Curaua Fibers Research Articles

Mechanical Characterization of Curaua Fiber/Babool Wood Particle Reinforced Polyester Hybrid Composite

Background: The researchers are in the situation to satisfy the demand for engineering materials by developing novel eco-friendly materials. The natural fiber composites are the substitutes for the synthetic material. Introduction: The mechanical properties of curaua fiber-reinforced polyester (CFRP) composites were investigated, as well as the effects of curaua fibre infusion with Babool Wood particles (BWP). Methods: The composite specimens were fabricated using a hand lay-up approach using varying amounts of curaua fibres (CF) and babool wood particles in a 1:1 ratio in order to test the tensile strength and flexural strength. Results: The results demonstrated that before weakening, the tensile strength and flexural strength of the composite samples rose by up to 40% for hybrid reinforcements. Comparing samples made of pure resin to those made of the composite at 40 weight percent (CF20/BWP20), the tensile and bending strengths of the composite are improved by 93.42% and 86.4%, respectively. Conclusion: The tensile and flexural modulus values of the hybrid composites increased by up to 50% fiber, but less successfully (CF25 and BWP25). The fracture mechanism of the shattered composite samples was examined using scanning electron microscopy.

Polypropylene matrix embedded with Curaua fiber through hot compression processing: characteristics study

Polypropylene matrix embedded with Curaua fiber through hot compression processing: characteristics study

The influence of alkaline treatment on the mechanical performance of geopolymer composites reinforced with Brazilian malva and curaua fibers

AbstractLignocellulosic fibers obtained from the curaua (Ananas erectifolius) and malva (Malva sylvestris) plants in Brazil can be used as suitable reinforcements for geopolymers (GPs) owing to their high strength, ready regional availability, and low cost. In this work, the tensile and flexural strengths of untreated and NaOH alkali‐treated curaua and malva fiber‐reinforced GP composites were measured according to ASTM standards. Curaua reinforced GP composites had an average tensile strength of 25.7 (±) 7.1 MPa and flexural strength of 18.9 (±) 4.72 MPa. Malva GP composites withstood 19.18 (±) 9.0 MPa in tension and 31.5 (±) 7.6 MPa in flexure. Additionally, pullout tests were performed to investigate the debonding mechanisms for both fibers, with and without alkaline treatment, finding increases in chemical bonding for the treated samples due to roughness enhancements through fiber surface modifications with alkali treatment. Thermogravimetric analysis and X‐ray diffraction were used to characterize the physical fiber modifications after alkali treatment, evidencing lignin and hemicellulose removals. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy were used to further examine the fiber–matrix interaction, with proofs of interfacial tailoring.

Pyrolysis Decomposition Kinetics of Microcrystalline Cellulose and Curaua Fiber: Insight of Reaction Models by Using Vyazovkin Method

ABSTRACT This paper provides a full understanding of the pyrolysis mechanism of plant biomass (curaua) and cellulose – two materials that involve complex degradation stages. The chemical/physical reactions occurring in the corresponding mass loss stages are described in detail for each material. Multi-step degradation stages are identified by using Vyazovkin and Flynn–Wall–Ozawa methods and the individual contribution are discussed in terms of the chemical and physical steps involved in the process. The determination of multi-stages processes are rapidly determined applying an easy-to-use method as a first approach. We expect that this study helps to develop an understanding of the thermal degradation for future complex materials as well as to establish the initial guesses and to give an insight into the overall biomass decomposition. Final results can help to design of pyrolysis reactor and to develop new kinetic approaches.

Hemicellulose Films from Curaua Fibers (Ananas erectifolius): Extraction and Thermal and Mechanical Characterization.

With growing environmental concerns over synthetic polymers, natural polymeric materials, such as hemicellulose, are considered a good sustainable alternative. Curaua fibers could be an excellent source of biopolymer as they have a relatively high hemicellulose content (15 wt%) and only a small amount of lignin (7 wt%). In this work, hemicellulose was extracted by an alkaline medium using KOH and the influence of the alkali concentration, temperature, and time was studied. A hemicellulose film was produced by water casting and its mechanical, thermal, and morphological properties were characterized. The results show that the best method, which resulted in the highest hemicellulose yield and lowest contamination from lignin, was using 10% (w/v) KOH concentration, 25 °C, and time of 3 h. The hemicellulose film exhibited better thermal stability and elongation at break than other polymeric films. It also exhibited lower rigidity and higher flexibility than other biodegradable polymers, including polylactic acid (PLA) and polyhydroxybutyrate (PHB).

Tensile Properties of Curaua-Aramid Hybrid Laminated Composites for Ballistic Helmet.

A typical ballistic protection helmet for ground military troops has an inside laminate polymer composite reinforced with 19 layers of the aramid, which are neither recyclable or biodegradable and are relatively expensive. The hybridization of synthetic aramid with a natural lignocellulosic fiber (NLF) can provide a lower cost and desirable sustainability to the helmet. In the present work, the curaua fiber, one of the strongest NLFs, is, for the first time, considered in non-woven mat layers to partially replace the aramid woven fabric layers. To investigate the possible advantage of this replacement, the tensile and impact properties of aramid/curaua hybrid laminated composites intended for ballistic helmets, in which up to four layers of curaua were substituted for the aramid, were evaluated. Tensile strength, toughness, and elastic modulus decreased with the replacement of the aramid while the deformation of rupture was improved for the replacement of nine aramid layers by two layers of curaua. Preliminary impact tests corroborate the decreasing tendency found in the tensile properties with the replacement of the aramid by curaua. Novel proposed Reduction Maps showed that, except for the replacement of four aramid layers by one layer of curaua, the decrease percentage of any tensile property value was lower than the corresponding volume percentage of replaced aramid, which revealed advantageous hybridization for the replacement of nine or more aramid layers.

Tensile behavior analysis combined with digital image correlation and mechanical and thermal properties of microfibrillated cellulose fiber/ polylactic acid composites

Microfibrillated cellulose (MFC) employed as reinforcement of polymeric matrices can increase elastic modulus, stiffness and strength of a composite. In this work, the assessment of the mechanical, thermal properties and tensile tests assisted by digital image correlation (DIC) was performed for curaua fiber MFC-reinforced polylactic acid (PLA) composites as a function of MCF content. First, MFC was incorporated into PLA using a solvent exchange technique and subsequent polymer solubilization to produce master batch composites. Then, more PLA was added to obtain composites with 0.5 and 1.5 wt% MFC by using double screw extrusion and injection molding. As a result, the addition of MFC caused the flexural, tensile, indentation, impact and modulus strengths to increase compared to those of pure PLA. The deformation gradient obtained from DIC verified that the 0.5 wt% MFC/PLA composite presented greater homogeneity in relation to load dispersion, corroborating the higher rigidity, maximum stress, and Poisson's ratio.

Green-reinforced Sedimentary Silt with Natural Curaua Fiber

ABSTRACT Lime and cement as traditional binders need to be reduced in soil stabilization to avoid carbon dioxide emissions. Infrastructure development like paved structures, buildings, foundations, and dams involves exhaustive use of natural resources and serious concern for the environment. Using natural fibers as reinforced soil is a green-novel technique that improves soil properties such as strength, deformation, and expansion. Thus, this paper advances the performance of soil reinforcement using natural fiber. Natural Curauá fiber was used to improve unconfined compressive strength (qu), splitting tensile strength (qt), shear direct, and deformation of sedimentary silt in southern Brazil. By studying strength properties, 0.50% fiber and a length of 6 mm were selected as an optimum percentage and optimum length, respectively. For direct shear tests, the increase in strength at low confining stresses is proportional to the increase in fiber content and fiber length. By natural biodegradation of fiber, expanded polystyrene (EPS)-based treatment was employed, influencing a reduction of 10% in water absorption of fiber and increasing fiber’s tensile strength by 5%. Finally, the results demonstrate that natural fiber is a friendly-environmental alternative to enhance soil properties by applying rammed earth and some short-use earthworks in green constructions.

Dynamic and Ballistic Performance of Graphene Oxide Functionalized Curaua Fiber-Reinforced Epoxy Nanocomposites.

Graphene oxide (GO) functionalized curaua fiber (CF) has been shown to improve the mechanical properties and ballistic performance of epoxy matrix (EM) nanocomposites with 30 vol% fiber. However, the possibility of further improvement in the property and performance of nanocomposites with a greater percentage of GO functionalized CF is still a challenging endeavor. In the present work, a novel epoxy composite reinforced with 40 vol% CF coated with 0.1 wt% GO (40GOCF/EM), was subjected to Izod and ballistic impact tests as well as corresponding fractographic analysis in comparison with a GO-free composite (40CF/EM). One important achievement of this work was to determine the characteristics of the GO by means of FE-SEM and TEM. A zeta potential of −21.46 mV disclosed a relatively low stability of the applied GO, which was attributed to more multilayered structures rather than mono- or few-layer flakes. FE-SEM images revealed GO deposition, with thickness around 30 nm, onto the CF. Izod impact-absorbed energy of 813 J/m for the 40GOCF/EM was not only higher than that of 620 J/m for the 40CF/EM but also higher than other values reported for fiber composites in the literature. The GO-functionalized nanocomposite was more optimized for ballistic application against a 7.62 mm projectile, with a lower depth of penetration (24.80 mm) as compared with the 30 vol% GO-functionalized CF/epoxy nanocomposite previously reported (27.43 mm). Fractographic analysis identified five main events in the ballistic-tested 40GOCF/EM composed of multilayered armor: CF rupture, epoxy matrix rupture, CF/matrix delamination, CF fibril split, and capture of ceramic fragments by the CF. Microcracks were associated with the morphological aspects of the CF surface. A brief cost-effective analysis confirmed that 40GOCF/EM may be one of the most promising materials for personal multilayered ballistic armor.

Modeling the mechanical behavior of epoxy Curaua reinforced composites

In recent decades, it has become essential to find and develop materials from non-petroleum sources that are more compatible with nature. The present work describes the mechanical properties of a composite with epoxy matrix reinforced with natural Curaua fibers. To improve the matrix-fiber interaction, the Curaua fibers were immersed in solutions with different concentrations of sodium hydroxide (NaOH) for different treatment times. After washing, they were mixed in epoxy and specimens were cut for use in tensile, flexural, and dynamic mechanical analysis tests. The results were compared to untreated fibers, showing improvement of maximum tensile strength up to 30% and 10% for maximum flexural strength. For this test, the flexural modulus improved by 12%. On the other hand, Young’s modulus did not change as much. This can be associated with degradation of the fibers when immersed for many hours in a high concentration of NaOH. In the conclusion, this topic is analyzed as a factor of how the alkaline solution can affect the fiber surface.

Mechanical Properties of Hybrid PVA–Natural Curaua Fiber Composites

This work presents the experimental study of hybrid cement-based composites with polyvinyl alcohol fiber (PVA) and alkali-treated, short, natural curaua fiber. The objective of this research is to develop composites reinforced with PVA and curaua fiber to present strain-hardening behavior with average crack width control. To achieve this objective, three groups of composites were investigated. The first group had only PVA fiber in volumes of 0.5, 1, and 2%. The composite with 2% PVA fiber was the only one with strain-hardening and crack width control. The second group had 0.5% PVA fiber and volume fractions of 2, 2.5, and 3% curaua fiber, and presented only deflection-hardening behavior. The third group had 1% PVA and volumes of 1, 1.5, and 2% curaua fiber, and presented strain-hardening behavior. Based on the results, the hybrid combination of 1% PVA and 1.5% curaua was the optimal mixture as it presented strain-hardening behavior and crack width control, with a lower volume of synthetic PVA fiber. Additionally, compressive strength and mix workability were calculated for the investigated composites for comparison.

Processing, thermal and mechanical properties of composite laminates with natural fibers prepregs

This work manufactured prepregs by impregnating discontinuous curaua fibers with B-stage epoxy resin. The prepreg layers were then stacked to produce laminates by hot compression. Alkaline treatments were previously applied to the curaua fibers to improve their interface with the polymer matrix. Then, the prepregs and the final composites were studied regarding their thermal, dynamic mechanical, mechanical, and morphological behavior. The treatments promoted defibrillation by removing lignin and hemicellulose from the fibers, which allowed better impregnation of the treated fibers with epoxy resin. In general, laminates that used treated fibers exhibited the largest storage modulus in the glassy region. The mechanical results showed the laminates produced with treated fibers prepregs presented a highest tensile and flexural resistance than those manufactured with untreated fibers and neat epoxy resin. The NaOH-treated curaua/epoxy laminate exhibited high tensile strength (56.2 MPa) and modulus (3.3 GPa). Overall, fracture morphology indicated better fiber adhesion for the treated fiber composites. The results demonstrate that natural fibers prepregs can be successfully produced and present proper physical and mechanical behavior in components.

Environmental and Durability Perspective of the Use of Curaua Fiber Treated in Mortars

The use of natural lignocellulosic fibers (NLFs) as a reinforcement mechanism for cementitious composites, such as mortar, has been investigated in the last decades. However, their application has often been restricted to technological evaluation research. A NLF with great potential the curaua, which after treatment with NaOH solution, proved to be technologically feasible for mortars reinforcement based on cement and lime. The objective of this research was the comparative evaluation between a traditional mortar, based on cement and lime, with 1:1:6:0.8 ratio of cement: lime: sand: water, and a modified mortar with addition of 2 wt.% treated curaua fiber in cement mass by evaluating environmental and durability aspects. After a curing time for 28 days, environmental assessments were carried out and durability methodologies were evaluated. The tests performed were: (i) attack by chlorides and sulfate, (ii) the wetting and drying cycles, and (iii) slake durability test. The results showed that the mortar with the addition of curaua fiber presented a similar behavior to the reference mixture, both in terms of environmental and durability aspects. This modified mortar is able to be used in internal and external environments, the latter with some conditions. Besides, it also contributes to the promotion of sustainable use of curaua fiber.

Application of the Artificial Neural Network (ANN) Approach for Prediction of the Kinetic Parameters of Lignocellulosic Fibers

Lignocellulosic fibers are widely applied as reinforcement in polymer composites due to their properties. The thermal degradation behavior governs the maximum temperature at which the fiber can be applied without significant mass loss. It is possible to determine this temperature using Thermogravimetric Analysis (TG). In particular, when curves are obtained at different heating rates, kinetic parameters can be determined by using Arrhenius-based equations, and more detailed characteristics of the material are obtained. However, every curve obtained at a distinct heating rate demands material, cost and time. Methods to predict thermogravimetric curves can be very useful in the materials science field, and in this sense, mathematical approaches are powerful tools, if well employed. For this reason, in the present study, thermogravimetric curves from curaua fiber were obtained at four different heating rates (5, 10, 20 and 40 °C·min−1) and Vyazovkin kinetic parameters were obtained using free available software. After, the experimental curves were fitted using an artificial neural network (ANN) approach followed by a Surface Response Methodology (SRM) aiming to obtain curves at any heating rate between the minimum and maximum experimental heating rates. Finally, Vyazovkin kinetic parameters were tested again, with the new predicted curves at the heating rates of 7, 15, 30 and 50 °C·min−1. Similar values of the kinetic parameters were obtained compared to the experimental ones. In conclusion, due to the capability to learn from the own data, ANN combined with SRM seems to be an excellent alternative to predict TG curves that do not test experimentally, opening the range of applications.

Dynamic Mechanical Behavior of Graphene Oxide Functionalized Curaua Fiber-Reinforced Epoxy Composites: A Brief Report.

The coating of natural fiber by graphene oxide (GO) has, over, this past decade, attracted increasing attention as an effective way to improve the adhesion to polymer matrices and enhance the composite properties. In particular, the GO-functionalized 30 vol% curaua fiber (Ananas Erectifolius) reinforcing epoxy composite was found to display superior tensile and thermogravimetric properties as well as higher fiber/matrix interfacial shear strength. In this brief report, dynamic mechanical analysis (DMA) was conducted in up to 50 vol% GO-functionalized curaua fiber reinforced epoxy matrix (EM) composites. The objective was not only to extend the amount incorporated but also for the first time investigate the composite viscoelastic behavior. The GO functionalization of curaua fibers (GOCF) improved the DMA storage (E′) and loss (E″) modulus compared to the non-functionalized fiber composites. Values at 30 °C of both E′ (13.44 GPa) and E″ (0.67 GPa) for 50 vol% GO-functionalized curaua fiber reinforced epoxy matrix composites (50GOCF/EM) were substantially higher than those of 20 GOCF/EM with E′ (7.08 GPa) and E″ (0.22 GPa) as well as non-functionalized 50CF/EM with E′ (11.04 GPa) and E″ (0.45 GPa). All these results are above the neat epoxy previously reported values of E′ (3.86 GPa) and E″ (0.09 GPa). As for the tangent delta, the parameters associated with damping factor and glass transition temperature were not found to be significantly changed by GO functionalization, but decreased with respect to the neat epoxy due to chain mobility restriction.

Characterization of expanded polystyrene and its composites by supercritical carbon dioxide foaming approach

Supercritical carbon dioxide (scCO2) has been used as a physical blowing agent to produce polymer expanded materials. Firstly, a statistic study was performed to determine the neat polystyrene (PS) expansion parameters, using the ANOVA and response desirability approach. The results suggested that the optimal parameters are 120 °C (temperature), 2500 psi/17.23 MPa (pressure), and 2 h (residence time). Secondly, defibrillated curaua fibers (CF) were used as reinforcement in the PS matrix, in three different proportions (1.0, 2.5, and 5.0% (w/w)), to produced expanded composites. The results showed that CF acted as a nucleating agent, facilitating scCO2 to sip into the composite due to the reinforcement/matrix interface. The expanded composites were characterized by SEM, apparent density, cell population density, void volume fraction, and mechanical properties by the compression test, water uptake, dye absorption and, water contact angle (WCA). CF incorporation in the composite increased the compressive strength value and modified the expanded composite final morphology, decreasing the cell size and increasing void content and density. The PS/CF 5.0% sample showed higher water and organic dye absorption and the addition of CF on the expanded composite slightly decrease WCA.

Recycling of polypropylene and curaua fiber-based ecocomposites: Effect of reprocessing on mechanical properties

The polypropylene with load of reinforcement of curauá fiber (PP-curauá) is a compound developed to be applied in the process of injection of automotive plastic parts. Polypropylene composites reinforced with mineral fillers (talc) or glass fibers have been widely applied in this segment. However, natural fibers are an important alternative considering the aspects of sustainability, recyclability, abundance and low cost, when compared with glass fibers, and industrial talc. This study was prompted by the growing need for materials that meet the constant cycles of use, disposal and reuse, and avoid the harmful effects on the environment. The mechanical properties of a curaua fiber and polypropylene-based ecocomposite reprocessed one, three and five times were assessed, since reprocessing is known to change the strength of these materials. Pure polypropylene (0%) and ecocomposites with 10 and 30 wt% of fiber were submitted to tensile and three-point bending tests. The results showed that polypropylene ecocomposites with 30% curaua fibers exhibited a higher modulus of elasticity. Moreover, reprocessing did not significantly affect the ecocomposite properties, demonstrating their viability for reuse.

Effects of Degradation of Vegetal Fibers on the Mechanical Behavior of Reinforced Sand

This paper presents the results of an experimental program about the behavior and durability of soils reinforced with randomly distributed vegetal fibers (sisal and curaua) submitted to natural aging by their exposure to environmental conditions, aiming to boost its use in earthworks. The experimental program consisted of triaxial compression tests on sand and sand-fibers samples at zero time (sample control) and in composites exposed to agents from the external environment for up to 8 months. In order to explain the variation in the obtained results, direct tensile tests, scanning electron microscopy and mass loss analysis were performed on the fibers after each exposure period (0, 60, 120 and 240 days). The overall analysis of the results allowed to identify that the effects of natural aging had a significant effect on the mechanical behavior of the vegetable fibers, which consequently affected the mechanical behavior of the sand-fiber composites. Shear strength losses were more relevant and accentuated in composites with curaua fibers, indicating that these fibers, even with higher tensile strength without exposure, are more susceptible to degradation in natural environments than sisal fibers. Even with the loss of mechanical behavior of the fibers, after 8 months of exposure to the climatic agents, they continued to contribute as a reinforcing element in the sandy matrix, since one of the resistance parameters remained higher when compared to the sandy soil without reinforcement.

Polyaniline and magnetite on curaua fibers for molecular interface improvement with a cement matrix

Modifications were used in the natural fibers, aiming for a more outstanding adhesion between vegetable fibers and cement-based matrices. As a reinforcement load, improvements in dimensional stability (due to high hydrophilicity) and compatibility between both phases are necessary. In this work, reinforcement fibers were developed from hornified curaua fibers (HF) modified with polyaniline (HF-PAni), magnetite (HF-Mag), and both (HF-PAni/Mag). The obtained materials were tested on adhesion compatibility with the Portland cement matrix through the fiber's pullout test and microstructural analysis. The modified fibers were analyzed by infrared spectrometry (FTIR), water retention value (WRV%), Scanning Electron Microscopy coupled with X-ray Dispersive Energy (SEM-EDS), Direct Traction, Electrical Resistivity, and Magnetic Force. The last two analyses are due to each surface modification specific properties. The water retention value results show a reduction in the water absorption capability for all the treated fibers, indicating a gain in dimensional stability, especially for the PAni covering samples, due to the waterproofing of the fiber promoted by the hydrophobic polymer. Furthermore, the mechanical results of the HF-PAni sample showed good tensile strength responses. With the coating of the hybrid HF-PAni/Mag, the pullout test results indicate a significant improvement in fiber-matrix adhesion, resulting in a 40% increase in the adhesion stress compared to hornified fiber (HF).

Optimal Tensile Properties of Biocomposites Made of Treated Amazonian Curauá Fibres Using Taguchi Method

Abstract Natural fibres have many advantages over synthetic ones, making them attractive for reinforcing polymer materials. This work evaluates the use of an Amazonian plant, namely Curaua (Ananas erectifolius), as a reinforcement phase of biocomposites fabricated by cold pressing. Curaua fibres have been shown to be a promising fibre for composite materials, especially due to their higher elastic modulus than other plant species. An L9 Taguchi design is used to investigate the effect of fibre fraction, NaOH concentration and immersion time on the tensile properties of biocomposites. Statistical models are able of predicting and revealing the optimal composition of the biocomposites. The tensile strength of Curaua biocomposites is significantly affected by the fibre fraction, followed by the factors of immersion time and NaOH concentration. High tensile strength is obtained by adding 25 wt.% of Curaua fibres treated under different conditions. There is an interaction between NaOH concentration and the immersion time; a higher concentration requires less time or vice versa to achieve ideal roughness, promoting strong fibre/matrix adhesion.