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Showing papers on "Flexural strength published in 2019"


Journal ArticleDOI
TL;DR: In this article, an experimental study on the relation between the 3DCP process parameters and the bond strength of 3D printed concrete is presented, in which the effect of 3 process parameters (interlayer interval time, nozzle height, and surface dehydration) on two mechanical properties (compressive strength and tensile strength, determined through flexural and splitting tests), has been established, in three perpendicular directions.

311 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the influence of binder composition and time interval between layers on layer-interface strength in 3D-printable cement-based compositions (3PCs).

258 citations


Journal ArticleDOI
TL;DR: In this paper, the mechanical properties of high performance concrete reinforced with basalt fiber and polypropylene fibers were investigated, and a conversion relationship between flexural strength and cube compressive strength was proposed.

239 citations


Journal ArticleDOI
TL;DR: In this article, an optimal basalt fiber content was determined basing firstly on suitable printability and then on mechanical performance using a self-developed 3D printer for extrusion of the cementitious material and also for mechanical enhancement of fiber alignment along the print direction.

224 citations


Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper investigated the rheological and harden properties of the high-thixotropy 3D printing concrete, and a large-scale components-bus station preliminarily was prepared by using this technology.

205 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of steel fiber content and shape on mechanical strength, toughness, and autogenous and drying shrinkage of UHPC was investigated, and three steel fiber shapes, including straight, corrugated, and hooked fibers, with volume fraction ranging from 0 to 3% were employed.
Abstract: Use of steel fibers in ultra-high performance concrete (UHPC) plays a significant role in enhancing strength and toughness and restraining shrinkage. This paper investigates the effect of steel fiber content and shape on mechanical strength, toughness, and autogenous and drying shrinkage of UHPC. Three steel fiber shapes, including straight, corrugated, and hooked fibers, with volume fraction ranging from 0 to 3% were employed. Compressive, flexural, and fiber-matrix bond strengths were evaluated. A statistical quadratic model and the Composite Theory were employed to predict the flexural strength of UHPC. Test results indicated that the increase in fiber volume can enhance the compressive and flexural strengths of UHPC and reduce shrinkage. The optimum fiber content for strength and shrinkage was found at 2%, beyond which the strength was slightly increased and the shrinkage was slightly decreased. For a given fiber content, the use of hooked fibers was most efficient in improving fiber-matrix bond and flexural strengths and reducing shrinkage. The flexural strengths of UHPC made with various fiber contents and shapes can be predicted using the proposed quadratic model and the Composite Theory. The latter considers the primary parameters affecting performance, including bond strength, matrix properties, and fiber characteristics. Finally, several models were used to simulate autogenous shrinkage behavior of UHPC and optimal models were found.

181 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of different PLA composites, build orientations and raster angles on mechanical responses are compared and analyzed in detail, and it is found that ceramic, copper and aluminum-based PLA composite parts have similar or even increased mechanical properties compared with virgin PLA made parts.
Abstract: Fused deposition modeling (FDM) has gained much attention in recent years, as it revolutionizes the rapid manufacturing of customized polymer-based composite components. To facilitate the engineering applications of these FDM-printed components, understanding their basic mechanical behaviors is necessary. In this paper, the mechanical characteristics, including tensile and flexural properties of samples fabricated by FDM with different additives, i.e. wood, ceramic, copper, aluminum and carbon fiber, based polylactic acid (PLA) composites are comprehensively investigated. The effects of different PLA composites, build orientations and raster angles on mechanical responses are compared and analyzed in detail. It is found that ceramic, copper and aluminum-based PLA composite parts have similar or even increased mechanical properties compared with virgin PLA made parts. In most cases, PLA composite samples that are FDM-printed in on-edge orientation with +45°/−45° raster angles have the highest mechanical strength and modulus. It is worth noting that the results in this research provide a useful guideline for fabricating complex functional PLA composite components with optimized mechanical properties.

177 citations


Journal ArticleDOI
04 May 2019-Polymers
TL;DR: The promising results in the present study prove the feasibility of 3D printed PLA-graphene composites for potential use in different applications such as biomedical engineering.
Abstract: Fused filament fabrication (FFF) is a promising additive manufacturing (AM) technology due to its ability to build thermoplastics parts with advantages in the design and optimization of models with complex geometries, great design flexibility, recyclability and low material waste. This technique has been extensively used for the manufacturing of conceptual prototypes rather than functional components due to the limited mechanical properties of pure thermoplastics parts. In order to improve the mechanical performance of 3D printed parts based on polymeric materials, reinforcements including nanoparticles, short or continuous fibers and other additives have been adopted. The addition of graphene nanoplatelets (GNPs) to plastic and polymers is currently under investigation as a promising method to improve their working conditions due to the good mechanical, electrical and thermal performance exhibited by graphene. Although research shows particularly promising improvement in thermal and electrical conductivities of graphene-based nanocomposites, the aim of this study is to evaluate the effect of graphene nanoplatelet reinforcement on the mechanical properties, dimensional accuracy and surface texture of 3D printed polylactic acid (PLA) structures manufactured by a desktop 3D printer. The effect of build orientation was also analyzed. Scanning Electron Microscope (SEM) images of failure samples were evaluated to determine the effects of process parameters on failure modes. It was observed that PLA-Graphene composite samples showed, in general terms, the best performance in terms of tensile and flexural stress, particularly in the case of upright orientation (about 1.5 and 1.7 times higher than PLA and PLA 3D850 samples, respectively). In addition, PLA-Graphene composite samples showed the highest interlaminar shear strength (about 1.2 times higher than PLA and PLA 3D850 samples). However, the addition of GNPs tended to reduce the impact strength of the PLA-Graphene composite samples (PLA and PLA 3D850 samples exhibited an impact strength about 1.2-1.3 times higher than PLA-Graphene composites). Furthermore, the addition of graphene nanoplatelets did not affect, in general terms, the dimensional accuracy of the PLA-Graphene composite specimens. In addition, PLA-Graphene composite samples showed, in overall terms, the best performance in terms of surface texture, particularly when parts were printed in flat and on-edge orientations. The promising results in the present study prove the feasibility of 3D printed PLA-graphene composites for potential use in different applications such as biomedical engineering.

169 citations


Journal ArticleDOI
TL;DR: In this article, the authors reported the first time manufacturing of hybrid fiber reinforced biodegradable composites using sisal and hemp fiber with polylactic acid employing melt processing and injection molding techniques.

163 citations


Journal ArticleDOI
TL;DR: In this article, a near fully dense mullite-TiB2-CNTs hybrid composite was prepared successfully trough spark plasma sintering, which showed uniform distribution of TiB2 reinforcements in mullite matrix without any pores and porosities.

153 citations


Journal ArticleDOI
TL;DR: In this paper, nano-SiO2 (NS) was introduced in a steam-cured cementitious system to induce the early hydration, with intention to promote the early strength.

Journal ArticleDOI
TL;DR: In this paper, a 3D-printable engineered cementitious composites (ECC) exhibiting ultra-high tensile strain capacity of more than 8%, which can be used for digital construction of self-reinforced concrete structures, reducing the reliance on conventional steel reinforcement.

Journal ArticleDOI
01 Feb 2019-Carbon
TL;DR: In this article, a binary nanofiller strategy was used to obtain high tensile strength and high electrical conductivity in epoxy with trace nanopolystyrene grafted with epichlorohydrin (nano g-PS).

Journal ArticleDOI
TL;DR: In this article, a CNT-reinforced mullite-based composite was prepared by spark plasma sintering at temperature of 1350°C, average heating rate of 60°C/min and a soaking time of 5´min.

Journal ArticleDOI
TL;DR: In this paper, an extensive experimental campaign was carried out to investigate the mechanical strength of fiber-reinforced lightweight foamed concrete, which was prepared with a viscosity enhancing agent that increases the cohesion and consistency of the cement paste at the fresh state.

Journal ArticleDOI
TL;DR: In this paper, the effect of filling pattern on tensile and flexural strength and modulus of the parts printed via fused deposition modeling (FDM), 3D printer was investigated.
Abstract: This experimental study investigates the effect of filling pattern on tensile and flexural strength and modulus of the parts printed via fused deposition modeling (FDM), 3D printer. The main downside of the printed products, with an FDM 3D printer, is the low strength compared to the conventional processes such as injection molding and machining. The issue stems from the low strength of thermoplastic materials and the weak bonding between deposited rasters and layers. Selection of proper filling pattern and infill percentage could highly influence the final mechanical properties of the printed products that were experimentally explored in this research work. Concentric, rectilinear, hilbert curve, and honeycomb patterns and filling percentage of 20, 50 and 100 were the variable parameters to print the parts. The results indicate that concentric pattern yields the most desirable tensile and flexural tensile properties, at all filling percentages, apparently due to the alignment of deposited rasters with the loading direction. Hilbert curve pattern also yielded a dramatic increase in the properties, at 100% filling. The dramatic increase could be mainly attributed to the promotion of strong bonding between the rasters and layers, caused by maintaining a high temperature of rasters at short travelling distances of nozzle for the hilbert curve pattern. Scanning electron microscopy (SEM) examination revealed the strong bonding between rasters and sound microstructures (less flaws and voids) for concentric and hilbert curve pattern at a high filling percentage of 100. Besides, SEM examination revealed large voids in honeycomb pattern, deemed to be responsible for its lower strength and modulus, especially at the filling percentage of 100.

Journal ArticleDOI
TL;DR: In this paper, a low-calcium (Class F) fly ash-based, polyvinyl alcohol (PVA) fiber reinforced EGC was developed and further modified by a ground-granulated blast-furnace slag (slag).
Abstract: Recently, the concept of engineered cementitious composites (ECCs) has been extended to the creation of engineered geopolymer composites (EGCs). Although showing similar mechanical characteristics (e. g., strain hardening and multiple cracking) to conventional ECC, the strength of existing EGC is generally low, and this sometimes restrains its applications. In the present study, a low-calcium (Class F) fly ash-based, polyvinyl alcohol (PVA) fiber reinforced EGC was developed and further modified by a ground-granulated blast-furnace slag (slag). The slag was used to replace the fly ash at content of 0%, 10%, 20%, and 30% (by weight). The effects of the slag on the mechanical properties (e.g., compressive strength, modulus of elasticity, uniaxial tensile behavior, flexural bending strength, and pullout bond strength) of the EGCs were investigated. The results revealed that all EGCs studied exhibited a strain/deflection hardening behavior under tension/flexure, and all slag replacements for fly ash enhanced strength-related properties but reduced ductility-related properties of the EGCs. The EGC mix with 20% slag replacement for fly ash (FA-20%S) had 102.3 MPa compressive strength, 6.8 MPa tensile strength, and 6.2 MPa bond strength, while the EGC mix with no slag (FA-0%S) had 72.6 MPa compressive strength, 4.7 MPa tensile strength, and 3.5 MPa bond strength at 28 days. These strength enhancements were mainly attributed to the improved density of the EGC matrix and the bond between the matrix and fiber. There are close relationships between the bond strength and other strengths, especially the tensile and flexural strengths, of the EGCs.

Journal ArticleDOI
TL;DR: In this article, the influence of glass fiber reinforcement on mechanical and durability performance of concrete made with recycled coarse aggregate (RCA) was investigated, and the results showed that 50% RCA concrete outperforms the plain natural coarse aggregate concrete at 0.5% GF in overall mechanical performance (compressive, split tensile and flexural strength).

Journal ArticleDOI
TL;DR: In this paper, the synergistic effect of combining macro polypropylene (PP) fiber and rubberized concrete was evaluated based on mechanical and durability performance, as well as microstructure.

Journal ArticleDOI
TL;DR: In this article, the simultaneous effect of nano-silica and steel fiber on the fresh and hardened state performance of self-compacting geopolymer concretes (SCGC) was investigated.

Journal ArticleDOI
TL;DR: In this article, the effect of silica fume content, ranging from 0 to 25%, by mass of cementitious materials, on rheological, fiber-matrix bond, and mechanical properties of non-fibrous UHPC matrix and uHPC made with 2% micro-steel fibers was investigated.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the engineering properties of normal strength and high strength FAGP and AAS concrete with OPC concrete and found that the tensile strength of both concrete types was comparable to OPC when the compressive strength of the concrete was about 35'MPa (normal strength concrete).

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the utilization of metakaolin as a mineral admixture in improving the properties of concrete mixes, containing varying percentages of recycled coarse aggregates (RCA).

Journal ArticleDOI
Junsong Fu1, Mengjie Zhang1, Lin Jin1, Liu Liu1, Na Li1, Lei Shang1, Ming Li1, Linghan Xiao1, Yuhui Ao1 
TL;DR: In this article, a facile and effective Layer-by-Layer self assembly method was proposed to deposit graphene oxide/silica (GO/SiO2) multilayers films onto CFs surface.

Journal ArticleDOI
TL;DR: In this article, the authors used hand lay-up technique to evaluate the best loading of date palm fibres (DPF) at different loading (40, 50, and 60% by wt.) and evaluate the flexural, thermal stability and dynamic mechanical properties of epoxy composites.
Abstract: The aim of the present study is to improve the flexural, thermal stability and dynamic mechanical properties of epoxy composites by reinforcing date palm fibres (DPF) at different loading (40%, 50% and 60% by wt.) and to evaluate the best loading through hand lay-up technique. Three point bending dynamic properties in terms of storage modulus (E′), loss modulus (E″) damping factor, Cole–Cole plot and thermal properties were analyzed by dynamic mechanical and thermogravimetric analyser, respectively. Flexural test results show that loading of 50% DPF increases both the flexural strength and modulus of pure epoxy composites from 26.15 MPa to 32.64 MPa and 2.26 GPa to 3.28 GPa, respectively. TGA results revealed that reinforcement of DPF in epoxy composites also improves the thermal stability and residual content. The residual content of epoxy (9.58%), 40% DPF/epoxy (12.51%), 50% DPF/epoxy (19.8%) and for 60% DPF/epoxy composites (15.2%) was noted, revealing that 50% DPF/epoxy composites confers the best result. Incorporation of DPF into epoxy also improves the E′ and E″ but 50% DPF show more remarkable improvement compared to 40% and 60% DPF loading. Moreover, damping factor decreases considerably by the reinforcement of DPF and are found lowest for 50% DPF/epoxy composites among all composites. Drawn Cole–Cole plot also suggests the existence of certain heterogeneity in DPF/epoxy composites compared to homogenous nature of epoxy composites. We concluded that 50% DPF loading is the ideal loading to enhanced flexural, thermal stability and dynamic properties of epoxy composites.

Journal ArticleDOI
TL;DR: In this paper, the effect of hybridization and chemical treatments on the mechanical properties of a novel intralaminar natural fibre hybrid composite was investigated, and it was found that the properties evaluated are significantly improved by addition of the natural fibres to pure jute based composites.
Abstract: The main objective of this work was to investigate the effect of hybridization and the effect of chemical treatments on the mechanical properties of a novel intralaminar natural fibre hybrid composite. Jute, sisal and curaua fibres were selected as natural fibre reinforcements for the epoxy matrix based composites which were produced by hand lay-up technique. The total volumetric fraction used in the fabrication of the hybrid composites was 30% of fibres and 70% of epoxy resin. Tensile, flexural and impact tests were carried out according to ASTM standards to characterize the novel hybrid composites. It was found that the mechanical properties evaluated are significantly improved by addition of the natural fibres to pure jute based composites. The fibre treatments had different effects on the mechanical properties of the hybrid composites. For sisal reinforced hybrid composites, the alkaline treatment had a positive impact on the composite properties (tensile, flexural and impact), while for the jute + curaua hybrid composites the alkali treatment had a negative effect on the tensile and impact properties. The mixed (alkalization + silanization) treatment had a positive effect on the jute + curaua flexural properties, while decreased the flexural properties for the jute + sisal composite. A scanning electron microscopy (SEM) was used to examine the fracture surface of the tested specimens.

Journal ArticleDOI
TL;DR: In this article, the effects of the GO content and water/cement ratio on the mechanical properties and microstructure of GO-cement composites were systematically investigated through experimental tests.

Journal ArticleDOI
01 Jan 2019-Carbon
TL;DR: In this article, a 3-phase model of the polymer matrix structure is interpreted in terms of a 3 phase model, in which the crystalline phase fluctuates from 39 to 34% upon GNP addition, and the Raman G band shows a progressive increment proportional to the bulk GNP percentage.

Journal ArticleDOI
TL;DR: In this article, the feasibility of directly entraining a continuous micro steel cable (1.2mm) during filaments (12mm) deposition process, forming a reinforced geopolymer composite material was explored.

Journal ArticleDOI
TL;DR: In this paper, a carbon fiber composite laminates were interfacially reinforced through in-situ synthesis of g-C3N4 on the carbon fibers, which greatly improved the roughness, functional groups and wettability of the carbon fiber surface.
Abstract: Carbon fiber composite laminates were interfacially reinforced through in-situ synthesis of g-C3N4 on the carbon fibers. The introduced g-C3N4 greatly improved the roughness, functional groups and wettability on the carbon fiber surface and markedly enhanced the interfacial properties of composite laminates. The surface free energy of carbon fibers was increased by 67.81%. Interlaminar shear strength and interfacial shear strength of composite laminates were increased from 51.84 to 72.09 MPa and 44.62–73.41 MPa, respectively. The significantly enhanced interfacial properties enabled the mechanical performance of composite laminates to reach a superior state. Tensile strength and bending strength were increased by 19.54 and 10.51%, respectively. The total absorbed energy of impact experiment was also enhanced from 1.14 to 1.78 J. Meanwhile, dynamic mechanical properties and hydrothermal aging resistance were also ameliorated significantly. The improved interfacial properties and mechanical properties were ascribed to the increased mechanical interlocking, enhanced chemical bonding and ameliorated wettability created by g-C3N4.