Deflection Mechanism Research Articles

Mechanical properties and crack deflection mechanisms in 3D-Printed porous geopolymers with cellular structures

ABSTRACT This study focuses on using helical design patterns via 3D printing to create geopolymer with a highly porous structure in order to enhance their strength-density relationship and fracture properties. In this regard, to create porous structure, different pitch angles and infill densities were chosen, and mechanical and fracture properties were examined. The results of mechanical strength tests revealed that while the pitch angle does not significantly affect compressive strength, flexural strength is improved by implementing a low pitch angle helical structure, which leads to the strength-density relationship improvement. Additionally, the work of fracture results demonstrated an enhancement for samples with low pitch angles, such as α15° and α30°, compared to cast and non-directional printed samples. The digital image correlation and fracture surface analysis showed several fracture mechanisms, predominantly crack deflection and twisting, in samples with low pitch angles, which contributes to the observed improvements in the work of fracture.

Influence of silane and polyethylene glycol functionalization of boron nitride nanosheets on mechanical and thermal properties of epoxy nanocomposites: Machine and deep learning forecasting

AbstractThe influence of hexagonal boron nitride (hBN) nanosheet surface modification on epoxy nanocomposites' mechanical and thermal properties were investigated. An innovative approach was developed for synthesizing hBN nanosheets (hBNNs) via optimized ultrasonic‐assisted liquid‐phase exfoliation (UALPE), followed by functionalization with 3‐aminopropyltriethoxysilane (APTS) and polyethylene glycol (PEG600) for nanocomposite preparation. Compared to unmodified epoxy, nanocomposites containing 0.3 wt% of pristine hBNNs exhibited significant enhancements in flexural strength (125.28 MPa) and tensile strength (53.35 MPa), with respective increases of 40.57% and 43.23%. PEG‐hBNNs improved flexural and tensile strengths to 136.83 and 58.57 MPa, respectively. The most substantial enhancements were observed with APTS‐hBNNs, yielding flexural and tensile strengths of 174.13 and 63.53 MPa, reflecting increases of 95.37% and 70.50%, attributed to better interfacial interactions and a more effective crack deflection mechanism. Thermal stability analyses revealed superior performance of modified hBNNs epoxy nanocomposites, increasing 8.2°C and 6.3°C at 50 wt% degradation as compared to the unmodified system, owing to enhanced physical barrier properties. Structural and morphological analyses validated the successful exfoliation and modification of hBNNs. Predictive models utilizing machine and deep learning (DL) techniques, particularly DL with the adaptive moment estimation (ADAM) optimizer, effectively forecasted mechanical properties, achieving high R2 values.HIGHLIGHTS 0.3 wt% modified hBNNs epoxy nanocomposite showed the highest mechanical strength Improved thermal stability of epoxy nanocomposite by modification of hBNNs Improved crack deflection mechanism in the presence of surface‐modified hBNNs Deep learning with ADAM optimizer showed high R2 and low prediction loss

Hydrocarbon trade deflection and supply‑chain trade restructuring under sanctions imposed during theRussia–Ukraine conflict

In response to international sanctions, Russia has restructured its hydrocarbon commerce through trade deflection, redirecting exports from sanctioning to non-sanctioning countries. Theresearch aimed to analyze hydrocarbon trade deflection under theRussia–Ukraine conflict within thecontext of theChina–Russia Strategic Partnership and BRICS, and to assess therestructuring of Russia’s crude oil and natural gas supply chains from 2020 to 2023. Two questions were addressed: Whether trade deflection shifted towards non-sanctioning countries, including China and other BRICS countries; whether Russia’s oil and gas supply chains were restructured towards these regions? Design incorporates themethod developed by theauthor which generates and utilizes an integrated database of Bill of Lading and export data to analyze supply-chain trade restructuring, identifying specific shifts in trade flows by product, country, and enterprises. Findings reflected that after sanctions were imposed in early 2022, Russian hydrocarbon exports to sanctioning countries declined sharply, while exports to non-sanctioning countries, particularly China and India, increased significantly. Findings demonstrate theeffectiveness of trade deflection as a strategic response to sanctions. This strategy has mitigated theadverse impacts on Russian oil and gas industry, with significant increases in exports to China and India. TheComprehensive Strategic Partnership with China has helped secure a substantial market for Russian crude oil and increased China’s energy security. This study enhances understanding of trade deflection mechanisms and provides a framework for analyzing theinterplay between international trade, geopolitical strategies, and economic resilience. Geopolitical alliances and trade partnerships have ensured ­resilience and continuity in global trade. This shift indicates strategic diversification towards Asian markets and increased Central Asian involvement. BRICS engagement has provided Russia with a platform to advocate for energy security and challenge Western dominance in global energy governance. Future research should explore other supply-chain components and analyze trade within theBRICS+ group and Russia–China bilateral trade.

Effect of grain morphology and interface on the toughness of nacre-like aluminas

Ceramic composites that are both tough and strong are needed for extreme environments, ranging from aerospace and nuclear, to medical applications. Bioinspired ceramic composites tackle this challenge by mimicking tough natural structures. Nacre-like aluminas (NLAs) are ceramics processed using advanced colloidal techniques to obtain a microstructure resembling the brick-and-mortar structure of nacre. NLAs can achieve flexural strengths up to 600 MPa and fracture toughnesses ranging from 5 MPa.m1/2 up to 16 MPa.m1/2 after crack propagation. These high values mainly rely on deflection mechanisms; these can operate at temperatures up to 1200°C and under impact testing. The fracture properties have been found to be highly dependent on the mortar composition and processing technique used. However, we still don't know how far we can extend the structural properties of NLAs by changing their mortar strength and brick morphology. In this study, we combine mode I wedge splitting testing and in situ synchrotron X-ray microtomography of mixed-mode SENB fracture testing along with a kinked crack analytical formulation to study the microstructure-properties relationship in NLAs having two mortar compositions/morphologies. We compare the toughness values obtained in mode I and II with deflection models and study the effect of mode-mixity on the NLA toughness. Our findings show the grain morphology strongly influences the fracture behaviour, with the longer grain material showing longer stable crack deflection which could be further optimised going forwards. By contrast the mortar properties which provide deflection and local toughening mechanisms may be nearing their optimal strength.

Track Deflection of Typhoon Chanthu (2021) near Taiwan as Investigated Using a High-Resolution Global Model

Abstract The Model for Prediction Across Scales (MPAS) with variable resolution (60-15-1 km) is used to investigate the track deflection of Typhoon Chanthu (2021) near Taiwan. Chanthu exhibited a rightward track deflection as it approached southeast Taiwan and underwent a leftward deflection when moving northward offshore of northeast Taiwan. Numerical experiments are conducted to identify the physical processes for the track deflection. The rightward deflection of the northbound typhoon is induced by the recirculating flow resulting from the effect of Taiwan’s topography. A wavenumber-one potential vorticity (PV) budget analysis indicates that horizontal PV advection dominates the earlier rightward deflection, while the later leftward deflection is mainly in response to stronger asymmetric cloud heating at low levels at the offshore quadrant of the typhoon. A pair of cyclonic and anticyclonic gyres in the wavenumber-one flow difference is induced by Taiwan’s topography. These rotate counterclockwise to drive the track deflection, most often in westbound typhoons. Idealized WRF simulations are also conducted to explore the track deflection under different northbound conditions. The simulations confirm the track deflection mechanism with similar PV dynamics to the MPAS simulations for Chanthu and illustrate the variabilities of the track deflection for different steering conditions and vortex origins. The rightward deflection of northbound typhoons is essentially determined by a reduced ratio of R/LE where R is the vortex size and LE is the effective length of the mountain range.

Mesoscopic simulations of a fracture process in reinforced concrete beam in bending using a 2D coupled DEM/micro-CT approach

In this study, a complex fracture process in a short rectangular concrete (RC) beam reinforced by one longitudinal bar (without vertical reinforcement) and subjected to quasi-static three-point bending was numerically explored in 2D conditions. A critical diagonal shear crack in the beam caused it to fail during the experiment. The numerical simulations were conducted with a classical particle discrete element method (DEM). A three-phase concrete description (aggregate, mortar, and interfacial transitional zones (ITZs) around aggregates) accounted for the concrete heterogeneity. In mesoscopic DEM calculations based on a 2D X-ray CT scan, the actual shape and placement of aggregate particles in concrete were taken for granted. In the study, the steel bar with ribs was replicated. ITZ was also assumed between the bar and mortar. Without imposing any bond-slip law, a geometrical bar/concrete interface condition was explicitly considered. The focus was on the force–deflection diagram, fracture process, contact forces, and stresses along the bar. A good level of agreement about the evolution of the vertical force versus the deflection and failure mechanism was attained between DEM analyses and in-house laboratory tests despite simplified 2D conditions. A strong effect of concrete mesostructure on the crack pattern was found.

The configuration design of cross-linked CNT networks to realize heterostructure in Cu matrix composite towards prominent mechanical-electrical property synergy

Developing reticular reinforcement and heterogeneous microstructure remains persistent challenges in one-dimensional carbon nanotube (CNT)-Cu system. We herein fabricated dual-heterostructured Cu composite by diazotizing CNT into cross-linked (CL) networks and achieving bimodal grain distribution. The CL-CNT networks uniformly dispersed in Cu matrix, forming strong C–N/O–Cu covalent bonds at the interfaces and effectively retarding grain growth to create ultra-fine grain (UFG) regions around them. The CL-CNT networks/UFG regions, along with the surrounding coarse grain (CG) regions, resulted in a remarkable synergy between mechanical and electrical properties within the composite. Systematic analysis indicates that CL-CNT network acts as a whole to bear loading, remarkably enhances the load-transfer strengthening and promotes the dislocation accumulation around the interface. Meanwhile, hetero-deformation between “hard” CL-CNT networks/UFG regions and “soft” CG regions lead to extra-strengthening and hardening associated with strain partitioning, generation of geometrically necessary dislocation (GND) and strain delocalization. In-situ tensile test further reveals that CL-CNT/Cu with dual-heterostructure introduces the extra-toughening via crack bridging and deflection mechanisms. Besides, CL-CNT network with the robust interface is considered to reduce the interfacial inelastic scattering and provide additional paths for electron transport, accounting for the high electrical conductivity. This work highlights the importance of configuration design of reinforcement in tailoring heterostructured metal matrix composites (MMCs) with outstanding comprehensive performance.

Conformally Decambered Natural Laminar Flow Blades for Vertical-Axis Wind Turbines

A two-element natural laminar flow airfoil—commonly used on medium-altitude, long-endurance, unmanned air vehicles—was conformally decambered for application on a two-bladed, H-rotor, vertical-axis wind turbine. Blade kinematics were used to determine the virtual camber line, which was then used to conformally map the original profile onto the chord line. Both decambered and original blade profiles were evaluated experimentally using large chord-radius ratios (0.6 and 0.75) that exploited dynamic stall to produce the driving torque. Decambered blades showed substantially greater power and torque coefficients than the original blades, up to 60 and 27%, respectively, which represents the first experimental validation of conformal decambering. Relatively large peak power coefficients of 0.28 were attained, despite maximum chord-based Reynolds numbers being less than 2×105. Depending upon the chord-radius ratio, either light or deep dynamic stall occurred in the second upstream quadrant, and the flap flow remained attached virtually throughout. In contrast, on the original profiles, massive separation was observed on the blades, and the flap flow remained separated due to assumed outer surface flow separation. Future research should consider surface pressure and flowfield measurements, significantly higher Reynolds numbers, and variable intracycle flap deflection mechanisms to optimize performance and minimize unsteady loads.

Compressive behavior of hierarchical brick‐and‐mortar structures obtained by fused deposition modeling

AbstractNature is a never‐ending fount of inspiration to solve engineering problems. In light of this, the goal of this work is to propose and study structures that mimic materials found in nature, more specifically nacre. These structures were designed to be manufactured using fused deposition modeling since this is an accessible way to reproduce complex geometries. The manufactured biomimetic materials were tested in uniaxial compression in two different directions. In addition, an elastoplastic numerical analysis was used to better understand the compressive behavior of the studied structures. The comparison between experimental and numerical analysis reveals that the overall behavior results from two competing mechanisms, that is, an increase in stiffness due to strain‐hardening and a stiffness decay promoted by damage propagation. Moreover, it was possible to see that the structures continue to bear load while they retain the structural integrity, which is dominated by the crushing strength of each type of structure.Highlights Additive manufactured nacre‐inspired structures were proposed. Influence of different geometries in the compressive behavior was assessed. Behavior was linked to competition between strain‐hardening and damage growth. Load‐bearing capacity was related to the structural integrity of elements. The crack deflection mechanism was identified in some specimens.

Effects of the metal-ceramic continuous transition region on the tensile strength and crack propagation behavior of 8YSZ/CoNiCrAlY coating

In this study, micro-8YSZ/CoNiCrAlY continuous transition coatings and double-layer coatings were prepared by atmospheric plasma spraying (APS) technology. The microhardness of the continuous transition coating changed in a manner consistent with the microstructure, and the average bond strength of the continuous transition coating was 1.40 times higher than that of the double-layer coating, and conducted an in-depth study of the role of the continuous transition zone in the coating stretching process. During the stretching process, not only the ceramic coating breaks, but also the continuous transition zone breaks. In the continuous transition zone, cracks undergo deflection and bridging during initiation and propagation. In addition, the existence of approximately saddle-shaped CoNiCrAlY metal splat was also found. The approximately saddle-shaped metal splat absorbs and dissipates energy by deforming during the stretching process. In summary, the interlocking structure, crack deflection and bridging mechanisms in the continuous transition zone, and the deformation of the approximately saddle-shaped metal splat synergistically improve the bonding strength of the coating.

Microstructure, mechanical properties, and bone cell interactions of ZTA composites reinforced with BN

Due to their remarkable mechanical properties and biocompatibility, zirconia toughened alumina (ZTA) based composites are preferred materials for dental and orthopedic uses. This study focuses on the production and characterization of hexagonal boron nitride (BN) containing ZTA ceramics. To achieve this, we formulated composite systems with a composition of 70Al2O3-(30-x)YSZ-(x)BN (in vol%, where x ranges from 1 to 5). These mixtures were densified via spark plasma sintering (SPS) at a temperature of 1350 °C under a pressure of 40 MPa, with a dwell time of 5 min. The densification, resulting microstructure, and mechanical properties, including Vickers hardness and indentation fracture toughness, were thoroughly examined. All ZTA-BN composites achieved sintering densities exceeding 98.5% of their theoretical values. Incorporating BNs into ZTA composites increased fracture toughness by ∼55% while maintaining Vickers hardness values. Notably, crack deflection mechanism played a dominant role in toughening, particularly for the composite containing 3 vol% BNs. Furthermore, in vitro biocompatibility assessment of the YZTAB3 sample demonstrated that the composite had no cytotoxic effects towards human bone cells, indicating its potential for biomedical applications.

Excellent combination of strength and elongation of TZM alloys achieved by c-ZrO2 and single cross rolling

In this study, new TZM-xZrO2 (x = 0, 0.5, 1, 1.5) (wt%) alloys were designed by powder metallurgy solid-solid mixing method combined with single cross rolling. The results show that c-ZrO2 in TZM alloys was mainly spherical, and the average size of c-ZrO2 particle increases gradually from 1.28 μm to 1.71 μm with the increase of its content. c-ZrO2 can effectively refine the molybdenum grain and adsorb the free brittle element O in grain boundaries in the form of TiO2 layer. The interface was composed of three phase: c-ZrO2, Y2O3 and TiO2, with the presence of [0−11] c-ZrO2 ǁ [−11−2] Y2O3 ǁ [−10−3] TiO2 crystal relationship. The rolled plates mainly exist 〈100〉//ND and 〈111〉//ND two kinds of grain orientation, the addition of c-ZrO2 particles promote <100>//ND orientation ratio, thus weakening the texture strength (maximum pole density value from 8.34 to 5.39), conducive to the improvement of plasticity. When the c-ZrO2 content was 0.5 wt%, the best performance was achieved, with good strength and elongation (ultimate tensile strength: 958 MPa; Elongation: 17.3%), showing excellent strength and elongation product (16.6 GPa·%), 31% higher than TZM alloy, better than most reported molybdenum alloys. With the further increase of c-ZrO2 content, the particles gradually coarsened, the hindering effect on dislocations was weakened, and it was easy to become the nucleation site of main cracks, resulting in the decrease of strength and plasticity. Fine grain strengthening and dislocation strengthening were important factors to improve the strength. The excellent ductility was mainly due to the deflection mechanism of microcracks and the blocking effect of grain boundary enrichment on crack propagation.

Normalized characterization of the causes of discontinuous yield and crystal orientation deflection mechanism of β-Ti alloy during high-temperature deformation

To investigate the changes in grain orientation resulting from dislocation slip systems and propose a novel approach to characterizing discontinuous yield behavior during hot deformation, Ti–6V–5Al–5Mo–5Cr–3Nb–2Zr-0.2Si alloy was melted using vacuum arc furnace and subjected to hot compressed at 740, 790, 840 and 890 °C, along with strain rates (ε˙) of 0.001, 0.01, 0.1 and 0.5 s−1. The results indicate that discontinuous yield is observed at temperatures (T) of 740 or 790 °C and ε˙ of 0.1 and 0.5 s−1. Discontinuous yielding occurs at all strain rates when T is 840 and 890 °C. The presence of discontinuous yield is only observed when the power dissipation value exceeds the critical value, which in this study is 0.2657. Notably, this is the first instance in which the power dissipation value has been utilized to characterize the presence of discontinuous yield. The microstructure of the discontinuous yield reveals the activation of dislocation slip in the β grain. The dislocation slip is initially activated in the <001> oriented β grains during hot compression, followed by activation in the adjacent <101> oriented β grains. When the power dissipation exceeds the critical value, the dislocations more readily spread to the <101> oriented β grains due to higher activation energy, which is an important reason for discontinuous yield. The <101> oriented β grains gradually deflect to <2−3−1> oriented and finally rotate to <001> oriented during the subsequent compression process, as a means of reducing deformation resistance.

Fracture resistance of binderless tungsten carbide consolidated by spark plasma sintering and flash sintering

Binderless tungsten carbide (WC) consolidated by spark plasma sintering (SPS) and electrical resistance flash sintering (ERFS) has emerged as a promising alternative to materials obtained by traditional sintering methods. In this study, we investigated the influence of SPS and ERFS techniques on the mechanical properties of binderless WC. Hardness, indentation fracture resistance and elastic modulus were compared and analysed with respect to the microstructure of the resulting material. The results show that SPS tungsten carbide is harder, stiffer and denser when compared to the material produced by ERFS. Nevertheless, the fracture resistance of SPS ceramics was limited due to the lack of macroscopic toughening mechanisms. Conversely, flash-sintered tungsten carbide, consolidated by ERFS, possesses unique biphasic WC/W2C microstructures that promote crack deflection and bridging toughening mechanisms. Additionally, flash-sintered materials exhibit a more ductile character and are characterised by a lower effect of the strain gradient on the material plasticity upon indentation. This study provides valuable insights into the mechanical properties of ultra-hard monolithic ceramics, such as WC, influenced by ultrafast/flash sintering techniques.

Influence of miscibility of PEG-B-PPG-B-PEG/EPOXY systems on thermal, mechanical and fracture properties

Epoxy matrix blends with poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) triblock copolymer (PEG-b-PPG-b-PEG) with 30% PEG blocks were elaborated and investigated. The systems were prepared by the casting method with cure at 100 °C, with different amounts of copolymer in the epoxy matrix, and with the aim of evaluating the influence of the modifier on the properties of the blends. By DSC it was verified that the glass transition temperature relating to the matrix phase decreased in systems with copolymer in relation to neat epoxy, thus the blends formed partially miscible systems. On the other hand, phases separation or microdomains of the block copolymer within the epoxy matrix were not discernible by scanning electron microscopy. In general, the addition of the block copolymer impaired the mechanical properties evaluated in the tensile test. However, the fracture mechanisms observed on the fracture surface of the blends indicate that an improvement in the toughness of the systems may have occurred due to the crack pinning and crack deflection mechanisms.

Fracture of all‐oxide ceramic composites: Crack path analysis by surface strain monitoring

AbstractCrack propagation in ceramic matrix composites is very difficult to observeand to quantify. To investigate crack formation in all‐oxide ceramic composites, single edge notched bending tests were performed including loading‐unloading cycles and online monitoring of surface deformation using digital image correlation. The crack length was calculated by the compliance method with the crack opening displacement determined optically using digital image correlation. Obtained crack length values were found to be too small considering the sample geometry. Secondly, surface strain monitoring was used to investigate the crack growth. Analysis of cyclic force‐crack opening displacement curves and the results from strain monitoring indicated no major crack growth for loads below maximum force but still a moderately decay of force after onset of cracking. Graphical analysis of the surfaces of broken samples showed crack flank lengths ranging from 3 to 6 mm. Due to highly individual crack deflection mechanisms throughout the thickness of the oxide ceramic composites, deviations between front and back of specimens are found. The results demonstrate the necessity to use individual crack length measurements of each specimen for quantitative fracture mechanical evaluation. Strain monitoring during testing was shown to be a valuable tool for online crack path investigation.

PPG-PEG-PPG/Epoxy systems cured at 100 °C: relationship between miscibility, microstructure, thermal and mechanical properties

This article evaluated the thermal, mechanical, morphological and fracture properties of systems with poly (ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (PPG-PEG-PPG) triblock copolymer, with molecular weight 2000 g•mol−1 and 50% PEG in its composition, in DGEBA/DDM epoxy matrix. Systems with 10, 20 and 30 wt.% copolymer were prepared by in-situ polymerization and curing at 100 °C. In the differential scanning calorimetry (DSC) analysis, the characteristic temperatures of both the copolymer and the matrix in the binary systems were verified, indicating that phase separation had occurred. However, the glass transition temperature referring to the epoxy phase (Tg-E) occurred at lower temperatures than in neat matrix, which indicates partial miscibility in binary systems. The epoxy/copolymer systems presented a Young's modulus higher than the neat matrix, and without loss of mechanical resistance, reinforcing the miscibility of the PEG block in the blends and a microstructure with nanophase separation. When evaluating the fracture surface of the blends by scanning electron microscopy, the presence of deflection and crack immobilization mechanisms was observed, but no phase separation of the copolymer was observed. In this way, the systems studied showed partial miscibility with the formation of nanophases at the curing temperature of 100 °C, influencing Tg-E and improving the stiffness of the matrix.

Enhancement of ductility characteristics of fiber-reinforced ternary geopolymer mortar

There is a need for ambient-cured geopolymer as a potential replacement for conventional ordinary Portland cement (OPC) based concrete. But geopolymers, that belong to the ceramic family, behave in a brittle manner and hence this research focusses on the enhancement of ductility using fibers. Thus, this experimental work was conducted to investigate the performance of polypropylene (PP) and micro steel fiber (MS) of fiber-reinforced geopolymer mortar (FRGM) on the hardened properties. The volume fractions of fiber used were 0%, 0.5%, 1%, and 1.5%. The ternary blended geopolymer mortar consisted of fly ash (FA), ground granular blast furnace slag (GGBS), and palm oil fuel ash (POFA). The hardened properties investigated are compressive strength, splitting tensile strength, modulus of elasticity (MoE), and ultrasonic pulse velocity (UPV). Furthermore, the load-deflection response was investigated in terms of deflection, load, flexural, and toughening mechanisms. The morphology of matrix mortar with the bonding of the fibers was examined through field emission scanning electron microscope (FESEM). The results revealed that the splitting tensile strength was enhanced with the inclusion of 0.5% of PP fibers and up to 1.5% of MS fibers by 27% and 177%, respectively. The enhancements in the ultimate flexural strength with 1.5% fiber were found 173% and 33% higher for MS and PP fibers, respectively compared to the control mixes. The inclusion of both MS and PP fibers showed a significant enhancement in the post-cracking flexural and toughness energy measured at L/150 mm. Furthermore, the addition of fiber volume of 0.5–1.5% enhanced the toughness by 33% (T600), 62% (T150), and 28% (T600), 46% (T150) for MS and PP mixes, respectively.

Impact of developed hybrid polypropylene fiber inclusion on the flexural performance of concrete beams reinforced with innovative hybrid bars

This paper investigates the impact of incorporating a hybrid combination of structural polypropylene fibers on the flexural behavior of concrete beams reinforced with steel, GFRP, and innovative hybrid bars. A new ductile hybrid bar with equivalent bilinear stress-strain characteristics has been developed to address steel corrosion and FRP ductility issues. Fourteen half-scale RC beams were fabricated and tested under four-point loading configuration to study the flexural response. The tensile reinforcement types (steel, GFRP, and hybrid), hybrid reinforcement ratios (0.85 %, 1.26 %, and 1.70 %), reinforcement hybridization schemes (hybrid-hybrid, hybrid-GFRP, and GFRP-steel), and hybrid fiber ratio (0.0 %, 1.0 %, and 2.0 %) are the major parameters studied. The test results were recorded and analyzed in terms of mid-span deflection, cracking load, flexural capacity, and failure mechanism. The results demonstrated that the addition of hybrid fibers and using hybrid bars significantly improved the peak strength, ductility index, and bending stiffness. Moreover, the hybrid-reinforced concrete beams exhibit large inelastic deformations similar to steel-reinforced concrete beams. The inclusion of hybrid fibers improves the post-peak response of the tested beam due to fiber bridging capabilities. For design purposes, a simplified formula proposed by ACI 544 for predicting the nominal flexural capacity of hybrid fiber concrete beams reinforced with hybrid bars was presented, compared with experimental results and validated with 44 specimens from other studies. The predicted and test results were in good agreement with a standard deviation of 0.12. Additionally, 3D nonlinear finite element analysis was developed to validate the test results, demonstrating reasonable accuracy in predicting the flexural behavior of the beams.

Mechanical and fracture properties of sugar beetroot-based nanosheets (SNS) doped cementitious composites

This paper examines the mechanical and fracture properties of cementitious composites doped with a new type of 2D bio-nanoplatelets sheets, synthesized from sugar beet pulp waste. The sugar beetroot nanosheets (SNS) were added to the cement pastes at different concentrations. The influence of SNS treatment and water-to-cement (w/c) ratio on the performance of the cementitious composites was elucidated. The experimental results showed that 0.2- wt% and 0.35 were the optimal SNS concentration and w/c ratio for increasing the compressive, splitting tensile and flexural strength, flexural modulus, fracture energy and fracture toughness. These properties were enhanced by as much as 12.15%, 36.87%, 39.91%, 32.69%, 69.01% and 49.06%, respectively. This enhancement was due to crack deflection and crack bridging mechanisms in the cementitious composites as a result of the high specific surface area of SNS and the strong chemical and physical bonding of SNS with the hydration phases. The SNS materials offers strong advantages over graphene-based materials on improving the engineering properties of cementitious materials and reducing their cost and CO2 emissions.