Analysis on degradation behaviors of sisal fibers at various pH conditions

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.

Mechanical Analysis of Sisal Fibers to Use as a Reinforced Material in Wood Beams

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.

Elements of Structural Masonry Reinforced with Sisal Fibers

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.

Dynamic Impact Compressive Behavior Investigation of Sisal Fiber-reinforced Coral Seawater Concrete

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.

Effects of Strain Rate and Fiber Content on the Dynamic Mechanical Properties of Sisal Fiber Cement-Based Composites

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.

Compressive and tensile strength of polymer-based fiber composite sand

Traditional soil additives like Portland cement and lime are prone to cause the brittle fracture behavior of soil,and possibly,environmental impacts.This study explores the potential use of polyurethane organic polymer and sisal fiber in improving the mechanical performance of sand.The effects of polymer content,fiber content,and dry density on the unconfined compressive strength(UCS)and direct tensile strength(DTS)of the polymer-fiber-sand composite were evaluated.The results showed significant increase in UCS and DTS of the reinforced sand with the increase of polymer content,fiber content,and dry density.At high dry density condition,a single peaked stress−strain curve is often observed.Higher polymer content is beneficial to increasing the peak stress,while higher fiber content contributes more to the post-peak stress.The combined use of polymers and fibers in soil reinforcement effectively prevents the propagation and development of cracks under the stress.Scanning electron microscopy(SEM)test was also performed to investigate the micro-structural changes and inter-particle relations.It was found through SEM images that the surface coating,bonding,and filling effects conferred by polymer matrix greatly enhance the interfacial interactions,and hence provide a cohesive environment where the strength of fibers could be readily mobilized.

Experimental Investigation on the Mechanical Properties of Natural Fiber Reinforced Concrete

Recently,addition of various natural fibers to high strength concrete has aroused great interest in the field of building materials.This is because natural fibers are much cheaper and locally available,as compare to synthetic fibers.Keeping in view,this current research conducted mainly focuses on the static properties of hybridized(sisal/coir),sisal and coir fiber-reinforced concrete.Two types of natural fibers sisal and coir were used in the experiment with different lengths of 10,20 and 30 mm and various natural fiber concentrations of 0.5%,1.0%,and 1.5%by mass of cement,to investigate the static properties of sisal fiber reinforced concrete(SFRC),coir fiber reinforced concrete(CFRC)and hybrid fiber reinforced concrete(HFRC).The results indicate that HFRC has increased the compressive strength up to 35.98%with the length of 20 mm and with 0.5%concentration,while the CFRC and SFRC with the length of 10 mm and with 1%concentration have increased the compressive strength up to 33.94%and 24.86%,respectively.On another hand,the split tensile strength was increased by HFRC with the length of 20 mm and with 1%concentration,CFRC with the length of 10 mm and with 1.5%concentration,and SFRC with the length of 30 mm and with 1%concentration have increased up to 25.48%,24.56%and 11.80%,respectively,while the HFRC with the length of 20 mm and with 0.5%concentration has increased the compressive strength of concrete but has decreased the split tensile strength up to 2.28%compared to PC.Overall,using the HFRC with the length of 20 mm and with 1%concentration provide the maximum output in terms of split tensile strength.

Production of Manganese Peroxidase by Trametes villosa on Unexpensive Substrate and Its Application in the Removal of Lignin from Agricultural Wastes

Manganese peroxidase (MnP) is a ligninolytic enzyme that is involved in the removal of lignin from the cell wall of plants. This removal facilitates the access of hydrolytic enzymes to the carbohydrate polymers that are hydrolyzed to simple sugars, which allows the subsequent fermentation to obtain bioproducts, such as ethanol. In this work, response surface methodology (RSM) was employed to optimize the culture conditions on unexpensive substrate for MnP secretion by Trametes villosa. Three independent variables were evaluated (i.e., temperature, moisture content and pH). The crude extract containing MnP was used in the delignification experiment and it caused a reduction in lignin content for all residues tested: 35.05 ± 1.45 (%) for the sugar cane bagasse;63.11 ± 0.06 (%) for the sisal fiber and 39.61 ± 0.39 (%) for the coconut shell, under the reaction conditions tested after 4 hours of fermentation. The preliminary results exhibited the potential application of this enzyme in the removal of lignin from plant residues. However, the conditions should be evaluated and optimized for each residue type.