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This study investigated the effect of various stacking sequences on the mechanical and acoustic characteristics of hemp and kenaf fibers reinforced hybrid composites. The mechanical study was done by using universal testing machine and izod imact tester. Further, acoustic study was done by using impendence tube method. Hemp/kenaf/kenaf/hemp hybrid laminates outperformed the other composites in terms of tensile strength, flexural strength and impact strength. In the mono reinforcements, hemp/epoxy composites demonstrated superior mechanical characteristics than the epoxy matrix and kenaf/epoxy composites. However, hybrid composites have superior mechanical behavior compared to pure composites. From the acoustic results revealed that the pure hemp and kenaf/hemp/hemp/kenaf hybrid composites exhibitted highest sound transmission loss level at lowest and highest frequency region. The bestmechanical characteristics of hybrid composites will be suggested for use in automobile door panels. Also, the optimal sound transmission coefficent values signifying their appropriateness for use in applications that encompass many frequency bands. Highlights: Hybridization of kenaf/hemp fibersImproved mechanical properties over the single fiber compositesBetter acoustic properties [ABSTRACT FROM AUTHOR]

This study presents an innovative approach utilizing Artificial Neural Network (ANN) strategies to evaluate the energy absorption capabilities of eco‐friendly rubber crumb/kenaf composites subjected to low‐velocity impact loads. The primary objectives of this research were to assess the energy absorption characteristics of these sustainable composites, understand their mechanical behavior under the impact, and provide valuable insights into their potential applications. To achieve these objectives, an experimental methodology was employed. Rubber crumb/kenaf composites with varying compositions were prepared, and low‐velocity impact tests were conducted using a drop‐weight impact testing apparatus to assess their energy absorption behavior and these parameters were used as inputs for training the ANN models. The weight percentage of waste tire rubber particle (WTRP), type of impactor and impact energies are considered as input data, whereas the absorbed energy is treated as the output. Through the advanced ANN strategies, accurate predictions of energy absorption performance were achieved for the rubber crumb/kenaf composites. The Levenberg–Marquardt optimisation algorithm with ten neurons and a tangent sigmoid activation function is used to train the ANN model. The trained ANN model is tested on an unseen dataset, different from the training data. It is shown to accurately predict the energy absorption characteristics of WTRP/KRE composites with a maximum error of 4.54%. The results revealed that the composite's energy absorption capabilities were influenced by the ratio of rubber crumb to kenaf, as well as the impact velocity. Additionally, the ANN models demonstrated excellent predictive capabilities, enabling efficient estimation of energy absorption behavior. The significance of these results lies in the potential applications of eco‐friendly rubber crumb/kenaf composites. By understanding their energy absorption characteristics, these composites can be effectively utilized in various industries. For instance, they could be employed in automotive parts manufacturing to enhance occupant safety during low‐velocity impact events. Furthermore, these composites can find applications in sports equipment, protective gear, and other impact‐prone products, contributing to sustainable and environmentally friendly materials. It is believed that by adopting the proposed ANN methodology, the experimentation costs and time can be significantly reduced without compromising the accuracy of the results. The obtained results provide valuable insights into the mechanical behavior of these sustainable composites and open avenues for their implementation in diverse industries where impact resistance is crucial Highlights: Development of sustainable Rubber crumb/kenaf compositesApplication of advanced ANN based predictive assessment of the impact responseParametric study of impactor shape and height of impact is performedThe damage mechanism contributing to energy absorption is micrographically studied [ABSTRACT FROM AUTHOR]

In this study, kenaf natural fibers were coated with acetone‐thinned epoxy resin before compounding with high‐temperature polyethylene terephthalate (PET). Thus, composites of sodium hydroxide treated and epoxy‐resin coated kenaf fibers (KF) reinforced PET (CTKF‐PET) were manufactured using extrusion and compression molding techniques at an optimized 10 wt% constant fiber loading and processing temperatures of 240, 250, and 260°C, and were characterized for mechanical, thermal, and morphological performances. The obtained results showed an optimum processing temperature of 240°C with maximum mechanical and thermal properties with good interfaces between the coated fillers and the matrix, compared to those obtained at 250 and 260°C. Thermogravimetric analysis recorded maximum onset degradation and decomposition temperatures of 338.9 and 381°C with 9.5% and 13% improvements respectively after resin coating which positively impacted the constituent coated composites compared to the uncoated KF. Differential scanning calorimetry glass transition (Tg) and melting temperatures (Tm) for the CKF‐PET composites was maximum at 119.0 and 262.8°C with 2.18% and 2.8% improvements respectively compared to uncoated composites. The overall properties of all coated kenaf‐reinforced PET (CKF‐PET) and coated‐treated (CTKF‐PET) composites were higher with improved morphological properties irrespective of the processing temperature compared to the raw kenaf (KF‐PET) composites. Hence, natural fibers can be treated with resin coating to improve the thermal stabilities of natural fiber engineering plastic composites, and the interfacial adhesion between the coated‐KF and the engineering plastic matrix. The resultant composites are suitable for high‐temperature engineering applications such as the automotive and construction industries. [ABSTRACT FROM AUTHOR]

The current experimental investigation examines the effect of the warp/weft orientation of jute/sisal and flax/kenaf fibers on the static and dynamic mechanical characteristics of intra‐woven hybrid composites. Jute (J), sisal (S), flax (F), and kenaf (K) hybrid woven mats were explicitly designed to keep fibers in the warp and weft directions. Intra‐hybrid‐composites with JJ, JS, SJ, SS, FF, FK, KF, and KK type hybrid woven mats with polypropylene matrix were processed using the compression molding/film stacking method. The tensile and flexural, and the dynamic mechanical behavior was investigated. Utilizing a scanning electron microscope, the fractured surface of tensile test specimens was examined. The results indicate that combining jute with sisal and flax with kenaf improved the mechanical properties of pure sisal and kenaf based composites. Hybridized composites exhibited the maximum increment in tensile strength (5.95% and 31.16%), tensile modulus (4.20% and 66.64%), flexural strength (12.59% and 5.69%), and flexural modulus (47.10% and 19.72%) for JS and FK composites, when compared with unhybridized SS and KK composites, respectively. The fiber hybridization and warp/weft sequence have a substantial effect on the dynamic mechanical performance of woven fiber laminated composites. It was identified that composites of JS and FK possess a higher storage modulus than pure SS and KK based composites, respectively. In addition, at a temperature of 50°C, the storage modulus was improved by 37.63% and 136.63%, for JS and FK hybrid composites, respectively in comparison to the unhybridized SS and KK composites, respectively. [ABSTRACT FROM AUTHOR]

Natural fiber‐based materials are widely accepted in the composite sector as a substitute for synthetic fiber, particularly in structural and semi‐structural implementations in the automotive and aerospace industries, reflecting a recent trend and increased awareness of the importance of sustainable product design. Hand lay‐up was used to create natural fiber bilayer hybrid composites with epoxy matrix reinforcing oil palm empty fruit bunch (EFB) and kenaf fiber matting. The overall effect of this hybridization of the natural fiber and the thermal characterizations were studied experimentally. Both the hybrid combinations kenaf fiber and oil palm EFB were made by maintaining the fiber loading at 50% (weight) and weight ratios at 1:1, 1:4 and 4:1. The Tan delta, loss modulus (E″), storage modulus (E′), and Cole‐Cole plot were found to be useful in investigating dynamic mechanical properties. Dynamic mechanical analysis results like coefficient of performance and Cole‐Cole plot clearly show that hybrid pure kenaf composite has the significant complex modulus because interfacial bond between fiber and matrix is strong. As a result, it has been determined that kenaf fibers have the best mixing ratio for improving the dynamic mechanical properties of these hybrid type composites and can be used for aerospace, automotive, and civil engineering applications requiring high dimensional stability and excellent mechanical properties. The thermal gravimetric analysis data demonstrated that as compared to pure, the kenaf fibers and hybrid oil palm empty fruit bunch composites have the best thermal stability, with the highest beginning and ultimate breakdown temperatures of 200 and 450°C, respectively. [ABSTRACT FROM AUTHOR]

The effect of jute, kenaf, and banana fiber reinforced epoxy hybrid composites with different stacking sequences were fabricated by compression molding techniques. The pure epoxy, pure jute, pure kenaf, pure banana composites are also fabricated for comparison purposes. Tensile, flexural, inter‐laminar shear strengths, and hardness properties of the fabricated composites were investigated. Physical parameters like density, water absorption, and thickness swelling were also examined. From mechanical properties, the results are evident that when compared to hybrid composites pure banana composites have the highest tensile, flexural, interlaminar shear strength and shore D hardness value of 41, 67, 18, and 86 MPa respectively. Also, pure banana composites have better water absorption and thickness swelling percentage of 4% and 1.6%. However, KBJJBK hybrid composites exhibit a maximum tensile strength of 34 MPa, flexural strength of 54 MPa. Further BJKKJB hybrid composites possess the highest hardness value of 87, intralaminar shear strength of 17 MPa and lowest water absorption of 8% and thickness swelling percentage of 2%. Certain pure and hybrid configuration have enhanced mechanical strength, stiffness, and lower water absorption and thickness swelling properties, indicating that they are suitable for automotive structural applications. [ABSTRACT FROM AUTHOR]

In this research, the flexural behavior of lightweight biodegradable sandwich panel consisting of the outer green composite facesheets with polylactic acid (PLA) matrix and natural kenaf and cotton fibers, with five various stacking types of standard cardboard egg boxes cores under three‐point bending loads as an environmentally friendly alternative to conventional synthetic sandwich structures is investigated. The stiffness of this structure in bending is also studied using finite element simulations. The thickest specimen absorbed the most energy during flexural testing, however, the specimens containing two egg boxes inside each other were found to have a higher strength and stiffness. Using finite element method simulations to investigate the influence of composite facesheet thickness on flexural loads, it was found that the amount of the load carried by each sandwich specimen with doubled thickness was increased at least by about 50%. By changing the core's material from cardboard egg box to bamboo/PLA or kenaf‐cotton/PLA egg boxes, stiffness and strength and also the energy absorption were significantly increased. Therefore, it is possible to fabricate composite sandwich structures which are light and biodegradable for green environment and has the potential to replace many plastic products and structures that are used in food packaging and medium loads structures applications. [ABSTRACT FROM AUTHOR]

The current research has produced engineering plastics composite for automotive applications using waste recycled plastic recycled polyethylene terephthalate (RPET) bottles as the matrix and compounded with chemically modified natural kenaf fibers in comparison with virgin polyethylene terephthalate (PET) composites under the same processing conditions. Kenaf fibers were surface modified by alkali and epoxy coating treatment methods. The waste RPET bottles which were mechanically recycled were pulverized using a 5 mm mesh size aperture into flakes and melt‐mixed with 10 wt% of short kenaf fibers in a twin‐screw extruder and compression‐molded at 240°С optimized temperature. Mechanical and thermal analyses were performed on both RPET, virgin PET (VPET), and their constituent kenaf composites. Scanning electron microscopy (SEM) was carried out to assess the composite's morphological characteristics. The results show that both treated (TKF/RPET and TKF/VPET) composites gave higher mechanical properties compared to untreated (KF/RPET and KF/VPET) composites. RPET and its constituent composites show higher impact properties than VPET composites. However, the tensile and flexural strength of VPET composites was higher than that of recycled RPET composites. RPET and VPET showed melting peak temperatures of 252.9°C and 245.8°C respectively. Both treated TKF/RPET and TKF/VPET composites were more thermally stable and decomposed at higher temperatures compared to the untreated composites. The SEM results for both treated composites showed a strong fiber/matrix adhesion with no clear evidence of fiber degradation as compared to untreated composites. It can be concluded that RPET possessed similar thermal properties compared to its virgin counterpart and can serve as a substitute for virgin PET in the composite formulation. [ABSTRACT FROM AUTHOR]

This work aims to optimize the mechanical performance of ramie and kenaf fibers in epoxy composites developed using the hand layup technique. Fiber reinforcement at 0–10 wt% and benzoyl chloride treatment at 0–5 wt% were incorporated with this composites. Taguchi‐based grey relational analysis (GRA) and technique for order preference by similarity to ideal solution (TOPSIS) methods were used to determine the optimized conditions for overall mechanical properties of the developed composites. Optimization techniques concluded that 10 wt% ramie (R)/10 wt% kenaf (K) with 5 wt% benzoyl chloride treatment (T) based epoxy composites observed good mechanical properties with ultimate tensile strength of 37.39 MPa, ultimate flexural strength of 63.53 MPa, and impact strength of 70.36 J/m due to hybridization and the reduction in hydrophilic nature by the surface treatment process. The optimized GRA and TOPSIS combination with 10 wt% R/10 wt% K/5 wt% of T observed reduced water absorption nature with a contact angle of 64.72°. [ABSTRACT FROM AUTHOR]

The dielectric properties of bio‐hybrid composites based on natural Oil Palm Empty Fruit Bunch (OPEFB), montmorillonite (MMT) and organomodified montmorillonite (OMMT) nanoclay reinforced kenaf (KF)/epoxy are reported in this study. The molecular mobility, interfacial adhesion between KF fibers and epoxy resin matrix, and fragility near the glass transition temperature were evaluated using Broadband dielectric spectroscopy over a wide temperature range from 20 to 180°C and a frequency range from 0.1 Hz to 1 MHz. Obtained results indicated different relaxations: the α glass‐rubbery transition and the interfacial polarization between KF/epoxy called Maxwell‐Wagner‐Sillars polarization "MWS(KF/epoxy)" whose amplitude, position and dielectric strength ∆εMWS(kenaf/epoxy) depends on the type of the added nanofillers. ∆εMWS(kenaf/epoxy) decrease for all the measured temperatures while the activation energy Ea of the α‐process and rigidity increase when the nanocharges are introduced. It has been found that the OPEFB, MMT, and OMMT are uniformly distributed in the matrix and act as a link between the KF fibers and the epoxy resin via the formation of new CO and SiOSi bonds. [ABSTRACT FROM AUTHOR]

This study evaluates the thermal and mechanical properties of epoxy hybrid composites reinforced with date palm fiber (DPF) and kenaf fiber (KF) at various fiber loadings. Flexural properties, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) of hybrid composites were reported. The flexural properties revealed the effect of fiber ratio on flexural strength and modulus; a higher kenaf ratio showed a higher flexural modulus. TGA revealed the effect of lignin present in the DPF, which affected the glass transition significantly. In DMA characterization, storage modulus revealed that 7DP3K showed higher modulus in the initial stage and had better glass transition than others. The loss modulus showed that the peak of 7DP3K had higher loss modulus, glass transition at a higher temperature, and wider relaxation period. Damping factor also showed that 7DP3K had peak at a higher temperature. The result showed that KF has positively impacted on DPF to improve the mechanical and thermal properties. The hybrid fibers in epoxy composites were effective in increasing the dynamic mechanical properties and flexural strength ascribed to the improved matrix/fiber bonding. The possible applications of the hybrid composites may be in building industry and automobiles. This study gives directions for further research on comparison of treated hybrid composites with untreated ones. [ABSTRACT FROM AUTHOR]

Kenaf cellulose fiber was extracted from kenaf locally grown in Thailand as a potential local renewable resource for the cellulose fiber. In this study, the biodegradable polymer composites, poly(butylene succinate) (PBS)/cellulose fiber composites with different types of cellulose were prepared. The kenaf fiber treated with hydrochloric acid (KTH), extracted cellulose fiber (EC), and commercial cellulose fiber (CC) were selected as alternative renewable fillers in the PBS (the biodegradable polymer). Regarding the fiber characteristics, the aspect ratio of the EC (11.5) was found to be higher than that of the CC (6.1). In a similar manner, the EC contained 65.9% crystallinity, which was higher than that of the CC (37.0%) and the KTH (58.9%). Moreover, the EC exhibited higher thermal stability (Td[Max] = 362.9°C) than the CC (Td[Max] = 302.0°C) and the KTH (Td[Max] = 353.8°C). For PBS/cellulose fiber composites, the rheological, tensile, and thermal properties were studied. The rheology results revealed that the addition of the fiber changed the PBS microstructure. The EC fiber dispersion in the PBS seemed to be better than the others; however, the KTH fiber dispersion was poor. The addition of the fiber raised the elastic moduli of the composites by 5‐26%; however, it reduced the tensile strengths (by 14‐53%) and the decomposition temperatures (by 1‐2%). Furthermore, the addition of the fiber slightly affected the crystallization temperatures and melting temperatures of the composites. The yellowness and whiteness of the composites were marginally reduced. The composite with the EC fiber showed a significant improvement in the elastic modulus as compared to the composite with the CC fiber, while the tensile strength and the strain at maximum stress were comparable. Thus, according to the rheological, thermal, and tensile properties of the composites, the EC fiber showed a possibility of using as an alternative reinforcement material from a local renewable resource. [ABSTRACT FROM AUTHOR]

Hybrid composites have shown innumerable benefits to the research communities in terms of environmental friendliness and mechanical properties. This research study presents the mechanical characterization and moisture uptake of kenaf/pineapple leaf fiber‐reinforced polypropylene hybrid composites with several relative fiber ratios. A comparison was also made between nonhybrid and hybrid kenaf/pineapple leaf fiber‐reinforced composites to investigate the hybridization effect. In this work, the composite materials were fabricated via the hot compression technique. Mechanical tests were performed to obtain the tensile, flexural, and Charpy impact properties of nonhybrid and hybrid kenaf/pineapple leaf fiber‐based composites. The water absorption characteristics were then obtained by immersing the composite materials in the water until the saturation point was reached. The findings concluded that the mechanical properties and moisture uptake behaviors of the composites were improved through the hybridization. The hybrid composites with a relative fiber ratio of 25:75 were particularly promising with the improvement of 10.90% in tensile strength; 16.13% in flexural strength; and 6.80% in impact strength in both flatwise and edgewise orientations compared to nonhybrid kenaf‐based composites. Meanwhile, the diffusion coefficient of hybrid composites (25:75) was 56.12% lower than nonhybrid pineapple leaf fiber‐based composites. Thus, the results indeed demonstrated that the balance between mechanical properties and moisture sensitivity can be obtained through the hybridization of kenaf and pineapple leaf fiber in the composite materials. [ABSTRACT FROM AUTHOR]

The type of reinforcement used in polymer composite is one of the main governing parameters to ascertain the performance of a polymer composite. Green composites using fiber mat as reinforcement have shown promising results. In the present study, three different types of kenaf fiber mat (ie, bidirectional, unidirectional, and randomly oriented) have been incorporated with polylactic acid (PLA) for fabrication of green composite laminates through compression molding. Static mechanical characterization (tensile, flexural, and impact) of the developed composites has shown that type of fiber mat affects the mechanical performance of laminated composites markedly. Unidirectional fiber reinforced PLA composite has shown the highest tensile strength in comparison to bidirectional fiber reinforced PLA composite (BDFRPC) and randomly oriented fiber reinforced PLA composite (ROFRPC). BDFRPC has shown better flexural properties whereas ROFRPC achieved higher impact strength. Dynamic mechanical analysis of different kenaf/PLA laminates was performed to investigate the visco‐elastic nature with respect to temperature. Results show that ROFRPC has observed the best results under dynamic loading condition. The morphological study of the fractured surfaces during various testing was performed using scanning electron microscope to investigate mechanisms and reasons of failure of composites. [ABSTRACT FROM AUTHOR]

Natural fibers are very versatile materials; their properties vary with chemical composition to physical structure. The present study deals with the incorporation of different ratios pineapple leaf fiber and kenaf fiber into a phenolic resin to develop hybrid composites. Incorporation of pineapple fibers in kenaf composites are supposed to improve the thermal properties due to higher cellulosic content of pineapple fibers and thermal characterization are studied by thermo‐gravimetric analysis, dynamic mechanical analysis and thermo‐mechanical analysis. Thermo‐gravimetric of 7P3K displayed lowest percentage of weight decomposition and highest residue indicated thermal stability among all the composites. The storage modulus showed decreasing trend with increasing temperature for all the hybrid composites due to constituents of natural fibers. Among all hybrid composites 3P7K hybrid composite showed highest storage modulus and loss modulus at 55.13°C and 101.68°C, respectively. The recorded peak heights of tan δ were minimum for 1P1K (128°C) and maximum for 7P3K hybrid composites (137°C). The Cole–Cole graph determines the heterogeneity of the hybrid composites. Thermo‐mechanical analysis was used to investigate the coefficient of thermal expansion and the mechanical stability of the composites against increasing temperature. Overall results showed that the hybridization of pineapple fibers and kenaf revealed various thermal properties on various fiber ratios. However, 7P3K improves the thermal stability of the obtained material, whereas the 3P7K hybrid composite showed the highest dynamic mechanical properties among all the hybrid composites. 7P3K improved the thermal properties due to presence of cellulosic content whereas 3P7K improved the dynamic mechanical analysis due to better interfacial bonding. POLYM. COMPOS., 40:3814–3822, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this work, three laminated Epoxy composites reinforced with five woven layers of E‐glass fabrics, jute fabrics and kenaf fabrics were characterized by broadband dielectric spectroscopy. The dielectric analysis was performed in temperature range from 20 to 180°C and frequency range from 0.1 Hz to 1 MHz. The Epoxy matrix shows the presence of four relaxation processes, which are attributed to the β relaxation process, α relaxation process, the quasi‐continuous conduction and the dc conduction. In the laminated composite reinforced with the E‐glass fabric, only one additional relaxation process was detected, which was attributed to the interfacial polarization effect known as Maxwell–Wagner–Sillar polarization. However, for the laminated composites reinforced with jute and kenaf fabrics, two additional relaxation processes were observed. While the first one was associated with the water dipoles polarization imputed to the presence of polar water molecules in jute and kenaf fabrics, the second was linked to the interfacial polarization effect. The latter phenomenon was investigated by an analytical study using the Havriliak‐Negami model. The best adhesion between reinforcement and Epoxy matrix was obtained with E‐glass fabrics. This study was supported by the thermal properties using a differential scanning calorimetry. POLYM. COMPOS., 40:2142–2153, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The aim of this work is to develop a Finite Element Model based on continuum damage mechanics to predict the structural response of Kenaf composite when subjected to high‐velocity impact. The stress–strain response of the Kenaf composite through the fiber direction was simulated to examine prediction accuracy of this simulation approach. A combined elastic‐damage material model, incorporating the 3D Hashin's failure criteria, was implemented into the ABAQUS/Explicit finite element code by user‐defined VUMAT material subroutines. The results from the model predictions were compared with experimental data obtained by SHPB compression testing. The developed Finite Element Model of the full‐scale test presented an accurate prediction of the strain waves in the bars and successfully replicated the structural impact response of Kenaf composite over the range of impact loadings studied. The model also provides a reasonably good agreement between numerical and experimental results on the effect of strain rate on the failure stress and failure strain. POLYM. COMPOS., 40:909–915, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A novel hybrid composition of sisal fibrils and kenaf fibers has been introduced first time as reinforcement in composite preparation for the environmental friendly high strength electrical insulation applications. Hybrid reinforcement was increased from 10 to 40 wt% in unsaturated polyester resin. The sisal fibril used in this study was extracted from sisal fiber. Alkali treatment was employed and FTIR analysis was done to study its effect on sisal fibrils and kenaf fibers. A positive hybridization effect was observed for the composites. Hybrid composite showed 24 and 18% increase in tensile strength, 30 and 36.4% increase in flexural strength, and 196.3 and 196% increase in impact strength as compared to the composites having same loading of 40 wt% with sisal fibrils and kenaf fibers, respectively. Scanning electron microscopy of the fractured mechanical testing samples was carried out to understand the nature of fibril/fiber/matrix interface. Electrical characterization showed high electrical insulation capability of the hybrid composites. Thermal stability of hybrid composites was also found higher than sisal fibrils and kenaf fibers reinforced composites. A comparative study of properties of sisal fibril/kenaf fiber reinforced hybrid polyester composites with various single and hybrid fiber composites is done. It has been concluded that the developed novel hybrid composite has the potential to replace various existing natural and synthetic fiber composites. POLYM. COMPOS., 40:664–676, 2019. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The hybridization of natural and synthetic fibers in composite materials has gained the attention in the research field due to environmental awareness. Therefore, this study focuses on the effects of fiber stacking configuration on the tensile and quasi‐static penetration of kenaf/glass hybrid fiber metal laminates (FMLs). Kenaf/glass reinforced polypropylene FMLs with two different hybrid stacking configurations were prepared using hot compression process. Non‐hybrid kenaf and glass fiber reinforced metal laminates were also prepared for comparison. The tensile test was conducted according to ASTM E8, while the quasi‐static penetration test was carried out in accordance with ASTM D 6264 using 12.7 and 20 mm hemispherical indenters. The fractured surface of FMLs due to tensile loading was examined using scanning electron microscope, while optical micrograph was used to investigate the failure mechanism of quasi‐statically penetrated laminates. From the results, FMLs with the glass plies at the outer layers of composite (H1) showed a positive hybrid effect as they displayed better tensile and penetration resistance, compared to the non‐hybrid kenaf and glass reinforced FMLs. Furthermore, it could be seen that the overall performance of FMLs decreased as the kenaf content in the laminates further increases for hybrid FML. POLYM. COMPOS., 40:568–577, 2019. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The interfacial and mechanical properties of nonwoven kenaf fibre (KF) reinforced acrylic based polyester composites fabricated by resin impregnation process were studied. Different types of treatments were applied to KF, i.e. alkali treatment with NaOH at concentration of 6% (at room and elevated temperature of 60°C) and heat treatment at 140°C for 10h. FT‐IR spectral data showed the chemical changes in KF that induced the modification of physical and interfacial characteristics of KF. Alkali treated KF was found to have smaller diameter but higher density. Significant increase in the crystallinity index of treated KF contributed to the improved fibre strength. AFM analysis revealed the exposure of cellulose micro‐fibril network and the increase in the area peak density value of treated KF. Surface energy of KF and surface tension of acrylic resin were obtained through Owens–Wendt–Rabel–Kaelble (OWRK) equation and Du Noüy ring approach, respectively, for the interfacial properties determination. The improved wettability of alkali treated KF was confirmed as higher surface energy of the fibre was recorded exceeding the surface tension of acrylic resin, thereby imparting better flexural properties and dynamic mechanical behavior, but conversely deteriorating the fracture toughness of the reinforced composites. POLYM. COMPOS., 40:E214–E226, 2019. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Mechanical properties of starch‐grafted‐polypropylene/kenaf fibers (KF) composites were investigated and compared to different theoretical models. In this work, the composites were prepared via melt compounding and compression molding processes at different KF loadings, that is, 10, 20, and 30 wt%. Tensile, fracture toughness and fatigue tests were performed. Generally, the mechanical properties increased with increasing kenaf fiber loadings. This is attributed to the good filler‐matrix interactions between KF and starch‐grafted‐polypropylene, as observed by scanning electron microscopy. Tensile properties were modeled using the rule of mixture, the Kelly‐Tyson and the Halpin‐Tsai models. Fatigue data were also modeled using different theoretical models to fit both S–N and normalized S–N curves with simple linear model and Boltzmann sigmoidal function. POLYM. COMPOS., 39:3289–3299, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Composites are primarily made using matrix and reinforcement as major components but may also contain several other fillers or additives. A majority of the composites are made using synthetic fibers and polymers. However, in the last few decades, focus has been on developing biocomposites using renewable resources. Conventionally, biocomposites are developed using natural fibers such as jute, Kenaf, or Ramie as reinforcement and synthetic resins such as polyethylene, polypropylene and epoxy as matrix. Typically, biocomposites contain either the reinforcement or matrix which makes the composites partially degradable. Such partially degradable composites provide good properties, but the presence of a nonbiodegradable component, particularly as a matrix limits their biodegradability. Alternatively, composites that contain both the matrix and reinforcement from renewable resources which make the composites completely degradable have also been developed. However, these completely biodegradablebiocomposites do not have the desired mechanical properties and stability at high humidities or in aqueous environments which restricts their application. In addition, natural fibers and resins used in biocomposites have inherent limitations and also not easily processable. To overcome limitation of using a single reinforcement or matrix derived from bioresources, hybrid composites that contain more than one reinforcement or matrix are developed. Such hybrid composites are manufactured by either intimately mixing two or more fibers or other reinforcing materials or by placing different layers of the reinforcement and molding them into composites using one or more resins. Conventionally, hybrid composites refer to metallic and ceramic based reinforcement, matrix and fillers. Although hybrid biocomposites are gaining significant attention, the presence of multiple reinforcements and/or matrix makes it difficult to process and also to predict the properties of such composites. Hence, understanding the properties and potential of using multiple reinforcements and/or matrix materials from renewable resources to develop biobased hybrid composites is highly desirable. This article discusses hybrid composites that contain a major proportion of renewable materials. Hybrid composites not only provide better properties but could also lead to substantial cost reduction due to the incorporation of inexpensive raw materials. These composites show potential for use in aeronautical, sporting goods, wind power turbine blades, helmets and civil construction such as pedestrian bridges and many other applications. This review provides an overview of the biobased materials used to develop hybrid composites, their processability and their potential applications. POLYM. COMPOS., 39:E30–E54, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The aim of this work includes modeling and optimization of the tensile properties of natural fiber biocomposites using the concept of experimental design. A three‐factor, three‐level Box–Behnken design, which is subset of the response surface methodology (RSM), has been applied to present mathematical models. The effect of three independent variables; kenaf fiber load, fiber length and polypropylene‐grafted maleic anhydride (PP‐g‐MA) compatibilizer content have been investigated on the tensile strength and modulus of polypropylene/kenaf fiber/PP‐g‐MA biocomposite. These models can be used as an interesting method for analytically evaluating both the tensile strength values and their corresponding tensile modulus as function of independent variables. The optimization results, obtained using the optimization part of Design‐Expert Software, showed that the most optimal tensile strength and tensile modulus were to be 32.70 MPa and 2,182.33 MPa, respectively; and achieved at 28.95 wt% of the kenaf fiber, fiber length of 6.22 mm and PP‐g‐MA content of 5 wt%. The obtained R 2 values and normal probability plots indicated a good agreement between the experimental results and those predicted by the model (above 0.95 for all the responses). Moreover, the tensile modulus of the biocomposite was analyzed by means of micromechanical models. The performance of the Halpin–Tsai and Cox–Krenchel models in predicting the tensile modulus of biocomposites was compared with available experimental results. In addition, the fracture surface morphologies and wettability of the samples were investigated by scanning electron microscopy (SEM) and contact angle measurement, respectively. It was found that the fiber load and PP‐g‐MA compatibilizer content play a significant role in the tensile properties and morphology of the biocomposites, as proven by SEM and contact angle measurement. POLYM. COMPOS., 39:E463–E479, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Hybrid natural fiber polymer nanocomposites were prepared using various natural fibers (kenaf, coir, and wood), polypropylene, and montmorillonite nanoclay through the hot compression method. The effects of fiber hybridization and nanoclay content on the physico-mechanical and biodegradable properties of the synthesized composites were investigated. Fourier-transform infrared and scanning electron microscopic analyses indicated that the structure and surface morphology of composites were transformed after fiber hybridization and the subsequent nanoclay incorporation. X-ray diffraction pattern revealed that the percent crystallinity of hybrid nanocomposites significantly increased. Furthermore, the tensile strength and tensile modulus also significantly improved for the hybrid nanocomposites due to the addition of montmorillonite nanoclay. The biodegradability and water absorption tests were conducted. The results show that biodegradability of the nanocomposites decreased and water absorption increased due to the addition of montmorillonite nanoclay. POLYM. COMPOS., 38:583-587, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This paper reports on comprehensive characterization of wettability and interfacial properties of kenaf fibers (KF) and its unsaturated polyester (UPR) composites fabricated by resin transfer molding (RTM). KF were chemically modified by immersing in 6% NaOH concentration for 1, 2, 3, 4, and 5 h to enhance the interaction between KF and UPR. FTIR spectral data showed the chemical changes in KF after treatment which induced the modification of physical and wettability characteristics of KF. The changes in crystalinity index (CrI) and thermal stability of KF content were analyzed using X-ray diffraction (XRD) and thermogravimetry (TGA) techniques, respectively. Scanning electron microscope (SEM) shows a cleaner KF surface upon KF treatment and atomic force microscopy (AFM) signify an increasing in available fiber-matrix specific contact area. Wettability of KF was investigated by means of surface energy measurement using Washburn contact angle principle via Owens-Wendt-Rabel-Kaelble (OWRK) method. Surface energy was found to increase with longer soaking time. The effect of soaking time of alkaline treatment in enhancing the interface bonding characteristic between the KF and UPR matrices can be reflected by the ILSS value of the composites. The highest value of ILSS was recorded by 3 h treated KF composite. POLYM. COMPOS., 38:507-515, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In the present study, mechanical and water absorption properties of the nonwoven kenaf fiber (KF)/unsaturated-polyester composites manufactured by resin transfer molding were investigated. Nonwoven KF mats with an aerial density of 1350 g/m2 were treated with a 6% NaOH solution for 3 h. The influence of the fiber treatment on the properties of the composites was investigated with Fourier transform-infra red (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM), and dynamic contact angle technique (DCAT). Mechanical properties measurements were conducted via determination of flexure and fracture toughness. A general trend was observed whereby alkalized KF composites gave superior mechanical properties compared to as-received KF composites. The XRD and DCAT results indicated an enhancement of the crystallinity index and surface energy of the alkali-treated KF. SEM and AFM of the treated KF showed the removal of impurities and a reduction of roughness on the KF surface with alkalization. Water immersion induced a drastic loss of the mechanical properties of the composites albeit better retention of properties was observed in the case of alkalized KF composites. The fracture surfaces were inspected by SEM which confirmed the quality of the interface. POLYM. COMPOS., 37:3516-3526, 2016. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this study, the effect of the relationship between yarn material and yarn count tex on the mechanical behavior of plainly woven hybrid fabrics impregnated with silica nanoparticles and epoxy resin has been investigated. First, various types of bicomponent and single-component fabrics with plain weaves are prepared using kenaf and nylon-66 yarns with yarn tex count of 334 and 427. To prepare the composite, silica nanoparticles with a particle size of 200 nm are mechanically mixed into glycol polyethylene with a molecular weight of 200 along with ethanol in proportions of 6:1. The weight percent of silica particles in the suspension has been selected as 60%. Using a round edge indenter, the concentrated indentation force test has been performed based on the 6264D standard to determine the strength of each fabric sample. Then, by impregnating the mentioned fabrics with polymer materials (silica nanoparticles and epoxy resin) and performing the concentrated force tests again, it is found that the hybrid fabrics with a yarn tex count of 427 and impregnated with polymer material enjoy the highest shear thickening properties. POLYM. COMPOS., 37:674-683, 2016. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The aim of this work is to study the effect of kenaf volume content and fiber orientation on tensile and flexural properties of kenaf/Kevlar hybrid composites. Hybrid composites were prepared by laminating aramid fabric (Kevlar 29) with kenaf in three orientations (woven, 0o/90o cross ply uni-directional (UD), and non-woven mat) with different kenaf fiber loadings from 15 to 20% and total fiber loading (Kenaf and Kevlar) of 27-49%. The void content varies between 11.5-37.7% to laminate with UD and non-woven mat, respectively. The void content in a woven kenaf structure is 16.2%. Tensile and flexural properties of kenaf/Kevlar hybrid composites were evaluated. Results indicate that UD kenaf fibers reinforced composites display better tensile and flexural properties as compared to woven and non-woven mat reinforced hybrid composites. It is also noticed that increasing volume fraction of kenaf fiber in hybrid composites reduces tensile and flexural properties. Tensile fracture of hybrid composites was morphologically analysed by scanning electron microscopy (SEM). SEM micrographs of Kevlar composite failed in two major modes; fiber fracture by the typical splitting process along with, extensive longitudinal matrix and interfacial shear fracture. UD kenaf structure observed a good interlayer bonding and low matrix cracking/debonding. Damage in composite with woven kenaf shows weak kenaf-matrix bonding. Composite with kenaf mat contains the high void in laminates and poor interfacial bonding. These results motivate us to further study the potential of using kenaf in woven and UD structure in hybrid composites to improve the ballistic application, for example, vehicle spall-liner. POLYM. COMPOS., 36:1469-1476, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The challenges of using natural fibers in polymer composites include high moisture uptake and poor interfacial bonding with thermoplastic matrix. In this study, the effect of hybridization was investigated to address the challenges of high moisture uptake and balanced mechanical properties in natural fiber reinforced polymer composites. Polyethylene terephthalate fiber (PET) was used in woven kenaf reinforced POM due to its hydrophobic characteristics. The results of tensile test showed that the tensile strength of the interwoven POM/kenaf/PET hybrid composite when tested along kenaf fiber direction, increased from 72 to 85 MPa due to increase in fiber content. Similarly, the tensile strength of the interwoven POM/kenaf/PET hybrid composite increased from 67 to 75 MPa. However, the flexural strength of the interwoven POM/kenaf/PET hybrid composite dropped from 160.1 to 104.9 MPa while that of woven POM/kenaf composite dropped from 191.4 to 90.3 MPa. The interwoven hybrid composite also showed significant improvement in impact strength compared to the woven POM/kenaf composite. The water absorption of the woven POM/kenaf composite dropped by approximately 30% due to hybridization with PET fiber. The results confirmed that hybridization with PET fiber significantly improved the tensile and impact properties of the woven composite and increased its resistance to moisture uptake. POLYM. COMPOS., 35:1900-1910, 2014. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this study, biodegradable poly(lactic acid) (PLA)/Kenaf core composites with different amount of Kenaf core were prepared using screw extrusion. The Structure, thermal stability, mechanical properties, and biodegradation of bio-composites are evaluated. FTIR result shows the possible interaction between the Ken core and PLA matrix. The FESEM result showed that Kenaf core was uniformly disperse in PLA matrix. Tensile and flexural strength of PLA was improved Up to the 30%vol of kenaf core content. Young's modulus and hardness properties were improved by adding kenaf core into PLA matrix. Bio-composite density has been decreased by adding more kenaf core and water absorption of the compound was increased linear. High Kenaf core content was also found to increase the rate of biodegradability of PLA/kenaf core. It can be proven by exposure of the samples to the environment and weight loss in soil burial analysis. POLYM. COMPOS., 35:1220-1227, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A challenge facing engineering with natural fibers is the high standard deviation of mechanical properties of natural fiber compared with synthetic fiber. Plants have a chemical and physical architecture reflective of their age. The region near the apex is more flexible than that near the base. In this paper we investigate the impact of increasing age of plant fiber on the corresponding composite. Bast fibers stems of kenaf (Hibiscus cannabinus, L.), a warm season tropical herbaceous annual plant extracted corresponding to different age, were dispersed into Poly- l-lactide (PLLA) matrix by melt blending followed by compression molding. The resulting bio-based hybrid composites were characterized by X-ray diffraction (XRD), attenuated total reflectance-Fourier transfer infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were conducted. DSC and XRD indicated that the kenaf was effective in promoting crystallization. TGA indicated that the thermal stability of composites is reduced compared with PLLA, but the older fiber sample based on 120-150 cm from the plant apex improved thermal stability compared with the rest. SEM and OM inferred good fiber dispersion while dynamic mechanical tests revealed increased modulus. POLYM. COMPOS., 35:915-924, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]