Improved mechanical properties of environmentally friendly jute fibre reinforced metal laminate sandwich composite through enhanced interface.

Natural plant based fibres are being increasingly used in sustainable fibre reinforced composite applications in order to meet the demand of using environmentally friendly materials for composites. Fibre metal laminates (FMLs) are used in aerospace, automobile, marine and civil engineering applications, due to their excellent mechanical behaviors compared to traditional metals and their alloys. This study describes a novel fabrication of jute fibre reinforced aluminum metal laminates, using different jute fibre architectures (plain and twill fabric structures), wherein jute fibres were used in the skins and aluminum in the core layers. Jute fibres and aluminum sheets were chemically treated to enhance the compatibility and interfacial bonding at fibre-metals-matrix interfaces. FMLs were manufactured by hot pressing technique, after the application of wet lay-up process for the resin impregnation and they were further tested under tensile, flexural and impact loading conditions. While comparing results, the twill architecture showed improved tensile and flexural properties compared to plain fabric based FMLs. Chemical treatments on twill jute fibres and metal sheets further exceptionally enhanced the flexural properties (151 MPa flexural strength and 21.3 GPa modulus and they were increased by 186.5 % and 722.7 % respectively compared to the untreated jute fibre counterparts) of the laminates due to a significant improvement in the adhesion between the jute fibre and aluminum sheet after alkali treatment applied. Therefore, with these enhanced properties, jute based FML laminates can be used as sustainable composite materials in many structural applications.

Short Jute Fiber Preform Reinforced Polypropylene Thermoplastic Composite: Experimental Investigation and Its Theoretical Stiffness Prediction.

Natural-based lignocellulose fibrous materials can be used as a sustainable alternative to conventional fossil-based fibers such as glass fibers, in lightweight fiber-reinforced thermoplastic composites for marine, automotive, aerospace, or other advanced applications. However, one of the main challenges in using natural fiber-based thermoplastic composites is the low mechanical performance of composite structures. This can be improved significantly through the development of an optimized novel fiber architecture with enhanced fiber packing properties, following a low-cost production process. In this context, this study demonstrates a less energy-consuming and cheaper manufacturing process, for developing highly individualized short jute fiber-based dry fiber preform architecture, with an improved fiber packing property. Short jute fibers were chemically treated with alkali and PVA sizing treatments in the processing of new fiber preform architectures, and they were used in manufacturing of ultimate short jute fiber/polypropylene (PP) thermoplastic composites. The newly developed short fiber thermoplastic composites showed a significant improvement in mechanical properties (tensile, flexural, and impact) compared to any other natural fiber architecture-based (woven, knitted, nonwoven, unidirectional, etc.) composites found in the literature. Due to the use of new fiber architecture, the developed composites' fiber content was observed to increase. In addition, the compatibility of jute fibers with the polypropylene matrix was strengthened with the application of chemical treatments on highly individualized jute fibers. These reasons were responsible for the enhancement of mechanical properties of developed composites. Micromechanics of the fibers in composites were evaluated using the modified rule of the mixture and Halpin-Tsai equations for stiffness prediction of the composites in order to develop a theoretical understanding of newly developed composites' mechanics. It is thought that the improved mechanical performance of short jute fiber/PP thermoplastic composites can extend the use of these composites in many load-demanding applications, wherein normally synthetic fiber composites are used.

Reprocessed Materials Used in Rotationally Moulded Sandwich Structures for Enhancing Environmental Sustainability: Low-Velocity Impact and Flexure-after-Impact Responses.

In the rotational moulding industry, non-used, scrap, and waste purge materials have tremendous potential to be reprocessed and applied in skin-foam-skin sandwich structures to replace and reduce the use of virgin polymers. This approach not only encourages the re-use of these waste materials but also significantly contributes to reduce environmental impacts associated with the use of virgin polymers in this sector. The demand of rotationally moulded sandwich structures is rapidly increasing in automotive, marine, and storage tanks, where investigating their impact and after-impact responses are crucial. Hence, this study investigated the low-velocity impact (LVI) and flexure-after-impact (FAI) responses of rotationally moulded sandwich structures manufactured using reprocessed materials. Results obtained from LVI induced damage at two different incident energy levels (15 J, 30 J), and the residual flexural strength of impacted structures evaluated by three-points bending tests were compared with non-reprocessed sandwich structures (virgin materials). The impact damage progression mechanism was characterized using the X-ray micro-computer-tomography technique. Reprocessed sandwiches demonstrated 91% and 66% post-impact residual strength at 15 J and 30 J respectively, while for non-reprocessed sandwiches, these values were calculated as 93% and 88%. Although reprocessed sandwich structures showed a lower performance over non-reprocessed sandwiches, they have a strong potential to be used in sandwich structures for various applications.

Optimizing the Fabric Architecture and Effect of γ-Radiation on the Mechanical Properties of Jute Fiber Reinforced Polyester Composites.

The fiber architecture can significantly influence the rate of impregnation of a resin in making composites and the load-bearing ability of individual fibers on testing of the loading directions. Moreover, achieving the maximum mechanical performance of a natural fiber composite selection of yarn liner density and optimization of fabric structure and further modification of the composites remains a great challenge for the composite research community. In this study, a number of jute-based woven derivatives (plain, 2/1 twill, 3/1 twill, zigzag based on a 2/2 twill, and diamond based on a 2/2 twill) have been constructed from similar linear densities of yarn. The effect of the fabric architecture and further modification of optimized composites by applying γ-radiation is also explained in this study. The experimental results show a 54% increase in tensile strength, a 75% increase in tensile modulus, a 69% increase in flexural strength, a 124% increase in flexural modulus, and 64% increase in impact strength of twill (3/1) structured jute fiber polyester composites in comparison to other plain and twill structured composites. A further mechanical improvement of around 20-30% is possible for the optimized twill structured composites by applying γ-radiation on the composites. An FTIR, TGA, and SEM study confirms the chemical, thermal, and fractographic changes after applying the modification of composites.

Fabrication and Mechanical Performance of Non-Crimp Unidirectional Jute-Yarn Preform-Based Composites.

This work developed novel jute-yarn, non-crimp, unidirectional (UD) preforms and their composites, with three different types of warp jute yarns of varying linear densities and twists in the dry UD preforms, in order to present a possible solution to the detrimental effects of higher yarn twists and crimp at the warp-weft yarn interlacements of traditional, woven, preform-based composites on their mechanical properties. In the developed UD preforms, warp jute yarns were placed in parallel by using a wooden picture-frame pin board, with the minimal number of glass weft yarns to avoid crimp at the warp-weft yarns interlacements, which can significantly enhance the load-bearing ability of UD composites compared to traditional, woven, preform composites. It was found that an optimal combination of jute warp yarn linear densities and twists in the UD preforms is important to achieve the best possible mechanical properties of newly developed UD composites, because it encourages a proper polymer-matrix impregnation on jute fibres, leading to excellent fibre-matrix interface bonding. Composites made from the 25 lb/spindle jute warp yarn linear density (UD25) exhibited higher tensile and flexural properties than other UD composites (UD20, UD30). All the UD composites showed a much better performance compared to the traditional woven preform composites (W20), which were obviously related to the higher crimp and yarn interlacements, less load-carrying capacity, and poor fiber-matrix interfaces of W20 composites. UD25 composites exhibited a significant enhancement in tensile modulus by ~232% and strength by ~146%; flexural modulus by 138.5% and strength by 145% compared to W20 composites. This reveals that newly developed, non-crimp, UD preform composites can effectively replace the traditional woven composites in lightweight, load-bearing, complex-shaped composite applications, and hence, this warrants further investigations of the developed composites, especially on long-term and dynamic-loading mechanical characterizations.

Improved mechanical performances of unidirectional jute fibre composites developed with new fibre architectures.

This study presents the mechanical performance enhancements of jute fibre composites, manufactured from two newly developed novel jute fibre unidirectional (UD) preforms, namely, stitching-based and sizing-based examples. To increase the use of jute fibres, which are naturally abundant and inexpensive, and to provide research into the use of mechanically advantageous continuous unidirectional (UD) preforms in composites (which are still limited in use), this study employed polyvinyl alcohol (PVA) sizing and stitching techniques, thus increasing the abilities of jute fibres to withstand higher loads and enabling them to be used for lightweight structural applications. Alkali treatment was used on jute fibres in stitched and sized preforms, and bamboo slices were introduced to the jute preforms to further optimize the mechanical properties. The jute composites exhibited significant mechanical property enhancements, with maximum improvement observed in the case of the PVA-sized alkali-treated specimen, thanks to the excellent compatibility between the sized and alkali-treated jute fibres.

Ultrahigh Performance of Nanoengineered Graphene-Based Natural Jute Fiber Composites.

Natural fibers composites are considered as a sustainable alternative to synthetic composites due to their environmental and economic benefits. However, they suffer from poor mechanical and interfacial properties due to a random fiber orientation and weak fiber-matrix interface. Here we report nanoengineered graphene-based natural jute fiber preforms with a new fiber architecture (NFA) which significantly improves their mechanical properties and performances. Our graphene-based NFA of jute fiber preform enhances the Young modulus of jute-epoxy composites by ∼324% and tensile strength by ∼110% more than untreated jute fiber composites, by arranging fibers in a parallel direction through individualization and nanosurface engineering with graphene derivatives. This could potentially lead to manufacturing of high-performance natural alternatives to synthetic composites in various stiffness-driven applications.

High-Performance Graphene-Based Natural Fiber Composites.

Natural fiber composites are attracting significant interest due to their potential for replacing synthetic composites at lower cost with improved environmental sustainability. However, natural fiber composites suffer from poor mechanical and interfacial properties. Here, we report coating of graphene oxide (GO) and graphene flakes (G) onto natural jute fibers to improve mechanical and interfacial properties. The coating of graphene materials onto jute fibers enhanced interfacial shear strength by ∼236% and tensile strength by ∼96% more than untreated fibers by forming either bonding (GO) or mechanical interlocking (G) between fibers and graphene-based flakes. This could lead to manufacturing of high-performance and environmental friendly natural fiber composites that can potentially replace synthetic composites in numerous applications, such as the automotive industry, naval vessels, household products, and even in the aerospace industry.