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1. Introduction In the current era, generating clean energy from renewable resources has been considered as one of the most critical research subjects [1]. One of the recent vital sectors used in the new and renewable energy field is wind energy, in which wind turbine is used to generate energy [2]. The functionality of the wind turbine is based on the blades' criteria, composi- tion, and manufacturing. Fiber reinforced polymers (FRPs) are the most widespread material used in manufacturing the blades of wind turbines [3]. Owing to many advantages such as mechanical characteristics and stability of thermal, elec- trical, and chemical properties, FRPs have been extensively used in several industries such as aerospace, automotive, and wind turbine [4e8]. Nevertheless, the usage of FRPs has some limitations due to the possible failure and damage of the weak parts of the blades caused by the exposure of different loads during the operating process [9,10]. Therefore, the properties of FRPs need to be improved by adding nanoparticles with extraordinary properties as reinforcements inside the matrix to increase the safety and durability of their usage in the wind turbine and several other applications. Many nanoparticles such as alumina (Al2O 3) [11e14], gra- phene nanoplatelets (GNPs) [15e18], and carbon nanotubes (CNTs) [18e21], as well as other nanoparticles of ceramic materials [22,23], are used as reinforcements inside the matrix of FRPs. Al 2O3 is an entirely known nanoparticle used in several industries such as electronic insulators, substrates, and wear resistance components [24]. This is due to its high strength, stiffness, hardness, excellent resistance to wear and acid, and good thermal conductivity [25]. On the other hand, GNPs are one of the most popular nanoceramic particles, characterized by different advantages such as extraordinary mechanical and tribological properties and lower density than other nanoparticles [15]. Accordingly, the addition of Al2O 3, GNPs, and CNTs to FRPs can improve the tensile strength, flexural strength, tribolog- ical properties, and fracture toughness [26e28]. The quality level of achievements depends on many factors such as the number of fillers, characteristics of nanoparticles (type, size, and shape, properties) and synthesis preparation, and tech- nique type [29e31]. The combination between Al2O 3 and GNPs as reinforcement nanoparticles inside the FRPs has a superior advantage in improving the mechanical, electrical, and ther- mal properties in various industries. Therefore, in the current literature, various articles have focused on the effect of nanoparticles such as Al2O 3, GNPs, SiO2, and CNTs on FRPs characteristics [23,32,33]. For instance, Abu Talib et al. [34] studied the effect of the addition of Al2O 3 nanoparticles on the toughness properties of hybrid FRPs. They used different raw materials such as woven aramid fiber Kevlar-29 as reinforce- ment, epoxy as a matrix, and nanoparticles of Al2O 3 as filler materials. They have been focused on three variables, namely elastic work, plastic work, and work done in the radial and tangential stretching to improve the impact characteristics of reinforced samples. They concluded that the reinforced samples were elucidated with higher energy absorption and velocity impact than unreinforced samples. A similar study was performed by Kaybal et al. [35]. They studied the influence of the addition of Al 2O3 nanoparticles on the low-velocity impact tests of carbon fiber reinforced polymer. They used several raw materials as woven carbon fiber (CF) as rein- forcement, MGS LR160 epoxy resin as matrix, while Al 2O3 nanoparticles was used as filler materials inside the matrix. They added different weights of Al2O 3 nanoparticles from 1 wt. % to 5 wt. % inside the resin epoxy to reinforce the strength of the matrix. They used a new route called vacuum assisted resin infusion method (VARIM) to fabricate carbon fiber reinforced polymer (CFRP) with Al 2O 3 nanoparticles without any defects such as bubbles, voids, and air spaces. They noted that the highest resistance of damage was detec- ted at 2 wt. % Al 2O 3. Furthermore, they concluded that when adding the nanoparticles of Al 2O3 with a weight fraction of 2% inside the resin, the energy absorption was minimized. Furthermore, Mohanty et al. [36] studied the effect of adding Al2O 3 nanoparticles on the impact and flexural characteristics of hybrid short glass and carbon fibers. They used some raw materials such as chopped glass and carbon fibers with a length of 1e7 mm as reinforcement; epoxy Bondtite PL-411 as the matrix, and Al2 O3 as nanofiller material. They used different weights percentage of Al2 O3 from 1 wt.% to 5 wt.% inside the matrix. They used the open casting technique by a mechanical stirrer to produce the samples with a homoge- nous dispersion of Al 2O3 nanoparticles inside the matrix. They elaborated that the nanoscale of Al2O 3 with 2% achieved the optimum impact and flexural characteristics (strength and modulus) and thermal stability. On the other hand, when the amount of Al2 O3 nanoparticles increased to 5 wt.%, the dispersion of Al 2O3 nanoparticles was aggregated, causing poor characteristics of the fabricated samples. Another study was carried out by Li et al. [37]. They studied the influence of the addition a hybrid CNTs þ Al 2O3 on the mechanical characteristics such as flexural modulus and shear strength as well as microstructural properties as inter- facial interactions of glass fiber reinforced polymer (GFRP). They used different raw materials such as woven GF as rein- forcement, epoxy resin as matrix, and a hybrid of CNTs þ Al 2- O3 as filler nanoparticles inside the resin. They mixed these materials by the chemical vapor deposition method. They observed that the dispersion of hybrid of CNTs þ Al2O 3 was homogenous inside the whole matrix, assisting on the hin- drance of the crack occurrence. They concluded that the reinforced samples with a hybrid of CNTs þ Al 2O3 showed the highest flexural modulus and shear strength properties. Moreover, Mudra et al. [38] synthesized and characterized fiber-reinforced ceramic composites. They selected some materials as monolithic Al2O 3 as reference material and Al 2O3 as the matrix. They synthesized two cases; the first case is GNPs coated Al 2O3 fibers, while the second case is GNPs coated Al2O 3 powders. The first and second cases were at the micro and nanoscale. They used different combination techniques such as electro-spinning, calcination, chemical-vapor- deposition (CVD), and spark-plasma-sintering (SPS) to pre- pare these compositions. They noted that the addition of GNPs assists in improving the lubrication characteristics, fracture toughness, and electrical conductivity of ceramic j o u r n a l o f m a t e r i a l s r e s e a r c h a n d t e c h n o l o g y |
