Lightning strike damage protection for single sided mounting

Abstract

The invention is entitled Lightning Strike Damage Resistant Single Side Installation. A fastener assembly includes a bolt having a head and a shank. The shank defines a thread, the bolt defines a channel extending circumferentially around the bolt, and the head defines a plurality of head channels, a first end of each of the plurality of head channels being in communication with the channel, and a second end of each of the plurality of head channels being in communication with an exterior of the head at an upper surface of the head. The fastener assembly further includes a sleeve having compatible threads that engage the thread of the bolt. The sleeve includes a sleeve portion comprising an annealed material and a plurality of slots defined through the sleeve. Each of the plurality of slots defined through the sleeve is positioned in communication with the channel with the bolt positioned within the sleeve.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a single-sided structural fastener, and more particularly to a single-sided structural fastener that provides protection against the occurrence of damage to the internal structure of an aircraft from the electromagnetic effects (EME) of a lightning strike. BACKGROUND

[0002] In constructing certain structures such as aircraft, fasteners are used from the exterior of the skin of the aircraft, where the fasteners extend through the skin and into the interior of the aircraft, where the fasteners are typically secured on the interior side of the skin. Certain locations on the exterior of the skin of the aircraft have corresponding interior sides of the skin that are associated with interior spaces that are small and confined, which makes such interior spaces of the aircraft difficult to access and likewise difficult to access the fasteners to be secured. This is particularly common in the construction of smaller aircraft, and particularly in the construction of the wings of smaller aircraft. As a result, single-sided installation from the exterior of the aircraft skin is a desirable technique for installing such fasteners.

[0003] In the example of constructing a wing on a small aircraft that contains fuel tanks, the installation of fasteners is particularly challenging in being able to fully satisfy electromagnetic effects (EME) requirements. The small and confined spaces within the wing limit the access that manufacturers can have to the fasteners on the interior side of the skin in order to apply a sealant or a sealant with a cap system for covering the fasteners and isolating the fasteners from the interior side of the aircraft skin and any gaps that can exist between the fasteners and the skin. As a result, there is a need to provide a fastener assembly that provides single-sided installation and that also protects the interior of the aircraft from damage from EME such as a lightning strike to the aircraft without accessing the interior side of the skin through which the fasteners extend.

[0004] Theoretically, the EEM of a lightning strike to an aircraft is limited by the theoretically continuous, electrically conductive outer skin of the aircraft in the manner of a so-called "Faraday cage" such that the interior of the aircraft is relatively unaffected by the lightning strike. In practice, however, the skin of the aircraft is actually discontinuous, for example, punctured by a relatively large number of typically electrically conductive fasteners.

[0005] As a result of the puncture discontinuities introduced into the skin by the fasteners, some lightning strikes can create a high-energy electrical arc at the interface between the fastener and the surrounding aircraft skin, which results in the production of hot gases and hot burning particles at the interface between the fastener and the skin, as well as elevated pressures. Without being effectively blocked or safely vented to the atmosphere, the hot gases and hot burning particles can penetrate along the interface between the fastener and the skin and into the interior space of the aircraft, causing unnecessary damage to the aircraft, particularly in EME-sensitive areas of the aircraft. The EME from a lightning strike can occur on a metallic skin or a composite skin.

[0006] For aircraft, and especially smaller aircraft, there is a need for unilateral fastener mounting on the exterior of the aircraft skin, at a location where the fastener has an interior skin space associated with small and confined spaces. Simultaneously, there is a need to provide protection for the aircraft interior in these small and confined spaces against EME damage, such as EME damage caused by lightning strikes. Summary of the Invention

[0007] One example includes a fastener assembly comprising a bolt having a head and a shank. The shank defines a thread, the bolt defines a channel extending circumferentially around the bolt, and the head defines a plurality of head channels, wherein a first end of each of the plurality of head channels communicates with the channel and a second end of each of the plurality of head channels communicates with the exterior of the head located on an upper surface of the head. The fastener assembly further includes a sleeve having a thread compatible with the thread of the bolt. The sleeve includes a portion of the sleeve comprising an annealed material and a plurality of slots defined through the sleeve. When the bolt is positioned within the sleeve, each of the plurality of slots defined through the sleeve is positioned to communicate with the channel.

[0008] One example includes a method for installing a fastener assembly, comprising positioning a bolt having a head and a shank within a sleeve. The shank defines a thread, the bolt defines a channel extending circumferentially around the bolt, the head defines a plurality of head channels, and a first end of each of the plurality of head channels communicates with a channel, and a second end of each head channel communicates with the exterior of a head located on an upper surface of the head. The sleeve has a thread compatible with the thread of the bolt. A portion of the sleeve comprises an annealed material, and a plurality of slots are defined through the sleeve such that, when the bolt is positioned within the sleeve, each of the plurality of slots is positioned to communicate with a channel.

[0009] The features, functions, and advantages already discussed can be implemented independently in each instance or combined in other instances, as can be seen in further details in the following description and figures. Attached Figure Description

[0010] Figure 1 It is a perspective detached view of the fastener assembly in the installation configuration, which includes the threaded bolt and the collapsible sleeve;

[0011] Figure 2 yes Figure 1 Exploded view of the fastener components in the diagram;

[0012] Figure 3It is a partial cross-sectional view of a fastener assembly with a fixing mechanism installed (the threads of the bolts are not in the cross-section), which aligns the fastener assembly for insertion into an opening defined by a layered structure secured by a bolt assembly.

[0013] Figure 4 yes Figure 3 The view shows the fastener assembly being inserted into the opening of the layered structure;

[0014] Figure 5 yes Figure 4 The view shows the bolt of the fastener assembly partially removed from the opening, causing a portion of the removable sleeve to collapse, providing a nutformation on one side of the layered structure opposite the head of the bolt.

[0015] Figure 6 yes Figure 5 The view shows the fixing mechanism having twisted the bolt to secure it to the thread of a removable sleeve that has reached a predetermined torque limit, causing the frangible portion of the bolt to detach from the bolt head.

[0016] Figures 7A-7C Each figure in the diagram includes, for example: Figure 1 and 2 A separate perspective view showing the different ends of a slot located within the removable sleeve of the bolt assembly; and

[0017] Figure 8 This is a flowchart of installing fastener components into a layered structure. Detailed Implementation

[0018] refer to Figures 1-3 Fastener assembly 10 is typically constructed of a metallic material. For example... Figure 3As can be seen, the fastener assembly 10 includes a bolt 12 having a head 14 and a shank 16. The shank 16 defines a thread 18. The bolt 12 defines a channel 20 extending circumferentially around the bolt 12. The head 14 defines a plurality of head channels 22, wherein a first end 24 of each of the plurality of head channels 22 communicates with the channel 20 and a second end 26 of each of the plurality of head channels 22 communicates with the exterior 28 of the head 14 located on the upper surface 30 of the head 14. This communication provides the ability to transfer gas and / or particles from one structure to another structure or to another location outside one structure. The fastener assembly 10 further includes a sleeve 32 having a compatible thread 34 that engages with the thread 18 of the bolt 12. A portion 36 of the sleeve 32 comprises an annealed material. In this example, the portion 36 of the sleeve 32 (excluding the remainder of the sleeve 32) undergoes a place-through annealing process to soften the metallic material of the portion 36. The sleeve 32 includes a plurality of slots 38 defined through the sleeve 32. With the bolt 12 positioned within the sleeve 32, each of the plurality of slots 38 defined by the sleeve 32 is positioned to communicate with the channel 20.

[0019] refer to Figures 2-6 The head 14 of the bolt 12 has a tapered configuration 40 and includes a plurality of head channels 22 extending along the outer surface 42 of the head 14. In this example, as... Figure 2 Multiple head channels 22 are visible, and adjacent head channels 22 are spaced apart by an equal distance "D", and as shown... Figure 1 The peripheral portion 44 extending to the head 14 is visible. (See example...) Figure 2 As can be seen, the first end 24 of each of the plurality of head channels 22 is positioned to communicate with channel 20, and is positioned at the interface 46 of head 14 and shank 16 of bolt 12.

[0020] When the bolt 12 is positioned inside the sleeve 32, such as Figures 1-3 As can be seen, the sleeve 32 includes a first portion 48, which extends circumferentially around the head 14 to multiple head channels 22 in an overlapping relationship, such as... Figure 1 As can be seen, the second portion 50 of the sleeve 32 extends from the first portion 48 and extends circumferentially around the shank 16 of the bolt 12. Each of the plurality of slots 38 extends along the second portion 50 of the sleeve 32 in a curved direction 52. Figure 2 As shown, the first end 56 of each of the plurality of slots 38 is in communication with the channel 20. Figure 1 and 2 As can be seen, the second end 58 of each of the plurality of slots 38 has a closed wall structure 60. Figures 7A-7C A variation of the closed-wall structure 60 can be seen. Figure 7A In the closed-wall structure 60, there is a "U" shape 62.Figure 7B In the closed-wall structure 60, there is an open rectangle 64. Figure 7C In the case of an EME event such as a lightning strike, the closed wall structure 60 will prevent pressurized superheated gas and combustible particles located between the bolts 12 and the materials secured by the bolts 12 from reaching the interior of the aircraft.

[0021] The head 14 of bolt 12 includes a brittle pintail 68 attached to and extending therefrom. The brittle pintail 68 defines a pintail thread 70, which allows a retaining tool 72 with a compatible threaded opening 74 to engage with the pintail thread 70, such that... Figure 5 As can be seen, the fastening tool 72 can apply a tensile force F1 to the bolt 12 and can apply torque to the head 14 to insert the bolt 12 into the sleeve 32 until a predetermined torque is reached. The predetermined torque applied to the brittle nail tail 68 allows the bolt 12 to be secured in the sleeve 32 and applies sufficient pressure to secure the material held by the fastener assembly 10. Once the predetermined torque is reached, the brittle nail tail 68 breaks, as... Figure 6 As can be seen. For example... Figure 3 As can be seen, the fracture of the brittle nail tail 68 occurs at the location where the brittle nail tail 68 and the head 14 have an interface 76, wherein in this example, the interface 76 includes a diameter "D1" smaller than the diameter "D2" of the brittle nail tail 68. Figure 3 As can be seen, the central axis 78 of bolt 12 and the central axis 80 of brittle nail tail 68 are collinear, providing a pull on the alignment of bolt 12 with respect to fixing bolt 12, and applying torque to the alignment of bolt 12, as will be discussed.

[0022] The sleeve 32 has a portion 36 made of annealed material, which provides a more flexible construction to portion 36 relative to the rest of the sleeve 32. For example... Figure 5 and 6 As can be seen, when the bolt 12 is positioned inside the sleeve 32, a portion 36 is positioned between the head 14 of the bolt 12 and the unannealed portion 82 of the sleeve 32, which includes a compatible thread 34 that engages with the thread of the bolt 12.

[0023] like Figures 1-6 As can be seen in the middle and respectively as Figure 1 and 6As can be seen, the fastener assembly 10, located in the mounting configuration or position, provides unilateral mounting. Additionally, the fastener assembly 10 prevents pressurized overheated gases and overheated combustible particles from entering the aircraft interior. In the event of an EME (Electronic Energy Regulator) incident, such as a lightning strike, a high-energy location is created between the bolt 12 and a material such as the aircraft skin. The fastener assembly 10 is secured in this location, and pressurized overheated gases and combustible particles enter from the skin into a plurality of slots 38. A closed wall configuration 60 of each of the plurality of slots 38 blocks the movement of pressurized overheated gases and combustible particles into the aircraft interior 106. The overheated gases and particles are removed from the closed wall configuration 60 along the plurality of slots 38 and enter a channel 20. The channel 20 allows pressurized overheated gases and combustible particles to reach a plurality of head channels 22 and exit from the second end 26 of the plurality of head channels 22, entering the exterior 28 of the upper surface 30 of the head 14 located outside the aircraft. When the fastener assembly 10 is installed on one side, it prevents the interior of the aircraft from coming into contact with overheated gases and flammable particles.

[0024] refer to Figure 8 The image shows a method 84 for installing a fastener assembly 10, including positioning 86 of a bolt 12 having a head 14 and a shank 16 within a sleeve 32. The shank 16 defines a thread 18, and the bolt 12 defines a channel 20 extending circumferentially around the bolt 12. The head 14 defines a plurality of head channels 22, wherein a first end 24 of each of the plurality of head channels 22 communicates with the channel 20, and a second end 26 of each of the head channels 22 communicates with the exterior 28 of the head 14 located on the upper surface 30 of the head 14. The sleeve 32 has a compatible thread 34 that engages with the thread 18 of the shank 16 of the bolt 12. The sleeve 32 includes a portion 36 comprising an annealed material. The sleeve 32 also includes a plurality of slots 38 defined through the sleeve 32, such that, when the bolt 12 is positioned within the sleeve 32, each of the plurality of slots 38 is positioned to communicate with the channel 20.

[0025] like Figure 3 As can be seen, method 84 further includes engaging the thread 18 of the bolt 12 with the thread 34 of the sleeve, wherein the thread 34 of the sleeve 32 is positioned further away from the head 14 of the bolt 12 than the portion 36 of the sleeve 32 having annealed material. Figure 3As can be seen, method 84 further includes inserting bolt 12 and sleeve 32 into a hole 88 defined by a layered structure 90, which is secured by fastener assembly 10. In this example, before inserting fastener assembly 10 into hole 88, a conductive coating 94, such as a gallium alloy, is applied to surface 92 of layered structure 90. This conductive coating 94 conforms to surface 92 of layered structure 90 and seals the gaps between layers of layered structure 90. It may include the metal or composite material of layered structure 90 and bolt 12, as well as conductive metal or fiber of composite material layers (one or more layers).

[0026] Method 84 further includes, for example, Figure 5 As can be seen, pulling the bolt 12 in a direction 96 away from the hole 88 simultaneously retains the sleeve 32 within the hole 88, causing the annealed material portion 36 of the sleeve 32 to buckle. The sleeve 32 is held in place by a retainer 98, which remains in contact with the head 14 of the bolt 12, while a retaining tool 72 engages with a brittle pin tail 68, securing it to the head 14, pulling the bolt 12 away from the hole 88 in direction 96. The pulling force F1 causes the thread 18 of the bolt 12 to be pulled on the thread 34 of the sleeve 32, which is positioned below the portion 36 of the sleeve 32 containing the annealed material, causing the annealed material to now collapse and spread across the bottom surface 100 of the layered structure 90, forming the nut structure 102 within the interior 106 of this aircraft example.

[0027] Furthermore, this disclosure includes examples pursuant to the following terms:

[0028] Clause 1. A fastener assembly (10) comprising:

[0029] A bolt (12) having a head (14) and a shank (16), wherein:

[0030] The shank (16) defines the thread (18);

[0031] Bolt (12) defines a channel (20) extending circumferentially around bolt (12); and

[0032] The head (14) defines a plurality of head channels (22), wherein a first end (24) of each of the plurality of head channels (22) communicates with a channel (20), and a second end (26) of each of the plurality of head channels (22) communicates with the exterior (28) of the head (14) located on the upper surface (30) of the head (14); and

[0033] A sleeve (32) having a compatible thread (34) that engages with the thread (18) of a bolt (12), wherein the sleeve (32) comprises:

[0034] The sleeve (32) portion (36) includes annealed material;

[0035] Passing through the multiple slots (38) defined by the sleeve (32); and

[0036] With the bolt (12) positioned inside the sleeve (32), each of the plurality of slots (38) defined by the sleeve (32) is positioned to communicate with the channel (20).

[0037] Clause 2. The fastener assembly (10) described in Clause 1, wherein the head (14) has a tapered construction (40).

[0038] Clause 3. The fastener assembly (10) described in Clause 1 or 2, wherein a plurality of head channels (22) extend along the outer surface (42) of the head (14).

[0039] Clause 4. The fastener assembly (10) of any one of Clauses 1-3, wherein the plurality of head channels (22) are spaced equidistantly from each other.

[0040] Clause 5. The fastener assembly (10) of any one of Clauses 1-4, wherein a plurality of head channels (22) extend to the peripheral portion (44) of the head (14).

[0041] Clause 6. The fastener assembly (10) of any one of Clauses 1-5 further includes a brittle nail tail (68) extending from the head (14).

[0042] Clause 7. The fastener assembly (10) described in Clause 6, wherein the central axis (78) of the bolt (12) and the central axis (80) of the brittle nail tail (68) are collinear.

[0043] Clause 8. The fastener assembly (10) described in Clause 7, wherein the interface (76) of the brittle tail (68) and the head (14) includes a diameter ("D1") smaller than the diameter ("D2") of the brittle tail (68).

[0044] Clause 9. The fastener assembly (10) of any one of Clauses 6-8, wherein the brittle nail tail (68) defines the nail tail thread (70).

[0045] Clause 10. The fastener assembly (10) of any one of Clauses 1-9, wherein the channel (20) is located at the interface (46) of the head (14) and the shank (16) of the bolt (12).

[0046] Clause 11. The fastener assembly (10) of any one of Clauses 1-10, wherein, when the bolt (12) is positioned within the sleeve (32), the sleeve (32) includes a first portion (48) extending circumferentially around the head (14) to a plurality of head channels (22) in an overlapping relationship.

[0047] Clause 12. The fastener assembly (10) described in Clause 11, wherein a second portion (50) of the sleeve (32) extends from the first portion (48) and extends circumferentially around the handle (16).

[0048] Clause 13. The fastener assembly (10) described in Clause 12, wherein:

[0049] Each of the plurality of slots (38) extends along the second portion (50) of the sleeve (32) in a curved direction (52);

[0050] The first end (56) of each of the plurality of slots (38) is in communication with the channel (20); and

[0051] The second end (58) of each of the plurality of slots (38) has a closed wall structure (60).

[0052] Clause 14. The fastener assembly (10) described in Clause 13, wherein the closed wall construction (60) includes one of a “U” shape; a “V” shape; or an open rectangle.

[0053] Clause 15. The fastener assembly (10) of any one of Clauses 1-14, wherein, when the bolt (12) is positioned within the sleeve (32), a portion (36) of the sleeve (32) comprising annealed material is positioned between the head (14) of the bolt (12) and the unannealed portion (82) of the sleeve (32), the sleeve (32) comprising a compatible thread (34) that engages with the thread (18) of the bolt (12).

[0054] Clause 16. A method (84) for installing a fastener assembly (10), comprising:

[0055] A bolt (12) having a head (14) and a shank (16) is positioned inside a sleeve (32), wherein:

[0056] The shank (16) defines the thread (34);

[0057] Bolt (12) defines a channel (20) extending circumferentially around bolt (12);

[0058] The head (14) defines multiple head channels (22).

[0059] The first end (24) of each of the multiple head channels (22) is connected to the channel (20), and the multiple head channels (22)

[0060] The second end (26) of each of them communicates with the outside (28) of the head (14) located on the upper surface (30) of the head (14); and

[0061] The sleeve (32) has a compatible thread (34) that engages with the thread (18) of the bolt (12), wherein:

[0062] The sleeve (32) portion (36) includes annealed material; and

[0063] Multiple slots (38) are defined through the sleeve (32) such that, with the bolt (12) positioned within the sleeve (32), each of the multiple slots (38) is positioned to communicate with the channel (20).

[0064] Clause 17. The method (84) of Clause 16 further includes engaging the thread (18) of the bolt (12) with the thread (34) of the sleeve (32) positioned further away from the head (14) of the bolt (12) than the portion (36) of the sleeve (32) having annealed material.

[0065] The method (84) described in Clause 18. Clause 16 or 17 further includes inserting a bolt (12) and a sleeve (32) into a hole (88) defined by a layered structure (90) secured by a fastener assembly (10).

[0066] Clause 19. The method (84) of Clause 18 further includes pulling the bolt (12) in a direction (96) away from the hole (88) while holding the sleeve (32) in the hole (88), causing the annealed material portion (36) of the sleeve (32) to bend.

[0067] The method (84) described in Clause 20 and Clause 19 further includes rotating the bolt (12) such that the thread (18) of the bolt (12) engages with the thread (34) of the sleeve (32), the thread (34) being positioned further away from the annealed material portion (36) of the sleeve (32) relative to the head (14) of the bolt (12), and applying a compressive force on the layered structure (90) defining the hole (88).

[0068] As bolt 12 is pulled to the desired position, the pulling force F1 is stopped. At this point, method 84 further includes, as follows: Figure 6The bolt 12 is rotated using a retaining tool 72, which in turn rotates a brittle rivet 68 connected to the head 14 of the bolt 12. The rotation of the brittle rivet 68 causes the bolt 12 to rotate, and the retainer member 98 keeps the sleeve 32 rotating, causing the thread 18 of the bolt 12 to further engage with the thread 34 of the sleeve 32, which is positioned further away from the portion 36 of the annealed material of the sleeve 32 relative to the head 14 of the bolt 12. The rotation of the bolt 12 applies compressive force to the layered structure 90 defining the hole 88. The retaining tool 72 continues to apply torque to the brittle rivet 68 until a predetermined torque is reached. The predetermined torque is incorporated into the construction of the interface between the brittle rivet 68 and the head 14 of the bolt 12. Thus, in this example, the diameter “D1” of the interface 76 between the brittle rivet 68 and the head 14, made of the material of the brittle rivet 68, fails and breaks, as... Figure 6 As can be seen. For example... Figure 1 As can be seen, when the brittle nail tail 68 breaks, the brittle nail tail 68 leaves the broken residue 104 on the head 14 of the installed bolt 12 and detaches from the head 14.

[0069] At this point, the fastener assembly 10 provides unilateral fixation of the layered structure 90, applying compressive force between the head 14, made of the annealed material of the portion 36 of the sleeve 32, and the nut structure 102. Unilateral fixation has achieved the desired predetermined torque guarantee. Additionally, in the case where the plurality of slots 38 are positioned along the sleeve 32, any high-energy event such as an EME (electromagnetic event) that generates any superheated gas and particles under pressure applied at the location of the plurality of slots 38 will be blocked by the closed wall structure 60 of the plurality of slots 38, preventing them from reaching, for example, the bottom surface 100 of the layered structure 90, and thus preventing them from reaching the interior of the aircraft. The superheated gas and combustible particles will travel within the plurality of slots 38 to the channel 20 extending circumferentially around the bolt 12 and exit through the plurality of head channels 22 via the upper surface of the head 14. In this example, with the fastener assembly 10 secured to the aircraft's outer skin, superheated gases and superheated combustible particles exit the aircraft to an exterior 28, which in this example is located on the exterior of the aircraft. As a result, unilateral mounting of the fastener assembly is achieved, while simultaneously protecting the aircraft's interior from unwanted pressurized superheated gases and superheated combustible particles.

[0070] Although various examples have been described above, this disclosure is not intended to be limited thereto. Variations may be made to the examples of the disclosure that are still within the scope of the appended claims.

Claims

1. A fastener assembly (10) comprising: A bolt (12) having a head (14) and a shank (16), wherein: The handle (16) defines the thread (18); The bolt (12) defines a channel (20) extending circumferentially around the bolt (12); and The head (14) defines a plurality of head channels (22), each head channel (22) having a first end (24) and a second end (26), the first end (24) communicating with the channel (20), and the second end (26) communicating with the exterior (28) of the head (14) located on the upper surface (30) of the head (14); and A sleeve (32) comprising an outer surface and an inner surface opposite to the outer surface, wherein the inner surface has a thread (34) engaging with the thread (18) of the bolt (12) when the bolt (12) is located inside the sleeve (32), wherein the sleeve (32) comprises: The sleeve (32) portion (36) is formed of annealed material to define the annealed portion; The sleeve (32) passes through a plurality of slots (38) defined by the sleeve (32), and the annealed portion of the sleeve (32) is disposed between the plurality of slots (38) and the thread (34) of the sleeve (32); A layered structure (90) defines a hole (88) in which the bolt (12) and the sleeve (32) are inserted and has a surface (92) and a bottom surface (100); A conductive coating (94) is applied, which conforms to the surface (92) of the layered structure (90) and seals the gaps between the layered structures (90). When the bolt (12) is located inside the sleeve (32), each of the plurality of slots (38) defined by the sleeve (32) is positioned to communicate with the channel (20) of the bolt (12); During the installation of the fastener assembly (10), the annealed material collapses and spreads on the bottom surface (100) of the layered structure (90), forming a nut structure (102); and The configuration of the plurality of slots (38) is maintained when torque is applied to the sleeve (32) in response to clockwise rotation of the bolt (12) relative to the central axis of the bolt (12).

2. The fastener assembly (10) according to claim 1, wherein the head (14) has a tapered configuration (40).

3. The fastener assembly (10) according to claim 1 or 2, wherein the plurality of head channels (22) extend along the outer surface (42) of the head (14).

4. The fastener assembly (10) according to claim 1 or 2, further comprising a brittle nail tail (68) extending from the head (14).

5. The fastener assembly (10) according to claim 4, wherein the interface (76) between the brittle nail tail (68) and the head (14) includes a diameter ("D1") smaller than the diameter ("D2") of the brittle nail tail (68).

6. The fastener assembly (10) according to claim 1 or 2, wherein when the bolt (12) is positioned within the sleeve (32), a portion (36) of the sleeve (32) comprising annealed material of the sleeve (32) is positioned between the head (14) of the bolt (12) and the unannealed portion (82) of the sleeve (32), the sleeve (32) comprising a compatible thread (34) that engages with the thread (18) of the bolt (12).

7. A method (84) for installing a fastener assembly (10), comprising: A bolt (12) having a head (14) and a shank (16) is positioned inside a sleeve (32), wherein: The handle (16) defines the thread (18); The bolt (12) defines a channel (20) extending circumferentially around the bolt (12); The head (14) defines a plurality of head channels (22), Each of the plurality of head channels (22) has a first end (24) and a second end (26), the first end (24) communicating with the channel (20), and the second end (26) communicating with the exterior (28) of the head (14) located on the upper surface (30) of the head (14); and The sleeve (32) includes an outer surface and an inner surface opposite to the outer surface, and wherein, when the bolt (12) is located inside the sleeve (32), the inner surface has a thread (34) that engages with the thread (18) of the bolt (12), wherein: A portion (36) of the sleeve (32) is formed of annealed material to define the annealed portion; A plurality of slots (38) are defined through the sleeve (32), and the annealed portion of the sleeve (32) is disposed between the plurality of slots (38) and the threads of the sleeve (32). The layered structure (90) defines the hole (88) into which the bolt (12) and the sleeve (32) are inserted and has a surface (92) and a bottom surface (100); The conductive coating (94) is aligned with the surface (92) of the layered structure (90) and seals the gaps between the layered structures (90). When the bolt (12) is positioned inside the sleeve (32), each of the plurality of slots (38) is positioned to communicate with the channel (20) of the bolt (12); Insert the bolt (12) and the sleeve (32) into the hole (88). While holding the sleeve (32) within the hole (88), pulling the bolt (12) in a direction (96) away from the hole (88) causes the annealed portion (36) of the sleeve (32) to bend; and The bolt (12) is rotated clockwise relative to its central axis to apply torque to the sleeve (32) and maintain the configuration of the plurality of slots (38) when the torque is applied to the sleeve (32).

8. The method (84) according to claim 7, further comprising engaging the thread (18) of the bolt (12) with the thread (34) of the sleeve (32), wherein the thread (34) of the sleeve (32) is positioned further away from the head (14) of the bolt (12) than the annealed portion (36) of the sleeve (32).

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