Fibre can enhance the mechanical properties of cement-based composites,but fibre also degrades their workability.However,the quantitative effects of fiber content and length-diameter ratio on alkali-activated material...Fibre can enhance the mechanical properties of cement-based composites,but fibre also degrades their workability.However,the quantitative effects of fiber content and length-diameter ratio on alkali-activated materials are still unclear.Various aspect ratio,volume fraction of polyvinyl alcohol fibre(PVAF),and various water-binder ratio were employed to prepare a total of 26 groups of fibre reinforced alkali-activated composite(FRAAC).The influence of PVAF fibre factor(product of fiber volume fraction and length-diameter ratio)on flowability,compactness,strength,and crack fractal dimension of FRAAC was researched.The influence of water-binder ratio on the plastic viscosity of FRAAC was more significant than that on the yield stress.When fibre factor was lower than critical value of 150,the influence of fibres could be overlooked.The reason was that the space between fibres was distant,so the flowability of FRAAC was not impacted by PVAF.At this time,fibres were challenging to restrict the cracks in matrix and increase their mechanical properties.When fibre factor was higher than critical value 150 and lower than density packing value 450,the flexural strength,compressive strength and crack fractal dimension of FRAAC were considerably enhanced,and the FRAAC could still flow easily under dead weight.When fibre factor were above 450,noteworthy fibre balling considerably decreased the flowability,leading to poor solidity and reduced compressive strength.Hence,the ideal content of PVAF in alkali activated composite is between 150/(l/d)and 450/(l/d).展开更多
In order to examine the biaxial compression-compression properties of rubber fibre reinforced concrete(RFRC),an experimental study on RFRC under different lateral compressive stresses was carried out by considering di...In order to examine the biaxial compression-compression properties of rubber fibre reinforced concrete(RFRC),an experimental study on RFRC under different lateral compressive stresses was carried out by considering different rubber replacement rates and polypropylene fibre contents.The failure modes and mechanical property parameters of different RFRC working conditions were obtained from the experiment to explore the effects of rubber replacement rate and polypropylene fibre content on the biaxial compression-compression properties of RFRC.The following conclusions were drawn.Under the influence of lateral compressive stress,the biaxial compression-compression failure mode gradually developed from a columnar pattern to a flaky pattern,suggesting that the incorporation of rubber and polypropylene fibres into the concrete resulted in a significant change in the development of cracks.For different rubber replacement rates and polypropylene fibre contents,the vertical compressive stress exhibited the same developing trend under the influence of lateral compressive stress.Specifically,the lateral compressive stress imposed the minimum effect on the vertical compressive stress when the rubber replacement rate and polypropylene fibre content were 20%and 0.4%,respectively,and imposed the maximum effect when the rubber replacement rate and polypropylene fibre content were 20%and 0%,respectively.With the increase of rubber replacement rate,the vertical peak stress was significantly reduced,which implies that an appropriate amount of polypropylene fibres can increase the vertical peak stress to a certain extent.Then,the biaxial compression-compression mechanism of RFRC was analysed from the microscopic level by using scanning electron microscope(SEM).Meanwhile,based on Kupfer’s biaxial compression-compression failure criterion and the octahedral stress space,a biaxial compression-compression failure criterion for RFRC was proposed,which was proven to have good applicability.The research results of this study provide important theoretical basis for the engineering application and development of RFRC.展开更多
Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to ...Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to the linear elastic fracture mechanics,the mechanics of composite material and the classical thin plate bending theory,a common theoretical model of the critical drilling thrust force for CFRP plates is established.Compared with the experimental data of previous studies,the results show that the theoretical values agree well with the experimental values.This model can be used to forecast the critical thrust force for the drilling-induced delamination of CFRP.展开更多
Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic...Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.展开更多
Recycled polypropylene filaments for fused filament fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure and mechanical properties of the filaments and 3D printed...Recycled polypropylene filaments for fused filament fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure and mechanical properties of the filaments and 3D printed specimens were characterized using scanning electron microscopy and standard tensile testing. It was observed that recycled polypropylene filaments with 14 wt% short carbon fibre reinforcement contained pores that were dispersed throughout the microstructure of the filament. A two-stage filament extrusion process was observed to improve the spatial distribution of carbon fibre reinforcement but did not reduce the pores. Recycled polypropylene filaments without reinforcement extruded at high screw speeds above 20 rpm contained a centreline cavity but no spatially distributed pores. However, this cavity is eliminated when extrusion is carried out at screw speeds below 20 rpm. For 3D printed specimens, interlayer cavities were observed larger for specimens printed from 14 wt% carbon fibre reinforced recycled polypropylene than those printed from unreinforced filaments. The values of tensile strength for the filaments were 21.82</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 24.22</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, which reduced to 19.72</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 22.70</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, respectively, for 3D printed samples using the filaments. Likewise, the young’s modulus of the filaments was 1208.6</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 1412.7</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, which reduced to 961.5</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 1352.3</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, respectively, for the 3D printed samples. The percentage elongation at failure for the recycled polypropylene filament was 9.83% but reduced to 3.84% for the samples printed with 14 wt% carbon fiber reinforced polypropylene filaments whose elongation to failure was 6.58%. The SEM observations on the fractured tensile test samples showed interlayer gaps between the printed and the adjacent raster layers. These gaps accounted for the reduction in the mechanical properties of the printed parts.展开更多
Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles.Rebounded concrete amount cause a significant difference between the initial mix de...Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles.Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions.Apart from the structural differences,it comes with a cost increase which was resulted by the splashed concrete amount.Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes;however,this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production.This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values.Glass fibre reinforced mixtures were also modelled with a finite element method based software and,the analysis results were compared with production line results.Results of the analysis and on-site studies showed a decisive correlation between,discharge distance,discharge angle and the viscosity of the concrete.展开更多
Material selection has become a critical part of design for engineers,due to availability of diverse choice of materials that have similar properties and meet the product design specification.Implementation of statist...Material selection has become a critical part of design for engineers,due to availability of diverse choice of materials that have similar properties and meet the product design specification.Implementation of statistical analysis alone makes it difficult to identify the ideal composition of the final composite.An integrated approach between statistical model and micromechanical model is desired.In this paper,resultant natural fibre and polymer matrix from previous study is used to estimate the mechanical properties such as density,Young’s modulus and tensile strength.Four levels of fibre loading are used to compare the optimum natural fibre reinforced polymer composite(NFRPC).The result from this analytical approach revealed that kenaf/polystyrene(PS)with 40%fibre loading is the ideal composite in automotive component application.It was found that the ideal composite score is 1.156 g/cm^(3),24.2 GPa and 413.4 MPa for density,Young’s modulus and tensile strength,respectively.A suggestion to increase the properties on Young’s modulus are also presented.This work proves that the statistical model is well incorporated with the analytical approach to choose the correct composite to use in automotive application.展开更多
The tensile behaviour of soil plays a significantly important role in various engineering applications. Compacted soils used in geotechnical constructions such as dams and clayey liners in waste containment facilities...The tensile behaviour of soil plays a significantly important role in various engineering applications. Compacted soils used in geotechnical constructions such as dams and clayey liners in waste containment facilities can suffer from cracking due to tensile failure. In order to increase soil tensile strength, discrete fibre reinforcement technique was proposed. An innovative tensile apparatus was developed to deter- mine the tensile strength characteristics of fibre reinforced soil. The effects of fibre content, dry density and water content on the tensile strength were studied. The results indicate that the developed test apparatus was applicable in determining tensile strength of soils. Fibre inclusion can significantly in- crease soil tensile strength and soil tensile failure ductility. The tensile strength basically increases with increasing fibre content. As the fibre content increases from 0% to 0.2%, the tensile strength increases by 65.7%. The tensile strength of fibre reinforced soil increases with increasing dry density and decreases with decreasing water content. For instance, the tensile strength at a dry density of 1.7 Mg/m^3 is 2.8 times higher than that at 1.4 Mg/m^3. It decreases by 30% as the water content increases from 14.5% to 20.5%. Furthermore, it is observed that the tensile strength of fibre reinforced soil is dominated by fibre pull-out resistance, depending on the interracial mechanical interaction between fibre surface and soil matrix.展开更多
Surface originated kink bands consist of an important failure mode for fibre-reinforced compo- sites under compression. The mechanical behavior of the fibre bridging kink bands is explored herein in the context of the...Surface originated kink bands consist of an important failure mode for fibre-reinforced compo- sites under compression. The mechanical behavior of the fibre bridging kink bands is explored herein in the context of the post-microbuckling theory. Expressions of bridging force are obtained for the entire postbuckling process of the fibres exhibiting weak or strong hardening. The postbuckling formulation of the fibres is applied to yield the toughness increment due to the advancing kink bands, and consequently leads to a quantitative pre- diction on the overall compressive stress strain curves of the fibre-reinforced composites.展开更多
The use of fiber reinforced polymer(FRP)bars to substitute the steel bars in internal reinforcement is now an alternative in some structures subjected by corrosion.The strength,stiffness and bond characteristics of FR...The use of fiber reinforced polymer(FRP)bars to substitute the steel bars in internal reinforcement is now an alternative in some structures subjected by corrosion.The strength,stiffness and bond characteristics of FRP bars are tested to understand their flexural behaviour.In this study is investigated the way of failure of beams reinforced internally with carbon FRP(CFRP)bars and their mechanical properties.Two sets of concrete beams reinforced with different diameters of CFRP bars are designed and tested under four-point loading methods.In general,beams reinforced with FRP bars show more deflections and greater values of crack width than beams reinforced with conventional steel,which is due to their low modulus of elasticity and general stiffness.In this paper is presented the calculation and comparison of deflection using different methods,such as ACI 440,CAN/CSA,Eurocode and experimental loading tests.The evaluation is done comparing the results of every method.This study is effective when we use beams with one layer of reinforcement.展开更多
Auxetic materials are cellular materials with a unique property of negative Poisson’s ratio.The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction.For...Auxetic materials are cellular materials with a unique property of negative Poisson’s ratio.The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction.For the first time,the quasi-static uniaxial compression performance of fused filament fabricated re-entrant diamond auxetic metamaterial is evaluated in the x-direction(in-plane)and z-direction(out-of-plane).The most commonly used thermoplastic feedstock,Acrylonitrile butadiene styrene,is considered a material of choice.The effect of influential geometrical parameters of the re-entrant diamond structure and printing parameter is systematically studied using Taguchi’s design of experiments.Grey-based multi-objective optimisation technique has been adopted to arrive at the optimal structure.Efforts are made to improve the stiffness and strength of the structure with fibre reinforcements.Micro glass fibre reinforcements have enhanced specific strength and stiffness in both in-plane and out-ofplane directions.A sevenfold and thirteen times increase in specific strength and energy absorption is evident for glass fibre-reinforced structures in out-of-plane directions compared to in-plane ones.Proper tuning of geometrical parameters of the re-entrant diamond structure can result in a Poisson’s ratio of up to-3.49 when tested in the x-direction.The parametric study has illustrated the tailorability of the structure according to the application requirements.The statistical study has signified each considered parameter’s contribution to the compression performance characteristics of the 3D printed re-entrant diamond auxetic metamaterial.展开更多
This paper aims to characterise surface morphology and 3D roughness parameters of unidirectional carbon fibre reinforced plastic(UD-CFRP)milled at 0°,45°,90°,and 135°fibre orientation angles(FOAs)....This paper aims to characterise surface morphology and 3D roughness parameters of unidirectional carbon fibre reinforced plastic(UD-CFRP)milled at 0°,45°,90°,and 135°fibre orientation angles(FOAs).Side milling experiments are conducted on UD-CFRP laminates.Surface damage forms and texture direction of milled surface are analysed.Spatial frequency of defects on CFRP surface is quantitatively determined using radially averaged 2D PSD.The kinematicdynamic surface topography is reconstructed considering feed,runout and vibration,then the ideal roughness parameters,S_(a),S_(q),S_(sk),and S_(ku)are calculated and compared with the measured ones,finally the material factor-induced roughness components are quantified.Results show that CFRP surface has no regular feed marks.The frequency of fibre breakage or surface defects is greater than tooth passing frequency.FOAs sorted by their average S_(a)in descending order is135°>90°>45°>0°,where surface defects contribute 93.9%,77.1%,73.2%,72.2%of the total roughness respectively,which suggests that surface defects show a more important role than tool kinematics and vibration in formation of milled surface.The negative Skewness(Ssk<0)and high Kurtosis(S_(ku)=4.0–11.5)of milled surface signify porosity and the presence of many anomalous deep valleys in milled surface,respectively.展开更多
Fused deposition modelling(FDM)printed short carbon fibre reinforced nylon(SCFRN)composites were fabricated.The friction and wear behaviour of printed materials were systematically investigated under both dry sliding ...Fused deposition modelling(FDM)printed short carbon fibre reinforced nylon(SCFRN)composites were fabricated.The friction and wear behaviour of printed materials were systematically investigated under both dry sliding and water lubricated conditions.The results showed that with short fibre enhancements,the printed SCFRN achieved a lower friction coefficient and higher wear resistance than nylon under all tested conditions.Further,under water lubricated conditions,the printed SCFRN exhibited a low,stable friction coefficient due to the cooling and lubricating effects of water.However,the specific wear rate of the printed specimens could be higher than that obtained under dry sliding conditions,especially when the load was relatively low.The square textured surface was designed and created in the printing process to improve materials’tribological performance.It was found that with the textured surface,the wear resistance of the printed SCFRN was improved under dry sliding conditions,which could be explained by the debris collection or cleaning effect of surface texture.However,such a cleaning effect was less noticeable under lubricated conditions,as the liquid could clean the surface effectively.On the other hand,surface textures could increase the surface area exposed to water,causing surface softening due to the higher water absorption rate.As a result,the samples having surface textures showed higher wear rates under lubricated conditions.The work has provided new insights into designing wear resistant polymer materials using three-dimensional(3D)printing technologies,subjected to different sliding conditions.展开更多
In conventional manufacturing processes of composites, Carbon Fibre Reinforced Plastic (CFRP) laminates have been made by stacking unidirectional or woven prepreg sheets. Recently, as a manufacturing process of CFRP, ...In conventional manufacturing processes of composites, Carbon Fibre Reinforced Plastic (CFRP) laminates have been made by stacking unidirectional or woven prepreg sheets. Recently, as a manufacturing process of CFRP, 3D printing of CFRP composites has been developed. The 3D printing process of CFRP composites enables us to fabricate CFRP laminates with arbitrary curvilinear fibre plies. This indicates that the optimization of the in-plane curved carbon fibre placement in a planar ply is strongly required to realize superior 3D printed composites. In the present paper, in-plane curved carbon fibre alignment of a ply with an open hole is optimized in terms of maximization of the fracture strength. For the optimization process, a genetic algorithm is adopted. To describe curved carbon fibre alignments in a planar ply, stream lines of perfect flow is employed. By using the stream lines of the perfect flow, number of optimization parameters is significantly reduced. After the optimization, the fracture strength of CFRP laminate is compared with the results of unidirectional CFRP ply. The curved fibre placement in a planar ply shows superior fracture improvement.展开更多
The effects of voids(void content,void shape and size)on the interlaminar shear strength of[(±45)_(4)/(0,90)/(±45)_(2)]_(S) and [(±45)/0_(4)/(0,90)/0_(2)]_(S) composite laminates were investigated.Speci...The effects of voids(void content,void shape and size)on the interlaminar shear strength of[(±45)_(4)/(0,90)/(±45)_(2)]_(S) and [(±45)/0_(4)/(0,90)/0_(2)]_(S) composite laminates were investigated.Specimens with void contents in the range of 0.2%-8.0%for [(±45)_(4)/(0,90)/(±45)_(2)]_(S) and 0.2%-6.1%for[(±45)/0_(4)/(0,90)/0_(2)]_(S) were fabricated from carbon/epoxy fabric through varying autoclave pressures.The characteristics of the voids were studied by using optical image analysis to explain the interlaminar shear strength results.The influences of voids on the interlaminar shear strength of the two stacking sequences were compared in terms of the void content and size and shape of the void.The effect of voids on the initiation and propagation of interlaminar failure of both stacking sequence composites was found.展开更多
Beam-Column joints are critical zones in reinforced concrete structures which are most vulnerable to earthquake forces. Hence strengthening beam-column joint is vital to save the structure and its inhabitants in case ...Beam-Column joints are critical zones in reinforced concrete structures which are most vulnerable to earthquake forces. Hence strengthening beam-column joint is vital to save the structure and its inhabitants in case of seismic forces. Numerous retrofitting works using fibre reinforced polymer (FRP) composites are being undertaken worldwide. This work aims to investigate the effectiveness of strengthening beam-column joints using natural and artificial fibres. In this study, basalt (natural fibres) as monolithic composite (BFRP) and as hybrid composite along with glass (artificial fibres) were used for strengthening of beam-column joints. Totally six specimens were prepared and tested under monotonic loading. Specimen details used were: two control specimen, two specimens for monolithic wrapping and remaining two specimens for hybrid wrapping. The test results were compared with control and rehabilitated specimens. The performance of the treated joints was studied using the following parameters: initial and ultimate cracking loads, energy absorption, deflection ductility and stiffness at ultimate. From the test results, it was found that the hybrid combination of Basalt and Glass FRPs were found to be more effective in the treatment of beam-column joints. The strong column weak beam concept was achieved by failure in beam portion which helped in preventing the catastrophic failure of the entire structure.展开更多
Adhesively Bonded Carbon Fibre Reinforced Plastic(CFRP)and titanium alloy have been extensively used as a hybrid structure in modern aircrafts due to their excellent combination of mechanical properties and chemical s...Adhesively Bonded Carbon Fibre Reinforced Plastic(CFRP)and titanium alloy have been extensively used as a hybrid structure in modern aircrafts due to their excellent combination of mechanical properties and chemical stabilities.This study utilised NaOH anodising method to create micro-rough titanium surfaces for enhancing adhesive bonding between titanium alloy and CFRP laminates.A special and simple technique named Resin Pre-Coating(RPC)was also employed to improve the surface wetting of anodised titanium and grinded CFRP substrates.The influences of anodising temperature and duration on the surface morphology,wettability and adhesive bond strength were investigated.The single lap shear test results showed that the bond strength of specimens anodised at 20℃for 15 min improved by 135.9%and 95.4%,respectively,in comparison with that of acid pickled and grinded specimens(without RPC treatment).Although increasing the anodising temperature and duration produced rougher titanium surfaces,the adhesively bonded joints were not strong enough due to relatively friable titanium oxide layers.展开更多
The objectives of this study are to review and evaluate the developments and applications of pultruded fiber-reinforced polymer composites in civil and structural engineering and review advances in research and develo...The objectives of this study are to review and evaluate the developments and applications of pultruded fiber-reinforced polymer composites in civil and structural engineering and review advances in research and developments.Several case applications are reviewed.The paper presents a state-of-the-art review of fundamental research on the behavior of pultruded fiber reinforced polymer closed sections and highlights gaps in knowledge and areas of potential further research.展开更多
Fibre reinforced polymer composites have become a new generation of structural materials due to their unique advantages such as high specific strength,designability,good dimensional stability and ease of large-area mo...Fibre reinforced polymer composites have become a new generation of structural materials due to their unique advantages such as high specific strength,designability,good dimensional stability and ease of large-area monolithic forming.However,the problem of interfacial bonding between the resin matrix and the fibres limits the direct use of reinforcing fibres and has become a central difficulty in the development of basalt fibre-epoxy composites.This paper proposes a solution for enhancing the strength of the fibre-resin interface using maize starch nanocrystals,which are highly yield and eco-friendly.Firstly,in this paper,corn starch nanocrystals(SNC)were prepared by hydrolysis,and were deposited on the surface of basalt fibers by electrostatic adsorption.After that,in order to maximize the modification effect of nano-starch crystals on the interface,the basalt fiber-epoxy resin composite samples were prepared by mixing in a pressureless molding method.The test results shown that the addition of basalt fibers alone led to a reduction in the strength of the sample.Deposition of 0.1 wt%SNC on the surface of basalt fibers can make the strength consistent with pure epoxy resin.When the adsorption amount of SNC reached 0.5 wt%,the tensile strength of the samples was 23.7%higher than that of pure epoxy resin.This is due to the formation of ether bond homopolymers between the SNC at the fibre-epoxy interface and the epoxy resin,which distorts the originally smooth interface,leading to increased stress concentration and the development of cracks.This enhances the binding of basalt fibers.The conclusions of this paper can provide an effective,simple,low-cost and non-polluting method of interfacial enhancement modification.展开更多
This paper presents a state-of-the-art review of research on the utilization of fibers(predominantly derived from waste materials)as reinforcement in adobe brick production.Recycling of these wastes provides sustainab...This paper presents a state-of-the-art review of research on the utilization of fibers(predominantly derived from waste materials)as reinforcement in adobe brick production.Recycling of these wastes provides sustainable construction materials and helps to protect the environment.Specimen preparation and test procedures are outlined.The effects of addition of these wastes on the physical and mechanical properties of adobe bricks as presented in the literature,are investigated.The main results for each additive are presented and discussed.It is concluded that improved adobe brick properties can be expected with the addition of combination of waste additives.The use of waste materials in the construction industry is generally of interest and useful for engineers and designers seeking sustainable solutions in construction.It is also of interest to researchers actively seeking to develop methodical approaches to quantifying,optimising and testing the performance in use of such waste material additives.展开更多
基金funding of Henan Province Transportation Science and Technology Plan Project(2021J3).
文摘Fibre can enhance the mechanical properties of cement-based composites,but fibre also degrades their workability.However,the quantitative effects of fiber content and length-diameter ratio on alkali-activated materials are still unclear.Various aspect ratio,volume fraction of polyvinyl alcohol fibre(PVAF),and various water-binder ratio were employed to prepare a total of 26 groups of fibre reinforced alkali-activated composite(FRAAC).The influence of PVAF fibre factor(product of fiber volume fraction and length-diameter ratio)on flowability,compactness,strength,and crack fractal dimension of FRAAC was researched.The influence of water-binder ratio on the plastic viscosity of FRAAC was more significant than that on the yield stress.When fibre factor was lower than critical value of 150,the influence of fibres could be overlooked.The reason was that the space between fibres was distant,so the flowability of FRAAC was not impacted by PVAF.At this time,fibres were challenging to restrict the cracks in matrix and increase their mechanical properties.When fibre factor was higher than critical value 150 and lower than density packing value 450,the flexural strength,compressive strength and crack fractal dimension of FRAAC were considerably enhanced,and the FRAAC could still flow easily under dead weight.When fibre factor were above 450,noteworthy fibre balling considerably decreased the flowability,leading to poor solidity and reduced compressive strength.Hence,the ideal content of PVAF in alkali activated composite is between 150/(l/d)and 450/(l/d).
基金supported by the National 12th Five Year Plan of Science and Technology Support Project(2015 BAL02b02)National Spark Plan Project(2015 GA690045),Jiangsu Province“Six Talent Peaks”Team Project(XCL-CXTD−007).
文摘In order to examine the biaxial compression-compression properties of rubber fibre reinforced concrete(RFRC),an experimental study on RFRC under different lateral compressive stresses was carried out by considering different rubber replacement rates and polypropylene fibre contents.The failure modes and mechanical property parameters of different RFRC working conditions were obtained from the experiment to explore the effects of rubber replacement rate and polypropylene fibre content on the biaxial compression-compression properties of RFRC.The following conclusions were drawn.Under the influence of lateral compressive stress,the biaxial compression-compression failure mode gradually developed from a columnar pattern to a flaky pattern,suggesting that the incorporation of rubber and polypropylene fibres into the concrete resulted in a significant change in the development of cracks.For different rubber replacement rates and polypropylene fibre contents,the vertical compressive stress exhibited the same developing trend under the influence of lateral compressive stress.Specifically,the lateral compressive stress imposed the minimum effect on the vertical compressive stress when the rubber replacement rate and polypropylene fibre content were 20%and 0.4%,respectively,and imposed the maximum effect when the rubber replacement rate and polypropylene fibre content were 20%and 0%,respectively.With the increase of rubber replacement rate,the vertical peak stress was significantly reduced,which implies that an appropriate amount of polypropylene fibres can increase the vertical peak stress to a certain extent.Then,the biaxial compression-compression mechanism of RFRC was analysed from the microscopic level by using scanning electron microscope(SEM).Meanwhile,based on Kupfer’s biaxial compression-compression failure criterion and the octahedral stress space,a biaxial compression-compression failure criterion for RFRC was proposed,which was proven to have good applicability.The research results of this study provide important theoretical basis for the engineering application and development of RFRC.
基金the financial support of Aeronautical Science Foundations of China(No.2013ZE52067,No.2014ZE52057)
文摘Exit delamination is excessive drilling thrust force.Therefore,it is necessary to investigate the critical thrust force which cause exit delamination when carbon fibre reinforced plastics(CRFP)is drilled.According to the linear elastic fracture mechanics,the mechanics of composite material and the classical thin plate bending theory,a common theoretical model of the critical drilling thrust force for CFRP plates is established.Compared with the experimental data of previous studies,the results show that the theoretical values agree well with the experimental values.This model can be used to forecast the critical thrust force for the drilling-induced delamination of CFRP.
基金This project is supported by National Natural Science Foundation of China(No.50175031).
文摘Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.
文摘Recycled polypropylene filaments for fused filament fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure and mechanical properties of the filaments and 3D printed specimens were characterized using scanning electron microscopy and standard tensile testing. It was observed that recycled polypropylene filaments with 14 wt% short carbon fibre reinforcement contained pores that were dispersed throughout the microstructure of the filament. A two-stage filament extrusion process was observed to improve the spatial distribution of carbon fibre reinforcement but did not reduce the pores. Recycled polypropylene filaments without reinforcement extruded at high screw speeds above 20 rpm contained a centreline cavity but no spatially distributed pores. However, this cavity is eliminated when extrusion is carried out at screw speeds below 20 rpm. For 3D printed specimens, interlayer cavities were observed larger for specimens printed from 14 wt% carbon fibre reinforced recycled polypropylene than those printed from unreinforced filaments. The values of tensile strength for the filaments were 21.82</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 24.22</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, which reduced to 19.72</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 22.70</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, respectively, for 3D printed samples using the filaments. Likewise, the young’s modulus of the filaments was 1208.6</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 1412.7</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, which reduced to 961.5</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa and 1352.3</span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">MPa, respectively, for the 3D printed samples. The percentage elongation at failure for the recycled polypropylene filament was 9.83% but reduced to 3.84% for the samples printed with 14 wt% carbon fiber reinforced polypropylene filaments whose elongation to failure was 6.58%. The SEM observations on the fractured tensile test samples showed interlayer gaps between the printed and the adjacent raster layers. These gaps accounted for the reduction in the mechanical properties of the printed parts.
文摘Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles.Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions.Apart from the structural differences,it comes with a cost increase which was resulted by the splashed concrete amount.Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes;however,this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production.This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values.Glass fibre reinforced mixtures were also modelled with a finite element method based software and,the analysis results were compared with production line results.Results of the analysis and on-site studies showed a decisive correlation between,discharge distance,discharge angle and the viscosity of the concrete.
文摘Material selection has become a critical part of design for engineers,due to availability of diverse choice of materials that have similar properties and meet the product design specification.Implementation of statistical analysis alone makes it difficult to identify the ideal composition of the final composite.An integrated approach between statistical model and micromechanical model is desired.In this paper,resultant natural fibre and polymer matrix from previous study is used to estimate the mechanical properties such as density,Young’s modulus and tensile strength.Four levels of fibre loading are used to compare the optimum natural fibre reinforced polymer composite(NFRPC).The result from this analytical approach revealed that kenaf/polystyrene(PS)with 40%fibre loading is the ideal composite in automotive component application.It was found that the ideal composite score is 1.156 g/cm^(3),24.2 GPa and 413.4 MPa for density,Young’s modulus and tensile strength,respectively.A suggestion to increase the properties on Young’s modulus are also presented.This work proves that the statistical model is well incorporated with the analytical approach to choose the correct composite to use in automotive application.
基金supported by the National Natural Science Foundation of China(Grant Nos.41072211,41322019)Natural Science Foundation of Jiangsu Province(Grant No.BK2011339)Opening Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology)(SKLGP2013K010)
文摘The tensile behaviour of soil plays a significantly important role in various engineering applications. Compacted soils used in geotechnical constructions such as dams and clayey liners in waste containment facilities can suffer from cracking due to tensile failure. In order to increase soil tensile strength, discrete fibre reinforcement technique was proposed. An innovative tensile apparatus was developed to deter- mine the tensile strength characteristics of fibre reinforced soil. The effects of fibre content, dry density and water content on the tensile strength were studied. The results indicate that the developed test apparatus was applicable in determining tensile strength of soils. Fibre inclusion can significantly in- crease soil tensile strength and soil tensile failure ductility. The tensile strength basically increases with increasing fibre content. As the fibre content increases from 0% to 0.2%, the tensile strength increases by 65.7%. The tensile strength of fibre reinforced soil increases with increasing dry density and decreases with decreasing water content. For instance, the tensile strength at a dry density of 1.7 Mg/m^3 is 2.8 times higher than that at 1.4 Mg/m^3. It decreases by 30% as the water content increases from 14.5% to 20.5%. Furthermore, it is observed that the tensile strength of fibre reinforced soil is dominated by fibre pull-out resistance, depending on the interracial mechanical interaction between fibre surface and soil matrix.
基金The project supported by the National Natural Science Foundation of China
文摘Surface originated kink bands consist of an important failure mode for fibre-reinforced compo- sites under compression. The mechanical behavior of the fibre bridging kink bands is explored herein in the context of the post-microbuckling theory. Expressions of bridging force are obtained for the entire postbuckling process of the fibres exhibiting weak or strong hardening. The postbuckling formulation of the fibres is applied to yield the toughness increment due to the advancing kink bands, and consequently leads to a quantitative pre- diction on the overall compressive stress strain curves of the fibre-reinforced composites.
文摘The use of fiber reinforced polymer(FRP)bars to substitute the steel bars in internal reinforcement is now an alternative in some structures subjected by corrosion.The strength,stiffness and bond characteristics of FRP bars are tested to understand their flexural behaviour.In this study is investigated the way of failure of beams reinforced internally with carbon FRP(CFRP)bars and their mechanical properties.Two sets of concrete beams reinforced with different diameters of CFRP bars are designed and tested under four-point loading methods.In general,beams reinforced with FRP bars show more deflections and greater values of crack width than beams reinforced with conventional steel,which is due to their low modulus of elasticity and general stiffness.In this paper is presented the calculation and comparison of deflection using different methods,such as ACI 440,CAN/CSA,Eurocode and experimental loading tests.The evaluation is done comparing the results of every method.This study is effective when we use beams with one layer of reinforcement.
文摘Auxetic materials are cellular materials with a unique property of negative Poisson’s ratio.The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction.For the first time,the quasi-static uniaxial compression performance of fused filament fabricated re-entrant diamond auxetic metamaterial is evaluated in the x-direction(in-plane)and z-direction(out-of-plane).The most commonly used thermoplastic feedstock,Acrylonitrile butadiene styrene,is considered a material of choice.The effect of influential geometrical parameters of the re-entrant diamond structure and printing parameter is systematically studied using Taguchi’s design of experiments.Grey-based multi-objective optimisation technique has been adopted to arrive at the optimal structure.Efforts are made to improve the stiffness and strength of the structure with fibre reinforcements.Micro glass fibre reinforcements have enhanced specific strength and stiffness in both in-plane and out-ofplane directions.A sevenfold and thirteen times increase in specific strength and energy absorption is evident for glass fibre-reinforced structures in out-of-plane directions compared to in-plane ones.Proper tuning of geometrical parameters of the re-entrant diamond structure can result in a Poisson’s ratio of up to-3.49 when tested in the x-direction.The parametric study has illustrated the tailorability of the structure according to the application requirements.The statistical study has signified each considered parameter’s contribution to the compression performance characteristics of the 3D printed re-entrant diamond auxetic metamaterial.
基金supported by the National Key R&D Program of China(No.2020YFB2010600)。
文摘This paper aims to characterise surface morphology and 3D roughness parameters of unidirectional carbon fibre reinforced plastic(UD-CFRP)milled at 0°,45°,90°,and 135°fibre orientation angles(FOAs).Side milling experiments are conducted on UD-CFRP laminates.Surface damage forms and texture direction of milled surface are analysed.Spatial frequency of defects on CFRP surface is quantitatively determined using radially averaged 2D PSD.The kinematicdynamic surface topography is reconstructed considering feed,runout and vibration,then the ideal roughness parameters,S_(a),S_(q),S_(sk),and S_(ku)are calculated and compared with the measured ones,finally the material factor-induced roughness components are quantified.Results show that CFRP surface has no regular feed marks.The frequency of fibre breakage or surface defects is greater than tooth passing frequency.FOAs sorted by their average S_(a)in descending order is135°>90°>45°>0°,where surface defects contribute 93.9%,77.1%,73.2%,72.2%of the total roughness respectively,which suggests that surface defects show a more important role than tool kinematics and vibration in formation of milled surface.The negative Skewness(Ssk<0)and high Kurtosis(S_(ku)=4.0–11.5)of milled surface signify porosity and the presence of many anomalous deep valleys in milled surface,respectively.
文摘Fused deposition modelling(FDM)printed short carbon fibre reinforced nylon(SCFRN)composites were fabricated.The friction and wear behaviour of printed materials were systematically investigated under both dry sliding and water lubricated conditions.The results showed that with short fibre enhancements,the printed SCFRN achieved a lower friction coefficient and higher wear resistance than nylon under all tested conditions.Further,under water lubricated conditions,the printed SCFRN exhibited a low,stable friction coefficient due to the cooling and lubricating effects of water.However,the specific wear rate of the printed specimens could be higher than that obtained under dry sliding conditions,especially when the load was relatively low.The square textured surface was designed and created in the printing process to improve materials’tribological performance.It was found that with the textured surface,the wear resistance of the printed SCFRN was improved under dry sliding conditions,which could be explained by the debris collection or cleaning effect of surface texture.However,such a cleaning effect was less noticeable under lubricated conditions,as the liquid could clean the surface effectively.On the other hand,surface textures could increase the surface area exposed to water,causing surface softening due to the higher water absorption rate.As a result,the samples having surface textures showed higher wear rates under lubricated conditions.The work has provided new insights into designing wear resistant polymer materials using three-dimensional(3D)printing technologies,subjected to different sliding conditions.
文摘In conventional manufacturing processes of composites, Carbon Fibre Reinforced Plastic (CFRP) laminates have been made by stacking unidirectional or woven prepreg sheets. Recently, as a manufacturing process of CFRP, 3D printing of CFRP composites has been developed. The 3D printing process of CFRP composites enables us to fabricate CFRP laminates with arbitrary curvilinear fibre plies. This indicates that the optimization of the in-plane curved carbon fibre placement in a planar ply is strongly required to realize superior 3D printed composites. In the present paper, in-plane curved carbon fibre alignment of a ply with an open hole is optimized in terms of maximization of the fracture strength. For the optimization process, a genetic algorithm is adopted. To describe curved carbon fibre alignments in a planar ply, stream lines of perfect flow is employed. By using the stream lines of the perfect flow, number of optimization parameters is significantly reduced. After the optimization, the fracture strength of CFRP laminate is compared with the results of unidirectional CFRP ply. The curved fibre placement in a planar ply shows superior fracture improvement.
基金Project supported by Harbin Aircraft Industry Co.,Ltd.,China。
文摘The effects of voids(void content,void shape and size)on the interlaminar shear strength of[(±45)_(4)/(0,90)/(±45)_(2)]_(S) and [(±45)/0_(4)/(0,90)/0_(2)]_(S) composite laminates were investigated.Specimens with void contents in the range of 0.2%-8.0%for [(±45)_(4)/(0,90)/(±45)_(2)]_(S) and 0.2%-6.1%for[(±45)/0_(4)/(0,90)/0_(2)]_(S) were fabricated from carbon/epoxy fabric through varying autoclave pressures.The characteristics of the voids were studied by using optical image analysis to explain the interlaminar shear strength results.The influences of voids on the interlaminar shear strength of the two stacking sequences were compared in terms of the void content and size and shape of the void.The effect of voids on the initiation and propagation of interlaminar failure of both stacking sequence composites was found.
文摘Beam-Column joints are critical zones in reinforced concrete structures which are most vulnerable to earthquake forces. Hence strengthening beam-column joint is vital to save the structure and its inhabitants in case of seismic forces. Numerous retrofitting works using fibre reinforced polymer (FRP) composites are being undertaken worldwide. This work aims to investigate the effectiveness of strengthening beam-column joints using natural and artificial fibres. In this study, basalt (natural fibres) as monolithic composite (BFRP) and as hybrid composite along with glass (artificial fibres) were used for strengthening of beam-column joints. Totally six specimens were prepared and tested under monotonic loading. Specimen details used were: two control specimen, two specimens for monolithic wrapping and remaining two specimens for hybrid wrapping. The test results were compared with control and rehabilitated specimens. The performance of the treated joints was studied using the following parameters: initial and ultimate cracking loads, energy absorption, deflection ductility and stiffness at ultimate. From the test results, it was found that the hybrid combination of Basalt and Glass FRPs were found to be more effective in the treatment of beam-column joints. The strong column weak beam concept was achieved by failure in beam portion which helped in preventing the catastrophic failure of the entire structure.
基金supported by the National Natural Science Foundations of China(No.52102115)the Natural Science Foundations of Sichuan Province,China(No.2023NSFSC0961)the Fundamental Research Funds of Jiangsu University of Science and Technology,China(No.1022932318)。
文摘Adhesively Bonded Carbon Fibre Reinforced Plastic(CFRP)and titanium alloy have been extensively used as a hybrid structure in modern aircrafts due to their excellent combination of mechanical properties and chemical stabilities.This study utilised NaOH anodising method to create micro-rough titanium surfaces for enhancing adhesive bonding between titanium alloy and CFRP laminates.A special and simple technique named Resin Pre-Coating(RPC)was also employed to improve the surface wetting of anodised titanium and grinded CFRP substrates.The influences of anodising temperature and duration on the surface morphology,wettability and adhesive bond strength were investigated.The single lap shear test results showed that the bond strength of specimens anodised at 20℃for 15 min improved by 135.9%and 95.4%,respectively,in comparison with that of acid pickled and grinded specimens(without RPC treatment).Although increasing the anodising temperature and duration produced rougher titanium surfaces,the adhesively bonded joints were not strong enough due to relatively friable titanium oxide layers.
文摘The objectives of this study are to review and evaluate the developments and applications of pultruded fiber-reinforced polymer composites in civil and structural engineering and review advances in research and developments.Several case applications are reviewed.The paper presents a state-of-the-art review of fundamental research on the behavior of pultruded fiber reinforced polymer closed sections and highlights gaps in knowledge and areas of potential further research.
基金Supported by National Key Research and Development Project of China (Grant Nos.2018YFA0703300,52105300)National Natural Science Foundation of China (Grant No.52075215)+2 种基金Science and Technology Development Plan Project of Jilin Province of China (Grant No.20200201061JC)Science and Technology Research Project of Jilin Provincial Education Department of China (Grant No.JJKH20221021KJ)Changchun Municipal Key Research and Development Program of China (Grant No.21ZGN22)。
文摘Fibre reinforced polymer composites have become a new generation of structural materials due to their unique advantages such as high specific strength,designability,good dimensional stability and ease of large-area monolithic forming.However,the problem of interfacial bonding between the resin matrix and the fibres limits the direct use of reinforcing fibres and has become a central difficulty in the development of basalt fibre-epoxy composites.This paper proposes a solution for enhancing the strength of the fibre-resin interface using maize starch nanocrystals,which are highly yield and eco-friendly.Firstly,in this paper,corn starch nanocrystals(SNC)were prepared by hydrolysis,and were deposited on the surface of basalt fibers by electrostatic adsorption.After that,in order to maximize the modification effect of nano-starch crystals on the interface,the basalt fiber-epoxy resin composite samples were prepared by mixing in a pressureless molding method.The test results shown that the addition of basalt fibers alone led to a reduction in the strength of the sample.Deposition of 0.1 wt%SNC on the surface of basalt fibers can make the strength consistent with pure epoxy resin.When the adsorption amount of SNC reached 0.5 wt%,the tensile strength of the samples was 23.7%higher than that of pure epoxy resin.This is due to the formation of ether bond homopolymers between the SNC at the fibre-epoxy interface and the epoxy resin,which distorts the originally smooth interface,leading to increased stress concentration and the development of cracks.This enhances the binding of basalt fibers.The conclusions of this paper can provide an effective,simple,low-cost and non-polluting method of interfacial enhancement modification.
基金The authors gratefully acknowledge the research support fund provided by the Sudanese Ministry of Higher Education,School of Engineering University of Khartoum and the School of Engineering,University of Aberdeen.
文摘This paper presents a state-of-the-art review of research on the utilization of fibers(predominantly derived from waste materials)as reinforcement in adobe brick production.Recycling of these wastes provides sustainable construction materials and helps to protect the environment.Specimen preparation and test procedures are outlined.The effects of addition of these wastes on the physical and mechanical properties of adobe bricks as presented in the literature,are investigated.The main results for each additive are presented and discussed.It is concluded that improved adobe brick properties can be expected with the addition of combination of waste additives.The use of waste materials in the construction industry is generally of interest and useful for engineers and designers seeking sustainable solutions in construction.It is also of interest to researchers actively seeking to develop methodical approaches to quantifying,optimising and testing the performance in use of such waste material additives.