Sandwich composite with shape memory alloy core and method of making same

Patent metadata

Field	Value
Publication number	US-10464281-B2
Application number	US-201414462906-A
Country	US
Kind code	B2
Filing date	Aug 19, 2014
Priority date	Aug 19, 2014
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

A composite sandwich structure for a vehicle includes a first sheet that has a first surface and an opposing second surface. The composite sandwich structure also includes a second sheet opposite the first sheet and a core coupled between the first and second sheets. The core is formed from a shape memory alloy and is configured to reversibly transform between (a) a substantially fully austenite state in response to the composite sandwich structure being within an expected operating temperature range and being subjected to a relatively low transverse force, and (b) an at least partially martensite state in response to the composite sandwich structure being within the expected operating temperature range and being subjected to a relatively high transverse force. Each of a plurality of first portions of the core correspondingly changes shape to accommodate the application of the relatively high force, such that the core reversibly deforms.

First claim

What is claimed is:

1. A composite sandwich structure for a vehicle, said composite sandwich structure comprising:
a first sheet comprising a first surface and an opposing second surface, wherein a transverse direction is defined normal to said second surface of said first sheet;
a second sheet opposite said first sheet; and
a core coupled between said first and second sheets, said core is formed from a shape memory alloy having an austenite finish transition temperature within a range of about −35 degrees Celsius to about −10 degrees Celsius, said shape memory alloy comprises a plurality of web portions that each extend from said first sheet to said second sheet, said core is configured to reversibly transform between:
a substantially fully austenite state in response to said composite sandwich structure being subjected to a relatively low force applied substantially parallel to the transverse direction, and
an at least partially martensite state in response to said composite sandwich structure being subjected to a relatively high force applied to said composite sandwich structure substantially parallel to the transverse direction, wherein each of a plurality of first portions of said core correspondingly changes shape to accommodate an application of the relatively high force, such that said core reversibly deforms.

2. The composite sandwich structure according to claim 1 , wherein said core has a stiffness in the substantially fully austenite state, said core is further configured such that said core substantially retains the stiffness after said core has transformed to the at least partially martensite state and back to the substantially fully austenite state.

3. The composite sandwich structure according to claim 1 , wherein said austenite finish transition temperature of said shape memory alloy is less than or equal to a lower end value of an expected operating temperature range of the vehicle.

4. The composite sandwich structure according to claim 1 , wherein said austenite finish transition temperature is about −15 degrees Celsius.

5. The composite sandwich structure according to claim 1 , wherein said shape memory alloy exhibits superelastic properties within a predetermined superelastic temperature range, and an expected operating temperature range of the vehicle is substantially contained within said superelastic temperature range.

6. The composite sandwich structure according to claim 1 , wherein said shape memory alloy is Nitinol.

7. The composite sandwich structure according to claim 1 , wherein said core comprises a thin-walled, fluted shape.

8. The composite sandwich structure according to claim 7 , wherein said core further comprises a plurality of first interface portions and a plurality of second interface portions, each of said plurality of web portions extends between one of said plurality of first interface portions and one of said plurality of second interface portions.

9. An aircraft comprising:
a composite sandwich structure comprising:
a first sheet comprising a first surface and an opposing second surface, wherein a transverse direction is defined normal to said second surface of said first sheet;
a second sheet opposite said first sheet; and
a core coupled between said first and second sheets, said core is formed from a shape memory alloy having an austenite finish transition temperature within a range of about −35 degrees Celsius to about −10 degrees Celsius, said shape memory alloy comprises a plurality of web portions that each extend from said first sheet to said second sheet, said core is configured to reversibly transform between:
a substantially fully austenite state in response to said composite sandwich structure being subjected to a relatively low force applied substantially parallel to the transverse direction, and
an at least partially martensite state in response to said composite sandwich structure being subjected to a relatively high force applied to said composite sandwich structure substantially parallel to the transverse direction, wherein each of a plurality of first portions of said core correspondingly changes shape to accommodate an application of the relatively high force, such that said core reversibly deforms.

10. The aircraft according to claim 9 , wherein said core has a stiffness in the substantially fully austenite state, said core is further configured such that said core substantially retains the stiffness after said core has transformed to the at least partially martensite state and back to the substantially fully austenite state.

11. The aircraft according to claim 9 , wherein said austenite finish transition temperature of said shape memory alloy is less than or equal to a lower end value of an expected operating temperature range of the aircraft.

12. The aircraft according to claim 9 , wherein said austenite finish transition temperature is about −15 degrees Celsius.

13. The aircraft according to claim 9 , wherein said shape memory alloy exhibits superelastic properties within a predetermined superelastic temperature range, and an expected operating temperature range of the aircraft is substantially contained within said superelastic temperature range.

14. The aircraft according to claim 9 , wherein said shape memory alloy is Nitinol.

15. The aircraft according to claim 9 , wherein said core comprises a thin-walled, fluted shape.

16. The aircraft according to claim 15 , wherein said core further comprises a plurality of first interface portions and a plurality of second interface portions, each of said plurality of web portions extends between one of said plurality of first interface portions and one of said plurality of second interface portions.

17. A method of forming a composite sandwich structure for a vehicle, said method comprising:
coupling a core between a first sheet and a second sheet to form the composite sandwich structure, wherein a transverse direction is defined normal to a second surface of the first sheet, and wherein the core is formed from a shape memory alloy having an austenite finish transition temperature within a range of about −35 degrees Celsius to about −10 degrees Celsius, the shape memory alloy including a plurality of web portions that each extend from the first sheet to the second sheet, wherein the core is configured to reversibly transform between:
a substantially fully austenite state in response to the composite sandwich structure being subjected to a relatively low force applied substantially parallel to the transverse direction, and
an at least partially martensite state in response to the composite sandwich structure being subjected to a relatively high force applied to the composite sandwich structure substantially parallel to the transverse direction, wherein each of a plurality of first portions of the core correspondingly changes shape to accommodate an application of the relatively high force, such that the core reversibly deforms.

18. The method according to claim 17 , further comprising selecting the shape memory alloy to have the austenite finish transition temperature less than or equal to a lower end value of an expected operating temperature range of the vehicle.

19. The method according to claim 17 , further comprising selecting the shape memory alloy to exhibit superelastic properties within a predetermined superelastic temperature range, wherein an expected operating temperature range of the vehicle is substantially contained within the superelastic temperature range.

20. The method according to claim

Assignees

• Boeing Co

Inventors

• Oehler Stephen D
• Calkins Frederick T

Classifications

• B32B2262/106

  Carbon fibres, e.g. graphite fibres · CPC title

• B32B3/30 Primary

  characterised by a layer formed with recesses or projections, e.g. {hollows, grooves, protuberances, ribs (apertured layer B32B3/266; layer with cavities or internal voids B32B3/26)} · CPC title

• B32B2250/40

  Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA · CPC title

• B32B2250/03

  3 layers · CPC title

• B32B37/0076

  characterised in that the layers are not bonded on the totality of their surfaces · CPC title