Sisal Fiber-reinforced Composites Research Articles

Circular alternatives in the construction industry: An environmental performance assessment of sisal fiber-reinforced composites

In the development of new products, both the use of residues and the use of renewable materials are important strategies for a more circular production. However, it is not enough just to idealize a new product as environmentally sustainable, it is also necessary to prove the hypothesis through scientifically accepted methodologies, such as life cycle assessment (LCA). Thus, the objective of this study was to evaluate and compare, through LCA, the environmental performance of two composites reinforced with sisal fibers, one produced with a Portland cement matrix and the other with a geopolymer matrix based on a residue, in this case, the sludge from a water treatment plant. When comparing the environmental performance of composites using the impact assessment methods ReCiPe 2016 Midpoint/Endpoint and EN 15804, the results were convergent; the composite with the cement matrix has less environmental impact. The composite with the Portland cement matrix and 0.4% superplasticizer, for example, in the category Global warming, using the ReCiPe 2016 Midpoint method, was 42.48% less impactful than the geopolymeric composite without the avoided product. In the category Climate change, using the EN 15804 method, the composite with the Portland cement matrix and 0.4% superplasticizer was 42.05% less impactful than the geopolymeric composite without the avoided product. The sensitivity analysis showed that the critical environmental points in the two composites are the production of potassium hydroxide and transport in the case of the geopolymer composite, and the production of cement and transport for the Portland cement composite. This research contributes scientifically by presenting potential alternatives for the construction industry that have already been evaluated from an environmental perspective. It is important to environmentally assess new products still in the development stage, since stating that a building material has superior environmental performance just because it is produced from residues or from a renewable raw material may not be a true reflection of the facts.

Waviness Effect of Fiber on Buckling Behavior of Sisal/Carbon Nanotube Reinforced Composites Using Experimental Finite Element Method

Sisal fiber-reinforced composites have huge potential applications in many industries. Different defects during the production process of the composite may decrease the performance of these composites. In the present work, one of the important defects such as the waviness of the sisal fiber has been studied under compressive loading. Two types of composite materials are considered for the study. One is sisal fiber-reinforced polymer matrix composite and another one is hybrid composite i.e sisal fiber and carbon nanotube reinforced polymer matrix composite. The sisal and hybrid sisal straight fiber composite specimens are prepared by using the hand lay-up technique. The buckling load of the sisal and sisal hybrid composites is estimated by conducting suitable experiments. Further, using the Finite Element method the effect of the waviness of sisal fiber on the buckling load is estimated. Two different wavy patterns such as Full Sine Waviness (FSW) and Half Sine Waviness (HSW) are considered for sisal fiber. The position effect of waviness of the fiber on the same property is also estimated by changing (A/λ) ratio from 0.1 to 0.35 by changing the amplitude of waviness from 5 to 17.5 mm (A) and maintaining the length of waviness (λ) to 100mm. The present study is used to design the buckling load of natural composite with waviness because the perfectly straight fibers are difficult to extract from plants.

Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance.

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

Effect of polyaramid reinforced with sisal epoxy composites: Tensile, impact, flexural and morphological properties

Natural fiber reinforced polymers have been intensively studied in a wide range of application in the material science. The sisal fibers, which extracted from Agave sisalana plant, stand out due to their good mechanical properties, simple cultivation and reasonable cost. In the present work, the effect of addition of 5% polyaramid fibers, in the structure and properties of epoxy matrix composite reinforced with modified sisal fibers investigated. The ratio of 40, 50 and 60 wt. % sisal fiber-reinforced composites were prepared by hand lay-up technique, with and without the addition of polyaramid. Tensile, flexural and Izod impact tests performed, and the fracture aspect observed. Analytical techniques such as SEM, TEM and TGA have performed to investigate the structural changes. The results also indicated epoxy matrix composite reinforced with modified sisal fibers possesses good tensile, flexural and impact strength.

Multi-layer interfacial fatigue and interlaminar fracture behaviors for sisal fiber reinforced composites with nano- and macro-scale analysis

In this study, fatigue performance of the multiple interfaces within sisal-fiber-reinforced composites (SFRCs) in the nanoscale was examined with nano-dynamic mechanical analysis technique. Cyclic loading with varying applied indentation loads at different frequencies was employed to study nanoscale interface failure. To correlate nanoscopic damage to macroscopic interfacial failure mechanisms, double-cantilever-beam (DCB) experiments were conducted to reveal the effects of hierarchical structure of sisal fibers on the interfacial failure behaviors of laminated SFRCs. Fiber bridging and fiber entanglement were observed during DCB test, which made the crack propagation path tortuous and introduced higher Mode I interlaminar fracture toughness compared with glass-fiber-reinforced composites. To model these actual multi-interfacial fracture behaviors, a numerical model subject to the DCB experiment was developed with designed cohesive-zone model in the pre-set crack front. Good consistency between numerical simulation and experimental results verified the efficiency of proposed model in simulating the multi-layer failure behaviors of laminated SFRCs.

Mechanical properties of sisal-epoxy composites as functions of fiber-to-epoxy ratio

Low density, low cost, environmental compatibility, wide availability, and high mechanical performance of raw materials are some considerable advantages of natural fiber composites. Sisal, very common type of natural fiber, is abundantly available in Ethiopia. This research aims to investigate mechanical properties of sisal reinforced composites such as tensile, flexural and impact strength. Fabrication of samples used the hand lay-up process with 15, 25, 30, 35, and 40 wt% sisal fiber to epoxy ratio. Tests for the properties indicated were made using the instron material testing system. Test results demonstrated, among the samples, that 30 wt% of sisal fiber-reinforced composites have the maximum tensile and flexural strength of 85.5 MPa and 85.79 MPa respectively. The impact strength has been found to be maximum for 40 wt% sisal fiber which is 24.5 kJ/m². As the result show, and compared with other researcher findings, the mechanical properties are acceptable as substitutes for applications demanding low-cost engineering applications such as automotive internal parts including interior door panel, back seat and body panels.

Modeling the longitudinal tensile behavior of unidirectional twisted plant fiber yarns-reinforced composites

In this paper, a theoretical model among strain, stress, and surface twist angle of plant fiber yarns, for unidirectional twisted plant fiber-reinforced composites under tensile forces, was proposed with a piecewise function. That model focused on yarn twist angle’s effect on tensile modulus and stress–strain relations of composites, which was based on the widely used rule of mixtures, classical laminate theory, and revised Krenchel orientation efficiency factor cos22θ (θ is the surface twist angle of fiber yarns). In the model, a surface twist angel θe was regarded as the threshold value where ε1 = ε (ε1 is the longitudinal tensile strain, and e is its numerical value) for the piecewise function, which cut off the experimental stress–strain curve from nonlinearity into linearity. The model was validated by the tensile test results of sisal fiber-reinforced composites made from twisted sisal filament yarns. A good agreement between the theoretical values and experimental results was obtained. This study would form the fundamentals for building up the constitutive model of plant fiber yarns-reinforced composites.

A micromechanical model of interfacial debonding and elementary fiber pull-out for sisal fiber-reinforced composites

The interfacial failure behavior of sisal fiber-reinforced composites (SFRCs) was studied experimentally and theoretically. The residual pull-out strength of the SFRCs was observed to gradually decrease during the single sisal fiber pull-out test, after which the SFRCs presented multiple failure modes, including at the interface between technical fiber and matrix and at the interface between elementary fibers. To further investigate the failure mechanisms of SFRCs, using the traditional shear lag model, a double-interface model tailored to the unique multi-layer interface structure of plant fibers was developed to describe the fiber pull-out behavior and the interfacial adhesion status of single plant fiber-reinforced composites (PFRCs). By comparison with other existing models, using the experimental applied stress as reference, the proposed double-interface model was found to provide a more accurate quantitative theoretical prediction of the interfacial failure behavior of PFRCs during multi-stage fracture of the two interfaces.

Novel fibre metal laminate sandwich composite structure with sisal woven core

Fibre metal laminates (FMLs) have been widely used to manufacture airframe components. This work describes novel sisal fibre reinforced aluminium laminates (SiRALs) that have been prepared by cold pressing techniques and tested under tensile, flexural and impact loading. The pristine sisal fabric and the sisal fibre reinforced composites (SFRCs) were also tested to understand the difference in mechanical performance of the sisal fibre metal laminates. The SiRALs achieved not only the highest modulus and strength, but also the highest specific properties. The mean specific tensile strength and modulus of the SIRALs reached increases of 132% and 267%, respectively, when compared to the sisal fibre reinforced composites (SFRCs). Moreover, the mean specific flexural strength and modulus of the SiRALs were significantly higher than SFRCs, revealing increases of 430% and 973%, respectively. A delamination fracture mode was noted for SiRALs under bending testing. The SiRALs can be considered promising and sustainable composite materials for structural and multifunctional applications.

Composites of sisal fiber/polypropylene based on novel vane extruder: Effect of interface and damage on mechanical properties

Sisal fibers were pretreated by alkali and maleic anhydride, and then mixed with polypropylene to fabricate sisal fiber-reinforced composites by a self-made vane extruder based on elongational flow field. Maleic anhydride-grafted polypropylene was used as compatilizer to increase the fiber/matrix interactions. The influence of treatment on the fibers structure, the damage to fibers in processing, interfaces of composites and the mechanical properties of composites were investigated. It was observed that the surface of treated fibers was improved obviously compared with that of untreated fibers, which was believed to increase the adhesion between the fibers and matrix. However, the treated fibers were more likely to be damaged during processing. In comparison to unmodified system, the incorporation of treated fibers could significantly enhance the mechanical properties of composites, especially adding the compatilizer of maleic anhydride-grafted polypropylene. The flexural and impact strengths were maximum for the sisal fiber/polypropylene and maleic anhydride-grafted polypropylene composites, and its tensile strength was also improved significantly. The major contribution of this change should be that the morphology of fibers could be well preserved in elongational flow field, which based on the vane extruder showed a good application in fiber-reinforced composites.

Mercerization of sisal fibers: Effect of tension on mechanical properties of sisal fiber and fiber-reinforced composites

Sisal fibers were mercerized, under tension and no tension, to improve their tensile properties and interfacial adhesion with soy protein resin. Mercerization of fibers under tension is known to minimize fiber shrinkage and to lower the microfibrillar angle by aligning them along the fiber axis. Mercerization improved the fracture stress and Young’s modulus of the sisal fibers while their fracture strain and toughness decreased. Mercerized sisal fiber-reinforced composites with soy protein resin showed improvement in both fracture stress and stiffness by 12.2% and 36.2%, respectively, compared to the unmercerized fiber-reinforced composites. Scanning electron microscope (SEM) photomicrographs of the composite fracture surfaces showed shorter fibrils protruding in the mercerized fiber-reinforced composites resulting in better sisal fiber/soy adhesion. Changed fiber surface properties were also responsible for better adhesion.