Types Of Aerospace Fasteners and Their Applications
The aircraft or aviation industry has continued to keep pace with technological advances, resulting in the production of newer, more durable aviation fasteners. These devices have helped effectively hold parts of commercial aircraft, military aircraft, jet aircraft, ballistic missiles, and space rockets.
Because of the extreme pressure and temperature conditions under which an aircraft’s fasteners operate while leaving Earth’s atmosphere, the design and construction must be extremely durable and of high quality to withstand these extreme conditions. Meanwhile, the production of commercial or space aircraft fasteners depends on the rapidly advancing technological developments in the aviation industry.
Combined with the above information, this article will give you a comprehensive understanding of these space fasteners, including their properties, materials, types and other relevant aspects. So, read on as we provide you with this great information.
What Are Aerospace Fasteners?
Aerospace fasteners serve the important purpose of keeping various aircraft body components attached together. Their role is crucial not only for performance but also for passenger safety. Think about the devastating outcome if one of the engines falls off or a door opens mid-flight –neglect is not an affordable luxury for aerospace engineers, even with fasteners!
The aerospace industry covers a wide range of products like commercial aircraft, military aircraft, spacecraft, and even missile technologies. Consequently, the topic of aircraft fasteners spans this whole gamut of applications.
Also, they need to be specially engineered for the intense and versatile environments they operate in and are quite different from the regular fasteners we generally know of. We will discuss all of these points in detail now.
Aviation or aircraft fasteners, a type of CNC aircraft parts specifically applicable in the production of aircraft structures. Aircraft parts are assembled at several production sites not only produced at a single factory. Also, these fasteners are necessary to connect these parts into a complete aircraft in the final assembly of the aircraft.
The fasteners can also assemble air structures such as the fuselage, wings, empennage, nose, pylon, nacelle, flight control surfaces, and many more. Besides, they provide attractiveness and durability to the designs of commercial and military aircrafts.
Characteristics of Are Aerospace Fasteners
Aerospace Fasteners must be extremely strong to withstand the enormous pressures of gravity. They are important pieces of hardware that affect the aircraft’s overall safety and efficiency. Moreover, to maintain efficient manufacture and use, these fasteners must pass strict standard certification.
High Strength
The first and most important quality of aerospace fasteners should be having high tensile and shear strength for withstanding load and force. Aircraft vehicles and equipment are usually exposed to immense pressure and stresses during operations thus having high-strength fasteners ensures they will not fail. Moreover, dynamic loads such as heavy turbulence are an important consideration that requires good fatigue strength and resistance from fastening components.
Thermal Resistance
Aircrafts and military airplanes are often exposed to extreme temperatures which can cause thermal failure and sometimes even breakage of devices. Fasteners intended for such applications should be capable of resistance to these conditions and have a high degree of resistance to temperature.
Corrosion Resistance
Corrosion resistance is generally required in almost all kinds of fastener applications, especially in the aerospace industry. Aerospace fasteners can be exposed to moisture and other elements that permit corrosion of materials so it is required that they have ultimate resistance to such conditions.
Lightweight
With the millions of fasteners and components around a single aircraft, it’s certainly required to have more lightweight properties. This is because any extra weight can lead to issues and failures in the overall operation of the aircraft. Materials like titanium and aluminum are one of the suitable metal fasteners that are often employed in the aerospace industry.
Commonly Used Fasteners in the Aerospace Industry
Aircraft Bolts
These are made of uncoated corrosion-resistant steel, corrosion-resistant zinc-cadmium-coated steel, or anodized aluminum alloy. Moreover, the commonly used bolts for aircraft are MS bolts, close tolerance bolts, NAS internal wrench, and AN bolts.
Aircraft Nuts
These are threaded fasteners made of cadmium coated carbon steel, stainless steel or anodized 2024T aluminum alloy. Besides, they are always used in conjunction with a mating bolt or screw. There are two types of aircraft nuts: non-locking and self-locking.
Aircraft Screws
These fasteners are the most common way to attach a thread to a helical edge called an external thread. They are often composed of materials with lower strength than bolts and are inserted with a loose thread.
Aircraft Rivets
These fasteners have a smooth cylindrical shaft with a head on one end and are used to fasten two or more sheets of metal, panels, or pieces of material. The shank of the rivet is placed into matched holes in two pieces of material, and the tip is turned upside down to produce a second head that holds the two parts securely together.
Special Aircraft Fasteners & Their Applications
These unique fasteners have applications instead of standard nuts and bolts, and have the high strength of metal while being lightweight. Most light sport aircraft also make extensive use of special fasteners (LSA). Below are some of the most commonly used special fasteners:
Blind Bolts/Rivets
Blind bolts and blind rivets are incredibly useful when one side of the joint is inaccessible. Thus, in aircraft, they are commonly found in hard-to-reach places. Also, this is the reason for the ‘blind’ in their name.
The fastener is inserted into the hole and tightened. In the case of blind rivets, the rivet’s head plastically deforms to provide a sturdy hold. Blind bolts are tightened into a pre-positioned collar which expands inside the hole and locks the assembly into position. Blind fasteners offer excellent strength and vibration resistance.
Lockbolts
Lockbolts, or huck bolts as they are called sometimes, are a unique hybrid between bolts and rivets. They come as two-part assemblies, one of which is quite similar to a normal bolt. On the other end, special collars are used that either swage into the grooves of the lockbolt’s pin shank or are tightened onto its threads to form the joint.
In some cases, a weaker section is machined into the pin and the extra, protruding part of the shank is removed post-assembly.
Lockbolts are easy to install and provide good fastening strength. Therefore, they are a more lightweight alternative to other common aerospace fasteners. Also, they are used in the assembly of structural components in landing gears, wing splice fittings, etc.
Hi-Lok Pins
Hi-Lok pins are two-part fasteners composed of a threaded pin and collar. Its special feature is its ability to maintain a constant preload, which is achieved as part of the pin detaches at a certain preload value.
The uniform preload makes it reliable and allows for relaxed quality checking. Additionally, they have good strength and fatigue life.
Turnlock
Turnlocks are innovative aircraft fasteners that provide a non-permanent joint. They are mostly used in securing doors, electric panels, and other similar components in aircraft bodies.
The real advantage they offer is the quick and easy removal of the assembled components, which is simply achieved by loosening its screw.
Adhesive Fasteners
These are unconventional fasteners that do not require a hole. Instead, they stick to surfaces with the help of high-performance aerospace adhesives and have anchors/hooks to fasten components together.
They are not as strong as the mechanical fasteners discussed above but do the job for low-intensity joints. Some of their common applications include wire management and joining sheet panels.
Materials Of Aerospace Fastenerss
Aerospace fasteners have to bear intense operating environments and they should be capable of maintaining their performance throughout their service life. We discussed the desired physical qualities of aviation fasteners.
Let’s preview the materials that are popular for manufacturing them.
Aluminum
It is a classic aerospace material owing to its qualities of being a lightweight, good strength-to-weight ratio, and corrosion resistance.
Aluminum alloys are often augmented with heat treatments and coatings. For example, the T6-AI70xx series is commonly known as ‘space-grade in most industries owing to its composition and heat treatment. Aircraft bodies are commonly made from aluminum alloys.
Steel
Various grades of steel are widely used to manufacture fasteners. They provide great strength and durability to joints.
However, steel material is generally heavier than its counterparts such as aluminum and titanium, and it requires certain treatments to make it resistant to heat and corrosion.
Still, it is certainly a popular material group when it comes to aircraft fasteners.
Titanium
Titanium alloys are stronger than steel but much lighter. They possess good thermal stability and corrosion resistance as well.
These properties make it an ideal choice for fasteners. However, the only reason inhibiting their popular utilization is their high price. For this reason, they are only an occasional replacement for aluminum and steel fasteners for special applications.
Special Alloys
The aerospace industry is widely regarded as one of the most innovative in terms of product development. This repute is partly owed to its major contributions to enhancing material sciences.
Numerous special alloys are out there that outperform the materials discussed above. They have higher strength, less weight, better thermal stability, and more longevity.
Some common special alloying metals for aerospace fasteners include nickel and chromium. Inconel, NIMONIC, Waspaloy, Hastelloy, etc. are some of the major special alloys in use currently.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.