Long jute fiber‐reinforced polypropylene composite: Effects of jute fiber bundle and glass fiber hybridization

Two types of long jute fiber pellet consisting of twisted‐jute yarn (LFT‐JF/PP) and untwisted‐jute yarn (UT‐JF/PP) pellets are used to prepare jute fiber–reinforced polypropylene (JF/PP) composites. The mechanical properties of both long fiber composites are compared with that of re‐pelletized pellet (RP‐JF/PP) of LFT‐JF/PP pellet, which is re‐compounded by extrusion compounding. High stiffness and high impact strength of JF/PP composites are as a result of using long fiber. However, the longer fiber bundle consequently affects the distribution of jute fiber. The incorporation of 10 wt % glass fibers is found to improve mechanical properties of JF/PP composites. Increasing mechanical properties of hybrid composites is dependent on the type of JF/PP pellets, which directly affect the fiber length and fiber orientation of glass fiber within hybrid composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41819.     

Mechanical behavior and correlation between dynamic fragility and dynamic mechanical properties of curaua fiber composites

In this study, the mechanical properties and physical–chemical characteristics of curaua composites were evaluated using tensile and short beam testing and dynamic mechanical analysis. Curaua/polyester composites with different pretreatment (washing and drying), fiber length (10–50 mm) and fiber volume fraction (%V_f) (11, 22, and 38 vol%) were studied. The results show that the composites produced using 50 mm long washed/dried fibers and %V_f of 38 vol% achieved better mechanical properties, such as tensile strength and modulus and short beam strength. Fragility index “m” of the composites increased upon curaua incorporation, which may be attributed to a reduction in polyester chemical interactions (due to fiber dwelling of the polyester network). The energy required in initiating the cooperative motion at the “ideal” glass transition temperature and the cooperative rearrangement regions (CRR) also increased upon curaua incorporation, since CRR is considered the subsystem of the sample and for higher fiber content the greater the molecular heterogeneity. Finally, the Angell fragility concept was successfully applied to polymer composite systems. POLYM. COMPOS., 35:1078–1086, 2014. © 2013 Society of Plastics Engineers     

Mechanical and viscoelastic properties of short fiber reinforced natural rubber composites: effects of interfacial adhesion,fiber loading,and orientation

The effect of a two-component dry bonding system consisting of resorcinol and hexamethylene tetramine on the mechanical and viscoelastic properties of short sisal fiber reinforced natural rubber composites has been studied. The studies were conducted with chemically treated and untreated short sisal fibers. Treated fibers impart better mechanical properties to the composites. By mixing with short fibers, the dynamic storage modulus (E') of natural rubber composites was improved. The effects of fiber-matrix adhesion on the mechanical and viscoelastic properties of the composites were investigated. The storage moduli and mechanical loss increased continuously with an increase in fiber loading but decreased with an increase of temperature. The influence of the fiber orientation on the mechanical and viscoelastic properties is discussed.     

Pineapple leaf fiber reinforced thermoplastic composites: Effects of fiber length and fiber content on their characteristics

Pineapple leaf fiber (PALF) was used as a reinforcement in polyolefins. Polypropylene (PP) and low‐density polyethylene (LDPE) composites with different fiber lengths (long and short fibers) and fiber contents (0–25%) were prepared and characterized. The results showed that the tensile strength of the composites increased when the PALF contents were increased. It was observed that the composites containing long fiber PALF were stronger than the short fiber composites as determined by greater tensile strength. An SEM study on the tensile fractured surface confirmed the homogeneous dispersion of the long fibers in the polymer matrixes better than dispersion of the short fibers. The unidirectional arrangement of the long fibers provided good interfacial bonding between the PALF and polymer which was a crucial factor in achieving high strength composites. Reduction in crystallinity of the composites, as evident from XRD and DSC studies suggested that the reinforcing effect of PALF played an important role in enhancing their mechanical strength. From the rule of mixtures, the stress efficiency factors of the composite strength could be calculated. The stress efficiency factors of LDPE were greater than those of PP. This would possibly explain why the high modulus fiber (PALF) had better load transfers to the ductile matrix of LDPE than the brittle matrix of PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polypropylene–glass fiber/basalt fiber hybrid composites fabricated by direct fiber feeding injection molding process

Hybrid composites of polypropylene reinforced with glass fibers and basalt fibers were fabricated by vented injection molding machine which is named the direct fiber feeding injection molding (DFFIM) process. Polyamide 6 and maleic anhydride‐grafted polypropylene has been used as a coupling agent to improve the interfacial bonding between the fibers and matrix. Two types of vented injection molding machines with a different check ring and mold were used for making specimens. The fiber lengths were analyzed to identify the most suitable check ring and mold for the DFFIM process. The mechanical properties of the hybrid composites were investigated by tensile, flexural and Izod impact tests. The interfacial morphology of the fractured tensile specimens was studied by using scanning electron microscopy and showed that there is a fiber agglomeration phenomenon that occurs in the hybrid composites, and it has a significant effect on the mechanical properties of hybrid composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45472.     

Impact of processing conditions and sizing on the thermomechanical and morphological properties of polypropylene/carbon fiber composites fabricated by material extrusion additive manufacturing

For the 3D printed composites, fiber alignment is affected by the direction of melt-flow during extrusion of filaments and subsequently through the printing nozzle. The resulting fibers orientation and the fiber-matrix compatibility have a direct correlation with mechanical properties. This study investigates the impact of processing conditions on the state of the carbon fiber types and their orientation on the mechanical properties of 3D-printed composites. Short and long carbon fibers were used as starting reinforcing materials, and the state of fibers at the beginning and on the printed parts were evaluated. Strong anisotropy in terms of mechanical properties (flexural and impact properties) was observed for the samples printed with different printing orientations. Interestingly, the number of voids in the printed composites was found to be correlated with the fiber types. The present work provides a step towards the optimization of tailored composite properties by additive manufacturing.     

Microstructure and fracture behavior of (co)injection‐molded polyamide 6 composites with short glass/carbon fiber hybrid reinforcement

The mechanical and fracture properties of injection molded short glass fiber)/short carbon fiber reinforced polyamide 6 (PA 6) hybrid composites were studied. The short fiber composites of PA 6 glass fiber, carbon fiber, and the hybrid blend were injection molded using a conventional machine whereas the two types of sandwich skin–core hybrids were coinjection molded. The fiber volume fraction for all formulations was fixed at 0.07. The overall composite density, volume, and weight fraction for each formulation was calculated after composite pyrolysis in a furnace at 600°C under nitrogen atmosphere. The tensile, flexural, and single‐edge notch‐bending tests were performed on all formulations. Microstructural characterizations involved the determination of thermal properties, skin–core thickness, and fiber length distributions. The carbon fiber/PA 6 (CF/PA 6) formulation exhibits the highest values for most tests. The sandwich skin‐core hybrid composites exhibit values lower than the CF/PA 6 and hybrid composite blends for the mechanical and fracture tests. The behaviors of all composite formulations are explained in terms of mechanical and fracture properties and its proportion to the composite strength, fiber orientation, interfacial bonding between fibers and matrix, nucleating ability of carbon fibers, and the effects of the skin and core structures. Failure mechanisms of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope, are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 957–967, 2005     

Hybrid effect on mechanical properties of M40‐T300 carbon fiber reinforced Bisphenol A Dicyanate ester composites

Interply and intraply hybrid composites based on Bisphenol A Dicyanate ester (BADCy), high strength carbon fibers T300, and high modulus carbon fibers M40 were prepared by monofilament dip‐winding and press molding technique. The tensile, flexural, interlaminar shear properties and SEM analysis of the hybrid composites with different fiber content and fiber arrangement were investigated. The results indicated that the mechanical properties of intraply hybrid composites were mainly determined by fiber volume contents. When the ratio of fiber volume content was close to 1:1, the intraply hybrid composites possessed lowest tensile and flexural strength. The mechanical properties of interply hybrid composite mainly depended on the fiber arrangement, instead of the fiber volume contents. The hybrid composites using T300 fiber layout as outside layer possessed high flexural strength and low flexural modulus, which was close to that of T300/BADCy composites. The hybrid composites ([(M40)_x/(T300)_y]_S) using M40 fiber layout as outside layer and T300 fibers in the mid‐plane had high flexural modulus and interlaminar shear strength. POLYM. COMPOS., 2010. © 2010 Society of Plastics Engineers     

In situ observations of fractures in short carbon fiber/epoxy composites

In contrast with traditional methods of observation, synchrotron radiation X-ray computed tomography (SR-CT) is an advanced technique that allows direct three-dimensional (3D) and non-destructive observation of microstructures in materials. High-resolution in situ observations (0.7 μm/pixel) of fractures in short carbon fiber/epoxy composites are achieved using the SR-CT technique, and the mechanical load response of short carbon fibers treated with oxidation and those untreated are compared. By the quantitative extraction and analysis of microstructure parameters in high-resolution 3D images, the failure mechanisms of the two materials were studied. The proportion of broken fibers to other types of fiber damage in the sample with oxidation-treated fibers increases by about 6%. Also, the oxidation treatment is able to reduce the ineffective length of the fibers by about 20%, thereby improving the mechanical properties of these composites. The results show that computed tomography can promote characterization of the internal microstructures in carbon fiber-reinforced polymer composites, which will facilitate further theoretical research on the failure mechanisms of these composites.     

Studies on mechanical properties of sisal fiber/phenol formaldehyde resin in‐situ composites

Phenol formaldehyde resin (PF) reinforced with short sisal fibers (SF) were obtained by two methods, direct‐mixing and polymerization filling. Impact and bending properties of resulting composites were compared. Under the same compression molding conditions, polymerization filled composites showed better mechanical properties than those of direct‐mixed composites. The influences of fiber modifications on the mechanical properties of SF/PF in‐situ (polymerization filled) composites have been investigated. Treated‐SF‐reinforced composites have better mechanical properties than those of untreated‐SF‐reinforced composites. The effects of SF on water absorption tendencies of SF/PF composites have also been studied. In addition, sisal/glass (SF/GF) hybrid PF composites of alkali‐treated SF were prepared. Scanning electron microscopic studies were carried out to study the fiber‐matrix adhesion. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Experimental analysis and theoretical modeling of the mechanical behavior of short glass fiber and short carbon fiber reinforced polycarbonate hybrid composites

In this research, polycarbonate (PC) composites with short glass fiber (SGF) and short carbon fiber (SCF) hybrid fiber reinforcements were compounded by single screw extruder and specimens were prepared by injection molding machine. This article aims to investigate the mechanical properties of PC hybrid composites, by means of the experimental and the theoretical methods. The composites were subjected to tensile test. Experimental results showed the improvements in tensile strength and modulus by increasing the SCF content of the hybrid composite. The theoretical tensile strength was predicted based on Kelly–Tyson model and rule of hybrid mixture. Kelly–Tyson model showed to be a good approximation to predict the tensile strength of composite. When the SCF was replaced by milled carbon fiber (MCF) to form a PC/SGF/MCF hybrid system, poorer mechanical properties are reported due to the weaker interfacial adhesion between MCF and PC, as proven by the scanning electron microscopy. POLYM. COMPOS., 37:1238–1248, 2016. © 2014 Society of Plastics Engineers     

Mechanical and viscoelastic properties of soybean oil thermoset reinforced with jute fabrics and carded lyocell fiber

Composites and hybrid composites were manufactured from renewable materials based on jute fibers, regenerated cellulose fibers (Lyocell), and thermosetting polymer from soybean oil. Three different types of jute fabrics with biaxial weave architecture but different surface weights, and carded Lyocell fiber were used as reinforcements. Hybrid composites were also manufactured by combining the jute reinforcements with the Lyocell. The Lyocell composite was found to have better mechanical properties than other composites. It has tensile strength and modulus of about 144 MPa and 18 GPa, respectively. The jute composites also have relatively good mechanical properties, as their tensile strengths and moduli were found to be between 65 and 84 MPa, and between 14 and 19 GPa, respectively. The Lyocell‐reinforced composite showed the highest flexural strength and modulus, of about 217 MPa and 13 GPa, respectively. In all cases, the hybrid composites in this study showed improved mechanical properties but lower storage modulus. The Lyocell fiber gave the highest impact strength of about 35 kJ/m², which could be a result of its morphology. Dynamic mechanical analysis showed that the Lyocell reinforced composite has the best viscoelastic properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological behavior of (short) carbon fiber/thermoplastic composites. Part I: The influence of fiber type,processing conditions and level of incorporation

The aim of this work is to understand the influence of type of (short) carbon fibers, processing conditions and fiber incorporation level on the rheological behavior of carbon fiber/polypropylene (PP) composites. For this purpose, two types of fibers (sub‐micron Vapor Grown Carbon Fibers, VGCF, and ex‐PAN, PAN), three different extruder screw geometries and three different fiber incorporation contents were studied. The rheological characterization was performed by means of capillary and rotational rheometry, results being presented and discussed in terms of reinforcing capability in both shear (steady and oscillatory) and extensional flows. The results show that VGCF have a generally higher influence on the rheological behavior of the composites than the PAN fibers. However, because of their higher intrinsic rigidity, PAN fibers give rise to composites with better mechanical properties than the VGCF ones. It is also shown that the influence of the screw geometry on fiber damage and, consequently, on the behavior of the composites, is weak, fiber degradation occurring mainly in the compounding stage. The incorporation level has the expected influence, i.e., it produces gradual changes in all the properties considered in this study.     

Effect of fiber type on mechanical properties of short carbon fiber reinforced B4C composites

In order to enhance the mechanical properties of B₄C without density increase, the short carbon fibers M40, M55J and T700 reinforced B₄C ceramic composites were fabricated by hot-pressing process. The addition of the carbon fibers accelerates the densification of the B₄C, decreases their densities, and improves their strength and toughness. The enhancement effects of the three kinds of carbon fibers were studied by investigating the density, Vickers hardness and the mechanical properties such as flexural strength, flexural modulus and fracture toughness of the composites. The fiber type has a great influence on the mechanical properties and enhancement of the short carbon fiber reinforced B₄C composites. The flexible carbon fiber with high strength and low modulus such as T700 is appropriate to reinforce the B₄C matrix ceramic composites.     

The influences of fiber feature and polymer melt index on mechanical properties of sugarcane fiber/polymer composites

The fiber characteristics (i.e., the fiber type, morphology, and dimension) and polymer melt flow index (MFI) significantly affected mechanical properties of sugarcane fiber/HDPE composites. The length and diameter of sugarcane fibers followed a lognormal distribution before and after compounding. The long fibers had a significant reduction in the dimension and aspect ratio during compounding. However, the short fibers had close values in these two properties before and after compounding. For the resultant sugarcane fiber/polymer composites, the HDPE resins with a low MFI value presented high tensile and impact strengths. Because of high sugar content, the pure rind fiber had a poor performance as filler in the HDPE resins with respect to the raw bagasse fiber and alkali‐extracted bagasse fiber. On the other hand, the aspect ratio was proportional to the mechanical performance of the fibers in the HDPE resins. As a result, the fibers with a large aspect ratio and low sucrose content improved the strength properties of the resultant composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5607–5619, 2006     

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     

Structure and properties of UHMWPE fiber/carbon fiber hybrid composites

Ultrahigh molecular weight polyethylene (UHMWPE) fiber/carbon fiber hybrid composites were prepared by inner‐laminar and interlaminar hybrid way. The mechanical properties, dynamic mechanical analysis (DMA), and morphologies of the composites were investigated and compared with each other. The results show that the hybrid way was the major factor to affect mechanical and thermal properties of hybrid composites. The resultant properties of inner‐laminar hybrid composite were better than that of interlaminar hybrid composite. The bending strength, compressive strength, and interlaminar shear strength of hybrid composites increased with an increase in carbon fiber content. The impact strength of inner‐laminar hybrid composite was the largest (423.3 kJ/m²) for the UHMWPE fiber content at 43 wt % to carbon fiber. The results show that the storage modulus (E′), dissipation factor (tan δ), and loss modulus (E″) of the inner‐laminar hybrid composite shift toward high temperature remarkably. The results also indicate that the high‐performance composite with high strength and heat resistance may be prepared by fibers' hybrid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1880–1884, 2006     

Preparation and properties of successive alkali treated completely biodegradable short jute fiber reinforced PLA composites

The natural fiber reinforced biodegradable polymer composites were prepared with short jute fiber as reinforcement in PLA (Poly lactic acid) matrix. The short jute fiber is successively treated with NaOH at various concentrations (5%, 10%, and 15%) and H₂O₂. The composites were prepared with untreated and treated short jute fibers at different weight proportions (up to 25%) in PLA and investigated for mechanical properties. The results showed that the composite with successive alkali treated jute fiber at 10% NaOH and H₂O₂ with 20% fiber loading has shown 18% higher flexural strength than neat PLA and untreated jute/PLA composite. The flexural modulus of the composite at 25% fiber loading was 125% and 110% higher than that of composites with untreated fibers and neat PLA, respectively. The impact strength of composite with untreated fibers at higher fiber weight fraction was 23% high as compared to neat PLA and 26% high compared to composite with treated fibers. The water absorption was more for untreated jute/PLA composite at 25% fiber loading than all other composites. The composite with untreated fibers has high thermal degradation compared with treated fibers but lower than that of pure PLA matrix. The enzymatic environment has increased the rate of degradation of composites as compared to soil burial. Surface morphology of biodegraded surfaces of the composites were studied using SEM method. POLYM. COMPOS., 37:2160–2170, 2016. © 2015 Society of Plastics Engineers     

The effect of ambient moisture and temperature conditions on the mechanical properties of glass fiber/carbon fiber/nylon 6 sandwich hybrid composites consisting of skin‐core morphologies

The concept of skin‐core (SC) morphology was used to make sandwich hybrid composites in which the skin and core were composed of different fibers in the same matrix. The sandwich blends comprising glass skin with carbon core and vice versa were compared with those of the hybrid composite, while the respective carbon (CF) and glass fiber (GF) composites served as points of reference. The composites were compounded and fabricated into injection molded tensile specimens and 3‐mm thick plaques. The effect of ambient temperature and moisture was studied. The fracture mechanical characterization of the various materials was done by using notched compact tension (CT) specimens. Tensile properties were also used to characterize the composites. Morphogical studies based on scanning electron microscopy and light microscopy were used to elucidate fracture characteristics. Deterioration of properties was noticed under hot and humid conditions. Synergism in flexural properties was observed in the CF/GF/PA hybrid composite. The mechanical properties of the CF/GF/PA hybrid are closer to those of CF/PA, suggesting a cost advantage by substituting half of the carbon fibers with glass fibers. Dynamic mechanical analysis results revealed that synergism in T_g is attained by blending or sandwiching glass and carbon fibers. Morphological studies reaffirmed the skin‐core morphology of the composites. POLYM. COMPOS., 26:52–59, 2005. © 2004 Society of Plastics Engineers.     

Mechanical and thermal properties of environment-friendly “green” composites made from pineapple leaf fibers and poly(hydroxybutyrate-co-valerate) resin

This paper presents the mechanical and thermal properties of unidirectional, degradable, environment-friendly “green” composites made from pineapple fibers and poly(hydroxybutyrate-co-valerate) (PHBV) resin. Tensile and flexural properties of the “green” composites with different fiber contents were measured in both longitudinal and transverse directions. Compared to those of virgin resin, the tensile and flexural strengths of “green” composites are significantly higher in the longitudinal direction while they are lower in the transverse direction. However, the mechanical properties are lower than those predicted by simple models. Scanning electron microscope (SEM) photomicrographs of the tensile fracture surfaces demonstrate fibers being pulled out from the matrix, the interfacial failure, fiber fibrillation, and the nonunidirectional nature of the “green” composites. The thermal behavior of the “green” composites, studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), showed that the presence of pineapple fibers does not affect the nonisothermal crystallization kinetics, crystallinity, and thermal decomposition of PHBV resin.