Ti-4.5Al-2.5Cr-1.2Fe-0.1C alloy (Ti-531C) is a recently developed titanium alloy with high mechanical properties at room temperature, similar to those of Ti-6Al-4 V (Ti64) and high hot-workability with low flow stress during deformation at high temperature, similar to that of commercially pure titanium (CPTi)1). 7.1). Comparison of the advantages and disadvantages of polymers for aircraft structural applications, Table 13.2. [0/± 45/90] carbon/epoxy; fibre volume content = 60%. Hence, these satellites are repositioned using these thrusters. Defects in metal alloys include gas holes, shrinkage, brittle inclusions and stress cracks formed during casting, quenching, heat treatment and shape forming (e.g. Listed below are several specialist properties which may be considered in materials selection: Electrical conductivity is an important property for materials used in the outer skin of aircraft. The maximum possible fibre content that can be achieved is about 70%, which is the upper limit of fibre packing within composites. The fatigue life generally increases with the stiffness and strength of the composite, which can be improved in several ways including maximising the volume percentage of load-bearing fibres and using high stiffness, high strength fibres. Regions of high stress occur when there is an abrupt change in the shape of the material, and this is often called a stress raiser. Based on a series of studies and evaluations [3], the Society of Automotive Engineers (SAE), which develops standards for aviation, published SAE AS8049 Revision C, in which a key paragraph has been changed from reading that “magnesium alloys shall not be used” to the new wording: “Magnesium alloys may be used in aircraft seat construction provided they are tested to and meet the flammability performance requirements in the FAA Fire Safety Branch document: Aircraft Materials Fire Test Handbook—DOT/FAA/AR-00/12, Chapter 25, Oil Burner Flammability Test for Magnesium Alloy Seat Structure.”, With this approval from the FAA, it is likely that the use of magnesium alloys in the interior of planes will start. The fatigue performance of composites can be improved in various ways. Magnesium alloys have good strength, although weaker than aluminium alloys, but poor corrosion resistance to certain substances. Guidelines for prevention of corrosion and SCC in aircraft, Krishnan K. Sankaran, Rajiv S. Mishra, in Metallurgy and Design of Alloys with Hierarchical Microstructures, 2017. However, polymers cannot be used on their own as structural materials because of their low stiffness, strength, creep properties and working temperature. Magnesium alloys suffer from a combination of “real” and “perceived” challenges. Typical applications are again as electrical contacts, spark-plug electrodes and as catalysts in exhaust systems. Flammability properties such as ignition temperature, flame spread rate and smoke may need to be considered. The fatigue strength increases with a reduction in the grain size of the material. This is due to the fact that magnesium is two-thirds the weight of aluminium. Although more costlier than aluminium alloys, magnesium alloys are used where further savings in weight are required. Nie. Flammability is a consideration for materials where there is the risk of fire, such as aircraft cabins and jet engines. This part covers the essential structural elements of aircraft and spacecraft. In practice, there is no such thing as a defect-free material or a crack-free aircraft structure. Many of the materials used in the earliest aircraft, particularly wood, were prone to sudden fracture which gave the pilot no opportunity to avoid crashing (Figure 18.1). and average weight loss (maximum 10%), with a requirement that two-thirds of the total number of specimens meet each of these criteria. It is the first book to date that includes all relevant aspects of this discipline within a single monologue. Stealth is an important property for materials used in the external surface of covert military aircraft. The performance criteria are based on the average burned length (maximum 17 in.) Cracks can also occur because of poor design, incorrect materials selection, and damage during normal flight operations from bird impacts, lightning strikes, large hail impact or other adverse events. That brings the other limitations or challenges in focus as compared to the mainstream alloys. The fracture behaviour of aerospace materials is examined in this chapter and chapter 19. Sudden fracture of structural materials was one of the most common causes of accidents in early aircraft. Since nano-materials possess unique, beneficial chemical, physical, and mechanical properties, they can be used for a wide spectrum of aerospace, defense and security technologies and applications. Once the reputation was set that magnesium alloys undergo sustained burning in the event of fire, the development of new rare earth (RE) and calcium bearing alloys were not evaluated effectively until the last decade. Fracture of materials caused many accidents in early aircraft. For example, Fig. They also tend to be more expensive than brasses. ( Log Out / Related terms: Graphene; Aircraft; Polymer Composite; Material Selection; Alloy; Aluminum Alloys; Fatigue of Materials Owing to the above considerations, the first part of Table 16.3 is of most relevance to the present discussion. Then, the burned length is measured to evaluate the propagation of the damage due to the flame along the materials. Non-ferrous metals, similar to ferrous metals, are mostly used as alloys. The fibre volume content of the composite used in aircraft materials structures is usually already high (55–65%), and there is little opportunity to increase it further. This chapter examines the types of fracture processes that occur in metals and fibre–polymer composites used in aerospace structures. Materials for early aircraft were selected for maximum strength and minimum weight, and their fracture resistance was not an overriding consideration. For stainless steels there is some additional information to consider with respect to alloy selection. 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