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The current work is focused on numerical and experimental studies of woven fabric composites modified by hybridisation with biological (cellulosic) filler materials. The mechanical performance of the composites is characterized under tensile, bending and impact loads and the effect of hybridisation is observed with respect to pure and nonhybrid composites. Numerical models are developed using computational tools to predict mechanical performance under tensile loading. The computational prediction results are compared and validated with relevant experimental results. This research is aimed at understanding the mechanical performance of basalt–epoxy composites partially reinforced with micro-/nano-sized bio-fillers from cellulose and intended for various application areas. Different weave structures, e.g., plain, twill, matt, etc., were investigated with respect to the mechanical properties of the hybrid composites. The effects of hybridizing with cellulose particles and different weave patterns of the basalt fabric are studied. In general, the use of high-strength fibres such as basalt along with cellulosic fillers representing up to 3% of the total weight improves the mechanical performance of the hybrid structures. The thermomechanical performance of the hybrid composites improved significantly by using basalt fabric as well as by addition of 3% weight of cellulosic fillers. Results reveal the advantages of hybridisation and the inclusion of natural cellulosic fillers in the hybrid composite structures. The material developed is suitable for high-end applications in components for construction that demand advanced mechanical and thermomechanical performance. Furthermore, the inclusion of biodegradable fillers fulfills the objectives of sustainable and ecological construction materials.

The mechanical features evaluated theoretically using Makishima-Mackenzie's model for glasses xBaO-(50-x) PbO–50P2O5 where x = 0, 5, 10, 15, 20, 30, 40, and 50 mol%. Wherefore, the elastic characteristics; Young's, bulk, shear, and longitudinal modulus calculated. The obtained result showed an increase in the calculated values of elastic moduli with the replacement of the PbO by BaO contents. Moreover, the Poisson ratio, micro-hardness, and the softening temperature calculated for the investigated glasses. Besides, gamma and neutron shielding ability evaluated for the barium doped lead phosphate glasses. Monte Caro code (MCNP-5) and the Phy-X/PSD program applied to estimate the mass attenuation coefficient of the studied glasses. The decrease in the PbO ratio has a negative effect on the MAC. The highest MAC decreased from 65.896 cm2/g to 32.711 cm2/g at 0.015 MeV for BPP0 and BPP7, respectively. The calculated values of EBF and EABF showed that replacement of PbO with BaO contents in the studied BPP glasses helps to reduce the number of photons accumulated inside the studied BPP glasses. © 2021 Korean Nuclear Society. Taif University, Saudi Arabia is kindly acknowledged for Supporting our work through the Project number (TURSP-2020/84).

Metallic cellular materials with triply periodic minimal surface (TPMS) topologies have great potential for lightweight and multi-functional applications. However, the effect of level-set values, which can control the topology of TPMS, on the performance of TPMS have not been fully understood because previous studies have mainly focused on the shell thickness, cell size and periodicity of TPMS. In this paper, Al-Si10-Mg gyroid surfaces with three different level-set values are fabricated by using selective laser melting (SLM). Micro computed tomography (Micro-CT) is used to reconstruct the 3D models of as-built samples, then the geometric deviations and surface quality are investigated. Mechanical behavior and energy absorption characteristics of these gyroid surfaces are investigated both experimentally and numerically, which provide a solid basis for predicting and controlling the deformation behavior in gyroid surfaces. Afterwards, the Gibson-Ashby model is used for understanding the effect of the level-set value on Young’s modulus and plateau stress of gyroid surfaces. Finally, the relationship between level-set values and densification strain and energy absorbed per unit volume is also presented to gain insight into the role of level-set values on the energy absorption capability of the gyroid surfaces. Such understanding provides a new method to develop desired properties of implants or energy absorption applications by selecting an optimal combination of level-set value, thickness, periodicity etc.

A series of Mg–Ti composites are fabricated by high-pressure solid-state sintering (HPSSS) technique developed in our lab. The correlation between microstructures and corrosion behaviors is comparatively studied. It is shown that the Mg/Ti interface primarily determines the corrosion resistance of the composites, and the corrosion process is a comprehensive action of material composition, interface content, corrosion potential and interfacial oxide. Besides, the present semi-degradable Mg–Ti composites retain superior structure stability after Mg degradation due to the strong interfacial bonding obtained by the high-pressure solid-state sintering. All of the derived porous Ti exhibits a superior compressive plasticity, and the mechanical properties of the porous Ti can be readily adjusted by tuning the porosity. With superior mechanical properties, low Young's modulus and favourable pore size, the present porous Ti offers superior mechanical compatibility, demonstrating promising prospect in the load bearing biomedical applications.

The microstructure, mechanical and magnetic properties of Zr–x (8, 9, 10, wt.%)Nb–4Sn alloys were investigated to obtain novel Zr-based alloy with low Young’s modulus and magnetic susceptibility for biomedical implants. After homogenization annealing, hot forging and solution annealing, Zr–8Nb–4Sn, Zr–9Nb–4Sn and Zr–10Nb–4Sn alloys were composed of β+α″ phase, β+α″ phase, β+ω phase, respectively. The temperature at which the α" and ω phase were transformed into β phase during the heating process was about 200 ​°C, and the phase transformation temperature decreased with the increase of Nb element. Among all the Zr–x (x ​= ​8,9,10)Nb–4Sn(wt.%) alloys, Zr–9Nb–4Sn alloy had the lowest Young's modulus of 46.6 ​GPa and the low magnetic susceptibility of 1.294 ​× ​10−6 cm3g−1, which has a good application prospect for biomedical applications.

Robocasting is an extrusion-based additive manufacturing (AM) technique, highly explored in the fabrication of porous structures or thin-walled ceramics. Comparing to other slurry-based AM technologies, robocasting presents a high potential to produce dense bulk ceramics, thanks to the low organic binder contents and high solids loading used in the feedstock. Despite these benefits, the robocasting fabrication of ceramics with similar mechanical performance as those produced by traditional methods remains a challenge. The goal of this work is to fine-tune the robocasting printing process of dense alumina ceramics by evaluating the influence of in-fill filaments orientation and the medium where the deposition process occurs (air or paraffin bath), on defects and mechanical performance of the sintered parts. Relative density, shrinkage, three-point flexural strength, Young's modulus and hardness were analysed. The specimens with the highest performance were sintered at 1550 °C or 1600 °C temperatures for 2 h holding time and the results were compared with slip casting (SC) samples sintered in the same conditions. Alumina robocasting samples, printed longitudinally in air with controlled humidity and sintered at 1600 °C, exhibited relative density ≈99% with flexural strength (≈350 MPa), Young's modulus (≈366 GPa) and hardness (≈17 GPa) values comparable to those obtained for SC samples. Numerical modelling and simulation were used to analyse the experimental values and the anisotropic behaviour of the printed specimens. Experimental Young's modulus results were compared with the Voigt-Reuss bound and the Hashin-Shtrikman upper-bound, as well as the analytical predictions of a Mooney-type exponential relation.

The influence of alloying elements and heat treatment on the microstructure and mechanical behaviors of extruded Mg–Gd–Nd ternary alloys was investigated in this study. The grain sizes dramatically decreased after extrusion, and the particles which distributed in Mg matrix had great effect on the grain size. The grain sizes of extruded alloys decreased from 26 to 5 ​μm with the alloying content increasing. The mechanical test results show that both Gd and Nd had positive effect on the hardness, yield strength and Young's modulus. The ultimate tensile strength (UTS) was enhanced by Gd content, decreased with Nd content. The elongation of alloys was lower with higher alloying elements. Those extruded alloys were aged for 200 ​h in 200 ​°C. The Young's moduli were decreased by ageing treatment. Combined with microstructure study, the part of the reinforcement which identified as Mg5(Gd/Nd) was dissolved in Mg matrix. Nd element obviously has influence on the solubility of Gd in Mg alloys.

To alleviate the “stress shielding” of metallic biomaterials used as artificial bone, the state of art Ti45Zr10Cu31Pd10Sn4 porous bulk metallic glass (BMG) with adequate compressive strength of 180 MPa and Young's modulus of 27.2 GPa similar to nature bone was produced by a novel partial densification method using spark plasma sintering (SPS). The thermal mechanistic (sintering temperature, sintering rate and holding time) during SPS contributions to the densification behavior and the structures and mechanical properties of porous BMG were systematically explored under low loading pressure condition to obtain the optimal sintering process. With the help of this work, the potential application value of Ti–Zr–Cu–Pd–Sn BMG as substitute of human bone will be further enhanced.

A three-dimensional finite element (FE) model for single-walled carbon nanotubes with armchair and zigzag shapes is proposed in this paper (SWCNTs). Nodes are positioned at the locations of carbon atoms to design the FE models. And three-dimensional elastic beam components are used to model the bonds between them. The effect of the diameter length/diameter ratio on the diameter length/diameter ratio, cross sectional aspect ratio and number of elements on the Young’s modulus of SWCNTs has been considered herein. From the conducted experiments it can be observed that, the larger tube diameter can lead to higher Young’s modulus for carbon nanotubes. Such that, maximum elastic modulus for the armchair and the zigzag models has been obtained to be 1.0285TPa and 1.0396TPa when the diameters for the armchair and the zigzag models were 2.034nm and 1.957nm respectively. Increasing the length/diameter ratio has led the Young’s modulus to be increased for armchair and zigzag models such that its values can reach 1.0451TPa and 1.0191TPa respectively. The cross sectional aspect ratio of SWCNTs showed an inversely proportional effect on the elastic modulus in this work. As a result of rising the cross sectional aspect ratio to be2, the Young's modulus for armchair and zigzag models has decreased to 0.7991TPa and 0.8873TPa, accordingly. The change in geometry has been observed to be a defect and it is in general can decrease the modulus of elasticity. The number of elements in the armchair model considered as prominent factor that increases the young’s modulus to be 1.0280TPa when the number of element is 10836. In zigzag model, the number of element has no effect on the elastic modulus since the number of nodes that exposed to the applied load is fixed in this case. The findings showed that the proposed FE model may be useful for studying carbon nanotube mechanical action in the future.

Taking high rank coal in Qinshui Basin as the research object, the mechanical parameters of the coal rocks after primary fracturing with quartz sand filling the fracture are measured, and the variation law of the mechanical properties of the coal rocks after sand filling is analyzed to provide reliable technological parameters for multiple fracturing. The results show that Poisson's ratio is 22.6% higher than the initial average, Young's modulus is 47% lower than the initial average, and permeability of low-permeability coal seam is nearly 10 times higher. The results indicates that in the development of high rank coalbed methane, the change of mechanical properties caused by quartz sand filling after the first fracturing of coal rocks can provide relatively real basic data for the design of the second fracturing process and improve the reliability of the design.

This work uses the molecular dynamics approach to study the effects of functionalization of carbon nanotubes (CNTs) on the mechanical properties of Cu64Zr36 metallic glass (MG). Three types of functional groups, carboxylic, vinyl and ester were used. The effect of CNT volume fraction (Vf) and the number of functional groups attached to CNT, on the mechanical properties and thermal conductivity of CNT-MG composites was analysed using Biovia Materials Studio. At lower values of Vf (from 0 to 5%), the percentage increase in Young’s modulus was approximately 66%. As the value of Vf was increased further (from 5 to 12%), the rate of increase in Young’s modulus was reduced to 16%. The thermal conductivity was found to increase from 1.52 W/mK at Vf = 0% to 5.88 W/mK at Vf = 12%, thus giving an increase of approximately 286%. Functionalization of SWCNT reduced the thermal conductivity of the SWCNT-MG composites.

Based on a great number of experimental data on various mechanical properties of rock in the literature, six empirical equations between the characteristic impedance (product of density and P-wave velocity) and mechanical properties of rock are proposed. These properties include uniaxial compressive strength, tensile strength, shear strength, mode I fracture toughness, Young's modulus, and Poisson's ratio. These empirical equations show that the values of the aforementioned properties increase with increase in characteristic impedance. It also implies that the characteristic impedance of rock may be considered as an index to represent the main properties of rock. In this sense, it is possible to consider using characteristic impedance to classify rock masses for studies in the future.

International audience; Here we describe the elaboration and investigation of composites prepared from the spincrossover (SCO) complex [Fe(pyrazine){Au(CN) 2 } 2 ] and poly(vinylidene fluoride) matrix, with different contents of the active phase (10-35 wt%). Optical measurements demonstrated that all composites preserve temperature induced hysteretic spin transitions. Tensile mechanical analysis showed a non-linear change of the Young's modulus upon increase of the complex content. Thermomechanical analysis upon a constant strain demonstrated pronouncable alterations of the applied stress in the SCO region. Composites with smaller loads require less stress to attain a given strain in the high-spin state, however for those with high loads the behaviour is more sofisticated. The modelling of stress vs. temperature behaviour revealed that this may be interpreted through a miscellaneous interplay of expansion of both the polymer and the complex, the contribution of both components to the elastic properties of composites, and the effects of SCO on these properties.

Rocks decay significantly during or after heating–cooling cycles, which can in turn lead to hazards such as landslide and stone building collapse. Nevertheless, the deterioration mechanisms are unclear. This paper presents a simple and reliable method to explore the mechanical property evolutions of representative sandstones during heating–cooling cycles. It was found that rock decay takes place in both heating and cooling processes, and dramatic modulus changes occurred near the α − β phase transition temperature of quartz. Our analysis also revealed that the rock decay is mainly attributed to the internal cracking. The underlying mechanism is the heterogeneous thermal deformation of mineral grains and the α – β phase transition of quartz.

The development of shale gas is faced with low reservoir porosity, low reservoir permeability and high formation fracture pressure. In order to deal with these problems, this paper selected shale samples from the bottom of the Lower Silurian Longmaxi–Wufeng Formation of Upper Ordovician in the Weiyuan Block of the southern Sichuan Basin as the research objects. After acid dissolution experiments were carried out, the microstructures and the mechanical parameters of shale after acidizing treatment were investigated by means of X-ray diffraction, scanning electron microscopy and triaxial mechanical test. Then, the effect of acidizing treatment on the microstructures and the mechanical properties of shale were analyzed. And the following research results were obtained. First, after acidizing treatment, the carbonate mineral content of shale decreases and the number and size of pores increase. In the process of dissolution, micro-fractures occur, leading to the increase of shale porosity and permeability. Second, after acidizing treatment, the mechanical properties of shale change. Its deformation mode transforms gradually from elastic–brittle deformation to elastic–plastic deformation, and its fracture mode transits from brittle to semi-brittle and semi-ductile. Third, after shale is treated with the acid with the concentration of 15% for 240 min, its permeability is increased by 3.09 times. After 3 days, its porosity is increased by 1.65 times. And after 7 days, its compressive strength, Young's modulus and brittleness index are decreased by 50.1%, 58.1% and 32.8%, respectively. Fourth, the mechanical parameters of shale of the Longmaxi–Wufeng Formation in the Weiyuan Block is in a quadratic relationship with an average pore size and permeability and in a quadratic or linear relationship with porosity, and their correlation is strong. In conclusion, the research results provide technical support for the prediction of the mechanical parameters of shale in this block after acidizing treatment and for the design of acid fracturing scheme.

Stress induced phase transformation from hexagonal close-packed titanium (HCP-Ti) to face-centered cubic titanium (FCC-Ti) is believed to be a reason for the pronounced work hardening of carbon nanotube-reinforced titanium (CNT/Ti) composites prepared by high-pressure torsion (HPT). Here, the correlation between the phase transformation from the HCP-Ti to the FCC-Ti structure in Ti and the improved mechanical properties of CNT/Ti composite is revealed by investigating the structural transformation mechanism, the stability, electronic properties, anisotropic elasticity and thermodynamics of the FCC-Ti and HCP-Ti crystals under pressure of 0–15GPa by means of first-principles calculations and comparing with the experimental findings. The results show that the formation enthalpies △HTi, the bulk modulus B, the shear modulus G and the Young's modulus E of the FCC-Ti and HCP-Ti structures gradually increase with increasing pressure, and the hybridization between the electronic orbitals of the atoms becomes stronger. The Young’s modulus of the cubic FCC-Ti structure shows strong anisotropy along the [0 1 0] and [1 1 ¯ 0] directions, while the HCP-Ti structure exhibits an obvious anisotropy of E in the (1 0 0) crystal plane. The thermodynamic stability of the HCP-Ti and FCC-Ti structures decreases under high pressure. The different relative stability of the two structures results in a high propensity of structural transformation from the HCP-Ti to the FCC-Ti structure. A large number of FCC-Ti structures are prepared, which can effectively improve the mechanical properties of CNT/Ti composites. Our results may help to better understand the phase transition from HCP-Ti to FCC-Ti under high pressure, and may reveal the structure-property relationship of CNT/Ti composites.

Made available in DSpace on 2021-07-14T10:26:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-13. Added 1 bitstream(s) on 2021-07-14T11:30:01Z : No. of bitstreams: 1 S0366-69132020000100030.pdf: 2969385 bytes, checksum: 6f7cb1d7980557e113a2dfcaefef07cc (MD5) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) O objetivo deste estudo foi caracterizar e avaliar as propriedades físicas e mecânicas de uma zircônia experimental para aplicação odontológica e comparar os resultados da resistência à flexão biaxial com a simulação de elementos finitos (MEF). Amostras de zircônia tetragonal estabilizada com ítria (Y-TZP) foram sinterizadas a 1475 °C/2 h e caracterizadas por difração de raios X, microscopia eletrônica de varredura, densidade relativa, resistência à flexão usando teste de pistão em três bolas (P-3B) e módulo de Young. A partir dos resultados de resistência à flexão, foram realizadas simulações numéricas utilizando o software Abaqus. O modelo completo utilizou 70216 elementos. Os resultados apontaram para densificação total em amostras sinterizadas, ZrO2 tetragonal e cúbica como fases cristalinas, tamanho de grão de 0,6±0,2 μm, módulo de Young de 195±4 GPa, resistência à flexão de 1191±9 MPa e módulo de Weibull m=16,3. A simulação numérica indicou uma resistência à flexão próxima de 1100 MPa, com diferença menor que 7% em relação aos resultados experimentais. Os resultados foram comparados associando as propriedades físicas e mecânicas de Y-TZP com seus fenômenos intrínsecos, como a transformação tgm e o domínio ferroelástico. The objectives of this study were to characterize and evaluate the physical and mechanical properties of an experimental zirconia for dental application and compare the biaxial flexural strength results with the finite element simulation (FEM). Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic samples were sintered at 1475 °C/2 h and characterized by X-ray diffraction, scanning electron microscopy, relative density, flexural strength using piston-on-three balls (P-3B) test and Young’s modulus. From the flexural strength results, numerical simulations were performed using Abaqus software. The complete model used 70216 elements, considering the components of the test. The results indicated full densification of sintered samples, ZrO2-tetragonal and ZrO2-cubic as crystalline phases, and average grain size of 0.6±0.2 μm. Mechanical characterization of sintered samples indicated Young’s modulus of 195±4 GPa, flexural strength of 1191±9 MPa and Weibull modulus m=16.3. FEM simulation indicated a flexural strength close to 1100 MPa, with a difference lower than 7% in relation to the experimental results. The results were compared associating the physical and mechanical properties of Y-TZP with its intrinsic phenomena such as tgm transformation and ferroelastic domain. Universidade Federal Fluminense, Escola de Engenharia Industrial Metalúrgica de Volta Redonda Universidade do Estado do Rio de Janeiro, Faculdade de Tecnologia de Resende Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá FAPERJ: E26-201.476/2014; E26-202.997/2017; E26-211.760/2015 CNPq: 311119/2017-4; 305194/2015-1

Made available in DSpace on 2020-12-12T02:31:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 This study evaluated the mechanical properties and cytocompatibility of recently developed Ti-15Zr-based alloys with Mo addition for potential use as load-bearing implants. The phase composition and microstructure were changed by the alloying elements, being the β phase fully retained on the Ti-15Zr-10Mo and Ti-15Zr-15Mo samples. The TEM analysis showed that a small quantity of ω phase was precipitated on the samples with a high amount of Mo. Regarding the mechanical properties, the Ti-15Zr-10Mo sample presented high mechanical strength and large elongation (854»±»63»MPa and 18.7»±»2.8 %). However, the Ti-15Zr-15Mo sample exhibited better mechanical compatibility, due to its combination of low Young's modulus (75»±»1»GPa) and high Vickers microhardness (346»±»4»HV). Some dimple-type structures found along the fractured surface confirmed the ductile behavior of these samples. The MTT test indicated non-cytotoxic effects of all samples when in contact with osteoblastic cells (p»

The understanding of physical and mechanical properties of rock is considered as critical in drilling, geo-engineering, and construction applications. As an example, the awareness of these rock parameters contributes to avoid or minimizing instability around the wellbore while drilling. The laboratory experiment of understanding of these parameters can be done in two-different ways: static, where the sample subjects to destruction after the test and dynamic, known as non-destruction method. The non-destructive method using ultrasonic waves under a series of different stress conditions, starting from 7 to 56 MPa with incrementation of 7MPa, has been used in this paper in order to characterize the mechanical properties of dry Zbylutów sandstone at 20 and 80°C. The velocity of primary (P) and secondary (S) waves within these ranges has been recorded in order to understand the behavior of the mechanical properties. The results showed that the Young’s modulus, bulk modulus, shear modulus, and Lame’s constant of Zbylutów sandstone have a positive correlation with good coefficient correlation with the increased stress, while the Poisson’s ratio showed a negative correlation. Besides, the effect of temperature on the rock parameters is approved by the decrease of primary wave velocity in this two-different temperature range. Such results are necessary when preparing the appropriate mud weight for drilling process, which is related to wellbore instability.

The production of high-modulus and high-strength polymer nanofibers using centrifugal or rotary jet spinning (RJS) was explored. Co-polyimide nanofibers based on 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride (BPDA)/p-phenylenediamine (PDA)/4,4′-oxydianiline (ODA) (BPO) were successfully spun by RJS from a polyamic acid precursor solution before conversion into highly oriented and chain extended BPO co-polyimide fibers via an imidization step. Fourier transform infrared (FTIR) characterization was used to evaluate the chemical conversion of the fibers. Nanocomposite laminates based on co-polyimide nonwoven fiber mats in epoxy were manufactured for mechanical testing. Analysis using the generalized rule of mixtures resulted in a back-calculated fiber modulus and strength of around 50 and 2 GPa, approaching that of high-performance fibers like Kevlar® 29, and equaling those of co-polyimide fibers obtained via electrospinning, making them the strongest centrifugal spun fibers ever reported.

Aiming at the mechanical response of geomembrane (GEM) in membrane-faced rockfill dam (MFRD) to different ambient temperatures, the mechanical properties in axial tension of polyvinyl chloride (PVC) GEM were studied by experiment and theoretical analysis. First, fifteen groups of axial tensile tests for longitudinal/transverse specimens were conducted at different temperatures in the temperature environment laboratory, the stress–strain curve and Young’s modulus were obtained, and the variation of Young’s modulus with temperature was analyzed by Boltzmann function fitting. Second, the glass transition temperature of PVC GEM was obtained by differential scanning calorimetry (DSC), and the difference in mechanical properties between longitudinal and transverse specimens of PVC GEM was analyzed by thermomechanical analyzer (TMA) thermodynamic test. The results showed that the lower the temperature, the greater the Young’s modulus, and the smaller the linear interval of stress and strain, while the higher the temperature, the result is opposite. The difference in mechanical properties between the two directions is related to the ambient temperature. The orientation of polymer structure accounts for the difference in mechanical properties by theoretical analysis. The fitting results of Boltzmann function have a certain reference value for numerical simulation. In design of the membrane impervious structure in MFRD, the ambient temperature should be considered fully, and the longitudinal/transverse welding splicing should be avoided as far as possible. The current test specification should test the mechanical performance of GEM at normal operating temperature of reservoir instead of the test and quality evaluation at a single temperature. The temperature should be considered comprehensively in construction to avoid damaging the performance of impervious structure and ensure the service life.

Recently, the research of innovative building materials is focused on applying supplementary materials in the form of micro- and nanopowders in cementitious composites due to the growing insistence on sustainable development. Considering above, in paper, a research on the effect of microsilica and SiO2 nanoparticles addition to cement paste, designed with Andreasen and Andersen (AA) packing density model (PDM), in terms of its physical and mechanical properties was conducted. Density, porosity, compressive strength, hardness, and modulus of indentation were investigated and compared regarding different amount of additives used in cement paste mixes. Microstructure of the obtained pastes was analyzed. The possibility of negative influence of alkali-silica reaction (ASR) on the mechanical properties of the obtained composites was analyzed. The results of the conducted investigations were discussed, and conclusions, also practical, were presented. The obtained results confirmed that the applied PDM may be an effective tool in cement paste design, when low porosity of prepared composite is required. On the other hand, the application of AA model did not bring satisfactory results of mechanical performance as expected, what was related, as shown by SEM imaging, with inhomogeneous dispersion of microsilica, and creation of agglomerates acting as reactive aggregates, what as a consequence caused ASR reaction, crack occurrence and lowered mechanical properties. Finally, the study found that the use of about 7.5% wt. of microsilica is the optimum in regards to obtain low porosity, while, to achieve improved mechanical properties, the use of 4 wt. % of microsilica seems to be optimal, in the case of tested cement pastes.

In recent years, buried bellows have often had safety accidents such as pipeline bursts and ground subsidence due to the lack of adequate mechanical properties and other quality problems. In order to improve the mechanical properties of bellows, fly ash (FA) was used as a reinforced filler in high density polyethylene (HDPE) to develop composites. The FA was surface treated with a silane coupling agent and HDPE-g-maleic anhydride was used as compatibilizer. Dumbbell-shaped samples were prepared via extrusion blending and injection molding. The cross-section morphology, thermal stability and mechanical properties of the composites were studied. It was observed that when 10% modified FA and 5% compatibilizer were added to HDPE, the tensile yield strength and tensile breaking strength of the composites were nearly 30.2% and 40.4% higher than those of pure HDPE, respectively, and the Young’s modulus could reach 1451.07 MPa. In addition, the ring stiffness of the bellows was analyzed using finite element analysis. Compared with a same-diameter bellows fabricated from common commercially available materials, the ring stiffness increased by nearly 23%. The preparation method of FA/HDPE is simple, efficient, and low-cost. It is of great significance for the popularization of high-performance bellows and the high value-added utilization of FA.

Polypropylene (PP) has a high recycling potential. However, the properties of mechanically recycled PP (R-PP) have not been fully compared to those of virgin PP (V-PP). Therefore, in this study, properties of R-PP and V-PP were compared using data from recyclers, virgin plastic suppliers, and the literature. The properties of recyclates could not be directly correlated either with the properties of the virgin polymers from which the recyclates were made or the recycling parameters. It was found that the MFR of R-PP was higher; MFR R-PP had a median value (m) of 11 g/10 min while MFR V-PP had a median value of 6.3 g/10 min (at 230 °C and with 2.16 kg). In terms of mechanical properties, in many cases R-PP exhibited stiffer and more brittle behavior, with a slightly higher Young’s modulus (ER-PP = 1400 and EV-PP = 1200 MPa), a reduced elongation at break (ɛbR-PP = 4 l.-% and ɛbV-PP = 83 l.-%), and notched charpy impact strength (NCISR-PP = 4.8 and NCISV-PP = 7.5 kJ/m2). However, the values for every property had a broad distribution. In addition to existing information from the literature, our research sheds fresh light on the variation of the characteristics of recycled polypropylenes presently on the market.

In the current study, molecular dynamics (MD) simulations were performed to study the pressure dependence of the structural and mechanical properties of single-crystal tungsten. The results show that single-crystal tungsten possesses noteworthy high-pressure stability and exhibits linear lattice contraction with increasing external pressure. Consistent with the results of the performed experiments, the predicted elastic moduli, including Young’s modulus, shear modulus, and bulk modulus, as well as Poisson’s ratio and Pugh’s modulus ratio, show a clear increasing trend with the increase in pressure. Under uniaxial tensile loading, the single-crystal tungsten at high pressures experiences a phase transition from BCC to FCC and other disordered structures, which results in a stripe-like morphology in the tungsten crystal. These results are expected to deepen our understanding of the high-pressure structural and mechanical behaviors of tungsten materials.

The anelastic deformation, resulting from partial reversal of {101¯2} twinning, is studied at room temperature to 150 °C on several commercial die-cast magnesium alloys for the first time. The magnitude of anelastic strain decreases with increasing temperature. For inter-alloy comparison, AZ91 shows the largest maximum anelastic strain, while AM40 and AM60 show similar maximum anelastic strain. The phenomenon is discussed in terms of solid solution softening and hardening of slip planes and how they influence twinning. T5-aged AE44 consistently shows smaller magnitude of anelasticity compared to as-cast AE44, suggesting that the precipitates formed during ageing may decrease the twin-boundary mobility and further suppress untwinning. Presence of anelasticity poses a challenge to yield strength measurement using the conventional 0.2% offset method, and a more accurate and consistent method of using a higher offset strain or a lower modulus is proposed in this study.

Materials made from active, living, or robotic components can display emergent properties arising from local sensing and computation. Here, we realize a freestanding active metabeam with piezoelectric elements and electronic feed-forward control that gives rise to an odd micropolar elasticity absent in energy-conserving media. The non-reciprocal odd modulus enables bending and shearing cycles that convert electrical energy into mechanical work, and vice versa. The sign of this elastic modulus is linked to a non-Hermitian topological index that determines the localization of vibrational modes to sample boundaries. At finite frequency, we can also tune the phase angle of the active modulus to produce a direction-dependent bending modulus and control non-Hermitian vibrational properties. Our continuum approach, built on symmetries and conservation laws, could be exploited to design others systems such as synthetic biofilaments and membranes with feed-forward control loops., Main text, 6 figures, methods, and supplementary information

To fully exploit the preponderance of three-dimensional (3D)-printed, continuous, fiber-reinforced, thermoplastic composites (CFRTPCs) and self-reinforced composites (which exhibit excellent interfacial affinity and are fully recyclable), an approach in which continuous fiber self-reinforced composites (CFSRCs) can be fabricated by 3D printing is proposed. The influence of 3D-printing temperature on the mechanical performance of 3D-printed CFSRCs based on homogeneous, continuous, ultra-high-molecular-weight polyethylene (UHMWPE) fibers and high-density polyethylene (HDPE) filament, utilized as a reinforcing phase and matrix, respectively, was studied. Experimental results showed a qualitative relationship between the printing temperature and the mechanical properties. The ultimate tensile strength, as well as Young’s modulus, were 300.2 MPa and 8.2 GPa, respectively. Furthermore, transcrystallization that occurred in the process of 3D printing resulted in an interface between fibers and the matrix. Finally, the recyclability of 3D-printed CFSRCs has also been demonstrated in this research for potential applications of green composites.

Plantar fascia plays an important role in human foot biomechanics; however, the morphology and mechanical properties of plantar fascia in patients with flexible flatfoot are unknown. In this study, 15 flexible flatfeet were studied, each plantar fascia was divided into 12 positions, and the morphologies and mechanical properties in the 12 positions were measured in vivo with B-mode ultrasound and shear wave elastography (SWE). Peak pressures under the first to fifth metatarsal heads (MH) were measured with FreeStep. Statistical analysis included 95% confidence interval, intragroup correlation coefficient (ICC1,1), one-way analysis of variance (one-way ANOVA), and least significant difference. The results showed that thickness and Young’s modulus of plantar fascia were the largest at the proximal fascia (PF) and decreased gradually from the proximal end to the distal end. Among the five distal branches (DB) of the fascia, the thickness and Young’s modulus of the second and third DB were larger. The peak pressures were also higher under the second and third MH. This study found a gradient distribution in that the thickness and Young’s modulus gradient decreased from the proximal end to the distal end of plantar fascia in the longitudinal arch of flexible flatfeet. In the transverse arch, the thickness and Young’s modulus under the second and third DB were larger than those under the other three DB in flexible flatfoot, and the peak pressures under the second and third MH were also larger than those under the other three MH in patients with flexible flatfoot. These findings deepen our understanding of the changes of biomechanical properties and may be meaningful for the study of pathological mechanisms and therapy for flexible flatfoot.

In this study, a micro-molding technology was used to prepare the microneedles (MNs), while a texture analyzer was used to measure its Young’s modulus, Poisson’s ratio and compression breaking force, to evaluate whether the MNs can penetrate the skin. The effects of different materials were characterized by their ability to withstand stresses using the Structural Mechanics Module of COMSOL Multiphysics. Carboxymethylcellulose (CMC) was chosen as the needle formulation material with varying quantities of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and hyaluronic acid (HA) to adjust the viscosity, brittleness, hardness and solubility of the material. The results of both the experimental tests and the predictions indicated that the hardest tip material had a solids content of 15% (w/w ) with a 1:2 (w/w) CMC: HA ratio. Furthermore, it was shown that a solid content of 10% (w/w) with a 1:5 (w/w) CMC: PVA ratio is suitable for making patches. The correlation between the mechanical properties and the different materials was found using the simulation analysis as well as the force required for different dissolving microneedles (DMNs) to penetrate the skin, which significantly promoted the research progress of microneedle transdermal drug delivery.

International audience; Injection moulded composite materials reinforced with wood fibres or particles can offer a credible alternative to other plant-derived fibres, particularly from an economic and environmental point of view. In this study, we compared the recycling behaviour of poly-(propylene) composites reinforced with ground wood particles versus wood and flax fibre reinforced composites. An experimental and numerical approach was used. In spite of the mechanical and morphological performances of fibres which were initially poorer than those of long fibres, the wood particles demonstrated their reinforcement potential (+84 % and +14 %, for the Young’s modulus and the strength at max, respectively, compared to the pure matrix), due to their good adhesion with the matrix and also to the stability of their aspect ratio after recycling (-24 % after 5 injection cycles against -66 % and -61 % for long flax and wood fibres, respectively). The numerical model developed and fed by the mechanical and morpho-logical measurements carried out on the reinforcements made it possible to compare the experimental and nu-merical values. Overall, a close match was obtained between the two sets of parameters. The small differences obtained can be explained by the increase in fibre dispersion as the recycling process progresses, as well as by the possible increase in wood stiffness after several processing cycles.

International audience; PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden composting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that flax fibres preferentially degrade ‘inwards’ from the edge to the core of the composite. In addition, progressive erosion of the cell walls occurs within the fibres themselves, ‘outwards’ from the central lumen to the periphery primary wall. This preferential degradation is reflected in the decrease in indentation modulus from around 23 GPa for fibres located in the preserved core of the composite to 3–4 GPa for the remaining outer-most cell wall crowns located at the edge of the sample that is in contact with the compost. Ageing of the PLA matrix is less drastic with a relatively stable indentation modulus. Nevertheless, a change in the PLA morphology, a significant decrease in its roughness and increase of porosity, can be observed towards the edge of the sample, in comparison to the core. This work highlights the important role of intrinsic fibre porosity, called lumen, which is suspected to be a major variable of the compost ageing process, providing pathways of entry for moisture and microorganisms that are involved in cell wall degradation.

Due to the softening at the heat-affected zone (HAZ) in ultra-high strength steels (UHSS), the mechanical properties can deteriorate depending on the steels’ grade, welding heat input, and its associated cooling rate. Hence, a design based on the properties of the base material (BM) may not be appropriate, and there is a need to retain the lost properties of the weldment. This study presents an effort to strengthen butt-welded UHSSs using ultra-high modulus (UHM) carbon fiber reinforced polymer (CFRP) plates. Although the rehabilitation and strengthening of steel structures using CFRPs have been available during the last two decades, they have not been used to strengthen higher grades of steel such as UHSSs. For this aim, a series of tensile tests were carried out on butt-welded UHSSs strengthened with adhesively bonded UHM CFRP plates on both sides of the weldment. Two welding processes, i.e. the gas metal arc welding (GMAW) and laser welding, were implemented separately to join the plates. Microhardness measurements and tensile tests were carried out for the experimental part, as well as finite element (FE) analysis of the joints. The results were also compared with other available methods, i.e. high-frequency mechanical impact (HFMI) treatment and TIG-dressing (tungsten inert gas) of the weld toe that are commonly used to increase the fatigue life of UHSS joints. It was found that CFRP strengthening can not only retain the lost properties of the weldment but can also increase the joint strength up to 32% compared to the BM, and a considerable 50% higher stiffness. In contrast, the other methods (HFMI and TIG-dressing) had no impact on the tensile characteristics of the weldments. Post-print / Final draft

Thermomechanical modeling of epoxy/graphene oxide under quasi-static and dynamic loading requires thermo-mechanical properties such as Young’s modulus, Poisson’s ratio, thermal conductivity, and frequency-temperature dependent viscoelastic properties. In this study, the effects of different graphene oxide (GO) concentrations (0.05, 0.1, and 0.2 wt%) within an epoxy matrix on several mechanical and thermal properties were investigated. The distribution of GO fillers in the epoxy was investigated using transmission electron microscopy (TEM). The digital image correlation (DIC) technique was employed during the tensile testing to determine Young’s modulus and Poisson’s ratio. Analytical models were used to predict Young’s modulus and thermal conductivity, with an error of less than 13% and 9%, respectively. Frequency–temperature dependent phenomenological models were proposed to predict the storage moduli and loss tangent, with a reasonable agreement with experimental data. A relatively high storage modulus, heat-resistance index (THRI), and thermal conductivity were observed in 0.2 wt% nanocomposite samples compared with pure epoxy and other lower concentration GO nanocomposites. A high THRI and derivative of thermogravimetric analysis peak temperatures (Tm1 and Tm2) were exhibited by adding nano-fillers in the epoxy, which confirms higher thermal stability of nanocomposites than that of pristine epoxy.

Made available in DSpace on 2022-04-28T19:46:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Objective: To evaluate the effects of curing time, post-space region and cyclic fatigue on the micromechanical properties of a fiber-post luting cement. The null hypotheses were that (1) curing time, (2) fatigue and (3) post-space region does not affect the nanoindentation modulus and hardness of the dual-curing cement. Materials and methods: 48 premolars were endodontically treated and a class I cavity and 8 mm deep post space was prepared. Fiber posts were luted with a universal, dualized adhesive system and a dual-curing cement following manufacturer's instructions. Specimens were divided into three groups (16 specimens for each group) according to light-curing time (no light-curing, 20 s light-curing and 120 s light-curing), which was performed with a LED lamp at 1000 mW/cm 2. The coronal part of the cavity was restored using a nano-filled resin composite. After 24 h, 8 specimens for each group were randomly extract in order to undergo to fatigue test in wet condition through a chewing simulator, while the other specimens were kept in distilled water as benchmark. All the restored teeth were then sectioned in 1 mm thick slices perpendicularly to the fiber post axis. Specimen slices were classified in coronal and apical to be tested through a nanoindenter. Data were analyzed through Kruskal-Wallis test with a significance level of 1%, in order to evaluate the influence of treatments (i.e., curing time and cyclic loading) on the micromechanical properties of the tested luting cement. Results: Both fatigue and curing time significantly influenced nanoindentation modulus and hardness of dual-curing cement (p < 0.01). No significant differences were reported for post space region. A significant interaction was found among the analyzed factors (p < 0.01). Significance: 120 s light-curing time is recommended in order to achieve optimal mechanical proprieties, independently from post space region and cyclic fatigue. As matter of fact, 120 s light-curing allowed to prevent strain hardening induced by the fatigue simulation. Department of Mechanical and Aerospace Engineering Politecnico di Torino Polito BIO Med Lab Politecnico di Torino Department of Surgical Sciences Dental School Department of Biomedical and Neuromotor Sciences University of Bologna Department of Restorative Dentistry Sao Paulo State University – UNESP Department of Restorative Dentistry Sao Paulo State University – UNESP

Steel-concrete (SC) composite widely used in military defensive project is due to its impressive mechanical properties, long-lived service, and low cost. However, the growing use of hypervelocity kinetic weapons in the present war puts forward higher requirements for the anti-explosion and penetration performance of military protection engineering. Here, inspired by the special ‘brick-and-mortar’ (BM) structural feature of natural nacre, we firstly construct a nacre-inspired steel-concrete (NISC) engineering composite with 2510 kg/m3, possessing nacre-like lamellar architecture via a bottom-up assembling technique. The NISC engineering composite exhibits nacreous BM structural similarity, high compressive strength of 68.5 MPa, compress modulus of 42.0 GPa, Mohs hardness of 5.5, Young’s modulus of 41.5 GPa, and shear modulus of 18.4 GPa, higher than pure concrete. More interestingly, the hypervelocity impact tests reveal the penetration capability of our NISC target material is obviously stronger than that of pure concrete, enhanced up to about 46.8% at the striking velocity of 1 km/s and approximately 30.9% at the striking velocity of 2 km/s, respectively, by examining the damages of targets, the trajectories, penetration depths, and residual projectiles. This mechanically integrated enhancement can be attributed to nacre-like BM structural architecture derived from assembling the special steel-bar framework-reinforced concrete platelets. This study highlights a key role of nacre-like structure design in promoting the enhanced hypervelocity impact resistance of steel-concrete composites.

This work aimed to assess the impact of acellularization and sterilization methods on the mechanical properties of biocomposites used as a skin substitute. On the basis of the statistical analysis, it was ascertained that the values of the Young modulus for the samples before the sterilization process—only in the cases of substances such as: trypsin, 15% glycerol and dispase—changed in a statistically significant way. In the case of dispase, the Young modulus value before the sterilization process amounted to 66.6 MPa, for trypsin this value equalled 33.9 MPa, whereas for 15% glycerol it was 11 MPa. In the case of samples after the completion of the sterilization process, the analysis did not show any statistically significant differences between the obtained results of Young’s modulus depending on the respective reagents applied. It was confirmed that different methods of acellularization and the process of sterilization effect the alteration of mechanical properties of allogeneic skins. In the case of the decellularization method using SDS (Sodium Dodecyl Sulfate), liquid nitrogen and 85% glycerol the highest values of strain were observed. In the authors’ opinion, it is the above-mentioned methods that should be recommended in the process of preparation of skin substitutes.

In this paper, a multiscale method is developed to predict Young's modulus of fullerene-reinforced polymer nanocomposites (FRPNs). Polymethyl methacrylate is chosen as the polymer matrix, while C60 fullerene is considered as the reinforcement. First, molecular dynamics (MD) simulations are conducted to calculate the Young modulus of nanocomposite unit cell with different weight fractions of fullerene. Then, a micromechanics model for a composite with multi-inclusion reinforcements is developed based on the extension of the Mori–Tanaka model and generalized Eshelby's results. Numerical results obtained from the proposed micromechanics model are compared with those calculated from the MD simulations, and good agreement is achieved. In addition, we propose an extension for the Halpin–Tsai model to predict Young's modulus of the FRPNs.