Claims
- 1. A method for fastening a threaded stud to project above a first surface of a composite laminate in a substantially leakproof manner as to cryogenic liquid gases, where said composite structure is subject to crushing above a predetermined pressure and delamination under excessive tension, said method comprising the steps of:
forming a through aperture through said composite material at the location at which said stud is to be installed, said through aperture having a first diameter adjacent said first surface of said composite laminate, a frustoconical surface in the form of the frustum of a cone lying adjacent a second surface of said composite laminate, and a second diameter, smaller than said first diameter, in a region lying between said frustoconical surface and said portion of said aperture having said first diameter: installing an internally threaded insert from said first side into said aperture so as to fasten said insert within said portion of said aperture having said first diameter; obtaining a bolt including a head, a nonthreaded shank portion adjacent said head, and a threaded portion remote from said head, said threaded portion of said shank mating with said internal threads of said insert, said bolt being made from a material having a known coefficient of thermal expansion less than the coefficient of thermal expansion of said laminated structure; obtaining a generally cylindrical collar made from a material having a particular coefficient of thermal expansion and a thickness, said collar having a bore about an axis no greater in diameter than the diameter of said nonthreaded shank, and an overall diameter about said axis no less than the diameter of said cone adjacent said second surface, said collar further having a planar first end surface orthogonal to said axis, and a second end surface, said second end surface including a peripheral planar annulus parallel with said surface of said first end, and also including a depressed frustoconical portion in the shape of the frustum of a cone depressed below said planar annulus; assembling onto said bolt (a) a first k seal, with the conical portion of said first k seal facing away from said head of said bolt, (b) said collar, with said depressed portion facing said first k seal, and (c) a second k seal, with said conical portion of said second k seal facing away from said first surface of said collar, to thereby generate an assembled bolt; inserting said assembled bolt through said aperture from said second side of said laminated composite, and threading it through said insert, so as to cause a portion of said threaded portion of said bolt to protrude from said first side of said laminated composite; and when the coefficient of thermal expansion of said collar is selected in conjunction with said coefficient of thermal expansion of said bolt and with the thickness of said laminated composite in such a manner that the pressure applied to said laminated composite does not change substantially over the expected temperature range, torquing said bolt into said insert to achieve a pressure in said laminated composite which is less than said pressure at which said composite laminate crushes.
- 2. A method according to claim 1, wherein said forming of said aperture in said laminated composite is performed by drilling from one of said first and second sides, and further comprising the step of:
supporting said laminated composite from the other one of said first and second sides to aid in preventing delamination during said drilling.
- 3. A method according to claim 2, wherein said drilling step is accomplished at the slowest drill feed rate at which reasonable cutting occurs, in order to reduce drill thrust loading.
- 4. A method according to claim 1, wherein said forming of said frustoconical portion of said aperture includes the step of forming to a 120E included angle, and said step of obtaining of said collar includes the step of obtaining a collar having a conical bore portion with a 120E total included angle.
- 5. A method according to claim 1, further comprising the step of polishing said frustoconical portions of said aperture and said bore.
- 6. A method according to claim 1, further comprising the step of countersinking a region around said conical portion of said aperture.
- 7. A method according to claim 1, wherein a step of adding adhesive to at least a portion of said threads precedes said step of inserting and threading.
- 8. A method according to claim 7, further comprising, before said step of torquing, the step of:
cleaning at least the frustoconical portion of one of said aperture and a corresponding conical portion of said second k seal.
- 9. A method according to claim 7, further comprising the step of cleaning said adhesive from a threaded portion of said bolt which is exposed on said first side of said laminated composite.
- 10. A structure including a laminated composite with a threaded stud extending from a first side thereof, said structure comprising:
a through aperture in said laminated composite, said through aperture defining an axis, said aperture including a first portion adjacent said first side of said laminated composite in which an internally threaded insert is fastened, said through aperture further including a second portion adjacent a second side of said laminated composite, said second portion having a frustoconical surface depressed below said second surface of said laminated composite; an annular collar defining an axial bore coaxial with said axis, a first end surface perpendicular to said axis, and a second end defining a planar annulus centered on said axis, and also defining a frustoconical surface depressed below said second end annulus; a bolt including a head, a nonthreaded shank adjacent said head, and a threaded portion remote from said head, said bolt being assembled with said laminated composite coaxial with said aperture, said collar, and two k seals having frustoconical surfaces so that (a) said first k seal lies between said head and said second end of said collar, with said frustoconical portion of said first k seal mated with said depressed frustoconical surface of said collar, (b) said second k seal lies between said first end surface of said collar and said frustoconical surface of said second portion of said through aperture, with said frustoconical portion of said first k seal mated with said frustoconical surface of said second portion of said through aperture, and (c) said threaded portion of said bolt threaded through said internally threaded insert sufficiently to extend above said first surface of said laminated composite.
- 11. A structure according to claim 10, further comprising adhesive lying in the interstice between the internal threads of said insert and said threads of said bolt.
- 12. A structure according to claim 10, wherein said unthreaded portion of said shank of said bolt is polished.
- 13. A structure according to claim 10, wherein at least one of said depressed frustoconical surface of said collar and said depressed frustoconical surface of said aperture is polished.
- 14. A structure according to claim 10, further comprising a region surrounding said frustoconical surface of said aperture which is countersunk below said second surface of said laminated composite.
- 15. A structure according to claim 10:wherein the material of said laminated composite has a coefficient of thermal expansion which exceeds that of the material of said bolt, so that the pressure exerted by said bolt on said laminated composite will increase with increasing temperature; wherein said collar is (a) made from a material, and (b) has a length selected (i) in conjunction with the length of said bolt lying within said laminated composite, (ii) the material of said bolt, and (iii) the material of said laminated composite, so that the pressure applied to said laminated composite by the combination of said bolt and said collar tends to remain constant with temperature; and wherein said bolt is torqued sufficiently to apply pressure to said laminated composite which is less than that pressure at which said laminated composite crushes.
- 16. A bolted structure including:
a containment barrier defining a containment vessel suitable for use with cryogenic fluids, said containment barrier further defining first and second surfaces, and a through aperture extending between said first and second surfaces, said through aperture being dimensioned to clear the shank of a bolt; a bolt including a head, an unthreaded shank portion, and a threaded shank portion, said bolt extending through said through aperture from one of said first and second surfaces in such a manner that at least said threaded portion of said bolt protrudes past the other one of said first and second surfaces; a CTE collar including a bore having a diameter selected to clear said shank of said bolt, said bore of said collar being penetrated by at least a portion of said shank of said bolt; a nut threaded onto at least a portion of said threaded portion of said bolt, said nut being torqued relative to said bolt to provide a predetermined tension in said shank of said bolt; and one of
(a) a seal interposed between, and in immediate contact with, said head of said bolt and that portion of said one of said first and second surfaces of said barrier which meets sealing standards for said seal; (b) a seal interposed between, and in immediate contact with, said nut and that portion of said one of said first and second surfaces which meets sealing standards for said seal; and (c) a first seal interposed between an end surface of said collar and that portion of one of said first and second surfaces which meets sealing standards for said seal; and a second seal interposed between a second end surface of said collar and a surface portion of another structure.
Parent Case Info
[0001] This patent application claims priority of provisional patent application Serial No. 60/210,136 filed Jun. 7, 2000.
Provisional Applications (1)
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Number |
Date |
Country |
|
60210136 |
Jun 2000 |
US |
Divisions (1)
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Number |
Date |
Country |
Parent |
09690964 |
Oct 2000 |
US |
Child |
10095146 |
Mar 2002 |
US |