Fibres are extracted from various parts of the plants like stem, leaf, bast, flower and fruits. These fibres are reinforced into composites and find their major applications in packaging, furniture, automotive, marine, infrastructure and aerospace industries. Amongst various parts of plant, majorly leaves were discarded as wastes in most of the cases. As a matter of fact, the fibres extracted from the leaves have equivalent strength when compared with the fibres extracted from other parts of the plant. Pineapple leaf, areca leaf stalk, abaca fibres, henequen, palm leaf stalk and many other leaf-based fibres were experimented by many researchers. It was determined that the leaf fibre–reinforced green composites possess better mechanical properties and modulus when compared with other class of polymer composites. This review mainly deals with the potentiality of various leaf-based fibres to be used as reinforcements, method of extraction, their properties and applications. This review covers finite element modelling, strength and commercial application aspects of leaf fibre–based composites.

Leaf fibres as reinforcements in green composites: a review on processing, properties and applications

Effect of bio-based derived epoxy resin on interfacial adhesion of cellulose film and applicability towards natural jute fiber-reinforced composites.

Towards green composites: Bioepoxy composites reinforced with bamboo/basalt/carbon fabrics

Natural fiber composites are hybridized nowadays to explore the synergetic effect of more fibers used in the properties of the composites. The natural fiber hybrid composite made with filler material has excellent wear resistance characteristics. This research work examined the mechanical properties, namely tensile, flexural, interlaminar shear strength, impact strengths, and hardness of the natural fiber reinforced hybrid composite that uses jute, snake grass, and kenaf fibers as reinforcement with various fiber volumes. Further, the wear behavior of the hybrid composites was enhanced by using Annona reticulata (custard apple) seed powder as a filler material. This study revealed that the sample has an equal proportion (12.5% of each) of snake grass and kenaf fiber (without filler) has excellent mechanical strengths. The wear behavior of the sample with 5 wt% filler shows a lower wear rate than other samples.

Experimental investigation on jute/snake grass/kenaf fiber reinforced novel hybrid composites with annona reticulata seed filler addition

The aim of the present paper is to evaluate the effect of the hybridization with external layers of glass fibers on the durability of flax fiber reinforced composites in severe aging conditions. To this scope, full glass, full flax and hybrid glass–flax pinned laminates were exposed to a salt-fog environment for up to 60 days. Double-lap pinned joint tests were performed to assess the pin-hole joints performances at varying the laminate stacking sequence. In order to better discriminate the relationship between the mechanical behavior and the fracture mechanisms of joints at increasing the aging time, different geometries (i.e., by varying both the hole diameter D and the free edge distance from the center of the hole E) were investigated after 0 (i.e., unaged samples), 30 and 60 days of salt-fog exposition. It was shown that the hybridization positively affects the mechanical performance as well as the stability of pinned composites: i.e., improvements in both strength and durability against the salt-fog environment were evidenced. Indeed, the hybrid laminate exhibited a reduction in the bearing strength of about 20% after 60 days of aging, despite to full flax laminate, for which a total reduction in the bearing strength of 29% was observed. Finally, a simplified joint failure map was assessed, which clusters the main failure mechanisms observed for pinned composites at varying aging conditions, thus assisting the joining design of flax–glass hybrid laminates.

Effect of Glass Fiber Hybridization on the Durability in Salt-Fog Environment of Pinned Flax Composites

This work deals with the manufacture and mechanical characterization of natural-fiber-reinforced biobased epoxy resins. Biolaminates are attractive to various industries because they are low-density, biodegradable, and lightweight materials. Natural fibers such as Ixtle, Henequen, and Jute were used as reinforcing fabrics for two biobased epoxy resins from Sicomin®. The manufacture of the biolaminates was carried out through the vacuum-assisted resin infusion process. The mechanical characterization revealed the Jute biolaminates present the highest stiffness and strength, whereas the Henequen biolaminates show high strain values. The rigid and semirigid biolaminates obtained in this work could drive new applications targeting industries that require lightweight and low-cost sustainable composites.

Mechanical Properties of Natural-Fiber-Reinforced Biobased Epoxy Resins Manufactured by Resin Infusion Process.

Sandwich composites are widely used in the manufacture of aircraft cabin interior panels for commercial aircraft, mainly due to the light weight of the composites and their high strength-to-weight ratio. Panels are used for floors, ceilings, kitchen walls, cabinets, seats, and cabin dividers. The honeycomb core of the panels is a very light structure that provides high rigidity, which is considerably increased with fiberglass face sheets. The panels are manufactured using the compression molding process, where the honeycomb core is crushed up to the desired thickness. The crushed core breaks fiberglass face sheets and causes other damage, so the panel must be reworked. Some damage is associated with excessive build-up of resin in localized areas, incomplete curing of the pre-impregnated fiberglass during the manufacturing process, and excessive temperature or residence time during the compression molding. This work evaluates the feasibility of using rigid polyurethane foams as a substitute for the honeycomb core. The thermal and viscoelastic behavior of the cured prepreg fiberglass under different manufacturing conditions is studied. The first part of this work presents the influence of the manufacturing parameters and the feasibility of using rigid foams in manufacturing flat panels oriented to non-structural applications. The conclusion of the article describes the focus of future research.

Innovation in Aircraft Cabin Interior Panels Part I: Technical Assessment on Replacing the Honeycomb with Structural Foams and Evaluation of Optimal Curing of Prepreg Fiberglass.

The manufacturing process of the aircraft cabin interior panels is expensive and time-consuming, and the resulting panel requires rework due to damages that occurred during their fabrication. The aircraft interior panels must meet structural requirements; hence sandwich composites of a honeycomb core covered with two layers of pre-impregnated fiberglass skin are used. Flat sandwich composites are transformed into panels with complex shapes or geometries using the compression molding process, leading to advanced manufacturing challenges. Some aircraft interior panels are required for non-structural applications; hence sandwich composites can be substituted by cheaper alternative materials and transformed using disruptive manufacturing techniques. This paper evaluates the feasibility of replacing the honeycomb and fiberglass skin layers core with rigid polyurethane foams and thermoplastic polymers. The results show that the structural composites have higher mechanical performances than the proposed sandwich composites, but they are compatible with non-structural applications. Sandwich composite fabrication using the vacuum forming process is feasible for developing non-structural panels. This manufacturing technique is fast, easy, economical, and ecological as it uses recyclable materials. The vacuum forming also covers the entire panel, thus eliminating tapestries, paints, or finishes to the aircraft interior panels. The conclusion of the article describes the focus of future research.

Innovation in Aircraft Cabin Interior Panels. Part II: Technical Assessment on Replacing Glass Fiber with Thermoplastic Polymers and Panels Fabricated Using Vacuum Forming Process.

Spray coating and vacuum-assisted resin infusion processes were implemented in this work to develop multifunctional biocomposite laminates. The biocomposites were fabricated using a bio-based epoxy resin reinforced with natural sisal fibers coated with graphene nanoplatelets (GNPs). A systematic characterization of material properties was performed to evaluate the mechanical, thermomechanical, electrical, and piezoresistive behavior of biocomposites with different GNPs contents (0, 1, 4, 6, and 8 wt.%). The mechanical tests revealed that adding GNPs to biocomposites has a slight positive effect on their flexural properties compared to the neat biocomposites (without GNPs). The electrical and thermomechanical tests showed that the electrical conductivity and glass transition temperature of biocomposites containing GNPs were enhanced significantly, achieving average values of 5.19 x 10-4 S/m and 63.29°C (26%), respectively. Regarding electromechanical tests, the biocomposites with 8 wt.% GNPs exhibited an excellent piezoresistive behavior under monotonic loading conditions, achieving a gage factor (strain sensitivity) of 3.56. Bending tests with cyclic loading were also performed, and cyclic reproducibility of the piezoresistive response of the biocomposites after 10 cycles was demonstrated, evidencing that the incorporation of GNPs onto sisal fibers by spray-coating produces an effective formation of conductive networks into biocomposites suitable for sensing applications.

Victoria Rentería-Rodríguez

Papers

Mechanical Properties of Natural-Fiber-Reinforced Biobased Epoxy Resins Manufactured by Resin Infusion Process.

Innovation in Aircraft Cabin Interior Panels Part I: Technical Assessment on Replacing the Honeycomb with Structural Foams and Evaluation of Optimal Curing of Prepreg Fiberglass.

Innovation in Aircraft Cabin Interior Panels. Part II: Technical Assessment on Replacing Glass Fiber with Thermoplastic Polymers and Panels Fabricated Using Vacuum Forming Process.

Spray-coating of graphene nanoplatelets on sisal fibers and its influence on electromechanical behavior of biocomposite laminates