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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]

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]

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 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]

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]