDielectric elastomer (DE), as an electrically active soft material, has enabled stretchable electronics, electronic skins, artificial muscles, biomimetic soft robots, and non‐magnetic motors. High permittivity is urgently desired for increasing the sensitivity of DE sensors and lowering the driving voltage of DE actuators. However, existing efforts for significantly enhanced permittivity is usually achieved at the expense of transparency of the DE by compositing external fillers, which limits the applications in optoelectronics, such as displays, touch screens, artificial eyes, etc. Here, by utilizing of transparent functional filler, ionic liquid micro‐droplet, and precise matching the refractive index with polydimethylsiloxane (PDMS) elastomer matrix, heterogeneous composites with high transparency and high permittivity are obtained simultaneously. The composites are transparent in the visible range (transmittance, 80%–95%). The permittivity reaches up to 22, which is more than seven times higher than the original value of the elastomer matrix. Moreover, the arbitrary deformability of ionic liquid filler endows the composites with better stretchability (300%) and much lower elastic modulus (0.5 MPa, about a quarter the value of PDMS), which is beneficial for soft electronics. Based on the as‐prepared high‐performance composites, high sensitivity and transparent soft sensors and touch panels have been realized, as well as wireless transmission of sensing signals.

Calcium Phosphate Coatings Deposited on 3D-Printed Ti–6Al–4V Alloy by Plasma Electrolytic Oxidation

In this article, the process of creating calcium phosphate coatings through plasma electrolytic oxidation was investigated. Calcium phosphate coatings were deposited onto titanium substrates fabricated via the selective laser melting (SLM) method. The correlation between the characteristics of the coating and the applied voltage (200, 250, and 300 V) of PEO was studied. The surface morphology analysis indicates that an increase in applied voltage results in a larger pore size. It was discovered that, when a voltage of 300 V was applied, a layer of hydroxyapatite formed. However, at 300 V, the coating cracked, producing a significantly rough surface. Our analysis of the elemental composition of sample cross sections indicates the presence of TiO2 layers that are enriched with calcium (Ca) and phosphorus (P). The coefficient of friction and wear rate are primarily influenced by the morphology, pore size, and density of the titanium dioxide layer. Furthermore, a rise in the quantity of the beta phase of the titanium on the surface can be noticed as the applied voltage increases. As a result, it also affects the mechanical and tribological characteristics of the coating. The sample treated to a voltage of 250 V demonstrates a higher resistance to wear and a lower elastic modulus in comparison to the other two coatings.

The Characteristics of Polyester Concrete with Local Sand of East Borneo as Filter

Concrete is a mixture of coarse aggregate and fine aggregate mixed with water and cement as a binder and filler. The disadvantages of traditional concrete are that high water absorption causes low chemical resistance, low modulus of elasticity, low impact strength and a long hardening time to reach its maximum properties, namely 28 days. The solution to these shortcomings that is being developed for construction material applications is by using polymers as polymer concrete. In this research, polyester resin and sand aggregate were used as basic materials. Polyester resin is a type of thermosetting polymer that is widely used in various applications such as automotive parts, composites and construction because of its suitable processing characteristics and affordable price. Meanwhile, the sand used is local Kalimantan sand, where from the XRF and XRD test results, local Kalimantan sand is included in the silica sand type. This research varies the weight fraction of polyester resin used to determine its effect on polymer concrete characteristics such as porosity, water absorption, compressive strength, and macro observations. Variations in the polymer weight fraction used were 20%, 25% and 30%. Compressive strength testing was carried out at the age of 7 days of concrete. The results of the porosity test show that the average porosity of all variations is ± 0.5%. Meanwhile, the average value of water absorption for all fractions is 0.2%. And the highest average value of compressive strength in the 30% polyester resin weight fraction was 66.9 MPa. So it can be concluded that all variations meet SNI standards to become concrete materials.

Effects of boron nitride nanoplates on the dielectric and mechanical properties of carbon nanotubes/silicone rubber composites

AbstractCarbon nanotubes (CNTs) have aroused great attentions in silicone rubber (SR) composites due to the excellent electrical and mechanical properties. However, the distribution of CNTs is not ideal because of the agglomeration effect of nanomaterials. Incorporating different dimensional nanofillers may be a solution. In this work, two‐dimensional boron nitride (BN) was added to fabricate CNTs/BN/SR composites. The results showed that BN could benefit the dispersion of CNTs and improve the dielectric and mechanical behaviors of the composites. Large dielectric constant (5.35, 92% more than pure SR) with extremely low loss tangent (0.00108) was obtained in the SR composites incorporated with 2 wt% CNTs and 5 wt% BN. High tensile stress (836 kPa) and elongation at break (332%) were also achieved, with a low elastic modulus of 557 kPa. Besides, the CNTs/BN/SR composites had thermal stability up to 400°C. Thus, enhanced dielectric and mechanical properties were achieved in CNTs/BN/SR composites by incorporating different dimensional nanofillers, which have great potential applications in dielectric elastomer composites.

A novel Cu-containing TiZrNb-based medium entropy alloy with excellent mechanical properties, antibacterial activity and biocompatibility

Bacterial infection and stress shielding remain significant challenges in the field of orthopedic implant applications. Therefore, it is imperative to develop novel medical implant materials that possess exceptional mechanical properties, antibacterial efficacy, and biocompatibility. The current study reports a novel Ti1.2Zr1.2Nb0.6Cu0.15 medium entropy alloy (MEA) with an optimal combination of mechanical properties, antibacterial activity and biocompatibility. In the Ti1.2Zr1.2Nb0.6Cu0.15 MEA, bits of copper-enriched phases were uniformly dispersed within the body-centered cubic matrix phase. The MEA exhibited good strength-ductility combination with the yield strength of 906 MPa and the fracture elongation of 17.4 %. It is noteworthy that the MEA had a significantly lower elastic modulus (∼67 GPa) compared to pure titanium and Ti6Al4V (∼110 GPa) thus mitigating stress shielding. Meanwhile, the Cu ions released by the alloy resulted in remarkable antibacterial efficacy with an antibacterial rate of 99 % against Escherichia coli. Furthermore, this alloy displayed corrosion resistance and biocompatibility comparable to those of the Ti6Al4V alloy. These findings provide novel insights for designing antibacterial implant materials with excellent comprehensive performance.

Design and Development of Ti–Zr–Nb–Ta–Ag High Entropy Alloy for Bioimplant Applications

A new non‐equiatomic 35Ti–35Zr–20Nb–5Ta–5Ag at% high entropy alloy (HEA) is designed by combining the HEA concept with the properties required for bioimplants. Mechanical alloying is used to synthesize the HEA, which is then compacted at 550 and 700 MPa and sintered at 1300 °C. The phases, microstructure, and mechanical properties are investigated, and in vitro corrosion properties are studied in a simulated body fluid. After 20 h of mechanical alloying, a single body‐centered cubic (BCC) phase with a nanocrystalline size of 3.6 nm was formed. After sintering, the microstructure is composed of dual‐phase BCC structures: the major BCC 1 phase, the grain boundary BCC 2 phase, and the ultra‐fine equiaxed phase. The results of the micro‐indentation test indicate that the elastic modulus of the HEA is 84.4 ± 8.7 and 113.2 ± 13.36 GPa, and its Vickers microhardness is 3.47 ± 0.1 and 5.35 ± 0.2 GPa when it was compacted at 550 and 700 MPa respectively. The corrosion resistance tests reveal that HEA compacted at 700 MPa has higher corrosion resistance than commercial Ti6Al4V alloy. The developed Ti–Zr–Nb–Ta–Ag HEA has improved corrosion resistance and a lower elastic modulus, making it a potential candidate for bioimplant applications.

Experimental-numerical study on axial compression performance of square concrete columns confined by new-type BFRP

Abstract Facing the substantial protection requirements for reinforced concrete structures exposed to severe erosion conditions, a novel composite material(Basalt Fiber Reinforced Polymer, BFRP) based on epoxy silicone resin as a matrix was introduced in this study. This material exhibits notable enhancements in resistance to acid and alkali corrosion, ultraviolet irradiation, as well as high and low temperature extremes. However, it exhibits lower elastic modulus and higher ductility. To evaluate the effectiveness of this new BFRP composite material in reinforced concrete structures, a comprehensive investigation was conducted by model testing, numerical simulations, and theoretical analysis. This study analyzed the impact of wrapping configuration, number of wrapping layers, concrete strength, and spacing-to-bandwidth ratio on the mechanical properties of concrete square columns. The findings revealed that the loading curve trends for specimens reinforced with the new BFRP sheet and CFRP sheet (Carbon Fiber Reinforced Polymer, CFRP) were almost similar, although the reinforcement effect was comparatively worse for the former. When both layers were fully applied, the axial compression bearing capacity increased by 28.45% and 64.73%, respectively. The number of wrapping layers and the parameters related to concrete strength significantly influenced the reinforcement effect, whereas the influence of spacing-to-bandwidth parameters was less pronounced. Current specifications demonstrate suitable applicability for CFRP-reinforced specimens but limited applicability for BFRP. The calculation model proposed in this paper accurately predicted the axial compression bearing capacity of a new BFRP-reinforced columns, with an error margin kept within 5%.

Analysis of mechanical characteristics and permeability of TPMS and Voronoi porous structure for bone scaffold

Bionic porous structure has been widely used in the field of bone implantation, because it can imitate the topological structure of bone, reduce the elastic modulus of metal bone implantation, and meet the mechanical properties and material transmission characteristics after implantation. This paper mainly studies the effects of different bionic porous structures on the mechanical and material transport properties of bone scaffolds. Firstly, under the same porosity condition, 12 groups of bionic porous structures with different shapes were designed, including G, P, D, I-type three period minimal surface (TPMS) and Voronoi porous structures with different irregularities. Then uses ABAQUS to carry out mechanical finite element simulation on different bionic porous structures, and uses Ti-6Al-4V alloy as forming material, uses laser powder bed fusion technology (LPBF) to prepare the scaffold, then carries out compression experiments. At the same time, COMSOL software is used to simulate the flow characteristics, analyze the permeability characteristics, and verified through cell experiment in vivo. The results show that the mechanical and permeability are different with vary scaffolds. In terms of topology, the morphological characteristics of TPMS are similar to trabecular bone, its compressive strength is relatively strong. Voronoi scaffold has lower elastic modulus, which can provide sufficient mechanical support while reducing stress shielding. In addition, the permeability of TPMS scaffold is better than Voronoi scaffold, which is helpful to promote cell proliferation and bone ingrowth. These bionic porous structures have their own advantages. Therefore, when designing porous structures for bone implantation, it is necessary to select the appropriate porous structure according to different bone implantation requirements. The research will help promote the clinical application of porous structures in the field of bone implantation, and provide theoretical support for the exploration of bone implantation structure design.

Evaluating flexure properties, hardness, roughness and microleakage of high-strength injectable dental composite: an in vitro study

BackgroundRecently, a new generation of high-strength flowable dental composites has been introduced by manufacturers. The manufacturers claim that these materials have enhanced mechanical and physical properties and are suitable for use in a wide range of direct anterior and posterior restorations, even in high-stress bearing areas.AimThe objective of this study was to assess certain physical and mechanical properties of these recently introduced high-strength flowable composites in comparison to conventional multipurpose dental composites.MethodsFour types of high-strength flowable composites (Genial Universal FLO, Gaenial Universal Injectable, Beautifil Injectable, and Beautifil Flow Plus) were tested in experimental groups, while a nanohybrid conventional composite (Filtek Z350 XT) was used as the control. For flexure properties, ten rectangular samples (2 × 2 × 25 mm) were prepared from each composite material and subjected to 5000 cycles of thermocycling. Samples were then subjected to flexural strength testing using the universal testing machine. Another twenty disc-shaped specimens of dimensions (5 mm diameter × 2 mm thickness) were fabricated from each composite material for surface roughness (Ra) (n = 10) and hardness (VHN) test (n = 10). All samples underwent 5000 cycles of thermocycling before testing. Additionally, microleakage testing was conducted on 60 standardized class V cavities prepared on molar teeth and divided randomly into five groups (n = 12). Cavities were then filled with composite according to the manufacturer’s instructions and subjected to thermocycling for 1000 cycles before testing using methylene blue solution and a stereomicroscope.ResultsAll tested materials were comparable to the control group in terms of flexural strength and surface roughness (p > 0.05), with Gaenial Universal FLO exhibiting significantly higher flexural strength compared to the other flowable composite materials tested. However, all tested materials demonstrated significantly lower elastic modulus and surface hardness than the control group (p < 0.05). The control group exhibited higher microleakage scores, while the lowest scores were observed in the Gaenial Universal FLO material (p < 0.05)ConclusionThe physical and mechanical behaviors of the different high-strength flowable composites investigated in this study varied. Some of these materials may serve as suitable alternatives to conventional composites in specific applications, emphasizing the importance of dentists being familiar with material properties before making material selections.

Preparation and formation mechanism of high-toughness organic polymers modified geopolymers

In recent years, geopolymers have shown potential to replace ordinary cement materials due to their simple preparation, low cost, and excellent performance. Adding organics to geopolymers can enhance toughness and broaden their application potential as building materials. However, the effect of common molding processes to enhance the toughness of organic polymers modified geopolymers remains very limited. In this study, high-toughness organic polymers modified geopolymers were prepared using vacuum-vibration-compaction (VVC) molding. The incorporation of 3-methacryloy loxypropyl trimethoxysilane (KH570) and sodium polyacrylate (PAAS), (KH-PAAS), was evaluated on the toughness system of the slag-based geopolymers. The micromechanical properties of the different hydrated phases were analyzed using a nano-scratch test (NST) and atomic force microscopy (AFM). The high fracture toughness (1.6–2.6 MPa*m0.5) and low elastic modulus (20–30 GPa) of the hydrated new phase C-(A)-S-H/Polymer gels were proposed. KH-PAAS modified geopolymers produced 57–59 % C-(A)-S-H/Polymer gels in which C-(A)-S-H/Polymer gels, C-(A)-S-H gels, and KH-PAAS were planarly cross-distributed to form a 3D network structure. The toughness of KH-PAAS modified geopolymers is related to the amount of C-(A)-S-H/Polymer gels generation and distribution form. Finally, the formation mechanism of the C-(A)-S-H/Polymer gels was analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to quantify the ratio of different chemical reactions. The specific ratio was C-(A)-S-H-KH: C-(A)-S-H-PAAS: Ca-PAAS: KH–C-(A)-S-H-PAAS = 2.42 : 6.78: 47.58 : 1. This study provides ideas for subsequent investigation of the toughening mechanism of organic polymers modified geopolymers.

Laser powder bed fusion of a β titanium alloy: Microstructural development, post-processing, and mechanical behaviour

β-Titanium alloys demonstrate unique properties, especially their low elastic modulus, good balance of strength and ductility, and strong heat treatment response. In this study, pre-alloyed powder of a β-Ti-alloy Ti–34Nb–13Ta–5Zr-0.3O (TNTZO) was processed using Laser Powder Bed Fusion (LPBF). Dense builds that demonstrate a full β microstructure with limited texture were achieved following process optimisation, with an elastic modulus of 56.5 GPa, tensile strength of 756 MPa, elongation-to-failure of 20 %, and recoverable strain of 1.3 %. Due to the high oxygen content, the β→α′′ deformation induced transformation was supressed, which resulted in a typical elastic-plastic stress-strain behaviour unlike the double-yielding behaviour typically experienced in superelastic Ti-alloys. The alloy was particularly sensitive to ageing heat treatments that resulted in needle α-precipitation, with tensile strengths exceeding 950 MPa, elastic modulus of ∼80 GPa, and recoverable strain of 1.5 %, yet at the expense of a reduced elongation-to-failure of 9 %. Transmission electron microscopy and electron backscattered diffraction investigations revealed the deformation mechanism was slip-dominated with no trace of twinning or stress induced phase transformation.

Numerical and experimental analysis of edge wave defect control during TA2 circular tube cold roll forming

AbstractThe increasing application of TA2 titanium profiles in marine and petrochemical industries has spurred in a growing demand for diverse forms, including U‐shaped, rectangular, and tubular thin‐walled profiles. Traditional methods like mechanical subtractive processing and extrusion, despite their prevalence, suffer from high production costs and low efficiency. As a metal sheet forming technology, roll forming stands out for its efficiency, accuracy, and capability of producing complex shapes continuously. Nevertheless, the application of cold rolling to TA2 profiles is challenging primarily due to its low elastic modulus and high yield strength. In view of this, this study employed finite element simulation to analyze the stress and strain distribution during the TA2 roll forming process, aiming to have a better understanding of edge wave defect formation mechanism. Orthogonal experiments were performed to assess the influence of frame spacing, forming speed, roll gap, and downhill amount, on edge wave defects. The findings revealed a predominant influence of the downhill amount. Maintaining the downhill volume at 0.6 times the tube diameter kept the longitudinal strain below 0.9%, effectively mitigating edge wave defects. Implementation of these optimized parameters in an actual TA2 roll forming process confirmed the reliability of the simulations. This study establishes a solid foundation for advancing the TA2 tube cold roll forming process, enhancing the production efficiency of titanium profiles, and shedding some light on current energy conservation and emission reduction.

Friction and Wear Behavior of Selective Laser Melted Ti6Al4V-Equine Bone Nanocomposites

Ti6Al4V is commonly used in implants because of its excellent mechanical properties, corrosion resistance, and biocompatibility. While Hydroxyapatite (HAp) is typically used for strong biological bonding between Ti6Al4V implants and bone tissue, this study takes a different approach by incorporating Equine Bone (EB), which has a chemical structure similar to human bone tissue, as a substitute for HAp. In this study, to develop implant materials with a low elastic modulus, high strength, and excellent wear resistance, Ti6Al4V used in biomedical applications was combined with natural EB. Subsequently, a Ti6Al4V-0.05EB composite was fabricated using ball milling followed by Selective Laser Melting (SLM). SLM can reproduce even the interior of a 3D structure, so various studies are being conducted to apply it as a biomaterial. However, Ti6Al4V alloys produced by SLM are known to have low ductility due to localized heat gradients, rapid solidification, and cooling rates. This reduced ductility can result in decreased formability of biomaterials, and the high elastic modulus may lead to stress shielding phenomena, potentially reducing the lifespan of the biomaterial. To minimize this, a post-heat treatment was applied to the Ti6Al4V-0.05EB composite material manufactured by SLM. Afterwards, the microstructure, mechanical properties, and wear resistance, which are important in biomaterials, were evaluated.

Bimodal nanomechanical performance of nanostructured Lu2Si2O7 environmental barrier coating

Lutetium disilicate (Lu2Si2O7) is considered a promising material for environmental barrier coatings because of its remarkable high-temperature stability and low thermal conductivity. In this study, nanostructured Lu2Si2O7 coating was prepared successfully using as-prepared feedstocks via atmospheric plasma spraying. The nanomechanical performance of the coating was studied. The results showed that the coating exhibited a bimodal nanomechanical performance attributed to the bimodal distribution of its microstructure; i.e., in the coating, the melted lamella exhibited higher elastic modulus and nanohardness, whereas the unmelted and semi-melted parts processed low elastic modulus and nanohardness. The elastic modulus and nanohardness of the coating were 143.438 ± 25.449 GPa and 9.239 ± 3.514 GPa, respectively. Furthermore, the elastic and plastic works were 9.018–14.752 nJ and 12.792–25.793 nJ, respectively. The average value of the microhardness dissipation parameter of the coating was 0.615, demonstrated that the remarkable wear resistance of the coating.

The Circulating Milieu Mediates Arterial Dysfunction with Aging: Protection by Habitual Aerobic Exercise

Age-related arterial dysfunction (aortic stiffening and endothelial dysfunction) is the key antecedent to cardiovascular diseases. Habitual aerobic exercise largely mitigates arterial dysfunction in mid-life/older (ML/O) adults; however, the mechanisms by which this occurs remain to be fully elucidated. The circulating milieu (bioactive factors in the bloodstream) shifts towards a pro-inflammatory/oxidative state with advancing age but is preserved with habitual aerobic exercise. However, it is unclear if the circulating milieu directly contributes to age-related arterial dysfunction and if habitual aerobic exercise preserves arterial function with aging, in part, by favorably modulating the circulating milieu. PURPOSE: To determine the influence of aging and habitual aerobic exercise on circulating milieu-mediated aortic stiffening and endothelial function. METHODS: Human serum was collected from healthy young (18-29 yr) and ML/O (50+ yr) men and women. Aerobic exercise status was determined by leisure-time physical activity (&gt;60 h/wk). Aortic rings (~1 mm) and common carotid arteries were obtained from young adult (3-4 mo), intervention naïve male and female C57BL/6N mice to assess aortic stiffness and endothelial function, respectively. Arteries were exposed ex vivofor 24-48 hours to 5% sex-matched human serum from one of the following groups: young sedentary (n=9; 4F), ML/O sedentary (n=14; 7F) or ML/O habitually aerobic exercise trained (n=8; 4F). Aortic stiffness was measured as elastic modulus (a measure of intrinsic mechanical wall stiffness). Endothelial function was assessed as endothelium-dependent dilation (EDD) and endothelium-independent dilation (EID) as peak response to acetylcholine and the nitric oxide (NO) donor sodium nitroprusside, respectively. Differences were determined via one-way ANOVA. RESULTS: Aortic Stiffness. Aortic elastic modulus was higher in aorta rings incubated with ML/O sedentary serum compared to young sedentary serum (ML/O sedentary, 4912 ± 588 v. Young sedentary, 3019 ± 522 kPa; p=0.020). Compared with ML/O sedentary serum, aorta rings incubated with ML/O trained serum had lower elastic modulus (2237 ± 426 kPa, p=0.002) which was not different to aorta rings incubated with young sedentary serum (p=0.369). Endothelial Function. Peak EDD was lower in carotid arteries incubated with ML/O sedentary v. young sedentary serum (79 ± 3% v. 92 ± 2%, p=0.001). Compared with ML/O sedentary serum, incubation with ML/O trained serum evoked higher peak EDD (93 ± 1%; p=0.001) that was similar to that produced by Young sedentary serum (p=0.866). There were no group differences in peak EID (p=0.228) suggesting that circulating milieu-induced differences were endothelium-specific and were not attributable to changes in smooth muscle sensitivity to NO. CONCLUSION: These findings suggest that the circulating milieu is a key mechanism by which aging induces arterial dysfunction and by which habitual aerobic exercise training preserves arterial function with aging. F31 HL165885, R21 AG078408, K99 HL159241, K99/R00 HL151818. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.