The study aims to analyze the synergistic effect of hybrid fiber reinforcements on wear resistance of epoxy based natural fiber reinforced polymer composites(NFPCs).The study employed jute and sisal fibers as reinforc...The study aims to analyze the synergistic effect of hybrid fiber reinforcements on wear resistance of epoxy based natural fiber reinforced polymer composites(NFPCs).The study employed jute and sisal fibers as reinforcements.Two distinct reinforcements were incorporated in equal percentages to each type of composite sample.Five distinct composite specimens were identified as follows:NFPC⁃8(containing 4%sisal and jute fibers each),NFPC⁃16(containing 8%sisal and jute fibers each),NFPC⁃24(containing 12%sisal and jute fibers each),NFPC⁃32(containing 16%sisal and jute fibers each),and epoxy(EP)(containing 0%reinforcements).The hand layup technique was used for developing hybrid natural composites.In accordance with ASTM G99,pin⁃on⁃disc wear test rig was used for the dry sliding wear tests.The effect of applied load and sliding velocities on wear volume loss and specific wear rate was studied.The obtained results indicated that wear volume and specific wear rate are significantly affected by applied load and sliding velocity.NFPC⁃32 composite exhibited minimum wear loss and specific wear rate compared to other specimens.Besides,wear loss and specific wear rate were found to increase with the increase in applied load owing to the high contact stress at counterface during sliding.Further,wear volume and specific wear rate have increased with the increase in sliding velocity.It may be due to the fact that,high shearing force has resulted in sheared transfer layer at higher velocity.Worn surface analysis using scanning electron microscopy images showed the evidence of fragmented fibers and their pullout.展开更多
Sisal filbre is a kind of natural filbre which possesses high specic strength and modu- lus, low price, recycalability, easy availability in some countries. Using sisal filbre as reinforcement to make sisal filbre r...Sisal filbre is a kind of natural filbre which possesses high specic strength and modu- lus, low price, recycalability, easy availability in some countries. Using sisal filbre as reinforcement to make sisal filbre reinforced polymer composites has aroused great interest of materials scientists and engineers all over the world. Many researches have been done in recent years which include the study of mechanical properties of the composites, nding an ecient way to improve the inter- facial bonding properties between sisal bre and polymeric matrices and bre surface treatment on the mechanical performance of the composites. Though many researches on sisal bre reinforced composites have been done so far, none deals with the fracture properties of this novel composite which is crucial for the actual application of this material. In this research, Charpy impact test and compact tension test were employed to study the fracture toughness of sisal bre reinforced vinyl ester and epoxy composites. The eect of bre surface treatment on the fracture properties of these composites by permanganate and silane was evaluated. The initiation and propagation of the crack were observed with optical microscopy (OM). The fracture morphologies revealed by OM explains the fracture phenomenon of sisal bre reinforced composites.展开更多
The objective of this work was to evaluate different superficial treatments of sisal fibres employing lignin,and their use as a reinforcement agent in cementitious composites.The treatments consisted of superficially ...The objective of this work was to evaluate different superficial treatments of sisal fibres employing lignin,and their use as a reinforcement agent in cementitious composites.The treatments consisted of superficially impregnating sisal fibres(S)with organosolv lignin(LO),organosolv lignin and glutaraldehyde(LOG),Kraft lignin(LK)and Kraft lignin and glutaraldehyde(LKG).The fibre modifications were verified by FTIR-ATR and SEM analyzes,and the presence of lignin on the surface of the fibres was evidenced,confirming the effectiveness of the treatments.The mechanical,thermal(by TGA)and water absorption properties of the fibres before and after the modifications were also investigated.After treatment,the modified fibres presented an expressive reduction of the water absorption and did not show significant changes in the mechanical properties when compared with the natural unmodified sisal fibre(SNAT).It was verified an increase in the thermal stability of the treated fibres which can be attributed to the insertion of lignin on the fibres.To evaluate the performance of the fibres in the cementitious composites,cement plates(CP)were produced with different treated fibres(CP-SLOG,CP-SLO,CP-SLKG,CP-SLK)and fibres without treatment(CP-SNAT).The composites were evaluated concerning to the water absorption,porosity and mechanical properties.The fractured regions were also investigated by SEM.All composites prepared showed similar values of absorption and porosity indexes.From the mechanical properties,the composites prepared with modified fibres showed a significant increase in the modulus of rupture and modulus of elasticity compared with CP-SNAT,while toughness was similar to all samples.From the SEM images,it was observed that the modified fibres immersed in the cementitious plates showed no degradation,indicating that the impregnation of lignin acted as a protective agent of the fibres.Therefore,the treatments of the fibres with lignin led to a significant improvement in the properties of the composites generating a treatment with potential for industrial application.展开更多
This Anaerobic Digestion of Sisal decortication residue (SDR) from sisal decorication unit at Hale biogas plant in Tanga (Tanzania) is presented. The study was done to address the challenges facing Katani limited at H...This Anaerobic Digestion of Sisal decortication residue (SDR) from sisal decorication unit at Hale biogas plant in Tanga (Tanzania) is presented. The study was done to address the challenges facing Katani limited at Hale biogas plant. This plant was built as pilot before building other biogas plants. These challenges were like high retention time of substrate which was SDR, low biogas productivity, high investment costs due to large tanks sizes and low plant availability. From the study, it was discovered that, when particle size was reduced biogas production increased, degradation of SDR also increased and no significant change in biogas composition. Increase in biogas yield of 30% and 129% were recorded for reduced SDR compared to raw size SDR digested at atmospheric condition and 40°C respectivelly. SDR degradation measured in TS and VS removal efficiency, showed increase in degradation of about 5% for the reduced particle size compared to raw size particle. The study concluded that SDR was good raw material for biogas production when 90% of the particles reduced to less than 2 mm. To maximize production, digestion must be conducted at high temperature around 40°C with constant monitoring and control of all para-meters. This will increase plant availability by increasing efficiency and life span of the pumps and stirrers.展开更多
In this study, the residual strength of sisal textile reinforced vinyl ester resin is studied using specimens with a central hole. Two kinds of chemicals, silane and permanganate, are used to treat sisal fibre surface...In this study, the residual strength of sisal textile reinforced vinyl ester resin is studied using specimens with a central hole. Two kinds of chemicals, silane and permanganate, are used to treat sisal fibre surfaces. The effects of fibre surface treatments on the residual strength of sisal fibre reinforced composites with different central hole sizes are analysed. Optical microscopy （OM） surveys provide sound evidence for the relationship between residual strength properties and fracture morphologies of sisal textile reinforced vinyl ester. Several theoretical models used to predict the residual strength of laminated composites are briefly reviewed. Point stress criterion （PSC） and average stress criterion （ASC） models are used to analyze the mechanical properties of sisal textile reinforced polymers with a central hole in this research. Material constant, characteristic length （d0 or lc）, is obtained and used to analyze the mechanical behavior of the composites. The residual strength of the composites predicted by PSC and ASC models is in good agreement with the experimental results..展开更多
Objective: To investigate the effects of Agave sisalana(A. sisalana) extract on Aedes aegypti(Ae. aegypti) primary cell culture.Methods: Cells of Ae. aegypti were exposed to different concentrations of A. sisalana cru...Objective: To investigate the effects of Agave sisalana(A. sisalana) extract on Aedes aegypti(Ae. aegypti) primary cell culture.Methods: Cells of Ae. aegypti were exposed to different concentrations of A. sisalana crude extract(0.18–6.00 mg/m L) for 24 h. Then, the cells were labeled with propidium iodide and subjected to fluorescence microscopy to verify cell viability. In addition, nitric oxide production was measured.Results: Results showed that cells exposed to 6 mg/m L of the crude extract presented a greater percentage of death when compared to control(73.8% ± 9.6% vs. 34.6% ± 9.6%).Furthermore, there was an increase in the nitric oxide production in cells exposed to 6 mg/m L of A. sisalana crude extract [(0.81 ± 0.08) mmol/L] compared to control group[(0.41 ± 0.18) mmol/L].Conclusions: The results show that A. sisalana is cytotoxic to Ae. aegypti and may be used as raw material for new eco-friendly and inexpensive insecticides, since sisal industry discards the liquid waste for the extraction of plant fiber.展开更多
Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynam...Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynamic compressive strength,peak strain and toughness index of SFCAC are all greater than its static properties,indicating that SFCAC is a kind of rate-sensitive material.When the sisal fiber was blended,the failure mode showed obvious ductility.At high strain rates,the SFCAC without sisal fiber specimen was comminuted,and the SFCAC showed a"cracked without breaking"state.The results indicated that the sisal fiber played a significant role in reinforcing and strengthening the properties of concrete.The finite element software LS-DYNA was used to simulate two working conditions with strain rates of 78 and 101 s-1.The stressstrain curves and failure patterns obtained were in good agreement with the experimental results.展开更多
Based on results of previous studies,through investigations,the status quo,main advantages and disadvantages of using small hand-power scutchers and large-scale automatic sisal production lines to process sisal fiber ...Based on results of previous studies,through investigations,the status quo,main advantages and disadvantages of using small hand-power scutchers and large-scale automatic sisal production lines to process sisal fiber were summarized and analyzed; the traditional uses and latest products of sisal fiber were studied,especially the comprehensive utilization of byproducts produced during sisal fiber processing as well as the broad prospects of new sisal products.展开更多
The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction a...The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.展开更多
In this paper,a split Hopkinson pressure bar(SHPB)was used to investigate the dynamic impact mechanical behavior of sisal fiber-reinforced cement-based composites(SFRCCs),and the microscopic damage evolution of the co...In this paper,a split Hopkinson pressure bar(SHPB)was used to investigate the dynamic impact mechanical behavior of sisal fiber-reinforced cement-based composites(SFRCCs),and the microscopic damage evolution of the composites was analyzed by scanning electron microscopy(SEM)and energy-dispersive X-ray spectrome-try(EDS).The results show that the addition of sisal fibers improves the impact resistance of cement-based composite materials.Compared with ordinary cement-based composites(OCCs),the SFRCCs demonstrate higher post-peak strength,ductility,and energy absorption capacity with higher fiber content.Moreover,the SFRCCs are strain rate sensitive materials,and their peak stress,ultimate strain,and energy integrals all increase with increasing strain rate.From the perspective of fracture failure characteristics,the failure of OCCs is dominated by the brittle failure of crystal cleavage.In contrast,the failure mode of the SFRCCs changes to microscale matrix cracks,multi-scale pull-out interface debonding of fibers(fine filaments and bundles),and mechanical interlock.This research provides an experimental basis for the engineering application of high-performance and green cement-based composites.展开更多
Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated be...Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated beams and also wood from reforestation, is in accordance with the current economic interest and ecological appeal. Specifically, the strengthening of wood laminated beams with Sisal fibers is more effective for structures that require an increase in their structural capacity without a significant increase in height of the cross section. Furthermore, it is recommended that this type of reinforcement is used in wood structural elements where the elastic modulus is at least equal to the Sisal fibers. The composition of Sisal fibers is basically of cellulose, lignin and hemicelluloses. In particular, the amount of cellulose and the angle that the micro-fibers with the axis of the fiber characterize the failure strength and the modulus of elasticity. The average mechanical characteristics of the Sisal fiber are： tensile strength 347 to 378 （MPa） and elastic modulus 15.2 （GPa） whereas these properties are lower for strips of Sisal fibers. In this context, this paper deals with the analysis and the viability of the use of Sisal fibers in wood structures as a reinforced material.展开更多
There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates...There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates the incorporation of sisal fibers of 20 mm and 40 mm in length and volume fraction of 0.5% and 1% for concrete masonry structural blocks, and determines the use of these units to build prisms and mini-walls. Laboratory tests were carried out to characterize the physical of blocks and mortar, in addition to the axial compression tests of the units, prisms, and mini-walls. The sisal had low apparent density and high water absorption, which is a common feature of such material due to the high incidence of permeable pores. The physical properties of the blocks with and without addition complied with the standard requirements established to validate their use. The obtained results showed that the fiber-reinforced mini-walls obtained values very close to or even higher than those obtained for the mini-walls without fibers, demonstrating better performance than the blocks and prisms.展开更多
The influence of different factors on the fiuidization of a binary mixture of sisal residue and sand was investigated.The particle sizes of the sand and sisal residue were varied from 0.2to 0.8mm and the biomass mass ...The influence of different factors on the fiuidization of a binary mixture of sisal residue and sand was investigated.The particle sizes of the sand and sisal residue were varied from 0.2to 0.8mm and the biomass mass fractions from 2% to 9%.Some segregation was noted,and a significant relationship was found among the final fluidization velocity (Uff),the biomass and sand sizes,and the biomass mass fraction.A novel model was developed for predicting Uff,leading to an average discrepancy of 12.69% between the measured and predicted Uff compared with the best match of 15.32% when using a model from a previous paper.The new model was applied to data from studies using other biomass and a broad range of particle characteristics.The average divergences from measured values when using the new model were 7.9% for corn cob and walnut shell,and 20.5% for sweet sorghum bagasse,tobacco residue, and soy hulls.These were superior to the values derived using other models.Our results confirm the accuracy of the model developed in this work and show that it represents a viable alternative way to calculate Uff for a binary mixture of sand and biomass.展开更多
The flow behaviors of the resin during the resin transfer molding(RTM) process of sisal fiber reinforced composites was studied at different scales with the consideration of the unique hierarchical and lumen structure...The flow behaviors of the resin during the resin transfer molding(RTM) process of sisal fiber reinforced composites was studied at different scales with the consideration of the unique hierarchical and lumen structures of sisal fibers compared to those of manmade fibers. The work mainly focused on the development of the multi-scale flow models which include the resin flow inside lumens, intra-bundles and inter-bundles. The models not only quantified the lumen flow based on the Hagen-Poiseuille equation,but also ensured the continuity of the velocity and stress on the boundaries between intra-bundle and inter-bundle regions by applying Brinkman equation. Three dedicated experiments were designed and implemented to validate the effectiveness of the proposed models. The absorbed resin mass over the infiltration time obtained from the single sisal fiber and sisal fiber bundle infiltration experiments showed good agreement with the calculated curves. In terms of the RTM process, the dynamic flow front of the resin was perfectly predicted by the proposed model at macro-scale.展开更多
Through careful analysis on the cross-section of sisal fibers, it is found that the middle lamellae between the cell walls have clear geometric characteristics: between the cell walls of three neighboring cells, the m...Through careful analysis on the cross-section of sisal fibers, it is found that the middle lamellae between the cell walls have clear geometric characteristics: between the cell walls of three neighboring cells, the middle lamellae form a three-way junction with 120° symmetry. If the neighboring three-way junctions are connected, a network of Steiner tree with angular symmetry and topological invariability is formed. If more and more Steiner trees are connected, a network of Steiner rings is generated. In another word, idealized cell walls and the middle lamellae are dominated by the Steiner geometry. This geometry not only depicts the geometric symmetry, the topological invariability and minimal property of the middle lamellae, but also controls the mechanics of sisal fibers.展开更多
文摘The study aims to analyze the synergistic effect of hybrid fiber reinforcements on wear resistance of epoxy based natural fiber reinforced polymer composites(NFPCs).The study employed jute and sisal fibers as reinforcements.Two distinct reinforcements were incorporated in equal percentages to each type of composite sample.Five distinct composite specimens were identified as follows:NFPC⁃8(containing 4%sisal and jute fibers each),NFPC⁃16(containing 8%sisal and jute fibers each),NFPC⁃24(containing 12%sisal and jute fibers each),NFPC⁃32(containing 16%sisal and jute fibers each),and epoxy(EP)(containing 0%reinforcements).The hand layup technique was used for developing hybrid natural composites.In accordance with ASTM G99,pin⁃on⁃disc wear test rig was used for the dry sliding wear tests.The effect of applied load and sliding velocities on wear volume loss and specific wear rate was studied.The obtained results indicated that wear volume and specific wear rate are significantly affected by applied load and sliding velocity.NFPC⁃32 composite exhibited minimum wear loss and specific wear rate compared to other specimens.Besides,wear loss and specific wear rate were found to increase with the increase in applied load owing to the high contact stress at counterface during sliding.Further,wear volume and specific wear rate have increased with the increase in sliding velocity.It may be due to the fact that,high shearing force has resulted in sheared transfer layer at higher velocity.Worn surface analysis using scanning electron microscopy images showed the evidence of fragmented fibers and their pullout.
基金Project supported by Australian Government Overseas Postgraduate Research Scholarship(OPRS)International Postgraduate Awards(IPA)by the University of Sydney and the Foundation of Technology Development in Science of Tongji University.
文摘Sisal filbre is a kind of natural filbre which possesses high specic strength and modu- lus, low price, recycalability, easy availability in some countries. Using sisal filbre as reinforcement to make sisal filbre reinforced polymer composites has aroused great interest of materials scientists and engineers all over the world. Many researches have been done in recent years which include the study of mechanical properties of the composites, nding an ecient way to improve the inter- facial bonding properties between sisal bre and polymeric matrices and bre surface treatment on the mechanical performance of the composites. Though many researches on sisal bre reinforced composites have been done so far, none deals with the fracture properties of this novel composite which is crucial for the actual application of this material. In this research, Charpy impact test and compact tension test were employed to study the fracture toughness of sisal bre reinforced vinyl ester and epoxy composites. The eect of bre surface treatment on the fracture properties of these composites by permanganate and silane was evaluated. The initiation and propagation of the crack were observed with optical microscopy (OM). The fracture morphologies revealed by OM explains the fracture phenomenon of sisal bre reinforced composites.
文摘The objective of this work was to evaluate different superficial treatments of sisal fibres employing lignin,and their use as a reinforcement agent in cementitious composites.The treatments consisted of superficially impregnating sisal fibres(S)with organosolv lignin(LO),organosolv lignin and glutaraldehyde(LOG),Kraft lignin(LK)and Kraft lignin and glutaraldehyde(LKG).The fibre modifications were verified by FTIR-ATR and SEM analyzes,and the presence of lignin on the surface of the fibres was evidenced,confirming the effectiveness of the treatments.The mechanical,thermal(by TGA)and water absorption properties of the fibres before and after the modifications were also investigated.After treatment,the modified fibres presented an expressive reduction of the water absorption and did not show significant changes in the mechanical properties when compared with the natural unmodified sisal fibre(SNAT).It was verified an increase in the thermal stability of the treated fibres which can be attributed to the insertion of lignin on the fibres.To evaluate the performance of the fibres in the cementitious composites,cement plates(CP)were produced with different treated fibres(CP-SLOG,CP-SLO,CP-SLKG,CP-SLK)and fibres without treatment(CP-SNAT).The composites were evaluated concerning to the water absorption,porosity and mechanical properties.The fractured regions were also investigated by SEM.All composites prepared showed similar values of absorption and porosity indexes.From the mechanical properties,the composites prepared with modified fibres showed a significant increase in the modulus of rupture and modulus of elasticity compared with CP-SNAT,while toughness was similar to all samples.From the SEM images,it was observed that the modified fibres immersed in the cementitious plates showed no degradation,indicating that the impregnation of lignin acted as a protective agent of the fibres.Therefore,the treatments of the fibres with lignin led to a significant improvement in the properties of the composites generating a treatment with potential for industrial application.
文摘This Anaerobic Digestion of Sisal decortication residue (SDR) from sisal decorication unit at Hale biogas plant in Tanga (Tanzania) is presented. The study was done to address the challenges facing Katani limited at Hale biogas plant. This plant was built as pilot before building other biogas plants. These challenges were like high retention time of substrate which was SDR, low biogas productivity, high investment costs due to large tanks sizes and low plant availability. From the study, it was discovered that, when particle size was reduced biogas production increased, degradation of SDR also increased and no significant change in biogas composition. Increase in biogas yield of 30% and 129% were recorded for reduced SDR compared to raw size SDR digested at atmospheric condition and 40°C respectivelly. SDR degradation measured in TS and VS removal efficiency, showed increase in degradation of about 5% for the reduced particle size compared to raw size particle. The study concluded that SDR was good raw material for biogas production when 90% of the particles reduced to less than 2 mm. To maximize production, digestion must be conducted at high temperature around 40°C with constant monitoring and control of all para-meters. This will increase plant availability by increasing efficiency and life span of the pumps and stirrers.
基金Project supported by Australian Government Overseas Postgraduate Research Scholarship (OPRS) and International Postgraduate Awards (IPA) by the University of Sydney the foundation of Technology Development in Science of Tongji University.
文摘In this study, the residual strength of sisal textile reinforced vinyl ester resin is studied using specimens with a central hole. Two kinds of chemicals, silane and permanganate, are used to treat sisal fibre surfaces. The effects of fibre surface treatments on the residual strength of sisal fibre reinforced composites with different central hole sizes are analysed. Optical microscopy （OM） surveys provide sound evidence for the relationship between residual strength properties and fracture morphologies of sisal textile reinforced vinyl ester. Several theoretical models used to predict the residual strength of laminated composites are briefly reviewed. Point stress criterion （PSC） and average stress criterion （ASC） models are used to analyze the mechanical properties of sisal textile reinforced polymers with a central hole in this research. Material constant, characteristic length （d0 or lc）, is obtained and used to analyze the mechanical behavior of the composites. The residual strength of the composites predicted by PSC and ASC models is in good agreement with the experimental results..
基金Supported by Conselho Nacional de Desenvolvimento Científico e Tecnologico(CNPq)[Grant No.467147/2014-0(VSL)]
文摘Objective: To investigate the effects of Agave sisalana(A. sisalana) extract on Aedes aegypti(Ae. aegypti) primary cell culture.Methods: Cells of Ae. aegypti were exposed to different concentrations of A. sisalana crude extract(0.18–6.00 mg/m L) for 24 h. Then, the cells were labeled with propidium iodide and subjected to fluorescence microscopy to verify cell viability. In addition, nitric oxide production was measured.Results: Results showed that cells exposed to 6 mg/m L of the crude extract presented a greater percentage of death when compared to control(73.8% ± 9.6% vs. 34.6% ± 9.6%).Furthermore, there was an increase in the nitric oxide production in cells exposed to 6 mg/m L of A. sisalana crude extract [(0.81 ± 0.08) mmol/L] compared to control group[(0.41 ± 0.18) mmol/L].Conclusions: The results show that A. sisalana is cytotoxic to Ae. aegypti and may be used as raw material for new eco-friendly and inexpensive insecticides, since sisal industry discards the liquid waste for the extraction of plant fiber.
基金National Natural Science Foundation of China(Nos.51508272,11832013,51878350,52078250)。
文摘Split Hopkinson pressure bar(SHPB)was used to investigate the dynamic compressive properties of sisal fiber reinforced coral aggregate concrete(SFCAC).The results showed that,with the increase of strain rate,the dynamic compressive strength,peak strain and toughness index of SFCAC are all greater than its static properties,indicating that SFCAC is a kind of rate-sensitive material.When the sisal fiber was blended,the failure mode showed obvious ductility.At high strain rates,the SFCAC without sisal fiber specimen was comminuted,and the SFCAC showed a"cracked without breaking"state.The results indicated that the sisal fiber played a significant role in reinforcing and strengthening the properties of concrete.The finite element software LS-DYNA was used to simulate two working conditions with strain rates of 78 and 101 s-1.The stressstrain curves and failure patterns obtained were in good agreement with the experimental results.
文摘Based on results of previous studies,through investigations,the status quo,main advantages and disadvantages of using small hand-power scutchers and large-scale automatic sisal production lines to process sisal fiber were summarized and analyzed; the traditional uses and latest products of sisal fiber were studied,especially the comprehensive utilization of byproducts produced during sisal fiber processing as well as the broad prospects of new sisal products.
基金The Natural Science Foundation of China(No.52108191)the China Postdoctoral Science Foundation(No.2021M690622)+2 种基金the Changzhou Sci&Tech Program(No.CJ20210153,CE20205050)the Qing Lan Project of Jiangsuthe Young Sci-tech Talents Promoting Project of Changzhou。
文摘The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.
基金supported within the framework of the Basic Research Project of the Yunnan Province-Young Program(No.2019FD097)Agricultural Joint Special Project of the Yunnan Province-General Program(No.202101BD070001-118).
文摘In this paper,a split Hopkinson pressure bar(SHPB)was used to investigate the dynamic impact mechanical behavior of sisal fiber-reinforced cement-based composites(SFRCCs),and the microscopic damage evolution of the composites was analyzed by scanning electron microscopy(SEM)and energy-dispersive X-ray spectrome-try(EDS).The results show that the addition of sisal fibers improves the impact resistance of cement-based composite materials.Compared with ordinary cement-based composites(OCCs),the SFRCCs demonstrate higher post-peak strength,ductility,and energy absorption capacity with higher fiber content.Moreover,the SFRCCs are strain rate sensitive materials,and their peak stress,ultimate strain,and energy integrals all increase with increasing strain rate.From the perspective of fracture failure characteristics,the failure of OCCs is dominated by the brittle failure of crystal cleavage.In contrast,the failure mode of the SFRCCs changes to microscale matrix cracks,multi-scale pull-out interface debonding of fibers(fine filaments and bundles),and mechanical interlock.This research provides an experimental basis for the engineering application of high-performance and green cement-based composites.
文摘Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated beams and also wood from reforestation, is in accordance with the current economic interest and ecological appeal. Specifically, the strengthening of wood laminated beams with Sisal fibers is more effective for structures that require an increase in their structural capacity without a significant increase in height of the cross section. Furthermore, it is recommended that this type of reinforcement is used in wood structural elements where the elastic modulus is at least equal to the Sisal fibers. The composition of Sisal fibers is basically of cellulose, lignin and hemicelluloses. In particular, the amount of cellulose and the angle that the micro-fibers with the axis of the fiber characterize the failure strength and the modulus of elasticity. The average mechanical characteristics of the Sisal fiber are： tensile strength 347 to 378 （MPa） and elastic modulus 15.2 （GPa） whereas these properties are lower for strips of Sisal fibers. In this context, this paper deals with the analysis and the viability of the use of Sisal fibers in wood structures as a reinforced material.
文摘There is great interest in the use of natural fibers as reinforcement to obtain new construction materials due to its low cost, high availability and reduced energy consumption for its production. This paper evaluates the incorporation of sisal fibers of 20 mm and 40 mm in length and volume fraction of 0.5% and 1% for concrete masonry structural blocks, and determines the use of these units to build prisms and mini-walls. Laboratory tests were carried out to characterize the physical of blocks and mortar, in addition to the axial compression tests of the units, prisms, and mini-walls. The sisal had low apparent density and high water absorption, which is a common feature of such material due to the high incidence of permeable pores. The physical properties of the blocks with and without addition complied with the standard requirements established to validate their use. The obtained results showed that the fiber-reinforced mini-walls obtained values very close to or even higher than those obtained for the mini-walls without fibers, demonstrating better performance than the blocks and prisms.
文摘The influence of different factors on the fiuidization of a binary mixture of sisal residue and sand was investigated.The particle sizes of the sand and sisal residue were varied from 0.2to 0.8mm and the biomass mass fractions from 2% to 9%.Some segregation was noted,and a significant relationship was found among the final fluidization velocity (Uff),the biomass and sand sizes,and the biomass mass fraction.A novel model was developed for predicting Uff,leading to an average discrepancy of 12.69% between the measured and predicted Uff compared with the best match of 15.32% when using a model from a previous paper.The new model was applied to data from studies using other biomass and a broad range of particle characteristics.The average divergences from measured values when using the new model were 7.9% for corn cob and walnut shell,and 20.5% for sweet sorghum bagasse,tobacco residue, and soy hulls.These were superior to the values derived using other models.Our results confirm the accuracy of the model developed in this work and show that it represents a viable alternative way to calculate Uff for a binary mixture of sand and biomass.
基金supported by the National Natural Science Foundation of China for Distinguished Young Scholars(Grant No.11625210)the Shanghai Outstanding Academic Leaders Plan(Grant No.16XD1402900)the Fundamental Research Funds for the Central Universities
文摘The flow behaviors of the resin during the resin transfer molding(RTM) process of sisal fiber reinforced composites was studied at different scales with the consideration of the unique hierarchical and lumen structures of sisal fibers compared to those of manmade fibers. The work mainly focused on the development of the multi-scale flow models which include the resin flow inside lumens, intra-bundles and inter-bundles. The models not only quantified the lumen flow based on the Hagen-Poiseuille equation,but also ensured the continuity of the velocity and stress on the boundaries between intra-bundle and inter-bundle regions by applying Brinkman equation. Three dedicated experiments were designed and implemented to validate the effectiveness of the proposed models. The absorbed resin mass over the infiltration time obtained from the single sisal fiber and sisal fiber bundle infiltration experiments showed good agreement with the calculated curves. In terms of the RTM process, the dynamic flow front of the resin was perfectly predicted by the proposed model at macro-scale.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 10602040, 10872114)
文摘Through careful analysis on the cross-section of sisal fibers, it is found that the middle lamellae between the cell walls have clear geometric characteristics: between the cell walls of three neighboring cells, the middle lamellae form a three-way junction with 120° symmetry. If the neighboring three-way junctions are connected, a network of Steiner tree with angular symmetry and topological invariability is formed. If more and more Steiner trees are connected, a network of Steiner rings is generated. In another word, idealized cell walls and the middle lamellae are dominated by the Steiner geometry. This geometry not only depicts the geometric symmetry, the topological invariability and minimal property of the middle lamellae, but also controls the mechanics of sisal fibers.
