Increase In Flexural Strength Research Articles

Epoxy-poly lactic acid blended composites reinforced with carbon fibres for engineering applications

When it comes to sustainability, bio-derived materials are one of the most promising sources of polymers. They are easily accessible, affordable, and may result in a decrease in carbon emissions. The use of bio-based polymer composites lowers the dependence on petroleum-based polymers, leading to environmental degradation issues. Because of this epoxy-based composites are synthesized by combining the same with a biopolymer of Poly Lactic Acid (PLA) in varied proportions from 20 to 50 wt.% of the holding matrix. Exhaustive tests are conducted to optimize PLA percentage in the epoxy matrix. Accordingly, composites are prepared with 80% epoxy resin and 20% PLA in terms of enhanced mechanical properties. Further, these composites are strengthened by reinforcing them with CFs in varied proportions. This research emphasizes the synthesis of composite with a matrix of 80% epoxy resin and 20% PLA reinforced with CFs at 0.2 and 0.3 wt.% of the holding matrix to test their potential as a feasible composite material for engineering applications. To understand the bonding nature, thermal, and microstructural behavior of the composite material, characteristic studies such as Fourier Transform Infrared (FTIR) Spectroscopy, Thermo gravimetric analysis (TGA), and Scanning Electron microscope (SEM) images are used. Experimental results on the mechanical properties of the composites showed an increase in flexural strength by 7.62% and 3.56% for 0.2 and 0.3 wt.% of CFs reinforcements in the polymer matrix compared to pristine coupons. Simulation studies are done with ANSYS Workbench to validate the same with experimental readings and are found to be in close agreement with an error of 10–15%.

Effect of infill pattern and ratio on the flexural and vibration damping characteristics of FDM printed PLA specimens

3D printing technology has started to be used in many different areas of our lives. In this study, the panels' flexural behaviors and vibration-damping capabilities produced in different infill patterns (Grid, Cross, and Tri-hexagon) and different infill ratios (0%, 20%, 40%, 60%, 80%, and 100%) were investigated. The specimen dimensions were 12.7 mm in width, 127 mm in length, and 3.2 mm in thickness. A biopolymer polylactic acid (PLA) filament with Ø 1.75 mm was used to produce test specimens. Fused Deposition Modeling is a modern additive manufacturing technique; however, optimization is needed to enhance the properties of 3D-printed parts. The flexural properties, as well as vibration-damping characteristics of the 3D-printed specimen, were evaluated experimentally. The results show that the infill pattern and ratio significantly affect flexural behavior and vibration-damping properties. The flexural tests showed that the highest flexural strength was obtained in the Tri-hexagon pattern, while the highest damping capability was obtained on Cross pattern specimens. Additionally, with the increasing infill ratio, the flexural modulus, and flexural strength increase. The specific strength value obtained for the 20% fill rate for all patterns was observed as maximum Best damping properties were obtained on a 40% infill ratio with all the different tested patterns. This study also showed that infill pattern and ratio design could improve the plastic parts' properties, and 3D printing provides an easy way to test the properties of different infill patterns and ratios.

Study on Physical and Mechanical Properties of Micro-Cement Grouting Materials with Different Water-Cement Ratio

The water-cement ratio is one of the key parameters of grouting materials, which greatly affects the working performance and mechanical properties of grouting materials. This paper studies the physical properties, such as density, fluidity, consistency, bleeding rate, and stone rate, and the mechanical properties of flexural and compressive strength of micro-cement grouting materials with a water-cement ratio of 0.8:1, 1:1, 1.5:1 and 2.0:1 are investigated through a variety of indoor experiments. The results show that with the gradual increase of water-cement ratio, the density, consistency value, stone rate, flexural strength, and compressive strength of micro-cement grouting material gradually decrease, while the fluidity and bleeding rate of micro-cement slurry gradually increases. Although the slurry with a water-cement ratio of 1.5:1 and 2:1 has good fluidity, the high bleeding rate and the low stone body strength result in more water injected into the reinforced formation and low reinforcement strength. On the contrary, the slurry with a water-cement ratio of 0.8:1 has a low bleeding rate and high stone body strength, but low fluidity. The grouting performance and mechanical properties of the slurry with a water-cement ratio of 1:1 are relatively balanced. This study provides a basis for the subsequent on-site ultra-fine cement grouting project. A reasonable water-cement ratio can be selected according to the specific needs to ensure the reinforcement quality and safety of the grouting operation.

Mechanical properties of high strength concrete incorporating chopped basalt fibers: experimental and analytical study

Many civil engineering structures are constructed in terms of aspect like economy, strength and serviceability requirement. The fibres play a prominent role in bridging the micro cracks at the early stage of crack propagation and makes the structure ductile. The impact of chopped basalt fibre on high-strength reinforced concrete composites is the focus of this research. The chopped basalt fibre hardened property of concrete was investigated and compared it with controlled concrete. Moreover, physical property of concrete i.e. slump cone and compaction factor incorporating chopped basalt fibre volume fraction in variation of 0%,0.75%,1.5%,2.25%,3% to the total volume of concrete mix was also investigated. To analyse the hardened properties of chopped basalt fibre high strength concrete, 135 test samples were made and cured for 7, 14, and 28 days. The test findings show that increasing the volume percentage of fibres reduces slump from 135 mm to 132 mm for BFHS0.75 but does not result in a significant increase in concrete compressive strength of 77.1 MPa for BFHS0.75 However, on addition of chopped basalt fibres at 2.25% (BFHS2.25) the percentage increment of flexural strength increases by 72.8% (10.3 MPa) with control mix (5.96 MPa) and after that it decreases when 3% fibres were incorporated. Similarly, split-tensile strength increases at all fibre dosage and fibre addition of 3% (BFHS3) increases by 12.28% (5.65 MPa) with controlled concrete (5.04 MPa). The analytical results and suggested regression model could be used in real-world situations with fiber reinforced high strength concrete related issues. There is a significant relationship between mechanical property and independent variable through ANOVA in SPSS.

Mechanical Properties of Steel Fiber Reinforced Geopolymer Concrete Incorporated with Fly-Ash and GGBS

As it expands, it is becoming easier to obtain fresh insights into the numerous modifications and advancements that are taking place in the concrete business. Aside from that, as infrastructure continues to expand, the need for specialised concrete continues to increase in the present market. In addition, cement, aggregates, and other additions are the major elements in the production of concrete, with the exception of water. The goal strength for this current experimental attempt was 40 N/mm2, which was achieved. In this experimental effort, steel fibres with a standard length of 25mm, a diameter of 0.5mm, and an aspect ratio of 50 are used to completely replace cement in a concrete mix. It is the crimpled sort of steel fibre that has been utilised in this experiment, and it has been used in equal numbers with flash and GGBS in this study. Steel fibres are added to the binder, which is GGBS, and low calcium-based flash is provided by a local thermal plant, up to a maximum of 2 percent by weight, in order to compensate for the stress created by strain. This kind of construction achieves a balanced concrete mix that can bear stress while still staying robust in compression. It was determined that the insertion of steel fibres resulted in the biggest gain in strength, with a 1.5 percent increase in strength. A considerable increase in compressive, flexural, and split tensile strength, among other attributes, was seen with the addition of steel fibres to the mix. The usage of fly ash and ground-granulated blast-furnace slag (GGBS) aids in the mitigation of air pollution by removing carbon dioxide and carbon monoxide from the environment, which are created during the cement-making process.

Mechanical Behavior of Crushed Waste Glass as Replacement of Aggregates.

In this study, ground glass powder and crushed waste glass were used to replace coarse and fine aggregates. Within the scope of the study, fine aggregate (FA) and coarse aggregate (CA) were changed separately with proportions of 10%, 20%, 40%, and 50%. According to the mechanical test, including compression, splitting tensile, and flexural tests, the waste glass powder creates a better pozzolanic effect and increases the strength, while the glass particles tend to decrease the strength when they are swapped with aggregates. As observed in the splitting tensile test, noteworthy progress in the tensile strength of the concrete was achieved by 14%, while the waste glass used as a fractional replacement for the fine aggregate. In samples where glass particles were swapped with CA, the tensile strength tended to decrease. It was noticed that with the adding of waste glass at 10%, 20%, 40%, and 50% of FA swapped, the increase in flexural strength was 3.2%, 6.3%, 11.1%, and 4.8%, respectively, in amount to the reference one (6.3 MPa). Scanning electron microscope (SEM) analysis consequences also confirm the strength consequences obtained from the experimental study. While it is seen that glass powder provides better bonding with cement with its pozzolanic effect and this has a positive effect on strength consequences, it is seen that voids are formed in the samples where large glass pieces are swapped with aggregate and this affects the strength negatively. Furthermore, simple equations using existing data in the literature and the consequences obtained from the current study were also developed to predict mechanical properties of the concrete with recycled glass for practical applications. Based on findings obtained from our study, 20% replacement for FA and CA with waste glass is recommended.

Effect of different crumb rubber particle sizes on the flexural properties of crumb rubber concrete

In this paper, a new method of substituting natural fine aggregates with crumb rubber (CR) is employed to discuss the effect of different CR particle size intervals on the flexural properties and microstructure of crumb rubber concrete (CRC). A total of 10 groups of mix proportions were designed, and four-point bending tests were conducted on thirty prismatic specimens. Apparent density, failure model, flexural strength, and microstructure of CRC were analyzed and discussed. The test results showed that incorporating CR improved the ductility of concrete, and the apparent density and flexural strength first decreased and then increased with the decrease of CR size. The flexural strength decreases only about 5.4% when the CR size interval is 4.75–2.36 mm; the most severe degradation of flexural strength occurs when the CR size ranges from 1.18 to 0.6 mm and 1.18–0.3 mm, about 27.3% and 29.4% respectively. The predicted model between flexural strength and apparent density of CRC was proposed. Scanning electron microscopy photographs show that smaller interfacial transition zone (ITZ) widths will be obtained for CR sizes less than 0.60 mm at the same magnification. This may be the reason for the slight increase in flexural strength and apparent density.

Investigation of mechanical properties of UHMWPE composites reinforced with HAP+TiO2 fabricated by solvent dispersing technique

This work seeks to contribute to solving the problems of inadequate artificial joint design from the mechanical perspective in total joint replacement (TJR) surgery. Ultra-high molecular weight polyethylene (UHMWPE)/hydroxyapatite (HAP) + titanium dioxide (TiO2) hybrid composites were fabricated and tested for use as artificial cartilages in the total joint prosthesis. Different amounts of TiO2 (1–10 wt%) and fixed amount of HAP (20 wt%) were dispersed in UHMWPE-based nanocomposites due to obtaining a material easy to be processed, inexpensive, with remarkable mechanical properties, and good cells interaction. The UHMWPE/HAP + TiO2 composites were prepared by using the solvent dispersing technique and twin-screw mixer, followed by hot compression molding, then mechanical testing was performed. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) are used to study the effect of the additives and the dispersion quality of the composites. The solvent dispersing technique shows better dispersion of the additives in the polymer matrix. The composites show an increase in Young's modulus, hardness, and flexural strength, by 71%, 33%, and 95% respectively concerning neat UHMWPE. The composite contains 3 wt% TiO2 showing the best enhancement percentage.

Properties and Durability Performance of Lightweight Fly Ash Based Geopolymer Composites Incorporating Expanded Polystyrene and Expanded Perlite

In this study, the use of expanded polystyrene and expanded perlite as lightweight aggregates for the preparation of lightweight geopolymers is tested. The geopolymers’ performance was evaluated through physical, mechanical and thermal testing. Polypropylene fibers were used as reinforcement agents, while the long-term durability was assessed though repeated wet–dry and freeze–thaw cycles and sorptivity tests. The results showed that the introduction of lightweight aggregates in the geopolymer mixes decreased the compressive and flexural strength of the specimens by 77% and 35%, respectively. However, the density and thermal conductivity were substantially improved because of the addition of low-density aggregates. The fiber reinforcement of lightweight samples led to a drastic increase in flexural strength by 65%, leaving unaffected the compressive strength and density of the specimens. The freeze–thaw and sorptivity tests were also improved after the introduction of both aggregates and fibers. Lightweight geopolymer composites exhibiting density in the range of 1.0–1.6 g/cm3, compressive strength of 10–33 MPa, flexural strength of 1.8–6.3 MPa, thermal conductivity of 0.29–0.42 W/mK, and sorptivity of 0.031–0.056 mm/min0.5 were prepared.

Characterisation of Nanoclay and Spelt Husk Microfiller-Modified Polypropylene Composites.

Current research is devoted to the investigation of spelt husk (SH) and nanoclay-modified compatibilised polypropylene (PP) binary and ternary composites for injection-moulding applications. PP composites were obtained using twin-screw extrusion. The content of mechanically milled SH microfiller with aspect ratio within 2 and 6 was fixed at 40 wt.%, whereas the amount of nanoclay functional filler in the polypropylene matrix was changed in the range from 0.5 to 5 wt.%. Nanoclay filler was introduced in the polypropylene matrix either in the form of nanoclay powder (C) or as a masterbatch (M). Regular distribution of the clay nanofiller within the polymer matrix has been observed, disregarding its form and concentration. The effects of the individual or combined addition of SH microreinforcement and nanoclay fillers on the rheological, mechanical, calorimetric, and thermal properties of the developed PP composites were investigated. It is revealed that the addition of the nanoclay fillers insignificantly influences the viscosity of both PP nanocomposites and hybrid composites with SH. Additionally, for PP nanocomposites, remarkable increases in tensile and flexural modules and strength are observed by maintaining considerable ultimate deformations, mainly in the case of M-containing systems. Concomitantly, because of the addition of the nanoclay filler, the improvement in thermal stability of PP nanocomposites and PP hybrid composites with SH is observed. As a result of SH addition, considerable increases in tensile and flexural modules are also observed. Results of the research demonstrate the potential of the use of natural materials (agricultural residues and clay minerals) for the development of PP composites with increased stiffness and thermal properties.

Effect of rice straw powder on properties of one-part alkali-activated slag

One-part alkali-activated slag (AAS) as a binder material has a promising application in the construction industry. The properties of one-part AAS incorporating agricultural wastes have been seldom studied. In this paper, the fresh and hardened properties of one-part AAS with the addition of rice straw powder (RSP) were investigated. The reaction rate in the acceleration period of AAS is reduced by RSP. The compressive strength of the mixture decreases with the introduction of RSP, while the flexural strength increases. The porosity of the hardened mixtures becomes lower when RSP was incorporated. N-(C)-A-S-H gel was detected in the system when 4.2% RSP was present. The RSP reduces the early-age autogenous shrinkage of AAS by providing internal curing to the matrix, but its effect on long-term drying shrinkage is limited.

Achieving superior high-strength geopolymer via the synergistic effect of traditional oven curing and microwave curing

Geopolymerization technology provides a green, pollution-free and economical method to solve the problem of massive accumulation of mine tailings in today’s society. The fabrication of geopolymer generally need a combination of oven curing and room temperature curing to take more than 3 days to have durable strength, which leads to the low production efficiency of the massive industrial production. In this paper, the feasibility of preparing spodumene tailings based high-strength geopolymer by the combination of oven curing and microwave curing was investigated. The obtained geopolymer products demonstrated excellent mechanical properties within 7 h, which indicates significantly improved production efficiency. Via the optimization of aggregate gradation and solid/liquid ratio, we achieved geopolymer with record-breaking compressive strength of 203.5 MPa and flexural strength of 34.1 MPa (exceeds 90 % of 28 days strength) after a combination of oven curing for 14 h and microwave curing for 16 min. The compressive and flexural strength increases by 30.5 % and 47.6 %, respectively, compared with those under conventional curing solely, and also increases by 128.1 % and 101.6 %, respectively, if compared to the sample cured by microwave only. The achieved high strength is mainly ascribed to synergistic effect of oven curing and microwave curing on the geopolymer matrix with optimized ratio of Si/Al and Na/Al which causes polymerization reaction almost completed in the early stage and leads to dense microstructure of the products. The obtained ultrahigh-strength geopolymer also has good thermal shock and freeze–thaw stability, and shows great application prospect in the field of construction and building materials.

Study on Flexural Behaviour of Ferrocement Composites Reinforced with Polypropylene Warp Knitted Fabric.

Ferrocement is a cost-effective construction material used in the low-cost constructions. It is produced with the combination of cement mortar with closely spaced wire mesh known as chicken wire mesh. Ferrocement process eliminates coarse aggregates when compared to reinforced concrete thus makes the process simple. This paper deals with the influence of various characteristics of warp knitted fabric on the flexural properties of ferrocement composites. Ferrocement composites have a wide range of applications in the construction industry and it has some limitations due to the durability issues. Among the various durability issues, corrosion is one of the main issues to be addressed to enhance the long-term service life of the ferrocement composites. The idea of using non-metallic mesh to eliminate the corrosion problem is discussed in this paper. In this experiment, warp knitted fabric reinforced ferrocement composites were produced using polypropylene warp knitted fabrics. This paper deals with the flexural properties of ferrocement composites made of warp knitted fabric coated with expoxy. This paper deals with the flexural properties of ferrocement composites made of warp knitted fabric coated with expoxy. These composites were analyzed for their flexural strength, energy absorption and ductile property. The variables in the experiment are filament thickness, warp knitted structure and number of layers in the composites. Experimental results proved that the replacement of chicken mesh wire by warp knitted fabrics has an impact in the flexural properties of the composites and the effect of variables in the experiment set up has been analyzed. There is an imporvement of 200% is observed in the first crack load and 120% improvement in the ultimate load of the warp knit fabric reinforced composite compared to control sample. Experimental results proved that there is an increase in flexural strength of ferrocement composites made up with warp knitted fabrics. Microstructure studies like SEM and EDX on ferrocement laminates confirmed good bonding between the mortar mix and warp knitted fabrics.

Effect of industrial waste molecular sieves on internally cured cement-based materials

Using waste molecular sieves (MS) instead of sand as water-absorbing fine aggregates in cement-based materials can effectively deal with factory adsorption waste and reduce sand consumption. In this article, the industrial waste molecular sieve is recycled and incorporated into cement-based materials. The effect of the molecular sieve as a hydration internal curing agent on the performance of cement-based materials is studied. A series of experiments are designed to find out the appropriate ratio and to evaluate and analyze the internal curing effect of waste molecular sieves. Compressive strength, flexural strength, and dry shrinkage properties of mortar with different dosages of the molecular sieve are tested. The water release behavior of the molecular sieve in mortar is comprehensively analyzed combined with the desorption test of the molecular sieve. Results show that the compressive and flexural strength increase by 5% and 10%, respectively, and the drying shrinkage decrease by 6% when 10% of sand is replaced by a molecular sieve under the same total water content. The hydration behavior of the sample is characterized by a microcosmic test of paste. Thermogravimetric analysis is used to calculate the content of corresponding hydration products and quantitatively describe the hydration degree of the internal curing paste mixed with MS. Results show that the content of hydration products is improved by the addition of the molecular sieve, which provides a theoretical basis for the enhancement of mortar to a certain extent.

Study on properties of copolymers based on different types of benzoxazines and branched epoxy resins

Previous studies on linear epoxy (bisphenol A epoxy) resin/benzoxazine composites showed that with the addition of epoxy (EP) resin, the resulting copolymers exhibited an increased glass transition temperature ( Tg) ( Tg reached a maximum value at a specific content), improved flexural strength, lower heat resistance, and reduced tensile strength. Herein, branched EP resin (AG-80)/benzoxazine copolymers featuring novolac (N-box) and siloxane (Si-box) chains were prepared without any external curing agent. In both systems, the EP resin endowed the copolymers with an increased crosslinking density; however, Tg continued to increase with increasing EP content. In addition, the heat resistance of the copolymers gradually enhanced. Different types of benzoxazines have various effects on the properties of copolymers. In terms of mechanical properties, AG-80/N-box copolymers exhibited brittle fracture characteristics; with increasing EP content, the flexural strength of the copolymer decreased while the tensile strength increased. AG-80/Si-box copolymers exhibited ductile fracture characteristics, with gradual increases in flexural and tensile strengths. Furthermore, with increasing EP content, the molecular chain migration ability and network homogeneity of the AG-80/N-box copolymers decreased gradually. Alternatively, in the case of the AG-80/Si-box copolymers, the molecular chain migration ability remained unchanged and network homogeneity improved. Hence, the developed copolymers can be used as resin matrices for the fabrication of advanced composites.

Experimental Investigation on the Mechanical Characteristics of Cement-Based Mortar Containing Nano-Silica, Micro-Silica, and PVA Fiber

This paper investigates bending and compressive strengths as mechanical characteristics of cement-based repair mortar containing nano-silica (NS) and micro-silica (SF) as cement replacements particles and polyvinyl alcohol (PVA) fibers. The mentioned materials were added to the mortar in three different conditions, including single (just one material), binary (mixture of two admixtures), and ternary (mixture of all three admixtures) modes. The use of PVA fibers, nano-silica and micro-silica in the triple combination of a cement-based mortar is the primary objective of the current research. In total, 28 mix designs with various percentages of particles and fiber were employed in the current study, and 112 different specimens were prepared to conduct the experimental research. The compressive and flexural strength results have been selected as the criteria for obtaining the optimum mix design for each condition. In order to specify the mechanical characteristics of specimens, a compressive test was carried out according to ACI 318, and the three-point bending test was utilized according to BS EN 1015-11. The results obtained from this study show that the mixture containing 10% silica fume (SF10) can be considered the optimum mix design for the single-mode condition. For such a mix design, a flexural strength increase of 27% and a compressive strength improvement of 48% were determined in comparison to the reference mixture design. The mixture containing nano-silica at 2% and silica fume at 8% (NS2SF8) was the optimum mix design in the binary mode condition. With the current mix design, a flexural strength improvement of 24% and a compressive strength increase of 49% in a 28-day specimen were recorded. Finally, under the ternary mode condition, a flexural strength enhancement of 3.5% and a compressive strength improvement of 4.6% were obtained. Additionally, the mixture design containing a PVA content of 0.75% and an SF content of 10% (PVA0.75SF10) was considered optimum.

A hybrid 1D/2D coating strategy with MXene and CNT towards the interfacial reinforcement of carbon fiber/poly(ether ether ketone) composite

Due to the inert carbon fiber (CF) surface and the poor wettability of CF with poly(ether ether ketone) (PEEK), the fiber-matrix interface bonding of CF/PEEK composite is relatively weak, which limits the mechanical performance of the composite. Herein, a complex sizing agent containing Ti3C2Tx MXene, carbon nanotube (CNT), and a dual compatibilizer of polyetherimide (PEI) was fabricated to graft on the CF surface. Compared with desized CF, the modified CF/PEEK composites showed a remarkable increase in flexural strength, flexural modulus, and interlaminar shear strength of 74.16%, 63.76%, and 62.79%, respectively. The improvement could be ascribed to the synergistic effects of multiple interactions, micromechanical interlockings, and substantially improved interfacial affinity by the hybrid grafting of MXene, CNT, and PEI. We also found that the interfacial failure mechanism changes from adhesive failure to cohesive failure with such a 1D/2D coating strategy. This facile and scalable approach demonstrates its potential for effectively improving fiber-matrix interfacial properties in CF/PEEK composites.

The Mechanical Behavior of Sustainable Concrete Using Raw and Processed Sugarcane Bagasse Ash

Sugarcane Bagasse Ash (SCBA) is one of the most common types of agricultural waste. By its availability and pozzolanic properties, sugarcane bagasse ash can be utilized as a partial replacement for cement in the production of sustainable concrete. This study experimentally investigated the impact of employing two types of sugarcane bagasse ash as a partial substitute for cement up to 30% on the compressive strength, flexural strength, and Young’s modulus of the concrete mixture. The first type of bagasse ash used was raw SCBA, which was used as it arrived from the plant, with the same characteristics, considering that it was exposed to a temperature of 600 °C in the boilers to generate energy. The second type of bagasse ash utilized, called processed SCBA, was produced by regrinding raw SCBA for an hour and then burning it again for two hours at a temperature of 600 °C. This was done to improve the pozzolanic activity and consequently the mechanical properties of the concrete mixture. The findings indicated that employing raw sugarcane bagasse ash had a detrimental effect on the mechanical characteristics of the concrete mixture but using processed sugarcane bagasse ash at a proportion of no more than 10% had a considerable effect on improving the properties of the concrete mixture. The utilization of processed SCBA up to 10% into the concrete mixture resulted in a 12%, 8%, and 8% increase in compressive strength, flexural strength, and Young’s modulus, respectively, compared to the normal concrete specimen. On the contrary, the inclusion of raw SCBA with varying content into the concrete mixture decreased compressive strength, flexural strength, and Young’s modulus by up to 50%, 30%, and 29%, respectively, compared to the normal concrete specimen. The experimental findings were validated by comparison with ACI predictions. ACI overestimated the flexural strength of SCBA concrete specimens, with a mean coefficient of difference between the ACI equation and experimental results of 22%, however, ACI underestimated the Young’s modulus of SCBA concrete specimens, with a mean coefficient of difference between the ACI equation and experimental results of −6%.

A novel seawater and sea sand concrete-filled CFRP-carbon steel composite tube column: Seismic behavior and finite element analysis

The seismic behavior of a novel seawater and sea sand concrete (SSC)-filled carbon fiber-reinforced polymer (CFRP)-carbon steel composite tube (SFSCT) column under combined axial compression and reversed cyclic loadings was studied in this paper. This structure makes use of seawater and sea sand resources, and CFRP was adopted to isolate the corrosion by chloride ions on the steel tube. Tests of eight composite columns were carried out. The test parameters include the axial compression ratio, the number of CFRP layers and the bonding direction. The test results revealed that all of the specimens displayed superb seismic performance with a drift ratio over 4%. The failure of the SFSCT column exhibits a typical compressive-flexural failure mode. Compared with the results of the SSC-filled steel tube columns, the hoop strain of the specimen under additional CFRP confinement is reduced by 1.6 times, and the flexural strength and drift capacity increase by 22% and 17%, respectively. A fiber model was created by finite element analysis, and parametric studies of the main design parameters were performed. The effects of the steel tube and CFRP on the seismic performance were evaluated. Using experiments and finite element analysis, the relationships among the drift capacity, axial compression ratio and confinement level were investigated. A design method for predicting the drift capacity of SFSCT columns was proposed.

Carbon Fibers and Graphite as Pore-Forming Agents for the Obtention of Porous Alumina: Correlating Physical and Fractal Characteristics

Porous alumina ceramics with different porosities were prepared via atmospheric pressure sintering using a sacrificial template method with alumina powder as the raw material and carbon fiber (CF) and graphite as pore-forming agents. The effects of the contents and ratios of the pore-forming agents and the aspect ratios of CF on the microstructure, mechanical properties, pore size, and pore-size distribution of the porous alumina samples were investigated. In addition, the surface fractal dimension (Ds) of porous alumina samples with different pore-forming agents was evaluated based on the mercury intrusion porosimetry data. The pore-size distribution of the prepared porous alumina samples showed single, double, or multiple peaks. The pore structure of the samples maintained the fibrous shape of the original CF and the flake morphology of graphite with a uniform pore-size distribution, but the pore structure and morphology were different. With the increase in the content of the pore-forming agent, the porosity of the samples gradually increased to a maximum of 63.2%, and the flexural strength decreased to a minimum of 12.36 MPa. The pore structure of the porous alumina samples showed obvious fractal characteristics. Ds was closely related to the pore structure parameters of the samples when the content of the pore-forming agent was 70 vol.%. It decreased with an increase in the sample porosity, most probable pore size and median pore size, but increased with an increase in the sample flexural strength.