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Ageing is associated with alterations in the structure and function of the contractile and elastic tissues that enable movement, posture, and balance. Alterations in structure and mechanical properties of the ankle plantarflexors and Achilles tendon are of particular interest due to their important ‘catapult-like’ function during efficient and healthy human locomotion. In this study, we examined age-related differences in the in vivo mechanical properties of both muscle and tendon in the human ankle plantarflexors in healthy younger (21 ± 3.25 years) and older (69 ± 2.86 years) adults. All participants were physically active, to represent healthy ageing. B-mode ultrasound coupled with force measurements was used to determine in vivo Achilles tendon stiffness and shear-wave elastography was used to measure shear modulus, an index of muscle stiffness, in the medial and lateral gastrocnemii. We found that older adults displayed 43% lower (p = 0.004) Achilles tendon stiffness, 59% lower (p < 0.001) Achilles tendon Young’s modulus, and 34% greater (p = 0.002) Achilles tendon cross-sectional area compared to younger participants. We found no difference in the shear modulus of the medial or lateral gastrocnemii between the younger and older individuals. The reduction in Achilles tendon stiffness coupled with similar gastrocnemii muscle shear modulus likely influences the integrated neuromechanical function of the ankle plantarflexor muscle–tendon units during locomotor tasks. Further investigations into the relationship between altered mechanical properties and in vivo muscle–tendon dynamics will provide greater insights into the age-related declines in mobility and locomotor function.

This article discusses the non-destructive evaluation of the mechanical properties of green wood. To estimate the dynamic flexural modulus of elasticity (MOED), a non-destructive test (NDT) method—the frequency resonance technique (FRT)—was used. A three-point bending test was carried out to determine the static bending properties as the bending modulus of elasticity (MOE), the modulus of rupture (MOR), and bending toughness (Aw). This article presents the results of a study comparing the correlations between the dynamic and static bending parameters of beech (Fagus sylvatica L.) and oak (Quercus robur L.) wood, which was further divided into heartwood and sapwood. These species were chosen as the most widespread representatives of diffuse-porous and ring-porous hardwoods. This study found statistically significant differences in most mechanical parameters between the two species, except for MOR. Among the investigated parameters, beech had higher values than oak (by 22.1% for MOED, 9.5% for MOE, and 12.1% for Aw). Furthermore, relevant correlations (R > |0.7|) were established between MOED and between some of the static flexural parameters. These correlations were stronger for beech, which due to its more homogeneous structure showed less data variability than the ring-porous oak.

We present an approach to understand geometric-incompatibility–induced rigidity in underconstrained materials, including subisostatic 2D spring networks and 2D and 3D vertex models for dense biological tissues. We show that in all these models a geometric criterion, represented by a minimal length ℓ̄min, determines the onset of prestresses and rigidity. This allows us to predict not only the correct scalings for the elastic material properties, but also the precise magnitudes for bulk modulus and shear modulus discontinuities at the rigidity transition as well as the magnitude of the Poynting effect. We also predict from first principles that the ratio of the excess shear modulus to the shear stress should be inversely proportional to the critical strain with a prefactor of 3. We propose that this factor of 3 is a general hallmark of geometrically induced rigidity in underconstrained materials and could be used to distinguish this effect from nonlinear mechanics of single components in experiments. Finally, our results may lay important foundations for ways to estimate ℓ̄min from measurements of local geometric structure and thus help develop methods to characterize large-scale mechanical properties from imaging data.

Determination of the mechanical behaviour of intact rock is one of the most important parts of any engineering projects in the field of rock mechanics. The most important mechanical parameters required to understand the quality of intact rock are Young’s modulus ( E ), Poisson’s ratio ( ν ), the strength of rock ( σ c ) and the ratio of Young’s modulus to the strength of rock known as modulus ratio ( M R ), which can be used for calculations. The particular interest of this paper is to investigate the relationship between these parameters for Hungarian granitic rock samples. To fulfil this aim, Modulus of elasticity ( E ), Modulus of rigidity ( G ), Bulk modulus ( K ) and the modulus ratio ( M R  =  E / σ c ) of 50 granitic rock samples collected from Bátaapáti radioactive waste repository were examined. Fifty high-precision uniaxial compressive tests were conducted on strong ( σ c  > 100 MPa) rock samples, exhibiting the wide range of elastic modulus ( E  = 57.425–88.937 GPa), uniaxial compressive strength ( σ c  = 133.34–213.04 MPa) and Poisson’s ratio ( ν  = 0.18–0.32). The observed value ( M R  = 326–597) and mean value of M R  = 439.4 are compared with the results of similar previous researches. Moreover, the statistical analysis for all studied rocks was performed and the relationship between M R and other mechanical parameters such as maximum axial strain ( ε a, max ) for studied rock samples was discussed. Finally, the validity of the proposed mathematical model by Palchik (Geomech Geophys Geo-energy Geo-resour 6:1–12, 2019 ) for stress–strain behaviour of granitic rock samples was investigated.

Cubic garnet Li 6.24 La 3 Zr 2 Al 0.24 O 11.98 (LLZO) is a candidate material for use as an electrolyte in Li–Air and Li–S batteries. The use of LLZO in practical devices will require LLZO to have good mechanical integrity in terms of scratch resistance (hardness) and an adequate stiffness (elastic modulus). In this paper, the powders were fabricated by powder processing of cast ingots. All specimens were then densified via hot pressing. The room temperature elastic moduli (Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio) and hardness were measured by resonant ultrasound spectroscopy, and Vickers indentation, respectively. For volume fraction porosity, P , the Young’s modulus was 149.8 ± 0.4 GPa ( P  = 0.03) and 132.6 ± 0.2 GPa ( P  = 0.06). The mean Vickers hardness was 6.3 ± 0.3 GPa for P  = 0.03 and 5.2 ± 0.4 for P  = 0.06.

In recent years, an emerging technology termed, “High-Performance Fiber-Reinforced Concrete (HPFRC)” has become popular in the construction industry. The materials used in HPFRC depend on the desired characteristics and the availability of suitable local economic alternative materials. Concrete is a common building material, generally weak in tension, often ridden with cracks due to plastic and drying shrinkage. The introduction of short discrete fibers into the concrete can be used to counteract and prevent the propagation of cracks. Despite an increase in interest to use HPFRC in concrete structures, some doubts still remain regarding the effect of fibers on the properties of concrete. This paper presents the most comprehensive review to date on the mechanical, physical, and durability-related features of concrete. Specifically, this literature review aims to provide a comprehensive review of the mechanism of crack formation and propagation, compressive strength, modulus of elasticity, stress–strain behavior, tensile strength (TS), flexural strength, drying shrinkage, creep, electrical resistance, and chloride migration resistance of HPFRC. In general, the addition of fibers in high-performance concrete has been proven to improve the mechanical properties of concrete, particularly the TS, flexural strength, and ductility performance. Furthermore, incorporation of fibers in concrete results in reductions in the shrinkage and creep deformations of concrete. However, it has been shown that fibers may also have negative effects on some properties of concrete, such as the workability, which get reduced with the addition of steel fibers. The addition of fibers, particularly steel fibers, due to their conductivity leads to a significant reduction in the electrical resistivity of the concrete, and it also results in some reduction in the chloride penetration resistance of the concrete.

In this paper, the synthesis of a new trifunctional sulfur and phosphorus epoxy architecture based on hydroxy diphenyl sulfone bis para-ester phosphoric triglycidyl ether (TGEHDSEP) is presented. The viscometric properties of the synthesized resin using an Ubbelohde type capillary viscometer were investigated and were thermally crosslinked using the hardener methylene dianiline (MDA). The viscosity values of the new trifunctional epoxy resin TGEHDSEP increased as the pre-polymer mass concentrations increased, as expected, and as the sample temperature increased, the viscosity of the system (TGEHDSEP/ethanol) decreased. A new nanocomposite composed of the prepared resin, TGEHDSEP, and carbon nanotubes (CNT) was developed using a variety of formulations to optimize the rheological behavior and thermal stability of the epoxy matrix. The effect of the CNT filler in admixture with the TGEHDSEP/MDA system in this series of formulations on the nanocomposites rheological properties was studied. The rheological and thermal properties of the formulated materials were assessed using the RHM01-RD Haaks rheometer and the thermogravimetric analysis (TGA) in the dynamic regime, respectively. The results showed that the G′ (storage modulus) and G′′ (loss modulus) of various nanocomposites increase as the filler CNT content increases. Over the entire frequency range studied, the storage modulus G′ is much higher than the loss modulus G′′ for methylene–dianiline crosslinked nanocomposites formulated with varying percentages of CNT. The storage modulus G′ of all prepared nanocomposites increases as the percentage of CNTs increases. These results also show that the addition of carbon nanotubes to the epoxy matrix improves its thermal properties significantly. The morphology of the prepared nanocomposites, analyzed by scanning electron microscopy (SEM), varies significantly with the percentage of carbon nanotube filler incorporated into the studied matrix, and the carbon nanotube filler is uniformly distributed in this epoxy resin. Finally, we utilized the Materials Studio software package to investigate the mechanical and thermal conductivity properties of TGEHDSP and single-walled carbon nanotube (SWCNT). The material exhibited the following mechanical properties: Young's modulus: 7.1508 GPa, shear modulus: 2.6169 GPa, bulk modulus: 8.9116 GPa, Poisson's ratio: 0.3663. Additionally, its compressibility is approximately 105.9918 TPa. On the other hand, the epoxy resin, TGEHDSP, performs relatively well as a heat conductor among epoxy-based materials, while SWCNT's high thermal conductivity highlights its exceptional heat transfer capabilities, characteristic of nanoscale structures.

For this study, bisphenol A epoxy resin (DGEBA) was used as the resin matrix, and 3,3’-diaminodiphenyl sulfone (33DDS) was used as the curing agent. The effects of different cross-linking densities on the mechanical properties of epoxy resins were studied by molecular dynamics (MD) simulation, and the changes in the mechanical properties of epoxy resins under five different cross-linking density levels were predicted [1] . The results showed that as the cross-linking density of the epoxy resin increased, the mechanical parameters (such as elastic modulus, shear modulus, and bulk modulus) of the epoxy resin system also increased. This indicates the importance of improving the curing process of epoxy resin to enhance its mechanical properties.

The relationship between the static and dynamic elastic modulus in rock materials has been frequently addressed in scientific literature. Overall, when it comes to the study of materials with a wide range of elastic moduli, the functions that best represent this relationship are non-linear and do not depend on a single parameter. In this study, the relationships between the static and dynamic elastic modulus of eight different igneous, sedimentary and metamorphic rock types, all of which are widely used as construction material, were studied. To this end, the elastic modulus values of 33 samples were obtained which, together with the values obtained for 24 other samples in a previous study, allowed a new relationship between these parameters to be proposed. Firstly, linear and nonlinear classical models were used to correlate static and dynamic moduli, giving R 2 of 0.97 and 0.99, respectively. A classical power correlation between static modulus and P-wave velocity has also been proposed, giving an R 2 of 0.99 and a sum of the squared differences (SSE) of 553.93. Finally, new equations relating static and dynamic modulus values have been proposed using new nonlinear expressions. These consider: (a) bulk density ( R 2  = 0.993 and SSE = 362.66); (b) bulk density and total porosity of rock ( R 2  = 0.994 and SSE = 332.16); and (c) bulk density, total porosity of rock and uniaxial compressive strength ( R 2  = 0.996 and SSE = 190.27). The expressions obtained can be used to calculate the static elastic modulus using non-destructive techniques, in a broad range of rock materials.

The effects of nanoclay (NC) addition on the thermal and mechanical properties of glass fiber-reinforced epoxy composites were investigated experimentally in this study. Nanocomposite plates were produced for this purpose using three different NC ratios (0.5%, 1%, and 1.5% by weight). Thermal characteristics of nanocomposites were investigated using dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetric analysis. The mechanical and thermal results obtained from composites with three different NC ratios were compared with the results obtained from pure composites. The structures of nanocomposites were investigated with the help of SEM–EDS analyses. Furthermore, the effect of nanoclay on the failure behavior of composites was also investigated. In this study, the highest values in all mechanical properties were obtained from samples with a 1% NC-added. Obtained from 1% NC-added samples: tensile, compressive, shear strengths, elasticity modulus, shear modulus, and Poisson's ratio values were 31.06%, 4.25%, 14.30%, 7.35%, 11.94%, and 12.5% higher, respectively, than the values obtained from pure samples. Maximum loss modulus and maximum storage modulus were obtained from samples with 1.5% and 0.5% NC-added, respectively. In samples with 1.5% NC-added, the highest Tan δ value was obtained. Glass transition temperatures increased with the added NC. It was observed that the fiber–matrix interfaces were more clearly separated in the samples with 1.5% NC-added. Graphical abstract