**4.6 Lignocellulosic composites**

*Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

making futuristic hypersonic fighter planes and aircrafts [1, 19].

**4.4 Structural composites**

**4.5 Laminar composites**

goods, sport items and trivial stuff infrastructures in building constructions [15–18]. Lightweight military aircrafts and helicopters are made with such rationally designed hybrid composites offering 20–40% reduced weights than contemporary materials. Glass fiber-reinforced carbon fiber yields hybrids/composites to be used to make rotor blades of helicopters due to innate superior fatigue resistivity as needed in

Structural composites are obtained through geometrically designed structural elements in homogeneous pattern derived through constituents. Laminar and sandwich plates come under the category of structural composites. The strength properties of advanced structural composites offer broad mechanical properties as controlled by many parameters like volume/weight proportions of reinforced fiber/ matrix components, built-up formulations, constituent mechanical features and orientations via uni- or bidirectional, besides various off-axis directional/random, arrangement. Sandwich panels are designed as lightweight structural composites owing to their comparatively elevated mechanical strengths. Such sandwich

configured composites are very unique as fabricated via attachment of two thin and rigid skins to yield lightweight but bulky core slotted panel own duel outer face of relatively stiff and strong template like metal alloy, fiber-reinforced plastics, steel, and plywood adhesively bonds to thicker light-mass inner hub materials. Sandwich panels consist of inner core material made up of lightweight and low elasticity modulus like polymeric skeleton phenolics, epoxy, polyurethanes, wood and honeycombs [15, 20], while outer sheets in sandwich panels consist of tough/rigid materials so as to communicate high mechanical strength under high tensile/compressive strain loading. Sandwich panels-based structural composites offer wide utilities including in buildings' roofs, floors and walls, besides being used in fabrication of

Some laminar composites yield through single layer fiber laminated mutual bonding or stacking own accordingly paved orientations of latent directional fluctuations achieved via consecutive depositions. The particulate platelet or laminar matrixes possess two long dimensions, e.g., wooden thin layer plywood with consecutive layers that are quite isotropic composites due to dissimilar grain/ fiber orientations that are weaker in any direction than it would be if constituting fibers could all be aligned in one direction [1]. Layers of assorted fiber reinforcement yield hybrid laminate revealing anisotropic and directional structures. Based on stacking order of each layers, laminated composites owing to their in-plane and out-plane bend-stretch coupling ultimately give in-plane loading. In fact, laminar composite has two-dimensional panels or sheets with favored directions to attain highest strength [6–8]. Wood and plywood material is basically a laminated composite holding constant reinforced and preferred directional stack layer of fiber orientation instead of adhesive joints. Such laminated composite layering fetches each grain at 90° angle with its neighbors. Laminated composite attains superior mechanical strength, stability and appearance as assembled via heat, pressure and adhesive treatments. Assorted laminated composites are obtained, depending on constituents and the processing applied in their manufacturing [1–4, 6–12, 14, 15, 24]. Certain plastic-laminated glassy-type composites behold tight fit adhesiveness at their solid countertop surfaces, which were found to protect the particleboard. Cellulosic templates appear good substrates for assorted matrixes as obtained

wings, fuselage and tail plane skins of aerospace and aircrafts [21–23].

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Environmental causes urge to develop green composites based on renewable sources like biopolymers as economic options for glass/carbon fiber-derived composites [25]. Thus, plant-, jute- and sugar cane-based lignocellulosic composite-derived matrixes can serve this purpose. Fabrication of organic-based nanocomposites arose as a multidisciplinary area in advanced nanotechnology, particularly procured through sustainable and eco-friendly resources and methods. Some green composites are also obtained via reframing natural/bio-polymeric framework via amalgamating other natural/synthetic material substrates that offer morphological/interfacial design characteristics in resultant products over conventional counterparts [26]. Assorted biopolymeric skeletons, viz. starch, alginate, dextran, carrageenan, chitosan and cellulose, are formulated/envisaged due to their innate functional features like nontoxicity, biodegradability and biocompatibility [2, 3]. Natural lignocellulosic fibers have semicrystalline cellulose microfibril orientation offering multifunctional nanotechnological fabrications so as to cater to advanced applications in S&T as mentioned below:
