Showing papers on "Flexural strength published in 2018"
TL;DR: In this paper, the Fused filament fabrication (FFFDM) is employed to fabricate continuous carbon and glass FRTP composites and its microstructural characteristics and the resulting tensile, flexural, and quasi-static indentation characteristics of the printed composites are examined.
328 citations
TL;DR: In this article, the effects of print-time interval on the inter-layer strength, along with compressive and flexural strengths of extrusion-based 3D printed concrete in different directions were investigated.
322 citations
TL;DR: In this paper, the tensile strength and elongation of the UHP-ECC achieved were 20 MPa and 8.7% respectively, which combines the strain-hardening and multiple crack characteristics and the high strength of mortar matrix.
322 citations
TL;DR: The main advantage of 3D concrete printing (3DCP) is that it can manufacture complex, non-standard geometries and details rapidly using a printer integrated with a pump, hosepipe and nozzle as mentioned in this paper.
311 citations
TL;DR: In this article, a series of experiments were carried out to measure workability, setting time, compressive strength, splitting tensile strength, flexural strength and dynamic elastic modulus of AAFS concrete.
267 citations
TL;DR: In this article, the effect of adding steel fibers with different lengths and diameters on the mechanical properties of concrete for three values of concrete strength was investigated, and the results indicated that the addition of different content and lengths of steel fiber with increasing water-to-cement ratios caused significant change in concrete, with an increase of about 10-25% in compressive strength and about 31-47% in direct tensile strength.
223 citations
TL;DR: In this paper, the strength and durability properties of concrete containing RCA were evaluated by a comprehensive experimental investigation involving nine control mixes, and the test results showed that up to 25% of natural crushed stone aggregates in concrete can be replaced with RCA, without significantly affecting the strength of concrete and that the partial replacement of natural aggregates with aggregate can be recommended in areas of moderate exposure conditions.
Abstract: Recycled concrete aggregates (RCA) sourced from waste concrete are a sustainable alternative to natural crushed stone aggregates. The strength and durability properties of concrete containing RCA were evaluated by a comprehensive experimental investigation involving nine control mixes. The variables considered in the experimental study are water cement ratio, cement content in concrete and percentage replacement of coarse aggregate. The strength properties such as compressive strength, modulus of elasticity, splitting tensile strength and flexural strength are studied. Durability properties such as water absorption, sorptivity, acid attack resistance and chloride permeability are also determined. The test results showed that up to 25% of natural crushed stone aggregates in concrete may be replaced with RCA, without significantly affecting the strength of concrete and that the partial replacement of natural aggregates with RCA can be recommended in areas of moderate exposure conditions. Mathematical models developed in the study can be used for the a priori prediction of the strength parameters of RCA concrete. A mix design methodology using the developed models is proposed to aid practicing engineers to determine the mix proportions of RCA concrete.
211 citations
TL;DR: In this paper, the thermal and mechanical properties of carbon fiber reinforced polyamide 12 (PA12) composites for fused deposition modeling (FDM) process were reported. And the results indicated that the tensile strength and flexural strength of 10 wt% CF/PA12 composites are enhanced by 102.2% and 251.1% respectively.
182 citations
TL;DR: In this article, the authors applied the Fuller Thompson theory and Marson-Percy model in designing cementitious materials for 3D Cementitious Materials Printing (3DCMP), and various gradation methods were adopted in this study.
178 citations
TL;DR: In this paper, an experimental investigation was carried out to study some mechanical and microstructural characteristics of fly ash based geopolymer mortars reinforced with three different fiber types: steel, polypropylene, and polyvinyl alcohol fibers.
174 citations
TL;DR: In this article, the tensile, flexural and fracture behavior of PEEK processed by fused filament fabrication (FFF) is reported, and three different configurations, viz., specimens built horizontally with a raster angle of 0° (H-0°) and 90°(H-90°).
TL;DR: The anisotropical behavior of printed specimens with regards to build orientation and positioning was revealed and it was found thataccuracies up to 10% along the Z-axis, as revealed in the present study, may restrict an accurate implant placement.
TL;DR: The volumetric wear of polished zirconia, lithium disilicate, and enamel were measured along with the wear of the opposing enamel cusps using a noncontact profilometer and the data were compared by ANOVA and Tukey‐Kramer analysis.
Abstract: Statement of problem Three mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) possesses excellent mechanical properties but is relatively opaque. Five mol% yttria-stabilized zirconia polycrystal (5Y-ZP) offers improved translucency, but many of its clinical properties have not been compared with those of 3Y-TZP and lithium disilicate. Purpose The purpose of this in vitro study was to compare the flexural strength, translucency parameter, bond strength, and enamel and material wear of 5Y-ZP (Katana UTML) with 3Y-TZP (Katana HT) and lithium disilicate (e.max CAD). Material and methods Flexural strength bars were sectioned (n=10, 25×4×2 mm), sintered or crystallized, polished, and fractured at 1 mm/min. Translucency specimens (1 mm thick) were fabricated (n=10). Their L*a*b* values were measured against a black-and-white background with a spectrophotometer, and ΔE 00 was calculated. Zirconia bond strength specimens were airborne-particle abraded with 50 μm alumina followed by the application of a 10-methacryloxydecyl dihydrogen phosphate–containing primer (Clearfil Ceramic Primer). Lithium disilicate bond strength specimens were etched with 5% hydrofluoric acid followed by application of a silane-containing primer (Clearfil Ceramic Primer). A Tygon tube filled with resin cement (Panavia SA) was fixed to the surface of the ceramics and light-polymerized. After 1 day or 150 days of water storage, the resin cement was debonded in a macroshear test (n=10). The cusps of extracted human molars were isolated and mounted into the University of Alabama at Birmingham wear-testing device. Wear testing was performed with a 20-N load for 300000 cycles in 33% glycerin. The volumetric wear of polished zirconia, lithium disilicate, and enamel were measured along with the wear of the opposing enamel cusps using a noncontact profilometer (n=8). The data were compared by ANOVA and Tukey-Kramer analysis (α=.05). Results No statistical difference was seen between the bond strengths ( P =.155) or the opposing enamel wear ( P =.533) of different ceramics. A statistically significant difference was seen between the flexural strength ( P P P 3 ) were 0 and 0.24 ±0.19 (Katana HT), 0 and 0.23 ±0.09 (Katana UTML), 0.28 ±0.13 and 0.31 ±0.10 (e.max CAD), and 0.09 ±0.03 and 0.31 ±0.14 (enamel). Conclusions 5Y-TZP has a flexural strength and translucency parameter between those of 3Y-TZP and lithium disilicate. Both the short-term and long-term bond strength of 5Y-ZP and 3Y-TZP was shown to be similar to lithium disilicate. 5Y-ZP demonstrated no measurable material wear and opposing enamel wear similar to that of all the other materials tested.
TL;DR: The results confirmed that fracture toughness and flexural modulus of the composites monotonically increased with fiber length and content, however, for all samples, composites showed negligible difference on the flexural strength.
Abstract: Bamboo fibers demonstrate enormous potential as the reinforcement phase in composite materials. In this study, in order to find suitable NaOH concentration for bamboo fiber treatment, bamboo fibers were treated with 2 wt.%, 6 wt.% and 10 wt.% NaOH solutions for 12 h, respectively. We determined that 6 wt.% NaOH treated bamboo fibers were optimal for the fabrication of bamboo fiber composites by single fiber tensile test, single fiber pull-out test, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The short length bamboo fibers treated with 6 wt.% NaOH solutions were well dispersed in the epoxy matrix by a new preparation method. The effect of fiber content and fiber length on the mechanical behavior of bamboo fiber reinforced epoxy composites was investigated. The results confirmed that fracture toughness and flexural modulus of the composites monotonically increased with fiber length and content. However, for all samples, composites showed negligible difference on the flexural strength. The fracture surfaces of the composites were observed by SEM, revealing that fiber breakage, matrix cracking, debonding, and fiber pull out were major failure types. In addition, thermogravimetric analysis (TGA) was carried out to investigate the thermal behavior of both bamboo fibers and composites.
TL;DR: In this paper, the dispersion of GO in water, alkali and several ionic species is investigated with the aid of UV-vis spectroscopy, showing that the amount of 0.03% GO by weight of cement can increase the flexural strength of GO-cement composite up to 67%.
TL;DR: In this article, important durability characteristics of concrete, including the chloride ion penetration, electrical resistivity, water penetration, water absorption, the pore size distribution, the carbonation, the sulfate resistance, frost resistance, shrinkage, and thermal properties were explored.
TL;DR: The results indicate the possibility of printing fibre-reinforced geopolymers which meet all the necessary properties in both the fresh and hardened states.
Abstract: This paper investigates the effect of polypropylene (PP) fibres on the fresh and hardened properties of 3D-printed fibre-reinforced geopolymer mortars. Different percentages of PP fibres ranging between 0.25% and 1.00% by volume were added to an optimised geopolymer mixture. All samples showed reasonable workability and extrudability. In addition, shape-retention ability in the fresh state was investigated as a major requirement for 3D-printing. The compressive strength of the printed specimens was tested in the hardened state in three loading directions, viz. longitudinal, perpendicular, and lateral. The flexural strength of samples was also tested in the longitudinal and lateral directions. In addition, the interlayer bond strength was investigated. Fibre addition seems to influence compressive strengths positively only when the loading is perpendicular to the interface plane. This is due to the preferential fibre alignment parallel to the direction of extrusion. The addition of fibre significantly enhanced the flexural performance of the printed samples. The use of fibre dosages of 0.75 and 1.00 vol % caused deflection-hardening behaviour of the 3D-printed geopolymers and, hence, a significantly higher fracture energy in comparison to specimens without fibre or with lower fibre content. However, an increase in the fibre volume caused some minor reduction in interlayer bond strength. With respect to properties in the fresh state, higher fibre volumes caused better shape-retention ability in the printed samples. The results indicate the possibility of printing fibre-reinforced geopolymers which meet all the necessary properties in both the fresh and hardened states.
TL;DR: In this paper, the interfacial bond properties between embedded steel fibers with different shapes (straight, hooked, and corrugated fibers) and UHPC matrices proportioned with either 15% or 20% silica fume, by mass of binder, under different curing times were investigated.
Abstract: The use of steel fiber is essential to secure high strength and ductility in producing ultra-high performance concrete (UHPC). In this study, the interfacial bond properties between embedded steel fibers with different shapes (straight, hooked, and corrugated fibers) and UHPC matrices proportioned with either 15% or 20% silica fume, by mass of binder, under different curing times were investigated. Flexural properties of UHPC reinforced with 2% different shaped fibers were also evaluated. Test results showed that corrugated and hooked fibers significantly improved the bond properties by three to seven times when compared to those with straight fibers. The flexural strength of UHPC with corrugated and hooked fibers were enhanced by 8%–28% and 17%–50%, respectively. Microstructural results from MIP, BSEM, and TG confirmed the change in bond properties. The bond strength of straight fibers exponentially increased with the decrease of calcium hydroxide content. Based on the composite theory, the flexural strengths of UHPC made with different shaped fibers can be efficiently predicted using the fiber-matrix bond strength, the flexural strength of the UHPC matrix (non-fibrous matrix), and the parameters of fibers. The ratios of predicted to measured flexural strengths ranged between 0.8 and 1.1, in which straight fibers showed a larger discreteness due to higher sensitivity of flexural strength associated with the orientation of fibers.
TL;DR: In this paper, the influence of incorporation of microfilament type polypropylene fibres into low strength recycled aggregate concrete on the basis of number of parameters such as compressive strength, split tensile strength, flexural strength, modulus of elasticity and non-destructive parameters was examined.
TL;DR: In this paper, the impact of the fiber orientation on mechanical properties and thermal conductivity of 3D-printed polypropylene (PP) composites filled with short carbon fibres was investigated.
Abstract: For composites based on polypropylene (PP) filled with short carbon fibres (CF), extrusion-based additive manufacturing provides a promising and cost-effective manufacturing technique that utilises the flow-induced orientation of the fibres for their targeted alignment through the control of the printing direction. This study investigates the impact of the fibre orientation on mechanical properties and thermal conductivity of 3D-printed PP composites filled with short-CF. Provided a homogeneous fibre-dispersion and a good fibre-matrix adhesion, the composites showed considerably improved mechanical properties compared to neat PP regardless of the fibre orientation. However, for the different printing orientations, a strong anisotropy in terms of flexural and impact properties and thermal conductivity was observed. For example, it was found that the thermal conductivity along the printing and, thus, the fibre direction was three times higher than perpendicular to that direction. The present work provides a key to the fabrication of parts with tailored, orientation-dependent properties.
TL;DR: This study characterized the mechanical properties, the crystalline microstructure and the surface topography of three yttrium-stabilized zirconia materials with different translucent properties, before and after aging in an autoclave, and found ML material obtained the highest survival rates for both fatigue strength and number of cycles to failure.
Abstract: This study characterized the mechanical properties (static and under fatigue), the crystalline microstructure (monoclinic - m, tetragonal - t and cubic - c phase contents) and the surface topography of three yttrium-stabilized zirconia (YSZ) materials with different translucent properties, before and after aging in an autoclave (low temperature degradation). Disc-shaped specimens were produced from second generation (Katana ML/HT – high-translucent) and third generations (Katana STML – super-translucent and UTML – ultra-translucent) YSZ ceramics (Kuraray Noritake Dental Inc.), following ISO 6872–2015 guidelines for biaxial flexural strength testing (final dimensions: 15 mm in diameter and 1.2 ± 0.2 mm in thickness), and then subjected to the respective tests and analyses. ML was mainly composed of tetragonal crystals, while STML and UTML presented cubic content. Aging increased the monoclinic content for ML and did not affect STML and UTML. Topographical analysis highlights different grain sizes on the ceramic surface (UTML > STML > ML) and aging had no effect on this outcome. Weibull analysis showed the highest characteristic strength for ML both before and after aging, and statistically similar Weibull moduli for all groups. ML material also obtained the highest survival rates (ML > STML > UTML) for both fatigue strength and number of cycles to failure. All fractures originated from surface defects on the tensile side. Third generation zirconia (Katana STML and UTML) are fully stabilized materials (with tetragonal and cubic crystals), being totally inert to the autoclave aging, and presented lower mechanical properties than the second-generation zirconia (Katana ML - metastable zirconia).
TL;DR: The crystallization degree of FDM-poly(lactic acid) controls its mechanical properties as mentioned in this paper, and post-printing thermal annealing of the polymer parts induces additional crystallization which positively affects the flexural stress of the samples.
Abstract: The crystallization degree of FDM‐poly(lactic acid) controls its mechanical properties. Post‐printing thermal annealing of the polymer parts induces additional crystallization, which positively affects the flexural stress of the samples. Application of radiation for sterilization of FDM‐PLA shapes may be done with restrictions.
TL;DR: In this article, a high-performance intrinsically flame-retardant epoxy resin (diglycidyl ether of daidzein (DGED)) was synthesized from renewable daidzen using an efficient one-step process, without the addition of additional flame retardants.
Abstract: Epoxy resins with high thermal and mechanical performance as well as good resistance to fire are difficult to synthesize. In this work, a high-performance intrinsically flame-retardant epoxy resin (diglycidyl ether of daidzein (DGED)) was synthesized from renewable daidzein using an efficient one-step process, without the addition of additional flame retardants. The structure of DGED was confirmed by Fourier transform infrared (FTIR), 1H NMR, and 13C NMR before it was cured with 4,4′-diaminodiphenylmethane (DDM). A commercial diglycidyl ether of bisphenol A (DGEBA) was cured with the same curing agent. Results indicated that the cured DGED/DDM system possessed glass transition temperature (Tg) of up to 205 °C (172 °C for DGEBA/DDM), and tensile strength, tensile modulus, flexural strength, and flexural modulus of 83, 2972, 131, and 2980 MPa, respectively, all much higher than those of cured DGEBA/DDM. The cured DGED/DDM system demonstrated excellent flame-retardant properties, showing a residual char of 4...
TL;DR: In this article, the performance of polyamide 12 (PA12) parts, fabricated using a production scale powder bed fusion printing process (HP Multi Jet Fusion printing process), was evaluated.
Abstract: Additive manufacturing (AM) is rapidly becoming one of the most popular manufacturing techniques for short run part production and rapid prototyping. AM encompasses a range of technologies, including powder bed fusion (PBF) process. The purpose of this paper is to evaluate and benchmark the mechanical performance of polyamide 12 (PA12) parts, fabricated using a production scale powder bed fusion printing process (HP Multi Jet Fusion printing process). This system has a build volume is 380 × 254 × 350 mm. The printed polymer parts were examined to determine their hydrophobicity, morphology, porosity and roughness. Chemical and thermal properties of the PA12 parts were also evaluated using attenuated total reflection infrared spectroscopy (ATR FT-IR), x-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC). The study highlights the influence of build orientation on the tensile (ISO 527-1:2012) and flexural (ISO 178:2010) properties. In terms of tensile strength, the parts exhibited isotropic behaviour with a maximum tensile strength of 49 MPa. In terms of flexural testing, the build orientations had a significant effect on the strength of the printed part. The Z orientation exhibited a 40% higher flexural strength, when compared to that of the X orientation. The maximum flexural strength observed was 70 MPa. The results of this rapid, production scale AM study are compared with previous studies that detail the mechanical performance of PA12, fabricated using PBF processes, such as selective laser sintering.
TL;DR: In this article, a roller compacted rubbercrete (RCR) was developed by partially replacing fine aggregate with crumb rubber (CR) in RCCP to improve its flexural resistance, ductile behavior and reduce the environmental effect of waste tires.
TL;DR: In this article, glass capsules containing one-component polyurethane healing agents are embedded in concrete to realize its self-healing properties, and their compatibility with concrete and survival rate are analyzed.
TL;DR: In this article, a combination of selective laser melting (SLM) additive manufacture and subtractive process was explored to produce maraging steel-copper bimetal, and a metallurgical bonded interface with a 30-40μm inter-diffusion region was formed.
TL;DR: In this paper, a comprehensive experimental program was undertaken to analyse the structural and material characteristics of synthetic fibre reinforced geopolymer concrete and the results indicated that the macro polyolefin fibres exhibited the largest fracture energy which was likely due to high mechanical bonding and low fibre aspect ratio.
TL;DR: In this paper, the authors evaluated the effect of jute fibers on the fresh and hardened properties of concrete cylinders and beams and found that the fiber length and volume had a positive influence on hardened concrete properties at early and extended curing ages, respectively.
TL;DR: In this paper, a steel cable reinforcement was used to improve the tensile strength and ductility of 3D printed concrete, which can be used for fiber reinforced concrete or concrete with in-process embedded steel reinforcement.