Reduction In Bending Strength Research Articles

Effect of calcium stearate on cellulose acetate-based mortars

The purpose of this study is to investigate the properties of cellulose acetate-based mortars with the addition of calcium stearate (CS), superplasticizer (SP) and metakaolin (MK). Previous research has shown that cellulose acetate (CA) fibers from industrial cigarette butts (CB) treatment can be incorporated into standard mortars at a rate of 1.3 wt%. CS was added in various proportions by weight (0.5, 1, 1.5 wt%), and their influence on cement hydration and microstructure was studied using various investigative techniques. The addition of CS was found to be beneficial in reducing the amount of water absorbed by CA, despite the significant absorption of these fibers. Furthermore, a CS rate of 1 wt% decreased CA-based mortar shrinkage. Additionally, 1 wt% CS improved by 18% the compressive strength of CA-based mortars manufactured with SP compared to the reference CA-mortar. CA fibers and CS seem to modify mortar microstructure by creating a plurimodal pore size distribution and reducing capillary pores. The CS addition, however, resulted in more cracks and reduced workability due to the weakening of the bond between the cement paste components. MK-mortars showed a slight 15% reduction in compressive strength and 13% reduction in bending strength; along with a 20% increase in shrinkage. By incorporating CA fibers as an additive along with CS or MK, CA-based mortars can improve some properties, including shrinkage and mechanical strength. Further, this approach offers a potential solution to CB pollution by reducing the environmental impact of this waste.

Degradation Effect of Moisture on Mechanical Properties of Kevlar/PVB Composites with TiO2 Nanoparticles

Kevlar fibers are widely used for industrial and military purposes due to their remarkable mechanical properties, such as their high tenacity and high strength-to-weight ratio. In this study, two-layered Kevlar composite specimens were impregnated with 10 wt.% poly (vinyl butyral)/ethanol solution which contained TiO2 nanoparticles as reinforcement. The concentrations of the nanoparticles were 1 wt.% or 2 wt.% with respect to the poly (vinyl butyral), PVB. The single-axial tensile test and three-point bending test of the Kevlar/PVB composites have been performed according to the ASTM D 3039 and ASTM D 790-03 standards, respectively. The tensile and bending properties of the dry and wet Kevlar/PVB composite specimens after a 56-day immersion are examined in this work. Upon the addition of the 2 wt.% TiO2 nanoparticles, the tensile strength and modulus of the dry specimens without reinforcement were increased by 39.8% and 24.3%, respectively. All the submerged specimens’ tensile and flexural property values were lower than those of the dry specimens. After comparing the wet composite specimens to their dry counterparts, the percentage decrease in tensile strength was approximately 20%. The wet Kevlar/PVB specimens with no TiO2 reinforcement showed the greatest reduction in bending strength, 61.4% less than for the dry Kevlar/PVB specimens, due to the degradation of the PVB matrix. In addition, a numerical simulation of the three-point bending test was carried out in Abaqus.

Microstructure, Mechanical Properties and Wear Behaviors of Ultrafine-Grain WC-Based Cermets with Different Binder Phases Fabricated by Spark Plasma Sintering.

In this work, to explore potential substitutions for the Co binder phase, ultrafine-grain WC-based cermets with various binder phases of Co, Ni and AlCoCrNiFeCu HEA were prepared using the SPS method. Based on SPS, WC-based cermets were fabricated at higher speed, showing fine carbide particles less than 410 μm. The microstructure, mechanical properties and wear properties were systematically evaluated. By comparison, the grain size of WC was the lowest for WC-10Co, while WC-10 HEA cermet held the coarsest WC particles. The hardness and fracture toughness of WC-10 HEA were the best among all three samples, with values of 93.2 HRA and 11.3 MP·m1/2. However, the bending strength of WC-10HEA was about 56.1% lower than that of WC-10Co, with a value of 1349.6 MPa. The reduction in bending strength is attributed to the lower density, formation of a newly Cr-Al rich phase and coarser WC grains. In dry sliding wear conditions, WC-10 HEA showed the lowest wear rate (0.98 × 10-6 mm3/(N·m)) and coefficient of friction (0.19), indicating the best wear resistance performance. This reveals that WC-based cermet with a HEA binder phase has superior wear performance due to the higher hardness and good self-lubricating effect of the wear products.

Biomechanical evaluation of variable angle locking systems. A micro-CT analysis.

Formerly poor bone stock and periprosthetic fractures used to jeopardize monaxial constructs. Polyaxial locking screws have substantially supported those particular fixation constructs. However, those systems rely on complex alignment between the screw head and the plate hole. This study aimed to investigate the mechanical properties of several polyaxial systems and to correlate these parameters with the screw head and the plate hole engagement. Polyaxial locking systems were tested with screws inserted into the corresponding plates at various angles (0°, 5°, 10°, 15°). A micro-CT scan of the plate-hole and screw-head interface with the quantification of average thread engagement was performed before destructive tests. The screw-plate interface of each system was tested in a cantilever bending setup. Representative screws and plates were also examined by SEM. The standard insertion at 0° sustained the greatest maximum bending strength in all analyzed systems. Point-loading thread-in and cut-in screws inserted off-axis showed a significant reduction in bending strength (p<0.001) (p=0.041) (p<0.001). In contrast, locking cap screws maintained similar bending strength with disregard to the angle of insertion (p<0.4849). A micro-CT analysis confirmed that the average thread engagement of point-loading thread-in, cut-in and locking-cap screws was significantly reduced when placed off-axis (p=0.005) (p<0.001) (p=0.002) (p<0.001). The locking-cap mechanisms maintained the highest average thread engagement among all analyzed systems. The mechanical performance of polyaxial locking plates usually comes at the price of reduced bending strength. Surgeons should limit polyaxial insertions depending on the particular system's characteristics.

Effect of CRT glass and TiO2 as a replacement for fine aggregate and cement on properties of pervious concrete paving flags

In the subject of pavement engineering, real-life conditions must be recreated using carefully selected materials and techniques. This is especially true for the evaluation of non-standard, waste materials prior to their usage in pavement structure. The objective of this study is to ascertain the effects of partial cement replacement with cost-effective micro TiO2 and full fine aggregate replacement with CRT (cathode ray tube) glass on the characteristics of pervious concrete paving flags and their capacity to reduce pollutants carried by rainwater. Within the research, standard test methods for paving flags characterisation are used (EN 1339) along with some new and innovative research approaches to environmental impact assessment simulating real-life conditions. Results indicate a high influence of used materials on pervious concrete properties, both separately and combined. When applied separately, CRT glass and TiO2 exhibited reduced bending strength; however, when put together, bending strength improved. TiO2 decreased the unpolished slip resistance value (USRV) of flags while CRT glass reduced wear resistance. Although the infiltration rate was greatly improved, neither component had a substantial impact on water absorption. Environmental impact assessment results support the safety of use of both materials in paving flags. Finally, by using CRT glass and micro TiO2, innovative, environmentally friendly, and cost-effective paving product can be produced for sustainable development improvement within pavement engineering.

Physical, Mechanical, and Biological Properties of PMMA-Based Composite Bone Cement Containing Silver-Doped Bioactive and Antibacterial Glass Particles with Different Particles Sizes.

In the present work, antibacterial composite bone cement was designed by introducing a bioactive and antibacterial glass into a commercial formulation. The effect of glass particles' addition on the curing parameters of the polymeric matrix was evaluated; moreover, the influence of the glass particle size on the glass dispersion, compressive and bending strength, bioactivity, and antibacterial effect was estimated. The results evidence a delay in the polymerization kinetics of the composite cement, which nevertheless complies with the requirements of the ISO standard. Morphological characterization provides evidence of good dispersion of the glass in the polymeric matrix and its exposition on the cement surface. The different glass grain sizes do not affect the composites' bioactivity and compressive strength, while a slight reduction in bending strength was observed for samples containing glass powders with greater dimensions. The size of the glass particles also appears to have an effect on the antibacterial properties, since the composites containing larger glass particles do not produce an inhibition halo towards the S. aureus strain. The obtained results demonstrate that, by carefully tailoring the glass amount and size, a multifunctional device for artificial joint fixing, temporary prostheses, or spinal surgery can be obtained.

Study on Physical Properties of Desulfurized Electrolytic Manganese Residue Cement and Properties of Mortar.

The desulfurized electrolytic manganese residue (DMR) was prepared by calcination and desulfurization of industrial waste electrolytic manganese residue, and the original DMR was ground to prepare DMR fine powder (GDMR) with specific surface areas of 383 m2/kg, 428 m2/kg, and 629 m2/kg. The effects of particle fineness and content of GDMR (GDMR content=0%, 10%, 20%, 30%) on the physical properties of cement and the mechanical properties of mortar were studied. After that, the leachability of heavy metal ions was tested, and the hydration products of GDMR cement were analyzed using XRD and SEM. The results show that the addition of GDMR can regulate the fluidity and water requirement for the normal consistency of cement, delay the hydration process of cement, increase the initial setting and final setting time of cement, and reduce the strength of cement mortar, especially the strength of early age mortar. As the fineness of GDMR increases, the reduction of bending strength and compressive strength decreases, and the activity index increases. The content of GDMR has a significant effect on short-term strength. With the increase in GDMR content, the strength reduction degree becomes higher and the activity index decreases. When the content of GDMR was 30%, the 3D compressive strength and bending strength decreased by 33.1% and 29%. When the content of GDMR in cement is less than 20%, the maximum limit of leachable heavy metal content in cement clinker can be met.

Skeletal phenotypes in secreted frizzled-related protein 4 gene knockout mice mimic skeletal architectural abnormalities in subjects with Pyle’s disease from SFRP4 mutations

Mutations in SFRP4 cause Pyle’s bone disease with wide metaphyses and increased skeletal fragility. The WNT signaling pathway plays important roles in determining skeletal architecture and SFRP4 is a secreted Frizzled decoy receptor that inhibits WNT signaling. Seven cohorts of male and female Sfrp4 gene knockout mice, examined through 2 years of age, had a normal lifespan but showed cortical and trabecular bone phenotypes. Mimicking human Erlenmeyer flask deformities, bone cross-sectional areas were elevated 2-fold in the distal femur and proximal tibia but only 30% in femur and tibia shafts. Reduced cortical bone thickness was observed in the vertebral body, midshaft femur and distal tibia. Elevated trabecular bone mass and numbers were observed in the vertebral body, distal femur metaphysis and proximal tibia metaphysis. Midshaft femurs retained extensive trabecular bone through 2 years of age. Vertebral bodies had increased compressive strength, but femur shafts had reduced bending strength. Trabecular, but not cortical, bone parameters in heterozygous Sfrp4 mice were modestly affected. Ovariectomy resulted in similar declines in both cortical and trabecular bone mass in wild-type and Sfrp4 KO mice. SFRP4 is critical for metaphyseal bone modeling involved in determining bone width. Sfrp4 KO mice show similar skeletal architecture and bone fragility deficits observed in patients with Pyle’s disease with SFRP4 mutations.

Mathematical modelling, multi-objective optimization, and compliance reliability of paper-derived eco-composites.

The quest for cost-effective and thermal efficient structural materials onto beating the high cost of construction is gaining more attention among researchers. This study focused on the blending of cement and sand with waste paper pulp into cost-effective structural materials. The composites were prepared in four mix groups with each containing a fixed amount of sand at 5, 10, 15, and 20 wt.% (by weight of pulp). Cement was varied at 10, 20, 30, and 40 wt.%in each group, and curing was done for 28days. Properties evaluated are compressive, bending, and splitting strengths. It was observed that increasing cement and sand contents enhanced strengths; howbeit, the blend of 30 wt.% cement/15 wt.% sand resulted in a reduction in bending strength even as 30 wt.% cement/20 wt.% sand engendered a decrease in bending and splitting strength. The microstructural features showed that inherent fibers of the pulp were well bonded with hydration products and sand content yielding good performance in the composites. The optimization procedure carried out depicted a combination of 35.27% cement and 20% sand as the optimum composition. Experimental outcomes were modelled for the purpose of prediction of responses. The models were confirmed statistically fitshowing how varying cement content affected strength responses at fixed sand proportion. ANOVA affirmed the significant contribution of cement and sand on the strength responses. Compliance reliability was observed to be dependent on the interactive pattern between cement and sand. Going by the standard prescription for the strength properties, cement and sand content of 35.27 and sand 20 wt.% satisfied all strength requirements for low-cost construction having a compliance reliability of 1.31.

Manipulation of the granular fluid-structure interaction via sliding coating layers

The use of sliding coating layers on structures is investigated as an approach to manipulate the transfer of momentum during the impact of granular matter with rigid and deformable structures. We first report an experimental investigation of the momentum transfer into rigid stationary targets with fixed and sliding coating layer impacted by high velocity granular slugs. Friction between the impacting granular particles and the target surface enhances the momentum transfer during the interaction with the target. By introducing a sliding coating layer with a lubricated target surface-coating interface, the momentum transfer is reduced: the coating slides on the target surface dragged along by friction between the coating and the particles but, the low friction between the coating and the target reduces the transfer of frictional forces into the target. Coupled discrete element and Lagrangian finite element simulations with rod-shaped granular particles are shown to capture the measurements with high fidelity. This numerical approach is then used to investigate the use of sliding coatings on deformable edge-clamped plates. Introduction of a coating layer while keeping the total mass of the plate constant, reduces the thickness of the plates and this in turn reduces their bending strength. The consequence is that momentum transfer reductions are lost as a result of the reduced bending strength and the minimum plate deflection is attained when no coating layer is present. We thus conclude that sliding coating layers can result in momentum transfer reductions when used on relatively rigid targets but result in a degradation of impact resistance performance when used on highly deformable structures.

Snap-buckling and failure studies on CFRP laminate with an embedded circular delamination under flexural loading

Carbon fiber reinforced polymer (CFRP) laminate having an embedded delamination may exhibit snap-buckling phenomenon under flexural loading, and its influence on the bending strength reduction and associated laminate failure mechanisms need to be understood for efficient structural design. In this paper, a multi-angle CFRP beam specimen with an embedded circular delamination is studied under four-point bending. Experimental techniques like digital image correlation and acoustic emission are used to evaluate the bending moment and strain at which the snap-buckling of sub-laminate occurs and the subsequent intra/inter-laminar failure propagation in the beam specimen. Detailed fractography studies are carried out on the post-failed specimens to get more insights on the various damage modes and failure mechanisms. Subsequently, a three-dimensional finite element framework is proposed for simulating the snap-buckling of the sub-laminate and the associated damage modes occurring within the laminate. Both cohesive zone and continuum damage mechanics models are used to simulate the delamination and fiber/matrix failures in the laminate, respectively. The sub-laminate buckling strain and damage evolution results predicted by the numerical simulations are compared with the experimental observations. Finally, the developed numerical model is used to understand the effect of various parameters like delamination size, shape, position, and stacking sequence on the flexural response of the delaminated laminate. The parametric studies provides new insights on the snap-buckling effect on failure response of the delaminated composite beam under flexural loading.

An Innovative Approach to Simulate Biocorrosion in Concrete Pipes

Abstract Concrete corrosion in wastewater concrete pipes is mainly caused by the diffusion of aggressive solutions and in situ production of sulfuric acid by sulfur oxidizing microorganisms, which affect the physicochemical properties of concrete. In this study, a novel pilot-scale experimental setup was designed to replicate conditions in sewage systems as well as the bacterial-induced corrosion process in concrete pipes. The reliability of this test was evaluated by conducting a flexural strength test on arch-shaped cement mortar specimens over a 6-month period. Quantitative assessments of the properties were carried out over the 6-month period, and the average corrosion rate of 3 mm/y with 73 % reduction in bending strength (of the initial strength) and an average weight loss of 15 % was observed in cement-based mortar specimens. The proposed methodology and the results provide a better understanding of the biocorrosion process and quantitative information on the performance and effectiveness of different pipe/coating materials, which is necessary in evaluating concrete pipe’s durability.

Topographical mapping of the mechanical characteristics of the human neurocranium considering the role of individual layers

The site-dependent load-deformation behavior of the human neurocranium and the load dissipation within the three-layered composite is not well understood. This study mechanically investigated 257 human frontal, temporal, parietal and occipital neurocranial bone samples at an age range of 2 to 94 years, using three-point bending tests. Samples were tested as full-thickness three-layered composites, as well as separated with both diploë attached and removed. Right temporal samples were the thinnest samples of all tested regions (median < 5 mm; p < 0.001) and withstood lowest failure loads (median < 762 N; p < 0.001). Outer tables were thicker and showed higher failure loads (median 2.4 mm; median 264 N) than inner tables (median 1.7 mm, p < 0.001; median 132 N, p = 0.003). The presence of diploë attached to outer and inner tables led to a significant reduction in bending strength (with diploë: median < 60 MPa; without diploë: median > 90 MPa, p < 0.001). Composites (r = 0.243, p = 0.011) and inner tables with attached diploë (r = 0.214, p = 0.032) revealed positive correlations between sample thickness and age. The three-layered composite is four times more load-resistant compared to the outer table and eight times more compared to the inner table.

Effect of bending on steel wire rope sling breaking load: Modelling and experimental insights

Behaviour of steel wire rope slings when they are bent over small diameter rigid bodies, e.g. pins, has been studied to determine the reduction of the slings’ static strength due to bending. For this purpose, the Papailiou model was extended by adding plasticity in the material behaviour and expanding the friction model from a single layer strand to multiple layers and multiple strands. It was shown that in addition to the diameter ratio, the sling bending strength reduction factor depends on the friction between the wires in the rope and the geometry of the rope, namely the lay angle and the number of wires in the rope. The actual breaking load was obtained from experiments on small and full-scale rope slings at rather low ratios of the pin to rope diameter and compared with modelling results and the sling capacity reduction factor associated with bending prescribed by guidelines for lifting operations.

The use of coffee bean post-extraction residues as a filler in plywood technology

The use of coffee bean post-extraction residues as a filler in plywood technology. The aim of the research was to determine the influence of post-extraction coffee beans used as a glue mass filler for the plywood glue joint on their selected mechanical and physical features. In the scope of the research the plywood of different content of post-extraction coffee beans in glue mass have been produced in laboratory conditions, as well, as reference material, the plywood with wheat flour as a glue mass filler have been made. The investigated material has been tested according to different features, including measurement of the plywood density profile, static bending strength and modulus of elasticity, shear strength, water absorption, as well as resistance to axial removal of screws. The significant reduction of bending strength, modulus of elasticity when bending, shear strength, as well as resistance to axial removal of screws has been found for samples with coffee bean residues, when referred to reference plywood. Also, decreasing penetration depth of coffee residues filled glue mass has been noted, with the coffee bean post-extraction residues content raise.

Influence of homogenization models on size-dependent nonlinear bending and postbuckling of bi-directional functionally graded micro/nano-beams

In this work, different homogenization schemes are employed to analyze both size-dependent postbuckling and nonlinear bending behavior of micro/nano-beams, made of a bi-directional functionally graded material (BDFGM), under external axial compression and distributed load. To such different homogenization models, including Reuss, Voigt, Mori-Tanaka, and Hashin–Shtrikman bounds schemes, together with nonlocal strain gradient elasticity theory are adopted within the framework of refined exponential shear deformation beam theory, to develop a comprehensive size-dependent BDFGM beam model. Deviation of associated physical neutral plane, from mid-plane counterpart, is also considered. Nonlocal strain gradient load-deflection responses of BDFGM micro/nano-beam are obtained by numerical solution methodology for both nonlinear bending and postbuckling behaviors corresponding to different values of the lateral and longitudinal material property indices and various small scale parameters. We observed that by decreasing the values of material property gradient indices, associated with BDFGM, difference between the estimations of various homogenization schemes is raised. We also indicated that increasing maximum deflection, decreasing the significance of nonlocal size effect on the bending strength of BDFGM micro/nano-beams, whereas strain gradient size effect becomes more important. In addition, we found that at lower material property gradient indices, bending strength reduction in BDFGM micro/nano-beams, causes by the axial gradient property is higher than lateral gradient property. At higher values of these indices, however, the trend is opposite.

Incorporation effect of olive pomace on the properties of tubular membranes

This study aims at investigating the use of abundant materials such as clay and pomace olive in the preparation of tubular membranes. The use of olive pomace as a porosity agent produces a porous clay tubular membrane with controlled microstructure (porosity and pore size). The raw materials were characterized by physicochemical methods, namely X-ray fluorescence, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TGA/DTA) and scanning electron microscopy (SEM). These techniques show that the studied clay consists essentially of quartz; calcite and kaolinite. Tubular membranes made from a mixture of clay / X% (0, 4, 6, 8, 10 and 12 %) by weight of olive pomace were prepared by extrusion and sintered at different temperatures (700, 800, 900 and 1000 °C).The results obtained show that the sintered tubular membranes at 1000 °C are characterized by range value of shrinkage is 0.75–3.94 %, apparent porosity of 5.5–41 % and the reduced bending strength from 23.26 to 7 MPa depending on the olive pomace content. The pore structure was analyzed by SEM and the chemical resistance tests were performed in a sodium hydroxide solution and a nitric acid solution; they have better chemical resistance to alkalis but less resistance to acids. These results allow to conclude that the tubular membranes containing 8 % of olive pomace are promising porous ceramic structure for wastewaters filtration applications due to their excellent properties.

Porous Si3N4 ceramics with hierarchical pore structures prepared by gelcasting using DMAA as gelling agent and PS as pore–forming agent

Porous Si3N4 ceramics with bimodal hierarchical pore structures were fabricated through combining aqueous gelcasting and adding pore–forming agent method wherein a low–toxic monomer N, N–dimethylacrylamide (DMAA) and spherical pore–forming agent polystyrene sphere (PS) were respectively applied. The results demonstrated that PS size and content played an important function in regulating microstructure and properties of slurries, green and sintered bodies. The slurry viscosity increased sharply with the introduction of fine PS and reached a maximum of 1.78 Pa⋅s when adopting 7 wt% PS with d50 = 2.51 μm. Fine PS addition caused higher porosity in green bodies than coarse one, resulting in a significant reduction in bending strength from 28.50 MPa to 11.50 MPa, however, overall, demonstrating high enough strength for mechanical processing. The formed spherical pores from PS in ceramic matrix facilitated high porosity and highly crosslinked microstructure, thus contributing to lowering dielectric constant and loss. With PS size increasing, the dominant role in mechanical properties was transferred from porosity to microstructure, whilst dielectric properties were merely controlled by porosity and spherical pores. The porosity, bending strength, fracture toughness, dielectric constant and loss at 15 GHz varied in ranges of 36.34–52.91%, 258.42–101.21 MPa, 6.02–3.38 MPa⋅m1/2, 4.29–2.98 and 1.48–1.18 × 10−3, respectively, displaying an excellent comprehensive properties.

A probabilistic approach to the evaluation of the bending strength of timber beams with integration of data from on-site tests

A probabilistic method to evaluate the bending strength of maritime pine beams (Pinus pinaster Aiton) was explored. The beams were subjected to an experimental campaign that started by allocating them to a visual strength grade and segmenting them lengthwise into clear wood and weak zones. The weak zones are associated with a reduced bending strength that is caused by the presence of knots or grain deviation. Non-and semi-destructive techniques were used to gather information regarding the physical and mechanical properties of the clear wood. Bending tests were carried out until failure to determine the strength of the beams. The method to predict the structural behaviour of the elements was developed under a probabilistic framework based on Monte Carlo simulations in which the reference properties of the beams were assigned randomly based on their probability distributions. The results show that the characteristic strength values assigned to the timber pieces after strength grading only frequently underestimate their strength and that the probabilistic method applied could be used to safely explore the capacity reserve of the timber elements.

Microstructure–mechanical properties correlation in spark plasma sintered Ti–4.8 wt.% TiB2 composites

Abstract Ti TiB2 composites were fabricated from powder mixtures via spark plasma sintering method. Mechanical behavior of the sintered composites were then investigated via both routine and nanoindentation methods. Results indicated a significant increase in ultimate tensile strength and hardness of the composite, when the sintering temperature is raised. Besides common increase in the relative density of the composite, such a behavior was also attributed to the higher amounts of in-situ formed TiB whiskers. The remarkable reduction in bending strength is probably due to limited formability of unreacted coarse TiB2 particles and agglomerated in-situ formed phases. Such findings were then discussed in detail, based on the nanomechanical behavior of the primary and in-situ formed phases in Ti TiB2 composite sintered at 1200 °C. It was concluded that the superiority of mechanical properties in the mentioned sample may be due to high strength primary and in-situ formed reinforcements distributed homogenously in the matrix. Such reinforcement also provided high strength interfaces, according to interfacial nanoindentation approaches.