Explore the vast range of titles available.

This paper presents a numerical investigation of the flexural behavior of timber beams externally strengthened with carbon-fiber-reinforced polymer (CFRP) sheets. At first, the accuracy of linear elastic and elastic-plastic models in predicting the behavior of bare timber beams was compared. Then, two modeling approaches (i.e., the perfect bond method and progressive damage technique using the cohesive zone model (CZM)) were considered to simulate the interfacial behavior between FRP and timber. The models were validated against published experimental data, and the most accurate numerical procedure was identified and subsequently used for a parametric study. The length of FRP sheets varied from 50% to 100% of the total length of the beam, while different FRP layers were considered. Moreover, the effects of two strengthening configurations (i.e., FRP attached in the tensile zone only and in both the tensile and compressive zones) on load-deflection response, flexural strength, and flexural rigidity were considered. The results showed that elastic-plastic models are more accurate than linear elastic models in predicting the flexural strength and failure patterns of bare timber beams. In addition, with increasing FRP length, the increase in flexural strength ranged from 10.3% to 52.9%, while no further increase in flexural strength could be achieved beyond an effective length of 80% of the total length of the beam. Attaching the FRP to both the tensile and compressive zone was more effective in enhancing the flexural properties of the timber beam than attaching the FRP to the tensile zone only.

Considering the inelasticity properties of eccentric compression columns of reinforced concrete, a uniform equivalent rigidity reduction factor is provided in specifications. As many factors affect the elastoplastic flexural rigidity of reinforced concrete columns and owing to load increase, some concrete tension zones crack, resulting in a lower flexural rigidity of concrete columns, however, the uniform equivalent rigidity coefficient cannot reflect this change rule. To investigate the change rule of flexural rigidity of reinforced concrete columns when considering the deflection second-order effect of compression columns, by testing reinforced concrete eccentric compression columns, a trilinear calculation model is established that can reflect the change rule of elastoplastic flexural rigidity of reinforced concrete columns by analyzing the relationship between bending moment and curvature. Additionally, a formula to calculate the elastoplastic flexural rigidity reduction factor of a reinforced concrete eccentric compression column is obtained via linear regression. This formula can reflect the effects of concrete cracking, axial compression ratio, eccentricity, and reinforcement ratio on the flexural rigidity of concrete columns, as well as predict the flexural rigidity reduction of existing reinforced concrete columns.

To address the limitations of mechanical shear connectors, adhesives are used in this research as shear connectors of steel-concrete composite beams (SCCBs). Several groups of bending tests were conducted to compare the flexural behavior of bonded and mechanical SCCBs. Moreover, the results show that the failure modes of the bonded SCCBs mainly include yielding of the bottom flange of the I-beam and the cracking of the concrete bottom surface, local detachment between the two bonding surfaces and the crushing of the concrete slab at the top surface. The rigidity of the bonded SCCB is higher than that of the mechanical one. In addition, the ultimate load of the bonded SCCB connected by 6 mm thick epoxy resin is the highest, which is about 16.8% higher than that of mechanical one. Furthermore, increasing the adhesive layer’s thickness can improve the adhesive performance to a certain extent. Thus, it is suggested that the adhesive thickness should exceed 4 mm, and 6 mm is the optimal. In addition, as local detachment of the adhesive layer occurred in this test, further research can be carried out to avoid such damage.

The northern Red Sea (NRS) is considered an extended continental region that has resulted in a rift system. Gravity and bathymetry data were used to estimate the Moho depth and the elastic thickness Te of the lithosphere beneath the NRS region to characterize its flexural rigidity and understand its mechanical behavior. Focusing on the Mabahiss Deep in NRS, we analyzed the lithosphere's flexural rigidity. The observed long-wavelength positive Bouguer anomaly is attributed to crustal thinning and lithospheric mantle uplift. The crustal thickness varies from 28 km in coastal areas to 24 km beneath the axial rift, supporting a regional compensation model over the Airy model. Forward modeling suggests that the optimal model explaining the regional Bouguer anomaly is a flexural model with Te equal to 7 km, indicating a weak and irregular continental crust. The primary factor contributing to this weakness is heating activity. Given the weakened state of the crust and the ongoing extension in the region, the NRS rift could evolve into a rupture, potentially leading to the formation of oceanic crust.

Primary cilia are ubiquitous, microtubule-based organelles that play diverse roles in sensory transduction in many eukaryotic cells. They interrogate the cellular environment through chemosensing, osmosensing, and mechanosensing using receptors and ion channels in the ciliary membrane. Little is known about the mechanical and structural properties of the cilium and how these properties contribute to ciliary perception. We probed the mechanical responses of primary cilia from kidney epithelial cells [Madin–Darby canine kidney-II (MDCK-II)], which sense fluid flow in renal ducts. We found that, on manipulation with an optical trap, cilia deflect by bending along their length and pivoting around an effective hinge located below the basal body. The calculated bending rigidity indicates weak microtubule doublet coupling. Primary cilia of MDCK cells lack interdoublet dynein motors. Nevertheless, we found that the organelles display active motility. 3D tracking showed correlated fluctuations of the cilium and basal body. These angular movements seemed random but were dependent on ATP and cytoplasmic myosin-II in the cell cortex. We conclude that force generation by the actin cytoskeleton surrounding the basal body results in active ciliary movement. We speculate that actin-driven ciliary movement might tune and calibrate ciliary sensory functions. Significance A single primary cilium extends from the surface of many mammalian cells—often into an aqueous lumen, such as a kidney duct. In kidney epithelial cells, primary cilia are believed to sense fluid flow. This mechanosensory function is critical for proper organ function. Fluid flow is assumed to deflect cilia, leading to activation of transmembrane ion channels. This study defines the mechanical contributions of both bending and pivoting at the base to ciliary deflection. In addition, we report that active intracellular forces drive ciliary pivoting. This cell-directed cilia movement may be important for tuning ciliary mechanosensitivity.

Microtubules are rigid cytoskeletal filaments, and their mechanics affect cell morphology and cellular processes. For instance, microtubules for the support structures for extended morphologies, such as axons and cilia. Further, microtubules act as tension rods to pull apart chromosomes during cellular division. Unlike other cytoskeletal filaments (e.g., actin) that work as large networks, microtubules work individually or in small groups, so their individual mechanical properties are quite important to their cellular function. In this review, we explore the past work on the mechanics of individual microtubules, which have been studied for over a quarter of a century. We also present some prospective on future endeavors to determine the molecular mechanisms that control microtubule rigidity.

Background The human nail has a three‐layered structure. Although it would be useful to quantitatively evaluate the changes in deformability of the nail due to various surface treatments, few studies have been conducted. Methods The effects of two types of surface treatment—a chemically acting nail softener and a physically acting nail strengthener—on the deformability of human fingernails were investigated. The Young's modulus of each plate of the nail samples before and after softening treatment was determined by nanoindentation. The Young's modulus of the strengthener was determined by conducting a three‐point bending test on a polyethylene sheet coated with the strengthener. Results Young's modulus decreased in order from the top plate against the softening treatment time, and the structural elasticity for bending deformation (SEB) of the nail sample, which expresses the deformability against bending deformation independent of its external dimensions, decreased to 60% after 6 h of treatment. The Young's modulus of the nail strengthener was 244.5 MPa, which is less than 10% of the SEB of the nail. When the nail strengthener was applied to the nail surface, the SEB decreased to 73%, whereas the flexural rigidity increased to 117%. Conclusion Changes in nail deformability caused by various surface treatments for softening and hardening were quantitatively evaluated successfully.

Vibrations generated during the operations of machine tools, especially at high-speed operation impact several issues in machined parts such as imprecision dimensions and a poor surface finish. This prompts research and studies into alternative materials for machine tool structures to provide considerable damping performance and acceptable stiffness compared to traditional materials. This paper deals with the experimental study of a developed granite-epoxy composite, made from waste granite and local epoxy as an alternative material for machine tool structures. A waste of Egyptian Red Aswan granite was used as filler after being crushed and sifted into three sizes: fine (less than 1 mm), medium (1 to 5 mm), and coarse (5 to 8 mm). A local commercial epoxy resin kemapoxy 150 was added to a granite aggregate mixture having grain proportions 50:25:25 for fine, medium, and large, respectively. The influence of the variation of the epoxy weight ratio on the static and damping characteristics of a proposed granite–epoxy composite material was experimentally investigated. To ensure a coherent granite-epoxy composite, the required minimum resin content of 13.88 wt% was determined, and the granite/epoxy ratios were selected as 85:15 wt%, 80:20 wt%, and 75:25 wt%. The findings exhibit that the largest compressive strength of 76.8 MPa and the greatest flexural strength of 35.4 MPa is achieved at the highest epoxy weight ratio of 25%. The largest damping ratio of 0.0202 is observed at the epoxy ratio of 20% and it decreases to 0.015 when the epoxy ratio is increased to 25%. An Egyptian granite-epoxy composite, made from waste granite and local epoxy, is a promising alternative material for machine tool structures. It offers both economic and environmental benefits, along with high mechanical and damping properties compared to traditional machine tool materials.

Cotton is the most widely used natural cellulosic polymer and polyester is a synthetic polymer. The use of polyester fiber is increasing gradually day by day due to its strength and longevity, while the use of cotton fiber is decreasing due to its unavailability. At present, the use of cotton‐polyester composites is ubiquitous. This research work aims to assess the physical, mechanical and comfort properties of the woven fabric using cotton‐polyester composite yarns in a weft direction and coarser yarn count because of the use of these fabrics in the future for the denim manufacturing process. Four different samples were fabricated by using 100% cotton (10 Ne) yarn in the warp direction and 100% cotton, cotton‐polyester composite, and 100% polyester yarn in the weft direction of the fabric. Similar fabric and machine parameters were maintained for manufacturing all the samples. The samples were then tested for areal density, tensile strength, thickness, abrasion resistance and pilling, drape, flexural rigidity, and air permeability to find the optimum capability of the fabric. Physico‐mechanical properties with the proportion of increasing polyester components in fabrics improves areal density (184 to 199 g/m2), strength (almost 19 times in weft direction), drape (0.655% to 0.789%), and flexural rigidity (almost double). On the other hand, increasing comfortability properties with the proportion of cotton components in fabrics improve air permeability (139.85 to 159.58 cc/s/cm2), abrasion (only 3.036% mass loss), and pilling resistance (grading 4 after 2000 cycles). Highlights Composite yarns made of cotton and polyester provide a method of improving fabric properties for better performance. Higher proportions of cotton make clothes more breathable and less likely to pill and wear out. Polyester parts make fabrics stronger, more durable, and less likely to wear out. Cotton‐polyester composites are ideal and have potential for various textile applications. Blending natural and synthetic fibers composite allows for customized fabrics that meet specific performance needs without compromising comfort. Preparation of woven fabric using cotton‐polyester composite yarn and evaluation of physico‐mechanical and comfort.

The research is focused on the design and development of woven textile-based structural hollow composites. E-Glass and high tenacity polyester multifilament yarns were used to produce various woven constructions. Yarn produced from cotton shoddy (fibers extracted from waste textiles) was used to develop hybrid preforms. In this study, unidirectional (UD), two-dimensional (2D), and three-dimensional (3D) fabric preforms were designed and developed. Further, 3D woven spacer fabric preforms with single-layer woven cross-links having four different geometrical shapes were produced. The performance of the woven cross-linked spacer structure was compared with the sandwich structure connected with the core pile yarns (SPY). Furthermore, three different types of cotton shoddy yarn-based fabric structures were developed. The first is unidirectional (UD), the second is 2D all-waste cotton fabric, and the third is a 2D hybrid fabric with waste cotton yarn in the warp and glass multifilament yarn in the weft. The UD, 2D, and 3D woven fabric-reinforced composites were produced using the vacuum-assisted resin infusion technique. The spacer woven structures were converted to composites by inserting wooden blocks with an appropriate size and wrapped with a Teflon sheet into the hollow space before resin application. A vacuum-assisted resin infusion technique was used to produce spacer woven composites. While changing the reinforcement from chopped fibers to 3D fabric, its modulus and ductility increase substantially. It was established that the number of crossover points in the weave structures offered excellent association with the impact energy absorption and formability behavior, which are important for many applications including automobiles, wind energy, marine and aerospace. Mechanical characterization of honeycomb composites with different cell sizes, opening angles and wall lengths revealed that the specific compression energy is higher for regular honeycomb structures with smaller cell sizes and a higher number of layers, keeping constant thickness.