Joining polymer workpieces to other components

• US 20080236720A1
• Filed: 03/27/2007
• Published: 10/02/2008
• Est. Priority Date: 03/27/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Mankame, Nilesh D., Browne, Alan L., Chen, Yen-Lung, Sigler, David R., Foss, Peter H.
• Granted Patent: US 8,250,725 B2
• Time in Patent Office: Days
• US Class Current: 156/73.5
• CPC Class Codes: B29C 2035/0827 using UV radiation
• CPC Class Codes: B29C 37/0085 by means of openings in the layers joining through openings B29C66/304
• CPC Class Codes: B29C 61/02 Thermal shrinking
• CPC Class Codes: B29C 63/0013 Removing old coatings
• CPC Class Codes: B29C 63/02 using sheet or web-like material B29C63/26 and B29C63/38 take precedence
• CPC Class Codes: B29C 65/10 using hot gases (e.g. combustion gases) or flames coming in contact with at least one of the parts to be joined
• CPC Class Codes: B29C 65/103 direct heating both surfaces to be joined
• CPC Class Codes: B29C 65/14 using wave energy , i.e. electromagnetic radiation, or particle radiation using mechanical waves B29C65/06; using ultrasonic waves B29C65/08; pressing means transparent to electromagnetic radiation B29C66/81267
• CPC Class Codes: B29C 65/1406 Ultraviolet [UV] radiation
• CPC Class Codes: B29C 65/16 Laser beams
• CPC Class Codes: B29C 65/30 Electrical means B29C65/38 takes precedence
• CPC Class Codes: B29C 65/44 Joining a heated non plastics element to a plastics element
• CPC Class Codes: B29C 65/606 the rivets being integral with one of the parts to be joined, i.e. staking
• CPC Class Codes: B29C 65/66 by liberation of internal stresses, e.g. shrinking of one of the parts to be joined
• CPC Class Codes: B29C 65/72 by combined operations or combined techniques, e.g. welding and stitching
• CPC Class Codes: B29C 65/76 Making non-permanent or releasable joints
• CPC Class Codes: B29C 66/0342 Cooling, e.g. transporting through welding and cooling zone
• CPC Class Codes: B29C 66/3494 while keeping the welding zone under pressure
• CPC Class Codes: B29C 66/43 Joining a relatively small portion of the surface of said articles B29C66/45 takes precedence
• CPC Class Codes: B29C 66/73773 the to-be-joined area of at least one of the parts to be joined being semi-crystalline
• CPC Class Codes: B29C 66/7392 : characterised by the material of at least one of the parts being a thermoplastic
• CPC Class Codes: B29C 66/7394 : characterised by the material of at least one of the parts being a thermoset
• CPC Class Codes: B29C 66/742 : to metals or their alloys
• CPC Class Codes: B29C 66/81423 : being concave
• CPC Class Codes: B29C 66/832 : Reciprocating joining or pressing tools B29C66/834 takes precedence
• CPC Class Codes: B29C 66/91411 : of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/91445 : by steps
• CPC Class Codes: B29C 66/919 : characterised by specific temperature, heat or thermal flux values or ranges specific electrical resistance values B29C66/81262
• CPC Class Codes: B29C 66/91943 : higher than said glass transition temperature
• CPC Class Codes: B29C 66/91945 : lower than said glass transition temperature
• CPC Class Codes: B29K 2101/10 : Thermosetting resins
• CPC Class Codes: B29K 2101/12 : Thermoplastic materials
• CPC Class Codes: B29K 2105/0085 : Copolymers
• CPC Class Codes: B29K 2105/0088 : Blends of polymers
• CPC Class Codes: B29K 2305/00 : Use of metals, their alloys or their compounds, as reinforcement
• CPC Class Codes: B29K 2995/0049 : Heat shrinkable
• CPC Class Codes: B29L 2031/737 : Articles provided with holes, e.g. grids, sieves nets B29L2028/00
• CPC Class Codes: B32B 43/006 : Delaminating
• CPC Class Codes: Y10T 29/49865 : by temperature differential [e.g., shrink fit]
• CPC Class Codes: Y10T 29/49993 : Filling of opening

Abstract

A shape memory polymer workpiece is attached to a second workpiece. A face of the SMP workpiece is placed against an attachment surface of the second workpiece. The second workpiece has an attachment hole(s). The SMP workpiece is activated (e.g., heated) to a softening temperature and a portion extruded into the attachment hole of the facing surface of the second workpiece. The SMP piece is held while still heated against the second workpiece, the material flowing as result of the shape memory effect to form an attachment. As the SMP material cools while still under load its modulus increases fixing the attachment geometry. Reheating the attached parts without pushing them together reverses the process.

Claims

1. A method of attaching a shape memory polymer workpiece to a second workpiece where the workpieces have facing surfaces for the attachment, the method comprising:

forming an attachment hole in the facing surface of the second workpiece;

placing the facing surface of the polymer workpiece overlying the attachment hole of the second workpiece, the facing surface of the polymer workpiece having no preformed protuberance for entry into the attachment hole;

activating at least a facing surface region of the shape memory polymeric workpiece to a softened condition;

applying a force to push and deform softened shape memory material from the surface region of the shape memory polymer workpiece into the attachment hole;

retaining a force against the softened polymeric material while the deformed softened shape memory material flows, in an attempt to recover its original shape, to form a mechanical attachment with the second workpiece; and

cooling the softened material, while maintaining an external force on it, to strengthen the mechanical attachment between the polymer workpiece and the second workpiece.

2. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is activated by heating to a softened condition before the polymer workpiece is placed overlying the attachment hole of the second workpiece.

3. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is activated by heating to a softened condition by direct application of heat to the polymer workpiece.

4. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the thickness of the polymer workpiece in the region of its facing surface is greater than the depth of the attachment hole in the second workpiece.

5. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is a sheet or strip with flat opposing faces and the second workpiece is a metal sheet or panel.

6. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 comprising

placing the facing surface of the polymer workpiece overlying the attachment hole of a metal workpiece as the second workpiece;

and

heating the metal workpiece to heat the polymer workpiece to a softened condition.

7. A method of attaching a polymer workpiece to a metal workpiece as recited in claim 6 comprising

placing the facing surface of the polymer workpiece overlying the attachment hole of the metal workpiece;

and

heating the metal workpiece with a heated block overlying the attachment hole to heat the underlying attachment region of the polymer workpiece to a softened condition.

8. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the second workpiece is a metal sheet having a thickness of about one-half millimeter to about three millimeters.

9. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece has a thickness of about two millimeters or greater.

10. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is activated by heating to a softened condition by contact with a heated body that is also used to apply force for pushing softened shape memory material into the attachment hole.

11. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is activated by heating to a softened condition by contact with a body that is initially heated and is also used also used to apply force for pushing softened shape memory material into the attachment hole, the body then being cooled and, by continued contact with the polymer workpiece, used to cool the softened material.

12. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is activated by heating to a softened condition by directing a stream of heated fluid against the polymer workpiece.

13. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the softened material is cooled by directing a stream of cooling fluid against the polymer workpiece.

14. A method of attaching a shape memory polymer workpiece to a second workpiece as recited in claim 1 in which the polymer workpiece is activated by heating to a softened condition by directing a stream of heated fluid against the polymer workpiece and softened material is subsequently cooled by directing a stream of cooling fluid against the polymer workpiece.

15. A method of separating a shape memory polymer workpiece and a second workpiece which have been attached by the method recited in claim 1;

the method of separating comprising;

heating at least the attachment portion of the shape memory polymer workpiece to a softened condition without restraining material flow in the attachment portion and

withdrawing the softened attachment portion of the shape memory polymer workpiece from the attachment hole of the second workpiece.

16. A method of attaching a shape memory polymer workpiece to a metal workpiece where the workpieces have facing surfaces for the attachment, the method comprising;

forming an attachment hole in the facing surface of the metal workpiece;

placing the facing surface of the polymer workpiece with its attachment portion overlying the attachment hole of the metal workpiece, the facing surface of the polymer workpiece having no preformed protuberance for engagement with the attachment hole;

heating at least the intended attachment region of the polymeric part to a shape memory softened condition;

pushing softened attachment portion material into the attachment hole;

retaining a pushing load against the heated region of the polymer workpiece while the pushed portion flows, in an attempt to recover its original shape, to form a mechanical attachment with the metal part at the hole; and

cooling the extruded softened material, while maintaining an external force on it, to fix and strengthen the mechanical attachment to the metal part.

17. A method of attaching a shape memory polymer workpiece to a metal workpiece as recited in claim 16 in which the thickness of the polymer workpiece in the region of its facing surface is greater than the depth of the attachment hole in the metal workpiece.

18. A method of attaching a shape memory polymer workpiece to a metal workpiece as recited in claim 16 in which the polymer workpiece is a sheet or strip with flat opposing faces and the metal workpiece is a sheet or panel.

19. A method of attaching a shape memory polymer workpiece to a metal workpiece as recited in claim 16 in which the polymer workpiece is activated by heating to a softened condition by direct application of heat to the polymer workpiece.

20. A method of attaching a shape memory polymer workpiece to a metal workpiece as recited in claim 16 in which the polymer workpiece is activated by heating to a softened condition by contact with a heated body that is also used to apply force for pushing softened shape memory material into the attachment hole.