Bonding thermoplastic layers via electrical heating

• US 4,871,412 A
• Filed: 02/24/1988
• Issued: 10/03/1989
• Est. Priority Date: 03/02/1987
• Status: Expired due to Fees

• Current Assignee: The Welding Institute
• Original Assignee: The Welding Institute
• Inventors: Felix, Michael C., Taylor, Nicola S., Hardy, Colin C.
• Primary Examiner(s): Cashion, Jr., Merrell C.
• Application Number:
  US07/159,726
• Time in Patent Office: 587 Days
• Field of Search: 156/272.4, 156/272.2, 156/274.2, 156/273.9, 156/379.6, 156/379.7, 156/304.1, 156/304.2, 156/304.3, 156/304.4, 156/304.7, 219/10.43, 219/10.53, 219/85 A, 219/535
• US Class Current: 156/273.9
• CPC Class Codes: B29C 65/3616 comprising discontinuous fibre-reinforcements
• CPC Class Codes: B29C 65/3636 comprising independent continuous fibre-reinforcements
• CPC Class Codes: B29C 65/364 being a woven or non-woven fabric or being a mesh
• CPC Class Codes: B29C 65/3668 characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special induction coils
• CPC Class Codes: B29C 65/3696 with a coating
• CPC Class Codes: B29C 65/8253 by the use of waves or particle radiation, e.g. visual examination, scanning electron microscopy, or X-rays B29C65/8292 takes precedence
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• 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 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/721 Fibre-reinforced materials B29C66/729 takes precedence
• CPC Class Codes: B29C 66/7212 characterised by the composition of the fibres
• CPC Class Codes: B29C 66/72141 Fibres of continuous length
• CPC Class Codes: B29C 66/73 characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
• CPC Class Codes: B29C 66/73921 characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/8122 characterised by the composition of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
• CPC Class Codes: B29C 66/81265 Surface properties, e.g. surface roughness or rugosity
• CPC Class Codes: B29C 66/81465 one placed behind the other in a single row in the feed direction
• CPC Class Codes: B29C 66/8181 characterised by the cooling constructional aspects
• CPC Class Codes: B29C 66/8221 Scissor or lever mechanisms, i.e. involving a pivot point
• CPC Class Codes: B29C 66/83411 Roller, cylinder or drum types B29C66/83431 takes precedence; rollers, cylinders or drums moving relative to and tangentially to the parts to be joined B29C66/8362
• CPC Class Codes: B29C 66/8362 : Rollers, cylinders or drums moving relative to and tangentially to the parts to be joined
• CPC Class Codes: B29C 66/91218 : using colour change, e.g. using separate colour indicators
• CPC Class Codes: B29C 66/91231 : of the joining tool
• CPC Class Codes: B29C 66/91651 : by controlling or regulating the heat generated by Joule heating or induction heating
• 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 66/949 : characterised by specific time values or ranges
• CPC Class Codes: B29K 2071/00 : Use of polyethers , e.g. PEEK, i.e. polyether-etherketone or PEK, i.e. polyetherketone or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2307/04 : Carbon
• CPC Class Codes: B29K 2909/08 : Glass
• CPC Class Codes: B29K 2995/0005 : Conductive

Abstract

A method of bonding a thermoplastic layer (22), such as APC-2, to a substrate (21) in which the thermoplastic layer (22) comprises electrical conductors such as carbon fibres, embedded in thermoplastic material such as PEEK. The method comprises placing the thermoplastic layer (22) in contact with the substrate (21); and inducing electric currents in the conductors whereby heat generated by the currents passing through the conductors causes thermoplastic material to bond the layer to the substrate.

Claims

1. A method of bonding a thermoplastic layer to a substrate, the thermoplastic layer and the substrate each comprising at least one layer which consists of substantially unidirectional electrical conductors embedded in and individually coated with thermoplastic material, the method comprising placing said thermoplastic later in contact with said substrate;

and applying an alternating electromagnetic field so as to induce electric currents in conductors whereby heat generated by said currents passing through said conductors causes thermoplastic materials to bond said later to said substrate.

2. A method according to claim 1, wherein said electrical conductors comprise carbon fibres.

3. A method according to claim 1, wherein said induction step comprises generating an alternating electromagnetic field with a frequency in the range 1-10 MHz.

4. A method according to claim 3, wherein said frequency of the electromagnetic field is in the range 2-4 MHz.

5. A method according to claim 1, wherein said thermoplastic layer comprises an aromatic polymer composite comprising layers of unidirectional carbon fibers coated in poly-ether-ether-ketone.

6. A method according to claim 1, further comprising positioning a further thermoplastic layer on said one thermoplastic layer wherein said one thermoplastic layer is positioned between said substrate and said further thermoplastic layer and wherein said step of applying an alternating electromagnetic field causes said further thermoplastic layer to be bonded to said substrate via said one layer.

7. A method according to claim 1, wherein said conductors in said layer of said thermoplastic layer extend transverse to said conductors in said layer of said substrate.

8. A method according to claim 1, wherein said electromagnetic field is applied by an induction coil having at least two laterally spaced turns.

9. A method according to claim 7, wherein said turns are positioned in a region of 30 mm×

30 mm.