Aerospace Fasteners: Know Varieties, Properties, & Materials

Properties Of Aerospace Fasteners 

Aerospace fasteners are built with defining physical and mechanical properties that make the components suited for the demanding environment. These properties include high strength, low weight, high corrosion resistance, and reliable thermal behavior. 

Each of these properties helps aerospace machines, whether it is a satellite hovering kilometers above the Earth, or a commercial airbus traversing continents. Here is a more detailed analysis of these properties. 

High Strength 

Aircraft fasteners must have high shear strength and tensile strength to support the huge aerospace forces and loads. The steady loads, dynamic loads, and static loads of an aircraft must be borne by the fasteners. 

The fastener material must be capable of withstanding the expected stresses and loads to avoid accidents such as the fracturing of a propeller bolt for Jabiru J170-C aircraft from Muchea Greenside airfield, north of Perth, on 22 December 2021. 

Propellor bolt fracture

Low Weight 

With a single aircraft potentially equipped with millions of fasteners, the collective weight of airplane nuts bolts, pins, and rivets can be staggering. Having these devices lightweight goes a long way in minimizing the overall aircraft weight. Aluminum is one of the best materials for aerospace fasteners due to its high strength-to-weight ratio, and the added advantage of excellent machinability. . 

High Corrosion Resistance

Most fasteners require this property, especially when in the demanding aerospace environment, where humidity and temperatures can be extreme. To counter this problem, manufacturers prefer materials such as titanium and stainless steel. 

Reliable Thermal Behavior

Heat can be challenging in the aerospace environment, where systems such as propulsion generate a lot of it. Without a way to minimize this, the systems would easily overheat and eventually collapse. An easy way around this is using thermally reliable materials for fasteners. 

Overheated aircraft engine

Aviation Standards For Fasteners

Precision and quality are nature to aviation products, fasteners included. This is due to standards such as AS9100, AS9120, BS9100, EN9100, EN9120. 

Every fastener has to adhere to strict requirements of the industry for various reasons – safety, reliability, and traceability. We have these aviation standards to thank for the largely secure aerospace experiences we have continuously enjoyed and witnessed. 

AS9100 Aviation Standard 

This is the fundamental quality standard for excellent aerospace fasteners. Of most importance in manufacturing, according to this standard, is traceability and control of the manufacturing environment. 

AS9120 Aviation Standard

Focus for this standard is on the Quality Management System, which is related to the AS9100 standard highlighted above. 

EN9100 Aviation Standard

This is another critical industry standard for the design and manufacture of fasteners and other components. Its focus is process consistency, quality assurance, regulatory requirements, and supply management. 

EN9120 Aviation Standard  

These standards should be differentiated from the general fastener standards, such as the American Society of Mechanical Engineers (ASME)’s B18.18 for Quality Assurance For Fasteners, B18.1.2 for Large Rivets, and B18.6.3 for Machine Screws, Tapping Screws, and Metallic Drive Screws. 

Every aviation manufacturing technology should comply with these and other industry standards. Discover the CNC machining process, its benefits, and applications—learn how it ensures precision and efficiency in modern manufacturing!

What Fasteners Are Used On Aircraft?

Bolts, screws, pins, and rivets – these are the common types of assemblies in aircraft assemblies. Yes, they sound ordinary, but their functions are in no way simple. These fasteners individually contribute to the stability, rigidity, and durability of aerospace components. 

Aircraft Bolts 

Bolts for aircraft assembly must exhibit superior strength, creep resistance, wear resistance, and be built according to existing aerospace standards. To withstand high environmental stresses these bolts must be made from appropriate materials.

Corrosion-resistant steel (CRES), titanium alloys, and heat treated steel are some bolt materials that meet these stringent requirements. 

Aircraft bolt

Aircraft Screws 

Precision machining is equally critical for aircraft screws, a type of fasteners with threads but have the threaded end hidden after installation – no accompanying nut. High tensile strength and corrosion resistance are some hallmarks of a quality aircraft screw. 

Aircraft screws

Aircraft Pins 

Stringent precision machining standards are also applied to aircraft pins. Pins are available in different shapes and sizes, and so are their applications. Aerospace fasteners manufacturers must follow standards such as NAS and MS to deliver the safest and most suitable aircraft pins.

An aircraft pin

Aircraft Rivets

As permanent mechanical fasteners particularly as replacements for welding, rivets play a fundamental function in aircraft assemblies. The NAS1097 standard is essential in ensuring these fasteners are built for optimal performance in the punishing aerospace environments. 

Aircraft rivets

What Is The Most Common Fastener In Aviation?

The most common fastener in aviation is the rivet, mostly because of its high strength-to-weight ratio, durability, and reliability. 

Special Types Of Aerospace Fasteners

What we have described above are standard but crucal fasteners for the aerospace industry. Beyond them is a special category of fasteners engineered for extreme performance where unique strength, corrosion resistance, wear resistance, and other properties are critical.

The most common products in this category are hi-tigue, taper-lok, turn-lock, and Dzus turn-lock fasteners. The details of these special components are provided below. 

Lockbolts

Also called huck bolts, these aerospace fasteners are a blend of rivets and bolts. One part of the assembly looks like a bolt while the other is a collar-like component. While easy to install, lockbolts are very strong, hence their use in places such as wing splice fittings and landing gears. 

Blind Bolts And Blind Rivets

Blind bolts and blind rivets are used when only one section of an assembly is accessible. Aircrafts have many hard-to-reach areas that use these fasteners. You only need to insert the blind bolt in the designated hole and tighten it, while for the blind rivet, plastic deformation of the hold completes the joint. 

Blind bolts

Turnlock Aerospace Fasteners

Turnlocks are types of temporary fasteners common in aerospace assemblies. You can find them in aircraft electric panels and doors. 

Hi-Lok Pins

Sometimes, the manufacturer wants a high tensile strength fastener in the harsh aerospace environment. That’s where hi-lok pins come in. Engineered to sustain a preload, this type of pin comprises a collar and threaded pin. 

Materials Used For Aerospace Fasteners

The popular materials used for aerospace fasteners include aluminum alloys, stainless steel, titanium alloys, and Inconel. Composite machining is also increasingly present in aerospace fastener manufacture as more composite parts get used in this industry. 

The choice of any of these is based on not just strength, but also other crucial properties such as corrosion resistance, suitability for the CNC machining process, and thermal performance. 

So, what makes each of these options unique for aerospace fasteners? It is a blend of how the fastener enhances structure rigidity, suitability for extreme conditions, durability, and heat treatment, and so forth. 

Aluminum Fasteners

Aluminum alloy fasteners are synonymous with aerospace application, chiefly due to their excellent strength-to-weight ratio and corrosion resistance. Further enhancement through heat treatment is common for aerospace-grade aluminum.

Take the T6-AI70xx series as an example. This material is prominent in aircraft bodies due to its superior properties derived from the heat treatment process of aluminum. 

Steel Grade Fasteners

Also common in the aerospace fabrication projects are steel grades, which manufacturers value for strength and durability. While the material is generally heavier than aluminum alloys, it is still relevant for the above reasons. Fasteners are subjected to heat treatment to optimize these properties. 

Titanium Alloys Fasteners

For a lighter yet stronger material, go for titanium alloy. However, the relatively high price is prohibitive for many users. That’s why these fasteners are mostly used selectively, usually as replacements for other materials in special circumstances. 

Titanium fastener for aircraft

Super Alloys For Aerospace Fasteners

Super alloys are special materials with high melting points, high strength, superb creep resistance, and excellent corrosion resistance. Fasteners made from these materials are ideal for temperature-limiting aerospace applications. 

The aerospace industry uses these superalloys for fasteners;

• Inconel 718
• Waspaloy
• iron-nickel-chromium alloy A286
• Chromium steel alloy H-11 
• MP35N
• Monel

Further reading: Sheet Metal Fabrication Services

Coatings For Aerospace Fasteners

Fasteners for the dynamic aerospace conditions require coverings – black oxide, silver, zinc, nickel, cadmium, and others  –  for enhanced protection against corrosion, scratches, air pressure, and other elements that could jeopardize performance. 

This is a critical aspect of engineered fasteners for aerospace application considering that even the slightest surface irregularity can result in a catastrophe. 

Black Oxide Coating

This coating is characterized by a thin chemically-generated layer applied to fasteners, particularly those of ferrous metals. The black oxide coating on aerospace fastners enhances dimensional stability, corrosion resistance, and thermal stability. 

Black oxide coated bolts for aircraft

Silver Coating

Silver coating enhances the corrosion resistance and electrical conductivity of a part. When used for aerospace fasteners, this plating solution gives an attractive finish fit for any part of the aircraft. 

Nickel Coating

Nickel coating entails covering the fasteners in a nickel layer, which not only provides a bright finish but also enhances corrosion resistance. It can be used for assembling aircraft parts that require both corrosion resistance and visual appeal. 

Cadmium Coating

This type of fastener coating enhances corrosion resistance, making the component ideal for harsh environments. The sacrificial layer formed is attacked by the corrosive agents instead of the fastener material. 

ProleanTech, The Best Aerospace Fastener Provider

Critical factors for manufacturers for aerospace fasteners are installation process, weight requirements, strength, and load requirements, among others. In an industry where a simple design miscalculation can cause unfathomable results, choosing the fastener manufacturer carefully in light of such factors is necessary.

ProleanTech is a popular CNC machining company with aerospace fasteners as part of the products portfolio. With years of experience supporting the aerospace industry with fasteners and other products, the company knows how to identify and meet customers’ needs. Contact us with all your aerospace fastener requests. 

All the different type of fasteners are available, from specialty fasteners to standard ones. Whatever the item, quality and reliability from advanced manufacturing processes coupled with high expertise are evident. 

When looking for modern, quality aerospace hardware, dont hesitate to call the team.  Get your quote today!

Conclusion 

Aerospace fasteners play a vital function in the performance, safety, and aesthetics of the aircraft. From the analysis provided in this article, these devices should be designed and manufactured expertly. 

Key aspects of the fasteners have been highlighted, including the basic types, properties, materials used, and common coatings.