Flexural Characteristics Research Articles

Experimental and numerical assessment of the flexural response of banana fiber sandwich epoxy composite

Recently, most service or product-oriented industries have been focusing on their activities to uphold the green and sustainable environment protocol owing to the increased environmental pollution. Concerning this issue, industries are now concentrating on developing recyclable or waste materials products. This research advocates developing and validating a banana fiber sandwich composite to promote the beneficial usage of bio-waste. The composite sandwich specimens were fabricated with resin-impregnated woven banana fiber mat as a skin, and the core was reinforced with three different weight percentages (5, 7.5 and 10%) of chopped banana fiber. The sandwich specimens were pressed into a three-point bending test to validate the structural integrity. The flexural characteristics like flexural strength and modulus were examined experimentally, whereas the key strength indices like flexural stiffness and core shear modulus were evaluated analytically. Post-fracture surfaces were studied through a scanning electron microscope to investigate the failure mechanism. The experimental and analytical results indicate that 10% banana fiber content in the sandwich core increases the flexural strength and flexural modulus to 225% and 147%, respectively, compared to the neat epoxy core. The numerical simulation was also performed through FEA to validate the experimental findings. The numerical results are in good concurrence with the experimental one.

Development of novel un-fired masonry unit manufactured using silica-rich sandstone mining and cutting waste

This paper aims to give a complete characterization of the novel un-fired bricks manufactured from base material comprising dimensional silica-rich sandstone cutting waste in combination with waste from coal-fired thermal plants with a minimum amount of cement and lime as binder. The study has given promising results with bricks able to achieve a compressive strength in the range of 16–20 MPa besides other enhanced parameters such as water absorption, the initial rate of absorption (IRA), and durability with favorable socio-economic impacts and climate benefits. 250 numbers of these industry-sized novel bricks were cast and subjected to an array of tests such as density, dimensional test, drop test, water absorption, IRA, efflorescence, compressive strength, flexural tensile strength, stress-strain characteristics and durability. The test results were substantiated with the micro-structural characterization through Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and Fourier transform infrared (FTIR). The novel bricks manufactured in this study are of exceptional quality satisfying all the requirements of Indian Standards. These bricks can mitigate the problems of landfills formed by wastes generated from the dimensional stone cutting industry and are eco-friendly as they require no burning in kilns, reduce carbon emissions and utilize waste materials thereby ensuing the benefit of reducing carbon footprint. The study of the sand free un-fired bricks in this paper is totally original and gives the most effective alternative to energy-intensive conventional masonry units such as burnt clay bricks and fly ash bricks. This work has also been granted a patent of 20 years by the patent office, the government of India on July 26, 2021 with patent no: 372690.

Insight into the flexural characteristics of rapid hardening ultra-high performance concrete (RH-UHPC) incorporating C-S-H seeds using acoustic emission technology

With the increasing requirements for emergency repair projects, there is a pressing need for high-quality repair materials. In this work, a series of rapid hardening ultra-high performance concrete (RH-UHPC) were prepared by using C-S-H seeds and SAC as early-strength agents. The effects of these early-strength agents on RH-UHPC’s flexural behaviors, including failure pattern, strength, energy absorption capacity, and toughness index, were investigated. Also, the variations of acoustic emission signals and microstructure were studied to provide a thorough insight into the influence of early-strength agents on RH-UHPC. The results show that C-S-H seeds and SAC exhibited a good effect on improving the 1-day flexural strength of RH-UHPC, but increased the risk of shear failure at 28 days. The flexural strength, energy absorption capacity, and toughness of RH-UHPC at 28 days were reduced by adding C-S-H seeds. However, combining C-S-H seeds with SAC alleviated this reduction. Moreover, incorporating early-strength agents enhanced the ringing counts, AE energy, damage rate, and the proportion of shear cracks. The noticeable increase in r value (i.e., RA/AF) judged the damage stage of RH-UHPC more reliably. Micro-analysis revealed that introducing C-S-H seeds increased the internal cracks and the Ca/Si ratio of C-S-H gel, but the hybrid of C-S-H seeds and SAC partially mitigated above problem. The incorporation of SAC notably increased the AFt content and decreased the CH content. C-S-H seeds presented little effect on the hydration degree of RH-UHPC, but roughened the pore size and enlarged the average pore size.

Influence Utilization Waste Plastic Polyethylene Terephthalate on the Flexural Strength of Concrete with Use East Kalimantan Aggregate

Environmental pollution is still an issue that cannot be ignored. This type of waste causes environmental pollution due to its large and difficult to be recycled is Polyethylene Terephthalate (PET) plastic. So it is important to make an effort to utilize the plastic. On the other hand in the world of construction, the use of concrete increases every day causing the need for many new material sources in order to cover the needs of concrete mixtures. One of the abundant sources of aggregate is East Kalimantan aggregate but has not been used much. so combining East Kalimantan aggregate and PET plastic as a concrete constituent material becomes interesting to be analyzed, especially to determine the characteristics of the flexural strength of concrete. The flexural strength is based on SNI 03-4431-2011 method and tested at the age of 14 and 28 days. PET plastic chopped to a size of 5 cm long and 1-3 mm wide with variations 0.5%; 0.65%; and 0.8% of the weight of sand. The total number of samples is 24 blocks size of 15 × 15 × 60 cm. The results indicate that the flexural strength characteristics of concrete using local East Kalimantan aggregates and using PET plastic as a partial substitute for fine aggregate increased as the number of PET substitutions. Concrete without PET plastic has 3.187 MPa. In comparison with to normal concrete, 0.5% PET substitution increased by 3.07%, 0.65% PET variation increased by 3.63% and 0.8% PET variation increased by 4.32%.

Seawater's impact on the mechanical properties of SiO2 and TiO2 fillers in glass reinforced epoxy composites

The purpose of this study is to investigate the mechanical characteristics and moisture absorption of GFRP composites with filler materials. The specimens are created in accordance with ASTM standards ASTM D3039 and ASTM D790 for the tensile and flexural tests, respectively. These samples were dipped in seawater for 48 days after manufacturing to assess their moisture absorption. Mechanical properties of dry and aged specimens are examined based on ASTM standards using a universal testing machine. The findings revealed that the moisture absorption is more for type B tensile glass/epoxy specimen. In comparison to the filled specimen, the unfilled (glass/epoxy type A tensile) specimen absorbed less water. The type C tensile and flexural glass/epoxy specimen absorbed a moderate amount of water. After analyzing the glass/epoxy with and without filled specimens the drop in flexural characteristics and tensile characteristics of type B glass/epoxy specimen is lesser compared with the other modification of glass/epoxy specimen.

Effect of notch location on flexural and fracture behaviors of UHPGC notched beam based on four-point bending test and acoustic emission monitoring

Ultra-high performance glass sand concrete (UHPGC) is a new composite material with superior mechanical properties and durability made by replacing quartz sand in traditional ultra-high performance concrete (UHPC) with environmentally friendly and economical glass sand recycled from waste glass. This study investigated the flexural and fracture characteristics of UHPGC notched beams with prefabricated notches at three different locations (mid-span, 100 mm off mid-span and 145 mm off mid-span) using four-point bending tests. Meanwhile, the damage evolution processes of notched beams under flexural load were monitored in real time and characterized by acoustic emission (AE) technology. Fracture modes were automatically classified based on Gaussian mixture model (GMM) and support vector machine (SVM) of rise angle (RA) and average frequency (AF). Outlier analysis of b-value were applied to provide a warning prior to complete failure of UHPGC notched specimen. The results revealed that notched position presents significant effects on flexural strength, flexural toughness and fracture energy, and exhibit considerable influence on AE parameters and cracking patterns. The farther the notch is away from the mid-span, the greater the flexural strength, flexural toughness and fracture energy exhibit due to the weakened stress concentration. As it takes longer to gather enough strain energy at the tip of the notch to crack, AE monitoring shows that higher amplitude and hysteretic nature of AE parameters such as accumulated energy and information entropy, etc., can be recorded as notch position away from the mid-span. The farther the notch is away from mid-span, the more shear cracks predominate at the later stages of damage. Cumulative AE energy and fracture energy throughout the damage process are found to exhibit a favorable exponential relationship. In addition, the b-value outlier analysis can provide failure warning for UHPGC notched beams. This study is of great significance in exploring the fracture behavior of UHPGC and providing reference for engineering applications related to UHPGC failure.

3D printed wood-fiber reinforced architected cellular composite beams with engineered flexural properties

This study explores the integration of cellulose-based compounds into a biobased polymer to create high-performance sustainable materials with improved properties. The elastic flexural characteristics of 3D printed composites, comprised of polylactic-acid (PLA) biopolymer reinforced by a variety of waste wood fiber weight percentage (2.5%−15%), are investigated. Initial steps involve producing wood-fiber reinforced PLA (WF-PLA) filaments and the 3D printing of test specimens. Experimental outcomes reveal enhanced flexural modulus (60% increase), rigidity (72% increase), strength (39% increase), and failure strain (21% increase) alongside reduced composite coupon density (5.2% decrease), attributed to wood fiber incorporation. To achieve lightweight and sustainable structural components with tunable attributes, architected composite cellular beams are introduced. These beams comprised of wood-fiber reinforced composites feature cross-sectional unit cells with one or two reflection symmetries, showcasing the synergy between architecture and material composition in enhancing quasi-isotropic flexural rigidity. Investigation on the flexural rigidity ratio ([EI]yy/[EI]xx) involves theoretical modeling, computational analysis, and experimental validation using 3D printed samples. WF-PLA filaments enable the 3D printing of engineered quasi-isotropic cellular beams, termed “Isoflex”, that demonstrate up to 130% enhanced specific flexural rigidity (bending rigidity-to-mass ratio) and up to 70% improvement in flexural rigidity ratio to have isotropic flexural properties, compared to pure PLA beams. This study introduces WF-PLA engineered cellular composites as a sustainable avenue for tuning structural properties, contributing to the realm of additive manufacturing.

A comprehensive study on the effect of hybridization and stacking sequence in fabricating cotton-blended jute and pineapple leaf fibre biocomposites

Developing biocomposites by hybridization, which is the combination of two or more materials, can be a potential solution for improving material recyclability and sustainability. This study focuses on creating a hybrid biocomposite reinforced with cotton-blended pineapple leaf fibre (PALF) fabric (174 GSM) and jute fibre fabric (265 GSM) which are thrown away by textile factories. The mechanical, moisture absorption, and vibration characteristics of four stacking sequences of hybrid composites and two unhybridized composites were analyzed. Results indicated that hybridization improved tensile and flexural characteristics compared to pineapple leaf fibre reinforced polymer (PFRP) composites. The jute fibre reinforced polymer (JFRP) composite exhibited the maximum tensile strength of 35.16 MPa, while the hybrid composites achieved a maximum of 32.16 MPa. Among the hybrid composites, jute layers on the outer plies (4P5J-2) demonstrated the maximum tensile modulus of 1.315 GPa. Additionally, the hybrid composite with three layers of jute plies between alternating layers of jute-pineapple plies showed the highest elongation at 15.94%. Among the hybrids, alternate stacking of jute/PALF plies (4P5J-1) gave a maximum flexural strength of 44.36 MPa, which is similar to JFRP (44.91 MPa) and a 78.57% increase in flexural modulus compared to PFRP composite, despite having the lowest tensile strength. Although the JFRP composite exhibited the highest impact strength, the hybrids still outperformed the PFRP composites. With hybridization, moisture absorption decreased, with a maximum of 29.50% compared to the JFRP composite. Furthermore, due to the spiral-like orientation of the yarns, stacking PALF plies on the outside can cause critical damping. Therefore, it is shown in this paper that both hybridization and stacking sequence can significantly influence composite performance. These findings also implies the utilization of textile industry's natural fibres to develop hybrid composites for automotive applications, like brake and accelerator pedals, for a greener future and effective waste material utilization.

FLEXURAL STRENGTH CHARACTERISTICS OF PAWPAW LEAF ASH AND BAMBOO LEAF ASH BLENDED CEMENT CONCRETE

This research focuses on flexural strength characteristics of pawpaw leaf ash and bamboo leaf ash blended cement concrete. Several tests were carried out, according to BS and ASTM requirements to determine the physical and mechanical properties of pawpaw leaf ash and bamboo leaf ash blended cement concrete, investigate the effects of curing age on flexural strength characteristics of pawpaw leaf ash and bamboo leaf ash blended cement concrete and examine the effects of percentage replacement of cement with pawpaw leaf ash and bamboo leaf ash blended cement concrete on flexural strength characteristics. A total of 60 cubes were cast, cured in water for 7, 14, 21 and 28days. Test results showed that the flexural strength of the concrete cubes increases with an increase in the curing age and decreases with increasing percentage replacement of cement with pawpaw leaf ash and bamboo leaf ash. The optimum replacement level of pawpaw leaf ash and bamboo leaf ash was obtained to be 5%. The study concluded that concrete containing the cement blends of cement and Pawpaw leaf ash and bamboo leaf ash at a replacement level of 5% is only recommendable for use in light concrete works construction.

Influence of Block-Copolymers' Composition as Compatibilizers for Epoxy/Silicone Blends.

The objective of this study was to prepare crosslinked epoxy networks containing liquid silicone particles in order to improve their mechanical properties and obtain less brittle materials. Different copolymers were used as compatibilizers. These copolymers vary in their chemical composition and structure. All of the copolymers contain hydrophobic (PDMS sequences) and hydrophilic groups. The effect of their chemical structure and architecture on the morphology of the dispersed phase, and on the final physico-chemical and flexural characteristics of epoxy/silicone blends, was explored. The morphology of crosslinked formulations was studied by scanning electron microscopy (SEM), and the thermal characteristics (glass transition temperature, Tg, and curing exothermic peak) were determined by differential scanning calorimetry (DSC). The experimental results have shown that the average diameter and particle size distribution of silicone particles depend on the chemical structure and architecture of the compatibilizers. One copolymer has been identified as the best compatibilizer, allowing a lower mean diameter and particle size distribution in addition to the best mechanical properties of the final network (less brittle character). This study has consequently evidenced the possibility of creating in situ silicone capsules inside an epoxy network by adding tailored compatibilizers to epoxy/silicone formulations.

An investigation into mechanical properties of a 3D printed two-matrix continuous fiber composites with multi-cavity structure

A continuous fiber reinforced two-matrix composites with multi-cavity structure was fabricated by a co-extrusion method, combining the excellent wettability of thermosetting resin to fiber and the wonderful extrusion forming ability of thermoplastic for nozzle based additive manufacturing (AM). Diversified component materials were utilized to enrich database for the AM of continuous fiber composites, including continuous carbon fiber (CCF), continuous basalt fiber (CBF), short fiber reinforced polyamide (SFRPA), polyamide (PA), polylactic acid (PLA) and epoxy resin. The tensile and flexural tests were conducted to investigate the effect of component materials on the mechanical properties. The micro-structures of printing filament and the fracture morphology of samples were characterized by optical microscope (OM) and scanning electron microscopy (SEM), respectively. A novel numerical model based on Peridynamics (PD) was proposed for the simulation of failure model. The three-dimensional (3D) printed continuous fiber reinforced two-matrix composites with multi-cavity structure show dissimilar mechanical behavior and failure characteristic for different combinations of component materials. The micro-structure of the fiber bundle pre-impregnated by epoxy resin after printing has a great influence on the mechanical properties and fracture modes of the samples. The failure modes mainly include pullout and breakage of fiber, stress whitening and crack of matrix, and interfacial debonding. The PD model effectively captures the tensile and flexural failure characteristic of 3D printed composites with multi-cavity structure. The results from experimental analysis and numerical simulation have reference significance for structural optimization and failure prediction of continuous fiber composites printed by co-extrusion process.

Thermo-Mechanical Behavior of Green Sandwich Structures for Building and Construction Applications

In this work, three different types of sandwich structures were manufactured, each using a Formica sheet (a paper-based sheet) as the skin and perlite/sodium silicate foam as the core, with or without a paper honeycomb. The sandwich structures were fabricated by attaching the Formica sheets on both sides of a paper honeycomb core panel, a perlite/sodium silicate foam core panel, and a perlite/sodium silicate foam-filled honeycomb core panel. The flexural characteristics were studied by a three-point bending test and the thermal conductivity was measured using Lee’s thermal conductivity apparatus. The results demonstrated a significant improvement in flexural properties, including core shear stress, facing stress, bending stress, and energy absorption, when incorporating the paper honeycomb reinforcement. The thermal conductivity and flexural properties of the paper honeycomb reinforced and unreinforced perlite/sodium silicate foam-based sandwich panels were found to be very compatible with existing building materials described in the literature that are used for similar applications. The failure investigation revealed that the sandwiches with paper honeycomb failed prematurely only due to core buckling, while the foam-filled honeycomb core-based sandwiches were able to sustain higher loads while exhibiting material failures such as core shear failure, skin rapture, and delamination. It was found that the foam-filled paper honeycomb sandwich structures can withstand higher bending loads than the foam core-based sandwich structure or the paper-honeycomb-based sandwich structure. These developed sandwiches offer potential as green materials due to the characteristics of their constituent materials and they can provide valuable applications in the thermal insulation of buildings.

Evaluation of Polycaprolactone Applicability for Manufacturing High-Performance Cellulose Nanocrystal Cement Composites.

This experimental study examined the aplication effect of polycaprolactone (PCL), an organic resin material with excellent elasticity and ductility, on improving the mechanical performance of cellulose nanocrystal (CNC) cement composites. PCL was compared according to its shape, and in the case of Granules, which is the basic shape, interfacial adhesion with cement was not achieved, so a dichloromethane (DCM) solution was used to dissolve and use the Granules form. As a method for bonding PCL to the CNC surface, the CNC surface was modified using 3-aminopropyltriethoxysilane (APTES), and surface silylation was confirmed through Fourier transform infrared spectroscopy (FT-IR) analysis. In order to evaluate the dispersibility according to the application of PCL to the modified CNC, particle size analysis (PSA) and zeta potential analysis were performed according to the PCL mixing ratio. Through the PSA and zeta potential values, the highest dispersion stability was shown at 1 vol.%, the cohesive force of CNC was low, and the dispersion stability was high according to the application of PCL. According to the results of the dispersion stability evaluation, the degree of hydration of the dissolved PCL 1 vol.%, CNC-only specimens, and plain specimens were analyzed. CNC acted as a water channel inside the cement to accelerate hydration in the non-hydrated area, resulting in an increased degree of hydration. However, the incorporation of PCL showed a low degree of hydration, and the analysis of strength characteristics also showed a decrease of approximately 27% compared with that of plain specimens. This was because the bonding with SiO2 was not smooth owing to the solvent, thus affecting internal hydration. In order to investigate the effect of the PCL shape, the compressive and flexural strength characteristics were compared using PCL powder as an additional parameter. The compressive strength and flexural strength were improved by about 54% and 26%, respectively, in the PCL powder 15 wt% specimen compared to the general specimen. Scanning electron microscopy (SEM) analysis confirmed that the filler effect, which made the microporous structure denser, affects the mechanical performance improvement.

Mechanical properties of geopolymer-based ultra-high performance concrete with ceramic ball coarse aggregates

This research reported the mechanical properties of geopolymer-based ultra-high performance concrete containing ceramic ball coarse aggregates. 10 mm straight steel fibres with various contents (0, 0.6 vol-%, 1.2 vol-% and 1.8 vol-%), medium-aluminium ceramic balls with various sizes (3 mm, 6 mm and 10 mm) and contents (0, 10 vol-%, 20 vol-% and 30 vol-%) were utilised. Mechanical properties, including the slump flow, uniaxial compressive, splitting tensile and flexural strengths, were investigated via a series of material tests. Fundamental contributions arisen from the steel fibre content, ceramic ball size and content towards the mechanical properties were analysed and discussed. In the light of the flexural load-midspan deflection curves, a constitutive flexural model was established, and the flexural toughness characteristics were quantitatively assessed using two indexes. Also, empirical equations to evaluate the strength relationships were proposed. Scanning electron microscope observation was carried out on the steel fibre-matrix interface to further explain the influencing mechanism of ceramic balls on the fibre reinforcement efficiency.

Design and analysis of longitudinal–flexural hybrid transducer for ultrasonic peen forming

Ultrasonic peen forming (UPF) is an emerging technology that exhibits great superiority in both its flexible operating modes and the deep residual stress that it produces compared with conventional plastic forming methods. Although ultrasonic transducers with longitudinal vibration have been widely studied, they have seldom been incorporated into UPF devices for machining in confined spaces. To meet the requirements of this type of machining, a sandwich-type piezoelectric transducer with coupled longitudinal–flexural vibrational modes is proposed. The basic structure of the transducer is designed to obtain large vibrational amplitudes in both modes. Experimental results obtained with a prototype device demonstrate the feasibility of the proposed transducer. The measured vibrational amplitude for the working face in the longitudinal vibrational mode is 1.0 μm, and electrical matching increases this amplitude by 40%. The flexural vibration characteristics of the same prototype transducer are also tested and are found to be slightly smaller than those of longitudinal mode. The resultant working strokes of the UPF impact pins reach 1.7 mm and 1.2 mm in the longitudinal and flexural modes, respectively. The forming capability of the prototype has been evaluated via 15-min machining on standard 2024-T351 aluminum plates. After UPF, an improved surface morphology with lower surface roughness is obtained. The aluminum plate test piece has an apparent upper deformation with an arc height of 0.64 mm. The measured peak value of the compressive residual stress is around 250 MPa, appearing at a depth of 100 μm. The proposed longitudinal–flexural hybrid transducer thus provides a high-performance tool for plate peen forming in confined spaces.

Machine learning and RSM-CCD analysis of green concrete made from waste water plastic bottle caps: Towards performance and optimization

This study aims to serve as a performance indicator for the workability and strength of concrete when coarse aggregate, sand, cement, and water are partially substituted with waste plastic bottle caps. The significance of these alternative plastic water bottle caps is to reduce plastic trash that is difficult to lapse and to prevent waste that can be transformed to something that may be employed in the advancement of technology in the future. The principle of "Reduce, Reuse, and Recycle" is used, which not only lowers environmental pollution but also reduces costs. In the building industry, concrete is the most often utilized material. In order to preserve natural resources and minimize the number of materials that end up in landfills, green construction is becoming a more significant worldwide issue. Empty cans and bottle tops from drinking water bottle produce a lot of garbage. The difficulty of biodegrading plastic trash and the need for techniques for recycling or reuse make this a problem for the environment. Such problems are being investigated in this study in order to determine whether it could be possible to partially replace coarse aggregate with 0, 6 and 12% in the manufacturing of concrete using discarded bottle caps. To evaluate the compressive strength, split tensile, and flexural strength test characteristics in a laboratory setting; waste bottle caps were used as replacements for coarse aggregate at different percentages. The highest compressive strength was determined to be 28.80 MPa with 12% replacement of used plastic bottle caps with a water cement ratio of 0.55. Advanced statistical methods, including RSM-CCD (Response Surface Method-Central Composite Design) and machine learning models ANN-LM (Artificial Neural Network- Levenberg Marquardt), were applied in this study to predict concrete performances based on mix design variations. It was found that ANN-LM model displayed more accurate prediction relative to RSM-CCD method.

The Strength and Fracture Characteristics of One-Part Strain-Hardening Green Alkali-Activated Engineered Composites.

Alkali-activated engineered composites (AAECs) are cement-free composites developed using alkali activation technology, which exhibit strain hardening and multiple micro-cracking like conventional engineered cementitious composites (ECCs). Such AAECs are developed in this study by incorporating 2% v/v polyvinyl alcohol (PVA) fibers into alkali-activated mortars (AAMs) produced using binary/ternary combinations of fly ash class C (FA-C), fly ash class F (FA-F), and ground-granulated blast furnace slag (GGBFS) with powder-form alkaline reagents and silica sand through a one-part mixing method under ambient curing conditions. The mechanical and microstructural characteristics of eight AAECs are investigated to characterize their strain-hardening performance based on existing (stress and energy indices) and newly developed tensile/flexural ductility indices. The binary (FA-C + GGBFS) AAECs obtained higher compressive strengths (between 48 MPa and 52 MPa) and ultrasonic pulse velocities (between 3358 m/s and 3947 m/s) than their ternary (FA-C + FA-F + GGBFS) counterparts. The ternary AAECs obtained a higher fracture energy than their binary counterparts. The AAECs incorporating reagent 2 (Ca(OH)2: Na2SO4 = 2.5:1) obtained a greater fracture energy and compressive strengths than their counterparts with reagent 1 (Ca(OH)2: Na2SiO3.5H2O = 1:2.5), due to additional C-S-H gel formation, which increased their energy absorption for crack propagation through superior multiple-cracking behavior. A lower fracture and crack-tip toughness facilitated the development of enhanced flexural strength characteristics with higher flexural strengths (ranging from 5.3 MPa to 11.3 MPa) and a higher energy ductility of the binary AAMs compared to their ternary counterparts. The tensile stress relaxation process was relatively gradual in the binary AAECs, owing to the formation of a more uniform combination of reaction products (C-S-H/C-A-S-H) rather than a blend of amorphous (N-C-A-S-H/N-A-S-H) and crystalline (C-A-S-H/C-S-H) binding phases in the case of the ternary AAECs. All the AAECs demonstrated tensile strain-hardening characteristics at 28 days, with significant improvements from 28% to 100% in the maximum bridging stresses for mixes incorporating 40% to 45% GGBFS at 365 days. This study confirmed the viability of producing green cement-free strain-hardening alkali-activated composites with powder-form reagents, with satisfactory mechanical characteristics under ambient conditions.

Flexural Characteristics of Functionally Layered Fiber-Reinforced Cementitious Composite with Polyvinyl Alcohol Fibers

The main purpose of this study is to investigate the flexural characteristics of a functionally layered fiber-reinforced cementitious composite (FL-FRCC) with polyvinyl alcohol fibers and to verify the adaptability of the proposed tri-linear stress-strain model based on the bridging law for large fiber orientation intensity, which shows the fiber orientation distribution as almost 2-D. The average maximum bending moment of FL-FRCC specimens is almost twice that of homogeneous (Hmg-FRCC) specimens, which indicates that the FL-FRCC specimens lead to larger bending capacity. The proposed wide-range stress-strain model based on the bridging law was verified and showed good adaptability with the experimental results through a comparison with the conducted section analysis.

Structural assessment of Basalt FRP reinforced self-compacting geopolymer concrete using artificial neural network (ANN) modelling

Basalt FRP geopolymer composites are considered a sustainable solution to address the conventional OPC-Steel composite structures' structural and environmental concerns, especially the increased carbon emissions and structural deterioration due to corrosion attacks. Recent research on novel composites reports the superior performance of these FRP-geopolymer concrete structural applications reporting high strength and durability. However, the existing design guidelines do not accurately predict the flexural capacity and strength characteristics, which hinders the broader use of FRP-based geopolymer composites. This study aims to develop a prediction tool to help the researchers model the structural performance of the novel FRP-geopolymer composite based on modern machine learning algorithms. It shall address the lack of data on novel composites' structural and long-term performance in various exposure conditions. This paper thus reports the suitability of Artificial Neural Network (ANN) based models to accurately predict the flexural strength of Basalt FRP reinforced self-compacting geopolymer concrete beams under various exposure conditions. The ANN model is trained and validated against the experimental data from the long-term study conducted on the beam specimens subjected to one-year ambient and marine exposures. The ANN prediction model developed in this study reported close agreement with the experimental data showing better prediction accuracy than the existing empirical and numerical models.

Influences of nano-SiO2 on the tensile, flexural, and compressive characteristics of the open-hole carbon fiber-reinforced polymer laminated composites: experimental study

Carbon fiber are of great importance materials exploited in various industrial applications in the recent years. Because of its strong flexural and compressive properties, these fibers have been commonly utilized as a reinforcement for producing polymer composite laminates. Carbon fiber-reinforced polymer (CFRP) laminates are subjected to extreme forces and damaged. In the component assembly of the structures, one of the conventional damages that still occurs on the CFRP laminates is holes that is created on the specimen by drilling tools, which causes a reduction in the laminates’ mechanical strength. One of the suggested ways to strengthen the mechanical properties of composites is to add nanoparticles. Therefore, the impact of silica nanoparticles (nano-SiO2) on the tensile, flexural, and compressive characteristics of the open-hole CFRP laminated composites is experimentally determined in this research. Nano-SiO2 with various weight percentage of 0, 1, 2, 3, and 4 is added into the CFRP. A scanning electron microscope images are used to observe the microscopic structure of the composites. The results showed that adding 1–3 wt.% of nano-SiO2 into the CFRP enhances the tensile, flexural, and compressive strength of the specimens and reduces the fiber pull out and delamination.