Advanced Composites in Aerospace Engineering Applications

Composite materials, mainly fiber-reinforced polymers, are now used in applications where lightweight, high specific modulus and resistance, and environmental impact are critical issues. This chapter covers various polymer composite materials used for aerospace applications. Most of the polymer composites in the aircraft are made of thermoset and thermoplastic polymer. Reinforcement with engineered fiber in the polymer matrix was found to improve the properties of the polymer matrix. The effects of fiber orientation and the number of plies on the mechanical properties of the thermoset polymer composite were presented. Various types of thermoplastic polymer composite were also highlighted. The application of biocomposite and geopolymer composite was also included. This chapter concluded the importance of polymer composite materials and its future in aerospace applications.

This chapter discusses the impact studies of hybrid nanocomposites. Glass fibers are used as primary reinforcement, and epoxy is used as matrix and is dispersed with nanofillers which act as secondary reinforcement. Nanoclay is varied from 1 to 5 weight percentage of epoxy. The nanocomposite laminates are prepared by hand lay-up and compression molding processes. They are subjected to projectile impact at various velocities below and above the ballistic limit using a gas gun. The energy absorbed by laminates is predicted using the velocities of projectile before and after penetration when subjected to impact above the ballistic limit. The failure modes of laminates are analyzed, and the energy absorbed in each failure mode is predicted experimentally and analytically. Results show nanofiller dispersion enhances the energy-absorbing capability of nanocomposite laminates. It is also seen that the nanoclay controls the delamination area of the laminates.

Polymer matrix composites are rate sensitive to mechanical properties, and in many instances the composite materials are subjected to high-velocity loadings. In order to understand the dynamic response of composite materials in tensile loading, high strain rate studies are carried out for polymer and hybrid nanocomposites using drop mass test setup and digital image correlation (DIC) technique. The drop mass setup is employed in this study for generating high strain rates ranging from 0.008 to 450 s⁻¹, which fills the gap between conventional testing machines (<10 s⁻¹) and split-Hopkinson pressure bar (SHPB) technique (>1000 s⁻¹). From the experimental results, it is observed that the tensile modulus and tensile strength increase with an increase in strain rate for polymer and hybrid nanocomposites. The fractography of tensile specimens is investigated using scanning electron microscopy (SEM) to discern the surface features and dispersion quality of nanofiller.

Recently there have been many successful attempts to implement the use of fiber-reinforced composite structures in the commercial aircraft engines. The author has been part of these efforts while working in the aviation industry. This article describes these efforts to design, analyze, manufacture, and implement the composite structures inside the low-pressure and low-temperature zones of the engine. Very innovative out-of-the-box design methodologies were used to design these components. These efforts elaborate on the design, optimization, and improvement of composite fan blade, composite fan platform, and composite booster blade inside the engine. It focuses on structural design, the aerodynamic efficiency, and specific fuel consumption improvement efforts along with the usual reduction of weight targets. This work successfully demonstrates the systematic steps in design and implementation like preliminary coupon-level simulations, coupon-level manufacturing, coupon/prototype testing, and final part-level simulations followed by part test.

Mechanical machining has been a critical procedure for fibrous composites and related stacks before their aircraft applications to ensure that the manufactured components meet the dimensional accuracy and surface quality requirements. However, it is rather challenging to conduct a successful composite machining operation due to the inherent anisotropy and heterogeneity of the workpiece material. Particular issues arise from the inferior surface quality and rapid tool wear. The present chapter aims to address fundamentally the machinability issues associated with the composite machining. Aspects including the chip removal mechanisms, cutting forces, machining temperatures, surface quality, and tool wear modes were discussed to shed light on the complexity behind the machining of the aerospace-grade composites. The chapter emphasizes the importance of selecting optimal cutting parameters and developing advanced cutting technologies to achieve the high-quality machining of fibrous composites for aerospace applications. Moreover, some perspectives regarding future developments in the research fields of aerospace-grade composites machining are outlined.

This chapter deals with the recent and emerging development of hybrid biocomposites. Hybrid composites have specific and idiosyncratic characteristics that can be used in a variety of structural components and structures without losing their structural efficiency and physical and mechanical properties; not only can hybrid biocomposites have improved structures, but they may also lead to major cost savings due to the inclusion of cheap raw materials of structural components and structures without losing their structural efficacy. Due to their advantages such as low cost, light weight, low density, biodegradability, environmentally safe and high specific mechanical properties, hybrid biocomposites have replaced conventional fibre composites for real practical applications over the last few years. In fields such as aerospace and automobile, there will be an improvement in the usage of natural fibre hybrid biocomposites, and there will also be demand for aerospace applications. Recently, many researchers are working on the research projects focusing on the creation of natural fibre composites and phenolic matrices to be used as commercial cabin interior panels. Efforts are ongoing to resolve concerns related to strength, adhesion between fibres and matrix, moisture and thermal resilience as well as compliance with airworthiness requirements. The latter section of the programme may deal with biopolymer matrices that will contribute to the production of advanced potential hybrid biocomposites for aerospace applications. With specific improvements, hybrid biofibres play an important role in multi-applications with unique improvement and increase the effectiveness of hybrid biocomposites. Hybrid biocomposites offer equal stiffness, resistance, strength-to-weight ratio and other physical and mechanical properties.

Resin-injection method can be employed to repair barely visible impact damaged composites in aircraft structures such as Boeing 787 and Airbus A350. The repair procedure involves drilling of vent and injection holes into the damaged site of composite followed by injecting the resins into the injection hole. However, drilling holes remove the materials and could result in diminution of material strength. This report examines the effects of holes on the mechanical behaviour of carbon fibre-reinforced polymer composites (24-ply laminates) by finite element analysis (FEA). FEA models of composites with different vent-hole numbers (viz. 4, 5, and 6) were developed and subjected to in-plane compression. The resulting stress-field patterns were compared to the pristine composite without holes. The results revealed high stresses developed at hole edges which emanates in the direction perpendicular to the loading direction. The high-stress patterns from adjacent holes could overlap, suggesting that hole-hole interaction could occur when the laminate undergoes loading.

In this study the AZ63 magnesium alloy which is known for its low coefficient of thermal expansion and good wear resistance is used along with silicon carbide (SiC) which is a semiconductor with high hardness wear resistance used in the form. This composite is manufactured using stir casting methodology where the magnesium alloy and silicon carbide with varying weight percentage (wt.%) of 0.5, 1.0, 1.5, and 2.0 wt.% are mixed together. Once the fabrication of the composite is completed, it is subjected to various mechanical tests to study their mechanical behaviors. The result shows that the hybrid composites have better mechanical behavior than others.

Composite materials have been subjected to permanent interest among engineers, scientists and research communities due to their various promising characteristics compared to metallic alloys. The technological evolution in the composite field has led to the development of advanced composite materials, namely, fibre-metal laminates (FMLs). FMLs are those sandwich materials that are formed by the coalescence of composites and metallic alloys. Through the years, FMLs such as glass laminate aluminium-reinforced epoxy (GLARE) have been employed as the fuselage structural materials in aerospace industries due to their excellent fatigue crack resistance. However, it has been identified that FMLs also encompass superior impact properties. This chapter intends to give a comprehensive overview of the FMLs in aerospace sectors, including the classification of standardised FMLs and manufacturing techniques. The various surface pre-treatment methods of FMLs are discussed and explained. Finally, the potential applications of natural/synthetic fibre-based FMLs in aerospace sectors are presented.

This experimental investigation presents analysis of surface integrity aspects and recast layer formation for the Wire_EDM of three considered different weight fractions of Al/ZrO_2(P)-metal matrix composites (MMCs). These MMCs are developed by varying weight fraction of reinforced ZrO_2(P) in Al alloy matrix from 5 to 15% in steps of 5%. The multi-objective parametric combinations for Wire_EDM of considered MMCs are obtained using grey relational analysis (GRA) for performance characteristics, material removal rate, spark gap, surface roughness (average height; R_a) and surface roughness (total height; R_t). In this chapter, surface veracity aspects and recast layer thickness are analysed for the obtained Wire_EDM surfaces using optimal parametric combination. From the experimental analysis, it can be concluded that lower values of pulse width and short pulse time and larger value of time between pulses are preferred for the Wire_EDM of Al/ZrO_2(P)-MMCs to improve the surface veracity aspects and to minimize the average recast layer thickness formed. The average recast layer thickness decreases from 24.19 μm to 18.89 μm as weight fraction of ZrO_2(P) increases in Al/ZrO_2(P)-MMC from 5 to 15%. The experimental investigation of surface veracity aspects and recast layer developed during Wire_EDM of Al/ZrO_2(P)-MMCs will offer significant guidelines to the production engineers to select the optimum values of input process parameters to improve the surface veracity aspects and to execute the subsequent operations to improve the life of the components fabricated utilizing these MMCs. Further, it can be safely concluded that Al/ZrO_2(P)-MMC is suitable to manufacture the parts used in aerospace and satellite industries.

In this research work, 10 wt. % Cu was deposited with 90 wt. % T64 alloy via the laser system. The deposition was performed on an ytterbium laser system with a maximum operating power of 3 kW. The effect of laser power on the laser-deposited T64 + 10 wt. % Cu was investigated. Microstructural analysis and microhardness profiling of the deposited samples were examined. Basket-weave-like Widmanstätten structures were observed in the heat-affected zone of the deposit, and these occur as a result of the cooling rate; however, it increases as the laser power was increased. The average microhardness values were obtained and sample 1 deposited at the laser power of 1000 Watts had the lowest hardness value of HV 309 ± 7, while the highest hardness value of HV 573 ± 7 was obtained for sample 4 deposited at the laser power of 1600 watts. Response surface methodology (RSM) was also implemented using the Design-Expert 11 software to determine the optimum and desirable parameters. The properties of the T64 alloy were improved with the addition of 10 wt.% Cu, and this can be recommended for the engine block of an aerospace application to serve as fire resistant.

This chapter investigates machining response (surface roughness) of Al2024/SiC/red-mud hybrid composites. The composite specimens are processed via stir casting route, and dry turning operations have been performed on the specimens using computer numerical control (CNC) lathe machine. The influence of various parameters, i.e. reinforcement parameters (red-mud wt.% and particle size) and cutting conditions (feed rate, depth of cut and cutting speed), has been studied using response surface methodology (RSM). The results indicate that depth of cut has the highest contribution (33.84%) on surface roughness of the Al2024 composites followed by red-mud wt.% (28.65%) and feed rate (26.57%). The results also indicate that the surface quality of the Al2024/SiC/red-mud composites is significantly enhanced with increase in red-mud wt.% and reduction in the values of feed rate and depth of cut. The study concludes that surface roughness of the hybrid composites is improved by a minimum value of 23% under optimized conditions of selected parameters.

The Laser Flash technique was employed to study the thermal diffusivity of Ti6Al4V (Ti64) and multi-walled carbon nanotubes (MWCNTs)-reinforced Ti64 nanocomposites with varying weight percents of graphitized MWCNTs between 50 and 300 °C testing temperature boundaries. Generally, the addition of MWCNTs to Ti64 improved the thermal diffusivity characteristics of the developed nanocomposites over that of the unreinforced alloy. Comparatively, the 2 wt.% MWCNTs nanocomposites sintered at 1000 °C exhibited the best thermal diffusivity performance, offering values of 2.71 and 3.48 mm²/s, respectively, at 50 °C and 300 °C, as against 1.92 and 2.65 mm²/s recorded, respectively, for the unreinforced Ti6Al4V alloy samples also sintered and tested at the same temperatures as the nanocomposites. The predicted thermal conductivity responses of the developed nanocomposites as affected by the measured thermal diffusivities are also discussed, hoping to open new grounds for fuselage and wing box structural applications.

Biocomposites have been developed by the researchers in recent years owing to rising pressure on the protection of the environment. Poor interface, moderate to lower mechanical properties, and moisture intake are some drawbacks of biocomposites for partial or full change with synthetic composites. To overcome these drawbacks, hybridizing, blending two or more reinforcements instead of single reinforcement in a polymeric matrix, is widely employed nowadays. Considerable increase has been observed in the utilization of biocomposites or hybrid biocomposites in the aerospace industry such as gas turbine engines (fan blade and cases) over the past decade for weight reduction. Therefore, in this chapter, the works about hybrid biocomposites and their applications in the aerospace industry (aircraft frames, engine construction, and interior cabin components) are reported. Also, this chapter aims to analyze the synergistic effect of hybrid biocomposites in the aerospace applications with a discussion of recent research in this area.

This book chapter focuses on developing carbon-epoxy composite laminates and prepregs through resin transfer and compression molding processes for applications in aerospace industries. At first, selection of judicious choice of process parameters in molding processes are presented. In the following sections, cure processing and practical difficulties during manufacturing of fully and partially cured composite laminates are addressed. Next, the effect of temperature and pressure cycles on physical and cure conditions of composite laminates are reported. In situ offshore transportation handling of semi-cured laminates are then reported. In the subsequent section, the effect of preprocessed panel cure on post processing of partially cured composite laminates is discussed. Finally, postprocess resin bleeding analysis of partially cured, hot-pressed, and resin transfer-molded composite laminates is presented.

Continual development and establishment of innovative materials in aerospace applications intends at reduction in weight, improved fuel efficiency, superior performance, and decreased cost. Progress of engineering materials for aerospace application affects both financial and ecological issues. Latest developments in advanced composites impact aerospace applications, due to superior strength-to-weight ratio, wear resistance, and thermal resistance compared to conventional materials. Composite materials, due to their unique features, lighter weight, high fatigue strength, and anticorrosion resistance, have begun to be used more prominently for almost a decade to produce wings and fuselages in major commercial aircraft. In the last 20 years, advanced hybrid composites have turned out to be established as exceptionally efficient, elevated performance structural materials, and their consumption is increasing rapidly. This review chapter on recent advancements in advanced composites for aerospace applications presents a brief review of the present status of hybrid composite materials technology, in terms of characteristics and classification of aerospace composites, selection criteria, manufacturing process, and application of advanced composites in the aircraft and aerospace industries.

The presence of fibers and fillers in a composite can be an effective way of arresting crack at the macro or micro level. PLA composites fabricated via a solvent casting process with different graphene loadings (1, 3, and 5 wt.%) were embedded in the PLA matrix to produce polymer nanocomposite. In this work, hybrid flax/Kevlar fiber and jute/carbon fiber reinforced with graphene in polylactic acid (PLA) composites have been prepared by using the hot press technique. The comparison to know the effect of different graphene nanofiller concentrations into different hybrid polymer composite was studied by mechanical properties such as flexural and low-velocity impact. Flexural strength and flexural modulus were found to increase at 3 wt.% of nanofiller loadings for graphene/jute/PLA nanocomposites with increment up to 37%, while 1 weight% of graphene loadings of flax/Kevlar composites shows 13.38% of the increment. Fracture from flexural failure was observed using a scanning electron microscope (SEM), where the rough surface of the composite structure is relatively related to slow-spreading crack and high-energy absorption in the mixed graphene/PLA matrix. The present study examined the correlation among the composites through flexural and impact properties while discussing the effect of graphene content in aerospace applications.

The composite materials utilized in the aerospace sector are discussed in this chapter. Fabrication of aviation materials begins with the use of natural composite materials, such as wood. The aerospace industries are then dominated by steel, which is followed by the plastic era. There has been significant development made on composite materials for aircraft due to concerns about lightweight aircraft structures, fuel efficiency, and high-strength aircraft structures and certain demands on high-temperature requirements. In the aircraft structure, composites such as polymer matrix composite (PMC), metal matrix composite (MMC), and ceramic matrix composite (CMC) were used. Composite materials were used to construct nearly half of the aircraft’s construction. Composite materials have evolved with improved reinforcing fillers that can improve composite qualities, thanks to cutting-edge technologies. Materials used in the composite include nanofiller, natural fibers, and self-healing materials. There was a thorough discussion of the various types of composites. Finally, in this chapter, the future of aerospace composite materials was examined.

In the current study, the influence of different contents of B₄C particles on microstructure and solidification behavior of Al-20%Mg₂Si in situ composite was investigated. The experimental characterization was carried out using the scanning electron microscopy (SEM) equipped with electron dispersive spectroscopy (EDS) and cooling curve thermal analysis (CCTA) approach. The results showed that introducing of B₄C particles up to 5 wt.% to Al-20%Mg₂Si composite resulted in decreasing the average size of primary Mg₂Si particles from 46.9 μm to 38.8 μm. In addition, thermal analysis depicted that the nucleation temperature (T_N) and growth temperature (T_G) of primary Mg₂Si reduced from 659.2 and 654.4 °C in the base condition to 655 and 650.5 °C after addition of 10 wt.% B₄C particulates. This study proffers a low-cost technique to control the size of primary Mg₂Si crystals in the Al-Mg₂Si-B₄C composite, which is beneficial to the design of lightweight hybrid composites with high strength and toughness.

The influence of various concentrations of B₄C particles (0, 2.5, 5.0, and 10 wt.%) on microstructure, mechanical properties, and dry sliding wear behavior of Al-20%Mg₂Si composite was examined. The obtained results showed that addition of B₄C ceramic particles to Al-20%Mg₂Si composite led to refinement of primary Mg₂Si particles, in which addition of 2.5 and 5.0 wt.% B₄C reduced the average size of the primary Mg₂Si to 43.6 and 38.8 μm, respectively, compared to 46.9 μm in the composite without B₄C. However, further addition of B₄C particles (10 wt.%) increased the Mg₂Si particles size to μm 40.21. The tensile results discovered that the UTS of the Al-20%Mg₂Si composite increased from 60.31 MPa in the base to 75.34 MPa after addition of 5.0 wt.% B₄C and decreased to 48.12 MPa with further addition of B₄C to 10.0 wt.%. Similarly, the sliding wear results demonstrated that Al-20%Mg₂Si-xB₄C hybrid composite owns the lowest wear rate (0.46mm³/km) and friction coefficient (0.39) under 20 N applied load compared to other fabricated composites.

This chapter is concerned with hybrid composite materials for very large lightweight wind turbine blades. It emphasizes the topic of structural and materials aspects of advanced composites in aerospace engineering applications. One of the perspectives of the development of high-energy wind turbines is dependent on the evolution of material concepts for wind turbine blades. Other prospective directions are reliant on the integrated structural health monitoring, active vibration reduction systems, advanced environmental durability, and novel maintenance issues. Upscaling of wind turbine blades requires specific solutions due to structural and material constraints. The chapter reviews several composite laminates including ply drop-off concepts, self-healing composites with nanostructures, and fracture mechanics of such material systems.

The laser metal deposition (LMD) process is an additive manufacturing process that can produce three-dimensional parts through material addition. LMD is still fairly new and some of the physics of the process is not fully understood. The experiment was conducted on the ytterbium laser system (YLS) with a maximum power of 3 kW. However, in this study, the influence of process parameters on the laser metal-deposited titanium alloy grade 5 with 10 wt. %molybdenum (Ti-6Al-4V-Mo) on titanium alloy substrate was carefully investigated through the microstructural analysis and microhardness profiling. The scanning speed used for the deposition process was varied from 0.5 m/min to 1.5 m/min while other parameters remain constant. In the microstructural analysis, elongated grains were observed in the entire deposits as a result of the density of the Mo stabilizer. Some unmelted Mo was also observed in the deposited alloy due to the high melting point of Mo. In the microhardness analysis, sample 1 deposited at a scanning speed of 0.5 m/min exhibited the lowest hardness value with the standard deviation of HV 327 ± 26, and this has contributed to the improvement in the ductility of the deposited Ti-6Al-4V-Mo alloy.

Nowadays, nanomaterials have been used for improving the mechanical properties of carbon fiber-reinforced polymer (CFRP) composite due to their outstanding properties. Among different nanomaterials, carbon nanofiber (CNF), graphene, and multiwalled carbon nanotube (MWCNT) are widely accepted nanofillers in CFRP hybrid composites. Owing to its distinctive mechanical and thermal characteristics, hybrid composites are highly advantageous for high-performance, lightweight fuselage and wing components in the aerospace industry. Therefore, the incorporation of nanofillers can significantly improve the mechanical properties of hybrid composites. However, the addition of nanofillers in a hybrid composite is limited due to the high aspect ratio, which generally causes agglomeration and improper adhesion. Herein, the effect of CNF, graphene oxide (GO), and MWCNT incorporation on the mechanical properties of hybrid carbon fiber composite is discussed. Furthermore, it consists of intense discussion on materials processing, properties, and significant challenges involved in a hybrid composite. Finally, the future scope of these nanofillers-reinforced hybrid composite for various applications will be enlightened in this chapter.

In recent years, a lot of progress has been created on aerospace materials for structural and engineering applications. Composites are made when two or more different materials are combined to create superior and distinctive materials. For aerospace engineering, there is considerable progress in material science and engineering with the technological challenges in terms of subtle and specialized materials like composite materials. These days composites materials have gotten necessary in aerospace engineering because of their high specific strength at lower weight, stiffness, and corrosion resistance. Apart from it, nanotube benefits also have an essential role in advancement in the aerospace applications. Carbon nanotubes (CNT) applications have progressively enlarged because of its excellent options exhibited by these materials. The potential applications of CNTs are enlarged by an oversized variety of various applications in scientific fields, like storing energy, biological applications, and emission. Besides that, various fillers were utilized to increase the thermal conductivity of the chemical compound composite matrix. In order to take full advantage of these nanofiller, it is critical to control the distribution of nanofillers within the polymer matrix, as this structural organization affects how the two constituent components interact with one another. Thus, this chapter investigates the advancement of composite in aerospace applications in terms of opportunities, challenges, and future perspective.