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.

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.

Modification of Fibers and Matrices in Natural Fiber Reinforced Polymer Composites: A Comprehensive Review.

Application of natural fiber-polymer composites (NFPCs) in different industrial applications provides competitive edge due to their lightweight, higher specific mechanical properties than glass fibers, sustainability, and lower cost involved in production. There are certain challenges associated with natural fibers and their reinforcement in composites such as poor bonding between the fibers and matrix due to their contradictory nature of characteristics, moisture absorption, lower thermal properties, and poor interfacial adhesion between the natural fiber and polymer matrix. The challenges involved in NFPCs need to be overcome to produce materials with relatively equivalent properties to those of conventional composites and other metallic structures. Several researchers around the globe have conducted investigations with the primary attention being paid to the modification of natural fibers and matrix by employing surface treatments and other chemical treatment methods. In order to address the need for eco-friendly and sustainable materials in different domains, a comprehensive review on natural fibers and their sources, available matrix materials, modification techniques, mechanical and thermal properties of NFPCs, is needed for better understanding of the behavior of NFPCs. This work provides the information and holistic view of natural fiber-reinforced composites based on the results obtained from modification techniques, with the view of focusing the review in terms of different chemical and physical treatment techniques, modification of fibers and matrix, and enhanced mechanical and thermal properties in the 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.

Effect of Fibre Orientation on Impact Damage Resistance of S2/FM94 Glass Fibre Composites for Aerospace Applications: An Experimental Evaluation and Numerical Validation.

This study aims to investigate the influence of fibre orientation and varied incident energy levels on the impact-induced damage of S2/FM94, a kind of aerospace glass fibre epoxy/composite regularly used in aircraft components and often subjected to low-velocity impact loadings. Effects of varying parameters on the impact resistance behaviour and damage modes are evaluated experimentally and numerically. Laminates fabricated with four different fibre orientations 0/90/+45/-458s, 0/90/90/08s, +45/-4516s, and  032 were impacted using three energy levels. Experimental results showed that plates with unidirectional fibre orientation failed due to shear stresses, while no penetration occurred for the 0/90/90/08s and +45/-4516s plates due to the energy transfer back to the plate at the point of maximum displacement. The impact energy and resulting damage were modelled using Abaqus/Explicit. The Finite Element (FE) results could accurately predict the maximum impact load on the plates with an accuracy of 0.52% to 13%. The FE model was also able to predict the onset of damage initiation, evolution, and the subsequent reduction of the strength of the impacted laminates. The results obtained on the relationship of fibre geometry and varying incident impact energy on the impact damage modes can provide design guidance of S2/FM94 glass composites for aerospace applications where impact toughness is critical.

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.

Long-term durability and ecotoxicity of biocomposites in marine environments: a review.

There is a growing interest in replacing fossil-based polymers and composites with more sustainable and renewable fully biobased composite materials in automotive, aerospace and marine applications. There is an effort to develop components with a reduced carbon footprint and environmental impact, and materials based on biocomposites could provide such solutions. Structural components can be subjected to different marine conditions, therefore assessment of their long-term durability according to their marine applications is necessary, highlighting related degradation mechanisms. Through an up-to-date review, this work critically discusses relevant literature on the long-term durability of biocomposites specific for marine environments. Importantly, in this review we report the effects of abiotic parameters, such as the influence of hygrothermal exposures (temperatures and UV radiation) on physical, mechanical and thermal characteristics of biocomposites. Furthermore, we identify and discuss the potential ecotoxicological effects of leaching substances and microplastics derived from biocomposites, as well as the change in mechanical, physical and thermal behaviours correlated to degradation in the fibre matrix interface, surface defects and overall deterioration of the composite's properties. Finally, the combined effects of various environmental exposures on the long-term durability of the biocomposites are critically reviewed.

Effect of Intra-Ply Hybrid Patches and Hydrothermal Aging on Local Bending Response of Repaired GFRP Composite Laminates.

This study investigates the influence of intra-ply hybrid patches and hydrothermal aging on the indentation properties of patch repaired GFRP composites. Fabrics with various proportions of glass and Kevlar fibers were employed as the patches to achieve enhanced mechanical properties by hybridizing Kevlar and glass fibers together. Hydrothermal aging behavior of repaired composite laminates modified with water-resistant glass fibers in the outer layers was further investigated. Specimens were immersed in an environmental chamber containing seawater at temperatures of 30 (ambient), 50, and 70 °C until up to saturation. Damage mechanisms of repaired laminates were monitored using real-time acoustic emission (AE) technique. The experimental results showed that specimens repaired with 50G:50K patches offered superior performance than the virgin specimens. The hydrothermal aging effect on indentation behavior of the modified repaired specimens showed a considerable reduction in indentation properties, with higher strength retention exhibited by the repaired specimens modified with chopped glass fibers compared to the particulate fibers.

Ballistic Impact Behaviour of Glass/Epoxy Composite Laminates Embedded with Shape Memory Alloy (SMA) Wires.

This paper aims to estimate the enhancement in the energy absorption characteristics of the glass fiber reinforced composites (GFRP) by embedding prestrained pseudo-elastic shape memory alloy (SMA) that was used as a secondary reinforcement. The pseudo-elastic SMA (PE-SMA) embedded were in the form of wires and have an equiatomic composition (i.e., 50%-50%) of nickel (Ni) and titanium (Ti). These specimens are fabricated using a vacuum-assisted resin infusion process. The estimation is done for the GFRP and SMA/GFRP specimens at four different impact velocities (65, 75, 85, and 103 m/s) using a gas-gun impact set-up. At all different impact velocities, the failure modes change as we switch from GFRP to SMA/GFRP specimen. In the SMA/GFRP specimen, the failure mode changed from delamination in the primary region to SMA-pull out and SMA deformation. This leads to an increase in the ballistic limit. It is observed that energy absorbed by SMA/GFRP specimens is higher than the GFRP specimens subjected to the same levels of impact energy. To understand the damping capabilities of SMA embedment, vibration signals are captured, and the damping ratio is calculated. SMA dampens the vibrations imparted by the projectile to the specimen. The damping ratio of the SMA/GFRP specimens is higher than the GFRP specimens. The damping effect is more prominent below the ballistic limit when the projectile got rebounded (65 m/s).

Ultrasound-assisted green economic synthesis of hydroxyapatite nanoparticles using eggshell biowaste and study of mechanical and biological properties for orthopedic applications.

Nanostructured hydroxyapatite (HAp) is the most favorable candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. Herein, we report for the first time ultrasound-assisted facile and economic approach for the synthesis of nanocrystalline hydroxyapatite (Ca10 (PO4 )6 (OH)2 ) using recycled eggshell biowaste referred as EHAp. The process involves the reaction of eggshell biowaste as a source of calcium and ammonium dihydrogen orthophosphate as a phosphate source. Ultrasound-mediated chemical synthesis of hydroxyapatite (HAp) is also carried out using similar approach wherein commercially available calcium hydroxide and ammonium dihydrogen orthophosphate were used as calcium and phosphate precursors, respectively and referred as CHAp for better comparison. The prepared materials were characterized by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy to determine crystal structure, particle morphology, and the presence of chemical functional groups. The nanocrystalline EHAp and CHAp were observed to have spherical morphology with uniform size distribution. Furthermore, mechanical properties such as Vickers hardness, fracture toughness, and compression tests have been studied of the EHAp and CHAp samples showing promising results. Mechanical properties show the influence of calcination at 600°C EHAp and CHAp material. After calcination, in the case of EHAp material an average hardness, mechanical strength, elastic modulus, and fracture toughness were found 552 MPa, 46.6 MPa, 2824 MPa, and 3.85 MPa m1/2 , respectively, while in the case of CHAp 618 MPa, 47.5 MPa, 2071 MPa, and 3.13 MPa m1/2 . In vitro cell studies revealed that the EHAp and CHAp nanoparticles significantly increased the attachment and proliferation of the hFOB cells. Here, we showed that EHAp and CHAp provide promising biocompatible materials that do not affect the cell viability and proliferation with enhancing the osteogenic activity of osteoblasts. Moreover, hFOB cells are found to express Osteocalcin, Osteopontin, Collagen I, Osteonectin, BMP-2 on the EHAp and CHAp bone graft. This study demonstrates the formation of pure nanocrystalline HAp with promising properties justifying the fact that the eggshell biowaste could be successfully used for the synthesis of HAp with good mechanical and osteogenic properties. These findings may have significant implications for designing of biomaterial for use in orthopedic tissue regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2935-2947, 2017.