Effect of fibers treatment on dynamic mechanical and thermal properties of epoxy hybrid composites

Epoxy hybrid composites fabricated by reinforcing 2‐hydroxy ethyl acrylate (2‐HEA) treated oil palm empty fruit bunch (EFB) and jute fibers. It assume that chemical modification of jute and oil palm EFB fibers increased fiber/matrix interfacial bonding and it results in enhanced thermal properties of hybrid composites. Dynamic mechanical and thermal analysis of treated hybrid composites was carried out. Results indicated that chemical modification of oil palm EFB and jute fibers affect the dynamic mechanical and thermal properties of hybrid composites. The storage modulus values of hybrid composites increases with chemical treatment and loss modulus increased with fiber treatment in hybrid composites. Damping factor peak values of treated hybrid composites shifted toward the lower temperature compared to both untreated hybrid composites. Cole–Cole analysis was made to understand the phase behaviour of the hybrid composites. Thermogravimetric analysis indicated an increased in thermal stability of hybrid composite with the incorporation of chemically modified fibers. POLYM. COMPOS., 36:1669–1674, 2015. © 2014 Society of Plastics Engineers     

Composites of Plasticized Polyamide 66 and Chemically Modified Vegetal Fibers

This work aims to prepare composites of polyamide 66 with vegetal fibers from curauá, jute, and flax. Alkaline treatment was conducted followed by silanization, improving the thermal properties of treated natural fibers. To reduce the processing temperature of polyamide 66, a combination of LiCl and N-butylbenzenesulfonamide was added to pure polyamide 66. It is shown that plasticizing polyamide 66 is one way to prepare composites with natural fibers using this high temperature polymer. The increase in elastic modulus of polyamide 66 and the decrease in strain at break were observed.     

Improvement of mechanical properties of natural fiber–polypropylene composites using successive alkaline treatments

The use of natural fibers (NFs) in polymer composites for structural applications has increased greatly in the last years, owing to their abundance and biodegradability. In this work, an innovative and simple successive alkali treatment has been developed to improve the mechanical properties of NFs/polypropylene (PP) composites. Three different cellulosic fibers (curauá, jute, and flax) were used, with a fixed proportion of 10 wt %. The fibers were immersed several times in a 5 wt % NaOH solution. Thermogravimetric analysis data showed an improvement in thermal properties of the fibers, as well as the increase of the crystallinity degree was measured by X‐ray diffraction. By Fourier transform infrared spectroscopy, disappearance of characteristics peaks of hemicelluloses and lignin was observed. Finally, mechanical behavior of the NF/PP composites was examined, using dynamic mechanical analysis. The results revealed that the curauá/PP mechanical properties were significantly improved, showing the positive effect of the successive alkali treatments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41710.     

Surface modification of sisal fibers: Effects on the mechanical and thermal properties of their epoxy composites

The aim of this paper is to evaluate the mechanical and thermal properties of sisal fiber reinforced epoxy matrix composites as a function of modification of sisal fiber by using mercerization and silane treatments. The changes introduced by the treatments on the chemical structure of sisal fibers have been analyzed by infrared spectroscopy (FTIR). Thermal behavior of both sisal fibers and composites has been studied by thermogravimetric analysis (TGA). Both treatments clearly enhanced thermal performance and also mechanical properties of fibers, being other physical properties also modified. Mercerization, above all when combined with silanization, led to significant enhancement on mechanical properties of composites as a consequence of increasing mechanical properties of fibers and improving fiber/matrix adhesion. POLYM. COMPOS., 26:121–127, 2005. © 2005 Society of Plastics Engineers     

A Comparative Study on the Mechanical Properties of Jute and Sisal Fiber Reinforced Polymer Composites

The aim of the present study is to investigate and compare the mechanical properties of raw jute and sisal fiber reinforced epoxy composites with sodium hydroxide treated jute and sisal fiber reinforced epoxy composites. This is followed by comparisons of the sodium hydroxide treated jute and sisal fiber reinforced composites. The jute and sisal fibers were treated with 20% sodium hydroxide for 2 h and then incorporated into the epoxy matrix by a molding technique to form the composites. Similar techniques have been adopted for the fabrication of raw jute and sisal fiber reinforced epoxy composites. The raw jute and sisal fiber reinforced epoxy composites and the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites were characterized by FTIR. The mechanical properties (tensile and flexural strength), water absorption and morphological changes were investigated for the composite samples. It was found that the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites exhibited better mechanical properties than the raw jute and raw sisal fiber reinforced composites. When comparing the sodium hydroxide treated jute and sisal fiber reinforced epoxy composites, the sodium hydroxide treated jute fiber reinforced composites exhibited better mechanical properties than the latter.     

Effect of layering pattern on the physical,mechanical, and thermal properties of jute/bagasse hybrid fiber‐reinforced epoxy novolac composites

In this study, randomly oriented short jute/bagasse hybrid fiber‐reinforced epoxy novolac composites were prepared by keeping the relative volume ratio of jute and bagasse of 1:3 and the total fiber loading 0.40 volume fractions. The effect of jute fiber hybridization and different layering pattern on the physical, mechanical, and thermal properties of jute/bagasse hybrid fiber‐reinforced epoxy novolac composites was investigated. The hybrid fiber‐reinforced composites exhibited fair water absorption and thickness swelling properties. To investigate the effect of layering pattern on thermomechanical behavior of hybrid composites, the storage modulus and loss factor were determined using dynamic mechanical analyzer from 30 to 200°C at a frequency of 1 Hz. The fracture surface morphology of the tensile samples of the hybrid composites was performed by using scanning electron microscopy. The morphological features of the composites were well corroborated with the mechanical properties. Thermogravimetric analysis indicated an increase in thermal stability of pure bagasse composites with the incorporation of jute fibers. The incorporation of hybrid fibers results better improvement in both thermal and dimensional stable compared with the pure bagasse fiber composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Influence of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites

The incorporation of natural fibers with polymer matrix composites (PMCs) has increasing applications in many fields of engineering due to the growing concerns regarding the environmental impact and energy crisis. The objective of this work is to examine the effect of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites. In this experimental study, sisal‐jute‐glass fiber‐reinforced polyester composites are prepared with fiber orientations of 0° and 90° and fiber volume of sisal‐jute‐glass fibers are in the ratio of 40:0:60, 0:40:60, and 20:20:60 respectively, and the experiments were conducted. The results indicated that the hybrid composites had shown better performance and the fiber orientation and fiber content play major role in strength and water absorption properties. The morphological properties, internal structure, cracks, and fiber pull out of the fractured specimen during testing are also investigated by using scanning electron microscopy (SEM) analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42968.     

Behavior of sisal fiber concrete cylinders externally wrapped with jute FRP

The use of environmentally friendly natural fibers as building materials is benefit to achieve a sustainable construction. This article performs a study on the use of natural jute fibers as reinforcement of concrete and natural sisal fibers in fiber reinforced polymer (FRP) composites as concrete confinement, i.e., sisal fiber reinforced concrete (SFRC) composite column wrapped by jute FRP (JFRP) (SFRC‐JFRP). Uniaxial compression test was conducted to assess the compression performance of the composite columns as axial structural member. A total of 24 specimens were tested. The effects of JFRP wrapping thickness and sisal fiber inclusion on the compressive performance of the composite columns were investigated. Results indicate that JFRP confinement significantly increases the compressive strength and ductility of both PC and SFRC with an increase in JFRP thickness. Besides, the inclusion of sisal fiber further enhances the strength as well as the efficiency of confinement under uniaxial compression. Also, the models for ultimate strength and ultimate strain of PC‐JFRP and SFRC‐JFRP are proposed. POLYM. COMPOS., 38:1910–1917, 2017. © 2015 Society of Plastics Engineers     

Mechanical properties of phenolic composites reinforced with jute/cotton hybrid fabrics

Mechanical properties (tensile, flexural, impact, and dynamic mechanical thermal analysis) of novolac type phenolic composites reinforced with jute/cotton hybrid woven fabrics were investigated as a function of fiber orientation and roving/fabric characteristics. Scanning electron microscopy (SEM) was carried out to investigate the fiber‐matrix adhesion. Results showed that the composite properties are strongly influenced by test direction and rovings/fabric characteristics. The anisotropy degree was shown to increase with test angle and to strongly depend on the type/architecture of fabric used, i.e., jute rovings diameter, relative fiber content, etc. It was possible to obtain composites with higher mechanical properties and lower anisotropy degree by producing cross‐ply laminates. Best overall mechanical properties were obtained for the composites tested along the jute rovings direction. Composites tested at 45° and 90° with respect to the jute roving direction exhibited a controlled brittle failure combined with a successive fiber pullout, while those tested in the longitudinal direction (0°) exhibited a catastrophic failure mode. Our results indicate that jute promotes a higher reinforcing effect and cotton avoids catastrophic failure. Therefore, this combination of natural fibers is suitable to product composites for lightweight structural applications. POLYM. COMPOS., 26:1–11, 2005. © 2004 Society of Plastics Engineers.     

Pretreatments of natural fibers and their application as reinforcing material in polymer composites—A review

In recent years, natural fibers reinforced composites have received much attention because of their lightweight, nonabrasive, combustible, nontoxic, low cost and biodegradable properties. Among the various natural fibers; flax, bamboo, sisal, hemp, ramie, jute, and wood fibers are of particular interest. A lot of research work has been performed all over the world on the use of natural fibers as a reinforcing material for the preparation of various types of composites. However, lack of good interfacial adhesion, low melting point, and poor resistance towards moisture make the use of natural fiber reinforced composites less attractive. Pretreatments of the natural fiber can clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. Among the various pretreatment techniques, graft copolymerization and plasma treatment are the best methods for surface modification of natural fibers. Graft copolymers of natural fibers with vinyl monomers provide better adhesion between matrix and fiber. In the present article, the use of pretreated natural fibers in polymer matrix‐based composites has been reviewed. Effect of surface modification of natural fibers on the properties of fibers and fiber reinforced polymer composites has also been discussed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

A study of the mechanical properties of randomly oriented short banana and sisal hybrid fiber reinforced polyester composites

The mechanical performance of short randomly oriented banana and sisal hybrid fiber reinforced polyester composites was investigated with reference to the relative volume fraction of the two fibers at a constant total fiber loading of 0.40 volume fraction (V_f), keeping banana as the skin material and sisal as the core material. A positive hybrid effect is observed in the flexural strength and flexural modulus of the hybrid composites. The tensile strength of the composites showed a positive hybrid effect when the relative volume fraction of the two fibers was varied, and maximum tensile strength was found to be in the hybrid composite having a ratio of banana and sisal 4 : 1. The impact strength of the composites was increased with increasing volume fraction of sisal. However, a negative hybrid effect is observed when the impact strength of the composites is considered. Keeping the relative volume fraction of the two fibers constant, that is, banana : sisal = 0.32 : 0.08 (i.e., 4 : 1), the fiber loading was optimized and different layering patterns were investigated. The impact strength of the composites was increased with fiber loading. Tensile and flexural properties were found to be better at 0.40 V_f. In the case of different layering patterns, the highest flexural strength was observed for the bilayer composites. Compared to other composites, the tensile properties were slightly higher for the composite having banana as the skin material and sisal as the core material. Scanning electron micrographs of the tensile and impact fracture surfaces of the hybrid composites having volume fraction 0.20 and 0.40 V_f were studied. The experimental tensile strength and tensile modulus of hybrid composites were compared with those of theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1699–1709, 2005     

An investigation of sound absorption coefficient on sisal fiber poly lactic acid bio‐composites

In this research, the mechanical, acoustical, thermal, morphological, and infrared spectral properties of untreated, heat and alkaline‐treated sisal fiber‐reinforced poly‐lactic‐acid bio‐composites were analyzed. The bio‐composite samples were fabricated using a hot press molding machine. The properties mentioned above were evaluated and compared with heat‐treated and alkaline‐treated sisal fibers. Composites with heat‐treated sisal fibers were found to exhibit the best mechanical properties. Thermo‐gravimetric analysis (TGA) was conducted to study the thermal degradation of the bio‐composite samples. It was discovered that the PLA‐sisal composites with optimal heat‐treated at 160°C and alkaline‐treated fibers possess good thermal stability as compared with untreated fiber. The results indicated that the composites prepared with 30wt % of sisal had the highest sound absorption as compared with other composites. Evidence of the successful reaction of sodium hydroxide and heat treatment of the sisal fibers was provided by the infrared spectrum and implied by decreased bands at certain wavenumbers. Observations based on scanning electron microscopy of the fracture surface of the composites showed the effect of alkaline and heat treatment on the fiber surface and improved fiber‐matrix adhesion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42470.     

Influence of fiber surface treatment on the properties of sisal-polyester composites

The effect of several chemical treatments, viz. organotitanate, zirconate, silane, and N-substituted methacrylamide, on the properties of sisal fibers used as reinforcement in unsaturated polyester resin (∼50 vol%) was investigated. An improvement in the properties was observed when sisal fibers were modified with surface treatments. Under humid conditions, a decrease of 30 to 44% in tensile and 50 to 70% in flexural strength has been noted. The strength retention of surface-treated composites (except silane) is high compared with untreated composites. It is observed that N-substituted methacrylamide-treated sisal composites exhibited better properties under dry as well as wet conditions. Fractographic evidence such as fiber breakage/splitting and matrix adherence on the pulled-out fiber surface explains such behavior.     

Effects of alkalization on tensile,impact, and fatigue properties of hemp fiber composites

The effects of alkalization surface treatment on hemp fiber properties and the properties of hemp fiber–reinforced polyester composites have been studied. Hemp fibers were exposed to 1, 5, and 10% sodium hydroxide (NaOH) solutions. The tensile properties and interfacial shear strength of all alkalized fibers were found to lie within the range of nonalkalized fibers. Laminates were made of alkalized fibers with unsaturated polyester resin, using hand lay‐up and compression moulding. Alkalization of fibers at low concentrations of 1 and 5% resulted in improvements in tensile and fatigue properties of composites made from these fibers, but no such improvements were observed for 10% alkalized fiber composites. The improvements were attributed to improvement in fiber/matrix bonding after this treatment, which was also confirmed by scanning electron microscopy images. No improvement in impact damage tolerance was observed for any of these three alkalized fiber composites. Immersion in distilled water reduced water absorption compared with nonalkalized fiber composites; however, the tensile properties in water were similar to those for nonalkalized fiber composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Elastomer composite based on EPDM reinforced with polyaniline coated curauá fibers prepared by mechanical mixing

Curauá fibers were used to reinforce elastomeric matrices with polyaniline (PAni) synthesized directly on the fiber surfaces to produce antistatic‐reinforced composites. In this work, composites of poly(ethylene‐co‐propylene‐co‐diene) with curauá fibers coated with PAni were prepared by mechanical mixing in a counter‐rotating twin rotor internal mixer. Then, mechanical and electrical properties of these composites were correlated to Raman and Fourier transformed infrared spectra (FTIR) using chemometric data analyze, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA). Raman spectra showed correlation with electrical properties of conductive composites while FTIR spectra showed good correlation with mechanical properties. EPDM reinforced with PAni coated curauá fibers presented higher tensile strength and modulus than EPDM reinforced with pristine curauá fibers, indicating that the reinforcement effect was obtained. Chemical interaction between the phases occurs with formation of hydrogen bonding between the aminic nitrogens of PAni and the carbonyl groups of lignin of the fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40056.     

Cardanol biocomposites reinforced with jute fiber: Microstructure,biodegradability, and mechanical properties

This work aims at studying the preparation and characterization of composites of phenolic resin (matrix) based on cashew nut shell liquid, reinforced by natural jute fibers. The fibers were chemically modified using alkaline treatment with solutions of NaOH (5 and 10%) and bleached with sodium hypochlorite NaClO/H₂0 (1:1) at 60–75°C. The microstructure was investigated by Scanning Electron Microscopy to observe the fiber surface after the treatment. As a result, there was an improvement in the thermal stability of the fiber, which was verified by Thermogravimetric Analysis. The jute fiber composites showed an improvement in their mechanical properties due to chemical treatment with 5% NaOH. Their biodegradability level depended on the employed alkali solution concentration. This study is important to evaluate the application of the fibers as renewable materials. POLYM. COMPOS., 31:1928–1937, 2010. © 2010 Society of Plastics Engineers.     

The effect of multiscale hybridization on the mechanical properties of natural fiber-reinforced composites

The main objective of this work was to investigate the effect of reinforcements at different scales on the mechanical properties of natural fiber-reinforced composites. Pure jute and interlaminar hybrid jute/glass fiber-reinforced polymer composites were fabricated. Different types of fillers in two weight fractions (1 and 3 wt. %) were used as second reinforcements in the hybrid jute/glass composites. Tensile, flexural, and impact tests were performed. It was found that the macroscale inter-play hybridization significantly improved the mechanical properties of the pure jute fiber based composites. When the fillers are used as second hybridization, the modified composites presented higher mechanical properties when compared to pure jute composites. However, the effect of fillers on the mechanical properties of the hybrid composites presented various trends due to the interaction between several factors (i.e., particle scale, content, and nature), which cannot always be separated. Increasing the synthetic filler content improved the tensile properties of the filled hybrid composites, while increasing the natural filler content worsen the tensile properties. The flexural strength of the multiscale hybrid composites was improved, while the impact properties were negatively affected.     

Jute fabric reinforced engineering thermoplastic sandwich composites. I. The effect of molding time

Jute fabric‐reinforced sandwich composites were fabricated using engineering thermoplastics. The jute fabrics were precoated with thermosetting resin to improve their thermal resistance before molding of the composites. Thermal gravimetric analysis (TGA) studies revealed that the resin coated fabrics decomposed at higher temperature than the uncoated jute. The onset of degradation of the coated fibers also falls between that of jute fibers and the thermoset resins. This indicates the presence of good interfacial bonding between jute fibers and both resins. Isothermal TGA studies revealed that jute could withstand brief exposure to higher temperature at 270 and 290°C. The sandwich composites were fabricated at 270°C by compression molding for 1.5 and 3 min in each case, and then characterized by flexural, tensile and morphological studies, i.e., SEM and optical microscopy. The uncoated jute fabric yielded composites of superior mechanical properties even with 3 mins molding at 270°C which is close to the degradation temperature of uncoated jute fibers. This is an indication that it is feasible to prepare jute fiber filled engineering polymer composites provided the exposure time at high temperature during processing does not exceed 3 mins as determined by TGA isothermal studies. SEM studies revealed strong fiber/matrix interfacial bonding between jute and the thermoset resins while the inferior mechanical properties of the resin coated sandwich composites could be attributed to the poor interfacial bonding between the already cured thermoset coating and the matrix based on optical microscopy of the polished cross‐sections. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Immersion Temperature Effects on the Water Absorption Behavior of Hybrid Lignocellulosic Fiber Reinforced-Polyester Matrix Composites

Although economic, ecological, processing and property considerations suggest that it is very attractive to use lignocellulosic fibers as reinforcement in polymer matrix composites, moisture can strongly and deleteriously affect their properties. In this work the water absorption behavior of sisal/cotton, jute/cotton and ramie/cotton hybrid fabric reinforced composites is evaluated. The effect of the temperature of immersion, fiber volume fraction, and predrying of the fabrics before their incorporation onto the composites are evaluated. Sisal was shown to be the most hygroscopic of the fibers analyzed, and its presence leads to higher values of the maximum water content and of the diffusion coefficient of sisal/cotton reinforced composites. Under the range of temperatures analyzed (30–60°C) the volume fraction of the fibers, rather than the temperature itself, was shown to be the main parameter governing water absorption. Predrying usually lowers maximum water content, although for sisal/cotton reinforced composites a reverse trend was observed for the composites with higher volume fractions. This behavior was again attributed to the higher hydrophilic behavior of sisal fibers.     

Preparation and characterization of chemically modified Jute–Coir hybrid fiber reinforced epoxy novolac composites

In this study, the effects of fiber surface modification and hybrid fiber composition on the properties of the composites is presented. Jute fibers are cellulose rich (>65%) modified by alkali treatment, while the lignin rich (>40%) coconut coir fibers consist in creating quinones by oxidation with sodium chlorite in the lignin portions of fiber and react them with furfuryl alcohol (FA) to create a coating around the fiber more compatible with the epoxy resins used to prepare polymer composites. The maximum improvement on the properties was achieved for the hybrid composite containing the jute–coir content of 50 : 50. The tensile and flexural strength are recorded as 25 and 63 MPa at modified coir fiber content of 50 vol %, respectively, which are 78% and 61% higher than those obtained for unmodified fiber reinforced composites, i.e., tensile and flexural strength are 14 and 39 MPa, respectively. The reinforcement of the modified fiber was significantly enhanced the thermal stability of the composites. SEM features correlated satisfactorily with the mechanical properties of modified fiber reinforced hybrid composites. SEM analysis and water absorption measurements have confirmed the FA-grafting and shown a better compatibility at the interface between chemically modified fiber bundles and epoxy novolac resin. Hailwood–Horrobin model was used to predict the moisture sorption behavior of the hybrid composite systems. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012