Joining of thermoplastic to metal with enhanced interfacial chemical bonding

Patent metadata

Field	Value
Publication number	US-10569477-B2
Application number	US-201515546547-A
Country	US
Kind code	B2
Filing date	Jan 26, 2015
Priority date	Jan 26, 2015
Publication date	Feb 25, 2020
Grant date	Feb 25, 2020

Abstract

A method of attaching a thermoplastic-based workpiece and a metal workpiece involves the use of a metal reaction coating. The metal reaction coating is applied over a base metal substrate of the metal workpiece such that the metal reaction coating faces and contacts the thermoplastic-based workpiece when the two workpieces are assembled in overlapping fashion. To attach the workpieces at their faying interface, an energy source such as, for example, a laser beam or an electric arc, is directed against the metal workpiece to create a zone of concentrated heat that at least warms up the metal reaction coating and melts a portion of the thermoplastic-based workpiece. Such heated activity at the faying interface promotes interfacial chemical bonding between the thermoplastic-based workpiece and the metal workpiece that contributes to an enhanced attachment between the workpieces.

First claim

The invention claimed is:

1. A method of attaching a thermoplastic-based workpiece and a metal workpiece, the method comprising:
providing a workpiece stack-up that includes a thermoplastic-based workpiece and a metal workpiece assembled in overlapping fashion, the thermoplastic-based workpiece having a faying surface that overlaps and contacts a faying surface of the metal workpiece along a faying interface of the workpieces, the thermoplastic-based workpiece comprising a thermoplastic polymer matrix that includes metal-reactive carbonyl moieties, and the metal workpiece comprising a base metal substrate and a metal reaction coating applied over the base metal substrate, the metal reaction coating providing the faying surface of the metal workpiece and contacting the faying surface of the thermoplastic-based workpiece;
directing an energy source at an outer surface of the metal workpiece, the energy source impinging the outer surface of the metal workpiece and creating a concentrated zone of heat that melts the metal workpiece to thereby form a pool of molten metal and further melts a portion of the faying surface of the thermoplastic-based workpiece while at least warming up the metal reaction coating, the metal reaction coating reacting with the portion of the faying surface of the thermoplastic-based workpiece that is melted to establish interfacial chemical bonding at the faying interface of the workpieces; and
allowing the metal reaction coating to cool and the portion of the faying surface of the thermoplastic-based workpiece melted by the energy source to cool and re-solidify, the interfacial chemical bonding established at the faying interface remaining after the metal reaction coating has cooled and the portion of the faying surface of the thermoplastic-based workpiece has re-solidified.

2. The method set forth in claim 1 , wherein the metal reaction coating is selected from the group consisting of chromium, nickel, titanium, aluminum, zinc, boron, manganese, silicon, and combinations thereof.

3. The method set forth in claim 2 , wherein the metal reaction coating is chromium.

4. The method set forth in claim 3 , wherein the base metal substrate is steel, and wherein the chromium coating is electroplated onto the steel substrate prior to assembly of the workpiece stack-up.

5. The method set forth in claim 1 , wherein the thermoplastic polymer matrix is an aliphatic polyamide, a polyphthalamide, a polyester, a polycarbonate, a polyacrylate, or a polyurethane.

6. The method set forth in claim 5 , wherein the thermoplastic polymer matrix is PA6, PA6,6, PA6/T, PET, or PMMA.

7. The method set forth in claim 1 , wherein the thermoplastic-based workpiece is a thermoplastic composite workpiece that comprises a reinforcement phase embedded in the thermoplastic polymer matrix.

8. The method set forth in claim 1 , wherein the base metal substrate of the metal workpiece is steel.

9. The method set forth in claim 1 , wherein the energy source is a laser beam.

10. A method of attaching a thermoplastic-based workpiece and a metal workpiece, the method comprising:
applying a metal reaction coating over a surface of a steel substrate to form a metal workpiece, the metal reaction coating being composed of chromium, nickel, titanium, aluminum, zinc, boron, manganese, silicon, or a combination of any of those materials;
assembling the metal workpiece in overlapping fashion with a thermoplastic-based workpiece such that a faying surface of the metal workpiece overlaps and contacts a faying surface of the thermoplastic-based workpiece along a faying interface, the thermoplastic-based workpiece comprising a thermoplastic polymer matrix that includes metal-reactive carbonyl moieties, and wherein an exposed surface of the metal reaction coating constitutes the faying surface of the metal workpiece;
directing an energy source against the metal workpiece to create a concentrated zone of heat that at least warms up the metal reaction coating at the faying interface and melts a portion of the faying surface of the thermoplastic-based workpiece in contact with the metal reaction coating; and
allowing the metal reaction coating to cool and the portion of the faying surface of the thermoplastic-based workpiece melted by the energy source to cool and re-solidify such that the thermoplastic-based workpiece and the metal workpiece are attached at the faying interface through interfacial chemical bonding between the carbonyl moieties of the thermoplastic polymer matrix of the thermoplastic-based workpiece and the metal reaction coating.

11. The method set forth in claim 10 , wherein the energy source is a laser beam.

12. The method set forth in claim 11 , wherein directing the laser beam against the outer surface of the metal workpiece comprises:
providing a laser optic head that includes a focusing lens;
focusing a near-infrared laser beam with the focusing lens; and
directing the near-infrared laser beam towards the outer surface of the metal workpiece, the near-infrared laser beam impinging the outer surface and forming a keyhole within the metal workpiece.

13. The method set forth in claim 12 , further comprising:
moving the laser optic head to move the near-infrared laser beam along a predetermined weld path.

14. The method set forth in claim 10 , wherein the thermoplastic polymer matrix includes repeating units that include one or more (a) ketone functional groups, (b) ester functional groups, (c) amide functional groups, or (d) sulfoxide functional groups.

15. The method set forth in claim 14 , wherein the thermoplastic polymer matrix is an aliphatic polyamide, a polyphthalamide, a polyester, a polycarbonate, a polyacrylate, or a polyurethane.

16. The method set forth in claim 10 , wherein the thermoplastic-based workpiece is a thermoplastic composite workpiece that comprises a reinforcement phase embedded in the thermoplastic polymer matrix.

17. The method set forth in claim 10 , wherein the steel substrate is an advanced high strength steel having an ultimate tensile strength of 600 MPa or greater.

18. The method set forth in claim 10 , wherein the metal reaction coating is composed of chromium, and wherein applying the chromium reaction coating comprises electroplating chromium over the surface of the steel substrate.

19. A method of attaching a thermoplastic-based workpiece and a metal workpiece, the method comprising:
applying a metal reaction coating over a surface of a mild steel substrate to form a metal workpiece, the metal reaction coating being composed of chromium;
assembling the metal workpiece in overlapping fashion with a thermoplastic composite workpiece such that a faying surface of the metal workpiece overlaps and contacts a faying surface of the thermoplastic composite workpiece along a faying interface, the thermoplastic composite workpiece comprising a polyamide polymer matrix and a carbon reinforcing phase embedded within the polyamide polymer matrix, and wherein an exposed surface of the metal reaction coating constitutes the faying surface of the metal workpiece; and
operating a laser optic head to direct a laser beam against the metal workpiece to create a concentrated zone of heat that extends to the faying interface and at least warms up the metal reaction coating at the faying interface and melts a portion of the faying surface of the thermoplastic composite workpiece in contact with the metal reaction coating, wherein, after the concentrated zone of heat subsides and the metal reaction coating has cooled and the portion of th

Assignees

• Gm Global Tech Operations Llc

Inventors

• Zhang Jing
• Yang David S
• Deng Shawn

Classifications

• B32B2255/06

  on metal layer · CPC title

• B29C66/74283

  Iron or alloys of iron, e.g. steel · CPC title

• B29C66/836

  Moving relative to and tangentially to the parts to be joined, e.g. transversely to the displacement of the parts to be joined, e.g. using a X-Y table (B29C66/65 takes precedence) · CPC title

• B29C66/43

  Joining a relatively small portion of the surface of said articles (B29C66/45 takes precedence) · CPC title

• B29C66/7392

  characterised by the material of at least one of the parts being a thermoplastic · CPC title