Rivetless nutplates for aircraft
Methods for attaching a window to an airframe, methods of maintaining structural integrity of an airframe while attaching a window to the airframe, and portions of an aircraft are set forth herein. One method for attaching a window to an airframe comprises the steps of: applying to a bonding surface of a nutplate an adhesive; inserting through an airframe hole a fixture attached to a nut of the nutplate, and applying tension to the fixture to hold the adhesive-coated bonding surface of the nutplate adjacent an interior surface of the airframe; allowing the adhesive to cure; removing the fixture from the nut of the nutplate; and installing a bolt through a hole of a retainer, through the hole in the airframe, and into the nutplate; the retainer being in contact with and securing the window to the airframe. The adhesive is selected such that very specific conditions are met.
1. A portion of an aircraft, comprising:
an airframe;
a nutplate coupled to the airframe by adhesive;
a retainer coupled to a window; and
a bolt passing through a hole of the retainer, through a hole in the airframe, and into the nutplate to secure the retainer to the airframe;
wherein the adhesive comprises at least one of composition 1 in Table 1 and composition 2 in Table 2:
TABLE 1
composition 1
approximate %
Ingredient
by Wt
Methyl Methacrylate
40-70
Chlorosulfonated Polyethylene
10-30
Acrylic Polymer
5-10
Acrylic Polymer
3-7
Maleic Acid
1-5
Cumene Hydroperoxide
0.5-1.5
2,6-di-tert-Butyl-p-Cresol
0.5-1.5
And
TABLE 2
composition 2
approximate %
Ingredient
by Wt
METHYLENE PHENYLENE ISOCYANATE
35
URETHANE PREPOLYMER
19-23
MDI HOMOPOLYMER
12-16
CALCIUM SODIUM ALUMINOSILICATE
8-12
TALC
8-12
URETHANE PREPOLYMER
3-7
AMORPHOUS SILICA
2-6.
2. A method of maintaining structural integrity of an airframe while attaching a window to the airframe during manufacture of an aircraft, the method comprising the steps:
applying to a bonding surface of a nutplate an adhesive;
maintaining the adhesive-coated bonding surface of the nutplate adjacent an interior surface of the airframe; and
allowing the adhesive to cure;
wherein the adhesive is selected such that the nutplate is secured by the adhesive such that:
the bond between the nutplate and the airframe will withstand a bolt-fastening torque of at least 60 inch pounds;
the bond between the nutplate and the airframe will withstand cycling over a temperature range from approximately −55 degrees Celsius to approximately 82 degrees Celsius;
wherein the adhesive comprises at least one of composition 1 in Table 1 and composition 2 in Table 2:
TABLE 1
composition 1
approximate %
Ingredient
by Wt
Methyl Methacrylate
40-70
Chlorosulfonated Polyethylene
10-30
Acrylic Polymer
5-10
Acrylic Polymer
3-7
Maleic Acid
1-5
Cumene Hydroperoxide
0.5-1.5
2,6-di-tert-Butyl-p-Cresol
0.5-1.5
and
TABLE 2
composition 2
approximate %
Ingredient
by Wt
METHYLENE PHENYLENE ISOCYANATE
35
URETHANE PREPOLYMER
19-23
MDI HOMOPOLYMER
12-16
CALCIUM SODIUM ALUMINOSILICATE
8-12
TALC
8-12
URETHANE PREPOLYMER
3-7
AMORPHOUS SILICA
2-6.
3. The method of claim 2 , wherein the adhesive is allowed to cure for at least 15 minutes.
4. The method of claim 3 , wherein the nutplate bonding surface is generally planar.
5. A method for attaching a window to an airframe via a rivetless nutplate, comprising:
applying to a bonding surface of the nutplate an adhesive;
inserting through a hole in the airframe an elastomeric fixture attached to a nut of the nutplate, and pulling the elastomeric fixture to apply tension to the elastomeric fixture to hold the adhesive-coated bonding surface of the nutplate adjacent an interior surface of the airframe;
allowing the adhesive to cure;
removing the elastomeric fixture from the nut of the nutplate; and
installing a bolt through a hole of a retainer, through the hole in the airframe, and into the nutplate; the retainer being in contact with and securing the window to the airframe;
wherein the adhesive comprises at least one of composition 1 in Table 1 and composition 2 in Table 2:
TABLE 1
composition 1
approximate %
Ingredient
by Wt
Methyl Methacrylate
40-70
Chlorosulfonated Polyethylene
10-30
Acrylic Polymer - N.J.T.S. Reg No. 800941-5008P
5-10
Acrylic Polymer - N.J.T.S. Reg No. 800941-5007P
3-7
Maleic Acid
1-5
Cumene Hydroperoxide
0.5-1.5
2,6-di-tert-Butyl-p-Cresol
0.5-1.5
And
TABLE 2
composition 2
approximate %
Ingredient
by Wt
METHYLENE PHENYLENE ISOCYANATE
35
URETHANE PREPOLYMER
19-23
MDI HOMOPOLYMER
12-16
CALCIUM SODIUM ALUMINOSILICATE
8-12
TALC
8-12
URETHANE PREPOLYMER
3-7
AMORPHOUS SILICA
2-6.
6. A method of maintaining structural integrity of an airframe while attaching a window to the airframe during manufacture of an aircraft, the method comprising the steps of not riveting a nutplate to the airframe, but instead:
applying to a bonding surface of the nutplate an adhesive selected from the group consisting of urethane adhesives and methyl methacrylate adhesives;
maintaining the adhesive-coated bonding surface of the nutplate adjacent an interior surface of the airframe;
allowing the adhesive to cure; and
installing a bolt through a hole of a retainer, through the hole in the airframe, and into the nutplate; the retainer being in contact with and securing the window to the airframe;
wherein the adhesive has a working time of at least 15 minutes; and
wherein the adhesive is selected such that the nutplate is secured by the adhesive such that:
the bond between the nutplate and the airframe will withstand a bolt-fastening torque of at least 60 inch pounds;
the bond between the nutplate and the airframe will withstand cycling over a range of temperatures expected to be encountered by an aircraft in flight;
the bond between the nutplate and the airframe will withstand a push out force of at least one hundred pounds over the range of temperatures; and
the bond between the nutplate and the airframe will withstand flexing of the airframe during pressurization cycles expected to be encountered by the aircraft;
wherein the adhesive comprises the composition in Table 1:
TABLE 1
approximate
Ingredient
% by Wt
Methyl Methacrylate
40-70
Chlorosulfonated Polyethylene
10-30
Acrylic Polymer - N.J.T.S. Reg No. 800941-5008P
5-10
Acrylic Polymer - N.J.T.S. Reg No. 800941-5007P
3-7
Maleic Acid
1-5
Cumene Hydroperoxide
0.5-1.5
2,6-di-tert-Butyl-p-Cresol
0.5-1.5.
7. The method of claim 6 , wherein the range of temperatures is from approximately −55 degrees Celsius to approximately 82 degrees Celsius.
8. A method for attaching a window to an airframe, comprising:
applying to a bonding surface of a nutplate an adhesive;
inserting through a hole in the airframe an elastomeric fixture attached to a nut of the nutplate, and pulling the elastomeric fixture to apply tension to the elastomeric fixture to hold the adhesive-coated bonding surface of the nutplate adjacent an interior surface of the airframe;
allowing the adhesive to cure;
removing the elastomeric fixture from the nut of the nutplate; and
installing a bolt through a hole of a retainer, through the hole in the airframe, and into the nutplate; the retainer being in contact with and securing the window to the airframe;
wherein the adhesive is selected such that the nutplate is secured by the adhesive such that:
the bond between the nutplate and the airframe will withstand a bolt-fastening torque of at least 60 inch pounds;
the bond between the nutplate and the airframe will withstand cycling over a range of temperatures expected to be encountered by an aircraft in flight;
the bond between the nutplate and the airframe will withstand a push out force of at least one hundred pounds over the range of temperatures expected to be encountered by the aircraft; and
the bond between the nutplate and the airframe will withstand flexing of the airframe during pressurization cycles expected to be encountered by the aircraft in flight; and
wherein the adhesive has a working time of at least 15 minutes;
wherein the adhesive comprises at least one of composition 1 in Table 1 and composition 2 in Table 2:
TABLE 1
composition 1
approximate %
Ingredient
by Wt
Methyl Methacrylate
40-70
Chlorosulfonated Polyethylene
10-30
Acrylic Polymer - N.J.T.S. Reg No. 800941-5008P
5-10
Acrylic Polymer - N.J.T.S. Reg No. 800941-5007P
3-7
Maleic Acid
1-5
Cumene Hydroperoxide
0.5-1.5
2,6-di-tert-Butyl-p-Cresol
0.5-1.5
and
TABLE 2
composition 2
approximate %
Ingredient
by Wt
METHYLENE PHENYLENE ISOCYANATE
35
URETHANE PREPOLYMER
19-23
MDI HOMOPOLYMER
12-16
CALCIUM SODIUM ALUMINOSILICATE
8-12
TALC
8-12
URETHANE PREPOLYMER
3-7
AMORPHOUS SILICA
2-6.
9. The method of claim 8 , wherein the nutplate bonding surface is generally planar.
10. The method of claim 8 , wherein the range of temperatures is from approximately −55 degrees Celsius to approximately 82 degrees Celsius.