Greater Stiffness Research Articles

Exploring the effects of fiber content and length on mechanical, free vibration, electrical, and water absorption properties of Phoenix sp. fiber‐reinforced polyester composites

AbstractThis work addresses the experimental investigation of the mechanical, free vibration, electrical resistivity, and moisture uptake characteristics of Phoenix sp. fiber‐reinforced polyester composites (PFRPC) fabricated using the compression molding method. The polyester matrix (PM) was added with Phoenix sp. fibers (PSFs) of different content (5, 10, 15, 20, and 25 wt%) and length (10, 20, and 30 mm) and studied their effect on the aforesaid properties. The results reveal that the composites having 20 wt% of 20 mm length PSFs exhibited optimum mechanical properties. At this loading, the ultimate tensile strength and modulus were 48.36 MPa and 2.86 GPa, respectively, while the flexural strength and modulus were 83.89 MPa and 2.91 GPa, respectively. Furthermore, this composite exhibits an impact strength of 22.04 kJ/m2 and an interlaminar shear strength of 41.88 MPa. The increase in PSF content and length resulted in greater stiffness and decreased mass of the composites, leading to an enhanced natural frequency. The inclusion of PSFs showed a decline in electrical resistivities due to their moisture‐absorbing capability. In contrast, the hydrophilic behavior of PSFs led to a rise in the water absorption rate of the composites due to the increase in fiber variables. Scanning electron microscopy examination shows that short fiber‐reinforced composites have more fiber pull‐outs due to the limited area of contact, whereas long fiber‐added composites possess better bonding with the PM.Highlights Various properties of Phoenix sp. fiber/polyester composites were investigated Increase in fiber content enhanced the mechanical performance of composites Variation in fiber length has only minimal effect on composite properties Phoenix sp. fiber/polyester composites exhibit better insulating property

Unlocking the potential of low-melting-point alloys integrated extrusion additive manufacturing: insights into mechanical behavior, energy absorption, and electrical conductivity

AbstractAdditive manufacturing is a commonly used manufacturing method in complex part fabrication, instant assemblies, part consolidation, mass customization and personalization, on-demand manufacturing, lightweight, and topological optimization due to its advantage of lower costs, flexibility to learn and use, reduced raw material wastage, digital design integration, high efficiency, environmental-friendliness. However, the current metal 3D printing, which is mainly fabricated layer by layer using laser, is expensive to manufacture metal parts. Therefore, in this paper, a low-cost high-quality metal manufacturing process called low-melting-point alloys (LMPAs) integrated extrusion additive manufacturing will be examined. This manufacturing process can fabricate complex metal structures and integrated circuits with simple fused deposition modeling, which is a cost-effective method for producing these objects. LMPAs with different melting points are used for performance comparison to find out the optimized mechanical behavior, energy absorption properties, and electrical conductivity. Our investigation into LMPAs integrated extrusion additive manufacturing has revealed significant findings. Tensile tests conducted on LMPAs with varying melting points have illuminated distinct mechanical behaviors. Notably, lower melting points contribute to increased ductility but reduced stiffness, while higher melting points result in greater stiffness but diminished ductility. These results emphasize the importance of tailoring LMPA selection based on specific application requirements. Furthermore, our examination of lattice and triply periodic minimal surface structures has demonstrated consistent energy absorption properties across different manufacturing temperatures, highlighting the adaptability and versatility of LMPAs for energy absorption applications. Additionally, our electrical conductivity assessments have shown that LMPAs with melting points of $${{47}^{\circ }C}$$ 47 ∘ C and $${{120}^{\circ }}\hbox {C}$$ 120 ∘ C exhibit higher electrical conductivity, making them suitable for applications requiring good electrical conduction properties. These findings collectively underscore the significance of LMPAs in additive manufacturing, offering valuable insights for material selection and applications in various domains.

Effect of box beam wall thickness on the stiffness of the camphor wood timber bridge truss

Bridges are vital for community development, and wood is a primary material due to its environmental benefits. However, wood’s moisture absorption can cause swelling and shrinkage, and low-density wood tends to have lower strength. The moment of inertia of a box beam is related to wall thickness and stiffness. Insufficient wall thickness can lead to plastic retention before peak load, reducing structural integrity. Thin walls can cause buckling under compressive loads, leading to failure. Truss bridge failures can also result from design errors. This study aims to analyze the effect of box beam wall thickness on the stiffness of camphor wood timber bridge trusses. Camphor wood with a cross-sectional area of 1,600 mm2 was used, with box beams of dimensions 45×45 mm (12 mm wall), 50×50 mm (10 mm wall), 58×58 mm (8 mm wall), and a solid beam of 40×40 mm (20 mm wall). Physical tests showed the wood’s specific gravity at 0.506 g/cm3 and moisture content at 12.47 %. The highest peak load was 19.613 kN for the BB.58.58.8 variation, which also had the greatest stiffness at 3.502 kN/mm. The BB.58.58.5 variation had the largest moment of inertia at 683,733 mm4 compared to the solid beam SB.40.40.20 at 213,333 mm4. The BB.45.45.12 sample had a t/D ratio 1.93 times larger than BB.58.58.8, indicating a more flexible structure with lower stiffness. This is confirmed by experimental results, showing that BB.45.45.12 had a stiffness 1.73 times lower than BB.58.58.8. Theoretical calculations also showed that BB.45.45.12 had a stiffness 2.03 times smaller than BB.58.58.8. Thus, the t/D ratio is inversely proportional to stiffness. This research contributes valuable insights for developing engineered wood products in construction and bridge design, particularly for village bridges in Indonesia

Effect of magnetic microbeads on sustained and targeted delivery of transforming growth factor-beta-1 for rotator cuff healing in a rat rotator cuff repair model

Structural failure is a well-established complication of rotator cuff repair procedures. To evaluate the effect of magnetic microbeads, designed for precise drug delivery via magnetic force, on sustained transforming growth factor-beta-1 (TGF-β1) release and rotator cuff healing in a rat rotator cuff repair model. TGF-β1 laden microbeads were prepared, and baseline in vitro experiments included the magnetization of the microbeads and TGF-β1 release tests. In an in vivo experiment using a rat rotator cuff repair model on both shoulders, 72 rats were randomly assigned to three groups (24 per group): group A, conventional repair; group B, repair with and simple TGF-β1 injection; and group C, repair with magnet insertion into the humeral head and TGF-β1 laden microbead injection. Delivery of TGF-β1 was evaluated at 1 and 7 days after the intervention using PCR, Western blot, and immunohistochemistry. At 6 weeks post-intervention, rotator cuff healing was assessed using biomechanical and histological analysis. The in vitro experiments confirmed the magnetization property of the microbeads and sustained delivery of TGF-β1 for up to 10 days. No difference in the TGF-β1 expression was found at day 1 in vivo. However, at day 7, group C exhibited a significantly elevated expression of TGF-β1 in both PCR and Western blot analyses compared to groups A and B (all P < 0.05). Immunohistochemical analysis revealed a higher expression of TGF-β1 at the repair site in group C on day 7. At 6 weeks, biomechanical analysis demonstrated a significantly higher ultimate failure load in group C than in groups A and B (P < 0.05) and greater stiffness than in group A (P = 0.045). In addition, histological analysis showed denser and more regular collagen fibers with complete continuity to the bone in group C than in groups A and B, a statistically significant difference according to the semi-quantitative scoring system (all P < 0.05). The use of the TGF-β1 laden magnetic microbeads demonstrated sustained delivery of TGF-β1 to the repair site, improving rotator cuff healing.

Exploring marine-based compounds as cross-linkers to improve the biocompatibility and sustainability of chitosan-based hydrogels

Chitosan is one of the most promising natural polymers, its fundamental scientific research is growing uninterruptedly and has been applied in a wide and varied range of domains, including biomedical and water treatment applications. Therefore, the search and implementation of non-synthetic and non-toxic cross-linkers for chitosan-based hydrogels is crucial for the development of more sustainable and biocompatible materials. Herein, an alternative approach has been developed to explore and exploit methanolic and aqueous extracts from five red seaweed species as covalent cross-linkers for chitosan-based hydrogels. The formation of a gel could be denoted for all extracts, whereas the protein-rich methanolic extractions afforded instantaneous gel-forming ability and greater stiffness and stability. The obtained hydrogels present large porous system with high degrees of swelling up to ca. 3000 %, and were successfully applied as dye adsorbent to remove industrial dye methyl orange withing a circular process with adsorption capacities of 728.46 ± 66.17 mg/g. Furthermore, cytotoxicity and cell-adhesion studies revealed the biocompatibility of the hydrogels and their potential applicability for tissue-engineering. This work demonstrated that methanolic and aqueous extracts from different red seaweed species could replace toxic cross-linkers. Furthermore, the unexpected ability of some extracts could pave the way for the development of new formulations for additive manufacturing, in particular for 3D printing approaches.

Viscoelastic, Optical, and Surgical Properties of Vitreous Body Replacement Hydrogels After Aging Compared to Porcine Vitreous Bodies And Silicone Oils.

First- (monomers), second- (pre-gelated), and third- (in situ gelating after injection) generation hydrogels were previously introduced to replace the vitreous body after vitrectomy surgery. In this study, we evaluated the surgical, optical, and viscoelastic properties of vitreous body replacement hydrogels before and after an accelerated aging protocol previously applied to intraocular implants. Measurements of injection force, removal speed using a clinically established vitrectomy setup, as well as evaluation of forward light scattering and viscoelastic properties before and after an accelerated aging protocol were conducted. Results were compared to porcine and human vitreous bodies, as well as currently clinically applied lighter- and heavier-than-water silicone oils. Removal speed of all tested hydrogels is substantially lower than the removal speed of porcine vitreous body (0.2 g/min vs. 2.7 g/min for the best performing hydrogel and porcine vitreous body, respectively). Forward light scattering in second-generation vitreous body replacement hydrogels was higher after the aging process than the straylight of the average 70-year-old vitreous body (9.4 vs. 5.5 deg2/sr, respectively). The viscoelastic properties of all hydrogels did not change in a clinically meaningful manner; however, trends toward greater stiffness and greater elasticity after aging were apparent. This study demonstrates surgical weaknesses of the hydrogels that need to be addressed before clinical use, especially low removal speed. Pre-linked hydrogels (second-generation) showed inferior performance regarding surgical properties compared to in situ gelating hydrogels (third-generation). This study highlights possible pitfalls regarding surgical and optical properties when applying vitreous replacement hydrogels clinically.

Implementation of a passive bi-articular ankle-knee exoskeleton during maximal squat jumping.

Owing to the unexplored potential to harness knee extension power during jumping, the current study aimed to examine how joint mechanics were altered with a biologically inspired, passive bi-articular ankle-knee exoskeleton, which could potentially facilitate greater jump height by increasing work production about the knee and ankle. Twenty-five participants (16 males and 9 females, 175.2 ± 8.2 cm, 72.9 ± 10.3 kg, 24.0 ± 3.4 years) performed maximal squat jumping with and without the exoskeletal device and we compared jump height, joint moment and joint work of the lower limbs. Despite a low exoskeleton stiffness and therefore a limited capacity to store energy, the bi-articular device resulted in decreased jump height (1.9 ± 3.1 cm, p = 0.006), decreased net work about the knee (0.23 J/kg, p < 0.001) and no increase in ankle joint work (p = 0.207), compared with jumping with no exoskeleton. Based on our findings, to mimic unassisted ankle joint moment profiles, a future bi-articular device would need increased elastic element slack length, greater stiffness and a larger moment arm about the ankle. Future designs could also employ attachment sites that have minimal overlying soft tissue, such as the pelvis, to improve comfort of the device.

KINEMATIC RESPONSES AND SEGMENTAL STIFFNESS OF NORMAL AND DEGENERATIVE L4/L5 MOTION SEGMENTS: FINITE ELEMENT STUDY

In this study, finite element (FE) models of an anatomical normal and a degenerated disc of L4–L5 motion segment, developed using different methodologies of volume mesh constructions, and ways of defining the spinal components’ material properties, were exercised and analyzed. The geometrics details were obtained using digitizing technique and segmentation of computed tomography (CT) scans; with material and structural properties of the spinal components defined based on the literature and greyscale values of CT images for the normal and degenerated L4–L5 motion segments, respectively. The predicted kinematic responses under five different physiological loadings in three anatomical reference planes for both models together with published data were analyzed. The predicted results correlated well within the range and in similar trends with published experimental results. The overall predicted responses showed different volume mesh constructions and the representation of spinal components’ material properties were accurate enough to predict the kinematic responses, although experimental results exhibit considerable divergence due to different experimental techniques. Both models exhibited different rotational and translation segmental stiffness in each corresponding loading configuration. The normal L4–L5 segment exhibited greatest axial torsional stiffness, and least extensional stiffness. The degenerated L4–L5 segment was least flexible (greatest stiffness) in extension and most flexible (least stiffness) in flexion. For compression, the axial stiffness of segment of normal segment was about 10% larger than that of the degenerated segment. The en-bloc efforts of all spinal components have contributed to the different nonlinear kinematic characteristics and segmental stiffness of these different L4–L5 motion segments.

Evaluation of Pylon Shape and Cable Layout Interaction on the Seismic Behavior of Cable-stayed Bridges

Nowadays, cable-stayed bridges are among the most widely used bridges. In these bridges, the seismic behavior is critical due to the nonlinear behavior of the cables and the high seismic weight. In recent years, some research has been done on measuring the seismic behavior of cable-stayed bridges. Most of them have evaluated the seismic behavior of the pylon shape or cable layout separately. Nevertheless, it seems very unlikely that these two elements’ reactions do not affect each other. Therefore, this article has tried to consider the mutual effect of these variables in a wide range of span lengths using spectral nonlinear dynamic analysis. On the other hand, the connection angle of the cables to the bridge deck has also been investigated as another variable. The results show that the response of the bridge may change entirely according to the combination of pylon shape and cable layout. For example, in A and diamond-shaped pylons, using a Harp configuration of cables reduces the period of free vibration of the bridge and, as a result, provides the greatest stiffness. On the other hand, the Fan configuration creates more stiffness in the H-shaped and single pylons.

A Dynamic, Self-Tensioning Suture Contracts in Saline to Counteract Changes in Loop Length From Cyclic Loading

To compare the biomechanical performance of a suture with proposed dynamic self-tensioning properties with that of commonly used high-tensile sutures by evaluating suture loop length changes, responses to cyclic loading, and failure testing with intermittent saline soaks. Six knots each of 4 different sutures were studied: 3 high-tensile sutures (ORTHOCORD, FiberWire, and ETHIBOND), and a dynamically self-tensioning suture (DYNACORD). After we measured loop length, knots were soaked in 37°C saline for 24 hours. Loop lengths were remeasured and tensile testing was performed. Cyclic elongation, first-cycle excursion, and elongation amplitude were recorded. Knots were then resoaked and retested. Finally, knots were pulled to failure, and peak load and stiffness were measured. Values were compared using nonparametric statistical tests. DYNACORD loop length decreased by 27% after the first soak (P= .002), whereas the other sutures demonstrated no length change (P > .05). Although DYNACORD loop length increased during cyclic load testing (P= .009), it was still significantly reduced after the second saline soak compared withits initial length (P= .002), whereas all other suture loops had elongated. ETHIBOND (P= .004) and ORTHOCORD (P= .002) had significantly less cyclic elongation from cycle I to cycle II testing compared with the other sutures. ETHIBOND had the lowest peak load at failure (P= .002). FiberWire had the greatest stiffness (P= .006). Compared with other suture types, the self-tensioning suture showed dynamic properties, demonstrating a decrease in loop length when soaked in a saline bath. This length was maintained after a second soak despite increased loop length during interval cyclic loading. Knot and loop security are of paramount importance to arthroscopic soft-tissue procedures. The ability for a suture to self-tension has implications for how it may interact with tissues invivo to increase construct stability after arthroscopic soft tissue repair procedures.

Characteristics of Changes in Contractile Properties of Muscle after Anaerobic Exercise

Tensiomyography (TMG) has been described as an effective method for identifying differences in muscle response to athletic training stimuli. However, there is a lack of studies that evaluated changes in muscle contractile properties in response to anaerobic effort and related these changes to Wingate test parameters in more than one lower limb superficial muscle. The main contribution of this work is to evaluate changes in the contractile properties of muscles in response to anaerobic exercise. In a group of 20 physically active men, the body composition analysis was performed using a Tanita DC-360 device. The anaerobic effort was assessed by a Wingate test (30 s), and the contractile properties of muscles were measured using a TMG S2 device. The TMG parameters were measured in selected superficial muscles of the dominant lower limb. The study also calculated indices of the differences (d) and the size of the effect (r). An anaerobic effort in the form of the Wingate test resulted in greater stiffness (Dm) in the vastus lateralis muscle (p = 0.0365; r = 0.47) and a delayed response to stimulus (Td) in the vastus lateralis (p = 0.0239; r = 0.51) and vastus medialis (p = 0.0031; r = 0.66) muscles. The half relaxation time (Tr) (p = 0.0478; r = 0.44) and sustained contraction time (Ts) (p = 0.0276; r = 0.49) in the rectus femoris muscle were also increased. In contrast, a prolonged stimulus-response time (Td) with a decrease in sustained contraction time (Ts) was observed in the gastrocnemius lateralis (Td: p = 0.0054; r = 0.64 and Ts: p = 0.0012; r = 0.74) and gastrocnemius medialis (Td: p = 0.0229; r = 0.52 and Ts: p = 0.0054; r = 0.64) muscles. A significant decrease in contraction time (Tc) (p = 0.0051; r = 0.63) occurred only in the soleus muscle. In addition, significant correlations were shown between selected changes in contractile properties of muscle and parameters of the Wingate anaerobic test. Anaerobic exercise has a significant effect on changes in skeletal muscle contractility parameters. TMG is an effective method for identifying differences in muscle response to sports training stimuli.

Mechanical properties of native and decellularized reproductive tissues: insights for tissue engineering strategies

Understanding the mechanical properties and porosity of reproductive tissues is vital for regenerative medicine and tissue engineering. This study investigated the changes in Young's modulus (YM), storage modulus (E′), loss modulus (Eʺ), and porosity of native and decellularized bovine reproductive tissues during the estrous cycle. Testis tunica albuginea had significantly higher YM, E′, and Eʺ than the inner testis, indicating greater stiffness and viscoelasticity. Endometrium showed no distinct differences in YM, E′, or Eʺ across the estrous cycle or between horns. Ovaries exhibited significant variations in YM, E′, Eʺ, and porosity, with higher YM and E′ in the ipsilateral cortex and medulla during the luteal phase. Decellularized ovarian tissues displayed increased porosity. The oviduct displayed no significant differences in YM or E′ in the isthmus, but the contralateral ampulla had reduced YM and E′ in the luteal phase. These findings offer valuable insights into the dynamic mechanical properties and porosity of reproductive tissues, facilitating the development of biomimetic scaffolds for tissue engineering applications.

ИССЛЕДОВАНИЕ ДИНАМИЧЕСКИХ СВОЙСТВ ГИБРИДНОГО ТИТАН-ПОЛИМЕРНОГО КОМПОЗИЦИОННОГО МАТЕРИАЛА

Low specific weight and high mechanical strength (especially at elevated temperatures) of titanium and its alloys make them very valuable aviation materials. In the field of aircraft construction and aircraft engine production, titanium is increasingly replacing aluminum and stainless steel. At present, aircraft developers are restructuring the whole material science concept of aircraft construction, actively involving and using various types of composite materials based on titanium alloys. Combined with the properties of titanium, FML composites based on titanium have greater stiffness, impact resistance, heat resistance, and corrosion resistance especially compared to similar aluminum-based materials. The paper investigates the dynamic characteristics of hybrid titanium-polymer composite materials (TPCM) based on titanium alloy BT-23 and fiberglass with a brief presentation of the main characteristics of prepregs. The process of manufacturing specimens for testing including heat treatment, ply laying scheme and reinforcement scheme in two variants is described. The results of experimental studies of natural frequencies and damping coefficient by the method of free damped oscillations in free oscillations of TPCM plates are presented. The tests are carried out on a specially designed unit with a triangulation sensor in the variant of vertical loading. Two identical specimens with different overall dimensions are tested.Each specimen was tested with a different amplitude. Five tests were conducted for each amplitude. The physical constants of the specimens were pre-determined in static tests. The natural frequencies and damping coefficients for the titanium-polymer composite specimens were found.

An optimized fatigue model of asphalt binder combining nonlinear viscoelastic and intrinsic healing characteristics

This paper proposed an optimized fatigue life prediction model of graphene oxide (GO) modified asphalt binder considering the coupled effects of nonlinear viscoelasticity (NLVE) and intrinsic healing compensation. The equivalent nonlinear complex modulus (|G*|NLVE) was quantified accordingly and an NLVE-based fatigue model was proposed in this study. The parameters damage healing (ΔS'), local life compensation (ΔN), damage healing index (%HS), and local lifetime compensation index (%ΔN) were employed to characterize the intrinsic healing capability and mechanism of GO-modified binders. There is a strong correlation mechanism between the healing compensation effect and the damage healing of asphalt binders during healing intervals, as evidenced by the linear relationship between ΔS' vs. ΔN and %HS vs. %ΔN. Furthermore, the analysis of the total stored pseudo-strain energy counteracting the damage healing reveals that GO-modified binder has greater stiffness and require more stored pseudo-strain energy to counteract ΔS'. The fatigue life of asphalt binder is further prolonged by the healing compensation effect on the basis of GO modification and NLVE effects.

The origin of different bending stiffness between double-stranded RNA and DNA revealed by magnetic tweezers and simulations.

The subtle differences in the chemical structures of double-stranded (ds) RNA and DNA lead to significant variations in their biological roles and medical implications, largely due to their distinct biophysical properties, such as bending stiffness. Although it is well known that A-form dsRNA is stiffer than B-form dsDNA under physiological salt conditions, the underlying cause of this difference remains unclear. In this study, we employ high-precision magnetic-tweezer experiments along with molecular dynamics simulations and reveal that the relative bending stiffness between dsRNA and dsDNA is primarily determined by the structure- and salt-concentration-dependent ion distribution around their helical structures. At near-physiological salt conditions, dsRNA shows a sparser ion distribution surrounding its phosphate groups compared to dsDNA, causing its greater stiffness. However, at very high monovalent salt concentrations, phosphate groups in both dsRNA and dsDNA become fully neutralized by excess ions, resulting in a similar intrinsic bending persistence length of approximately 39 nm. This similarity in intrinsic bending stiffness of dsRNA and dsDNA is coupled to the analogous fluctuations in their total groove widths and further coupled to the similar fluctuation of base-pair inclination, despite their distinct A-form and B-form helical structures.

Muscle contraction time after caffeine intake is faster after 30 minutes than after 60 minutes.

This study aimed to determine the optimal time point, either 30 or 60 minutes, at which muscle reactivity to caffeine administration is highest. Unlike previous studies that focused on the nervous system response, we employed tensiomyography (TMG) to directly assess the effects of caffeine on muscle fibers. TMG measurements were performed on the gastrocnemius medialis muscle of 42 male athletes who regularly consumed caffeine. Participants received a dose of 6 mg/kg body weight and TMG measurements were taken prior to caffeine intake, as well as 30 and 60 minutes afterward. Analysis of TMG parameters including time to contraction (Tc), time delay (Td), and maximal displacement (Dm) revealed that muscles exhibited faster contractions and greater stiffness at the 30-minute mark compared to both pre-caffeine intake and the 60-minute time point. Time exerted a significant main effect on Tc (F(2, 246) = 12.09, p < .001, ή2p = 0.09), Td (F(2, 246) = 3.39, p = .035, ή2p = 0.03), and Dm (F(2, 246) = 6.83, p = .001, ή2p = 0.05), while no significant effect of body side was observed. The findings indicate that muscle contraction time (Tc) and delay time (Td) are influenced by the time elapsed since caffeine ingestion, with the fastest responses occurring after 30 minutes. Additionally, a systemic effect of caffeine was observed, as there were no discernible differences in measurements between the two sides of the body. TMG proves to be an effective noninvasive method for assessing muscle responses following caffeine administration.

Mechanical properties of the patellar tendon in weightlifting athletes - the utility of myotonometry. Adaptations of patellar tendon to mechanical loading.

Purpose: Tendons adapt to loads applied to them, by changing their own mechanical properties. The purpose of the study was to examine the influence of practicing sport in the form of weightlifting/strength training by individuals of various age groups upon the mechanical properties of the patellar tendon. Methods: 200 people participated in the study. Group 1 (n = 109) comprised individuals training strength sports as amateurs, group 2 (n = 91) consisted of people who were not physically active. The patellar tendon was examined in various positions of the knee joint: 0, 30, 60, 90, 120° respectively. The following mechanical parameters were measured with the use of a device for myoto-nometric measurements, MyotonPRO: frequency [Hz], stiffness [N/m], decrement [log], relaxation time [ms] and creep [De]. The results were compared as regards physical activity, training history, BMI value, and gender. Results: Stiffness and tone increased while elasticity decreased with patellar tendon stretching degree. In the group of individuals in training, greater stiffness and tone and lower elasticity were noted. Moreover, stiffness and tone appeared to be higher in elderly people and individuals with longer training experience. Conclusions: Mechanical loads connected with strength training result in development of adaptive changes in the patellar tendon, in the form of higher stiffness and tone, as well as lower elasticity. The MyotonPRO device is useful for quantitative assessment of the mechanical properties of patellar tendon.

Investigation of flexural performance of concrete beams with nonwoven/polymer composites versus steel-rebar reinforcement

The research investigates the unique characteristics and benefits of using nonwoven fabrics and polymer I cross-section composites in concrete beams. These materials show improved strength, flexibility, and corrosion resistance compared to conventional steel-reinforced beams, offering promising solutions for various construction applications. This study constructed an I-beam structure using a nonwoven polyester fabric/polyester composite cast in a concrete beam. Other designs included woven carbon fabric or Kevlar nonwoven fabric applied to the bottom flange of the I-beam for reinforcement. The flexural behavior of an I-beam polyester nonwoven/polyester composite with Kevlar or carbon-reinforced concrete beams was examined. The comparison between the different samples indicates that: flexural strength: the carbon sheet-reinforced sample exhibits the highest flexural strength, followed by the steel rebar and Kevlar-reinforced samples. The ductility: The steel rebar-reinforced sample shows the highest ductility, indicating better deformation capacity before failure. Carbon sheet reinforcement also provides substantial ductility. Bending stiffness: The highest bending stiffness is observed in the Kevlar-reinforced sample, suggesting a stiffer and less flexible beam. These observations highlight the trade-offs between stiffness, strength, and ductility in reinforced concrete beams. The reinforcement material choice depends on the application-specific requirements, such as the need for higher bending strength, better flexibility, or greater stiffness.

First-Principles Study of Elastic Properties and Electronic Properties of Al-Ni-Ce Ternary Intermetallic Compounds

The materials of the Al-Ni-Ce ternary system have promising application potential in additive manufacturing, and the systematic study of Al-Ni-Ce IMCs is an important part of the design and performance development of Al-Ni-Ce alloys. In this paper, the mechanical properties and electronic properties of seven major Al-Ni-Ce IMCs are studied using first-principles calculations, and the differences in their mechanical properties are discussed. The enthalpy of formation and cohesion energy of the Al-Ni-Ce IMCs showed that Ce4Al23Ni6 had the highest enthalpy of formation and cohesion energy, which were −49.57 kJ/mol and −4.47 kJ/mol, respectively. This demonstrated that all Al-Ni-Ce IMCs had excellent thermodynamic stability. The elastic modulus calculation of the Al-Ni-Ce IMCs showed that the Young’s modulus of CeAl3Ni2 was the largest at 178.15 GPa, the bulk modulus of CeAlNi4 was the largest at 125.78 GPa, and the shear modulus of CeAlNi2 was the largest at 62.53 GPa. This proved that among the Al-Ni-Ce IMCs, CeAl3Ni2 had the greatest stiffness, CeAlNi4 had the strongest resistance to uniform deformation, and CeAl3Ni2 had the strongest resistance to plastic deformation. The electronic density of states of Al-Ni-Ce IMCs was analyzed, and the results showed that the main bonding types of Al-Ni-Ce IMCs were metallic and covalent bonds. This work can provide a theoretical basis for the material design and development of the Al-Ni-Ce ternary system.

The Biomechanical Effects of Intramedullary Fixation to the Level of the Physeal Scar on Distal Tibia Fracture Stability.

The purpose of this study was to evaluate whether intramedullary nail contact with physeal scar improves construct mechanics when treating distal tibial shaft fractures. Axially unstable extra-articular distal tibia fractures were created in 30 fresh frozen cadaveric specimens (15 pairs, mean age 79 years). Specimens underwent intramedullary nailing to the level of the physeal scar locked with one or two interlocks or short of the physeal scar locked with two interlocks (reference group). Specimens were subjected to 800N of axial load for 25,000 cycles. Primary outcomes were stiffness before and after cyclic loading. Secondary outcomes were load to failure, load at 3 mm displacement, plastic deformation, and total deformation. The physeal scar with one interlock cohort demonstrated 3.8% greater stiffness before cycling ( P = 0.75) and 1.7% greater stiffness after cycling ( P = 0.86) compared with the reference group. The physeal scar with two interlocks group exhibited 0.3% greater stiffness before cycling ( P = 0.98) and 8.4% greater stiffness after cycling ( P = 0.41) in relation to the reference group. No differences were identified regarding load to failure or load at 3 mm displacement. In specimens with two interlocks, those in contact with the physeal scar demonstrated significantly less plastic ( P = 0.02) and total ( P = 0.04) deformation. Constructs ending at the physeal scar demonstrated stiffness and load to failure similar to those without physeal scar contact. Less plastic and total deformation was noted in two-interlock constructs with physeal scar contact, suggesting a possible protective effect provided by the physeal scar. These data argue that physeal scar contact may offer a small mechanical benefit in nailing distal tibia fractures, but clinical relevance remains unknown.