Introduction
Manufacturers have been discovering innovative methods to reduce the weight of aircraft since their invention. This allows for increased passenger capacity, faster speeds, and expanded operational range.
With advancements in technology, it is now possible to develop materials by re-arranging their atomic structure. This has led to improved performance levels and reduced emissions in aircraft. This assignment examines the benefits of selecting the right material for use in the airline and manufacturing industries, as well as the potential disastrous consequences of using incorrect materials or parts.
The use of Light
Alloys in aviation are a great choice for aircraft manufacturing because they offer the desired combination of strength and lightweight.
Magnesium and Aluminium are lightweight metals that can be alloyed to enhance their strength. The main skin of an aircraft necessitates both strength and lightness, thus Duralumin, an Aluminium-Copper based alloy, is often employed. This particular alloy, also referred to as 2024, consists of 93.5% Aluminium, 4.4% Copper, along with 0.5% to 1.5% Magnesium and 0.5% to 1% Manganese.
Both the aircraft skin and the rivets that hold the skin panels together can be made from a specific type of Aluminium alloy known as 2024. However, the rivets are heat treated differently and have specific instructions for use. According to page 501-509, when the rivets are taken out of cold storage, they must be used within twenty minutes. Additionally, rivets can also be made from a light alloy called Hidiminium, which has similar strength to steel and is useful for fasteners in aircraft components.
Aircraft piping utilizes Duralumin, a soft material suitable for low pressure systems. Additionally, Magnesium alloys are present in the aerospace industry. These alloys are revered for their extreme lightness and are combined with metals like Zincronium, Zinc, and Silver to provide exceptional strength and shock resistance. Consequently, they are extensively employed in aircraft gear box castings (Page 107- 122).
A popular alloy used as the primary skin material for helicopters like Eurocopter EC120 is RZ5, chosen for its enhanced corrosion resistance. The alloy’s lightweight nature reduces the power required to generate sufficient lift for the helicopter to take off. Additionally, Magnesium alloys are commonly employed in aircraft undercarriages, particularly in the wheels.
The reason why it is utilized in this region is due to its capability to be effortlessly molded, which also offers the advantage of decreased weight in the undercarriage area.
The use of Composites in Aviation
Historically, metal was the favored choice for aircraft construction because of its perceived superiority. Nevertheless, composites have gained popularity among manufacturers due to recent advancements in their strength and lightweight characteristics.
The Airbus A380, the largest passenger airline in the world, heavily depends on composite materials for its construction. These materials make up approximately 22 to 23 percent of the aircraft’s total weight. The specific composite material used is called GLARE (glass fibre reinforced aluminium alloy). GLARE is made by combining an aluminium alloy sheet with a glass fibre resin film, resulting in a strong material that is suitable for various components such as skin panels, pressure bulkhead, and flying control surfaces like ailerons and air brakes.
The A380 is a relatively new aircraft that incorporates composites in several key components. However, the Boeing 787 has elevated the use of composites in aircraft to a greater extent. About half of its weight comprises composites, with most of the outer skin being made from composite material. Only specific sections like the leading edge and engine casing are constructed using different materials. Kevlar, akin to fiberglass or carbon fiber, is another commonly employed composite in aviation for multiple sections of an aircraft.
Kevlar, also referred to as aromatic polyamide fibre, is utilized in aircraft components due to its strength and lightweight properties. It is commonly found in a honeycomb formation, which further enhances the structure’s strength without significantly increasing its weight. Kevlar is extensively used in various internal structures of aircraft, such as the flooring and overhead luggage storage areas.
Kevlar’s fire resistance makes it suitable for various components. This helps reduce the risk of fire spreading on board, resulting in cost and weight savings as well as added safety. One instance where Kevlar is used is in the construction of rotor blades for helicopters. These blades utilize the honeycomb structure, similar to internal components, providing both lightness and stiffness while maintaining the necessary flexibility for proper functionality.
Comparison between Light Alloys and Composites
To optimize aircraft performance, manufacturers employ light alloys and composites in different areas due to the advantages and disadvantages they provide in specific applications. The primary motivation for using these materials is their remarkable strength to weight ratio. Nevertheless, it should be noted that composites offer a 20% weight reduction compared to light alloys (Page 179-204).
Both Magnesium and Aluminium are susceptible to corrosion, which is a significant issue for the aircraft’s skin. To address this, Alc-lad can be applied to the Aluminium alloy as an additional finish, although this increases production costs. Alternatively, corrosion-resistant composites like GLARE can be used, eliminating the need for extra coatings and special treatment to prevent corrosion on the aircraft.
Composites have the ability to modify their structure to enhance or reduce strength through diverse weaving techniques or the addition of more directions to the laminate. This flexibility allows composites like GLARE to be highly adaptable for aircraft panels. Additionally, the composite material can be molded into various shapes, providing the advantage of a tailored fit for specific areas, unlike light alloys that would need to be bent and formed, potentially compromising their atomic structure and weakening them.
GLARE also allows for pressurizing the cabin to a higher level, enhancing passenger comfort. The comfort of the passengers is a primary consideration in the aircraft design process, which makes composite materials an appropriate choice for accomplishing this goal.
One issue in the aviation industry regarding composites is the difficulty in detecting damage. When aluminum is dented, the damage is visually apparent, allowing for easy inspections with the naked eye. In contrast, composites may only exhibit a small mark on the surface, hiding more severe damage underneath. If surface damage is observed during a visual inspection, it may be necessary to remove paint or even the entire panel to conduct a more thorough examination.
Ultra sonic test equipment can be utilized for detecting damage, such as de-lamination, in materials. When it comes to repairing Aluminium alloys, it is generally considered easier compared to repairing composite material. In the event of damage to an Aluminium panel, only a small portion of the skin needs to be removed, as the panels are typically smaller in size. On the other hand, composite panels are larger to facilitate production, but if they require replacement, the entire panel needs to be removed just to address a small section of damage. Moreover, the manufacturing process for composites must adhere to specific conditions.
In order to prevent the decrease in strength of composite layers due to dirt or impurities, a specially designed composite bay is utilized during the lay up process. This bay provides a safe location for the lay up process and ensures that no dirt or impurities mix with the composite layers. On the other hand, alloys are typically produced in a large-scale industrial process that yields a significant quantity of alloys at once.
Both materials differ in cost. As mentioned earlier, composites reduce weight by approximately 20% compared to Aluminium alloys. However, the manufacturing process for composites is more difficult, resulting in a reasonably higher cost.
Finance is a critical aspect of aircraft production. Companies must make careful decisions about material selection. They can either pay more for a composite structure, which offers benefits like passenger comfort, or reduce costs by choosing a light alloy, which requires more maintenance to combat corrosion.
