Joining composites using Z-pinned precured strips

• US 5,876,540 A
• Filed: 05/31/1996
• Issued: 03/02/1999
• Est. Priority Date: 05/31/1996
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Pannell, Shawn D.
• Primary Examiner(s): STEMMER, DANIEL J
• Application Number:
  US08/660,060
• Time in Patent Office: 1,005 Days
• Field of Search: 156/91, 156/92, 156/272.4, 156/275.5, 156/275.7, 156/306.9, 156/307.1, 428/119, 428/223
• US Class Current: 156/91
• CPC Class Codes: B29C 65/344 being a woven or non-woven fabric or being a mesh
• CPC Class Codes: B29C 65/3476 being metallic
• CPC Class Codes: B29C 65/364 being a woven or non-woven fabric or being a mesh
• CPC Class Codes: B29C 65/3648 said strip being perforated
• CPC Class Codes: B29C 65/3676 being metallic
• CPC Class Codes: B29C 65/368 with a polymer coating
• CPC Class Codes: B29C 65/564 hidden in the joint, e.g. dowels or Z-pins B29C65/603 takes precedence
• CPC Class Codes: B29C 65/76 Making non-permanent or releasable joints
• 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 66/4344 Joining substantially flat articles for forming fork connections, e.g. for making Y-shaped pieces
• CPC Class Codes: B29C 66/43441 with two right angles, e.g. for making T-shaped pieces, H-shaped pieces
• CPC Class Codes: B29C 66/474 said single elements being substantially non-flat
• CPC Class Codes: B29C 66/524 Joining profiled elements
• CPC Class Codes: B29C 66/532 Joining single elements to the wall of tubular articles, hollow articles or bars
• CPC Class Codes: B29C 66/54 Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles
• CPC Class Codes: B29C 66/61 Joining from or joining on the inside for making tubes by bending sheets and joining from the inside B29C53/387
• 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 66/72525 comprising honeycomb cores
• CPC Class Codes: B29C 66/727 : being porous, e.g. foam
• CPC Class Codes: B29C 66/73921 : characterised by the materials of both parts being thermoplastics
• CPC Class Codes: B29C 66/7394 : characterised by the material of at least one of the parts being a thermoset
• CPC Class Codes: B29C 66/8122 : characterised by the composition of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
• CPC Class Codes: B29C 66/81455 : being a fluid inflatable bag or bladder, a diaphragm or a vacuum bag for applying isostatic pressure inflatable element positioned between the joining tool and a backing-up part B29C66/82421
• CPC Class Codes: B29C 66/81821 : of the welding jaws
• CPC Class Codes: B29C 66/8322 : Joining or pressing tools reciprocating along one axis
• CPC Class Codes: B29C 70/24 : oriented in at least three directions forming a three dimensional structure
• CPC Class Codes: B29K 2025/06 : PS, i.e. polystyrene
• CPC Class Codes: B29K 2063/00 : Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2079/08 : PI, i.e. polyimides or derivatives thereof
• CPC Class Codes: B29K 2079/085 : Thermoplastic polyimides, e.g. polyesterimides, PEI, i.e. polyetherimides, or polyamideimides; Derivatives thereof
• CPC Class Codes: B29K 2307/04 : Carbon
• CPC Class Codes: B29K 2309/08 : Glass
• CPC Class Codes: B29K 2909/02 : Ceramics
• CPC Class Codes: B29L 2031/3076 : Aircrafts blades, propellers B29L2031/08
• CPC Class Codes: B64C 1/06 : Frames; Stringers; Longerons ; Fuselage sections
• CPC Class Codes: B64C 2001/0072 : from composite materials
• CPC Class Codes: B64C 2001/0081 : from metallic materials
• CPC Class Codes: Y02T 50/40 : Weight reduction
• CPC Class Codes: Y10T 428/24033 : including stitching and discrete fastener[s], coating or bond
• CPC Class Codes: Y10T 428/24058 : including grain, strips, or filamentary elements in respective layers or components in angular relation
• CPC Class Codes: Y10T 428/24116 : Oblique to direction of web
• CPC Class Codes: Y10T 428/24174 : including sheet or component perpendicular to plane of web or sheet
• CPC Class Codes: Y10T 428/24182 : Inward from edge of web or sheet
• CPC Class Codes: Y10T 428/249923 : Including interlaminar mechanical fastener

Abstract

Prefabricated composite detail parts use precured strips that include Z-pin reinforcement along the bond line. Each strip has Z-pin stubble protruding from opposed faces so that the pins are embedded into the detail parts when the joint forms.

Claims

1. A method for forming a reinforced joint at a bond line in composite structure, comprising the steps of:

(a) positioning along the bond line between at least two composite elements a Z-pinned precured strip,

the strip having reinforcing pins generally extending in the Z-direction, embedded in a cured resin and projecting on opposed faces of the strip to define stubble, the strip being positioned so that the Z-direction pins extend substantially perpendicular to or at an angle with the plane of the bond line;

(b) optionally, applying an adhesive on the interfaces between the strip and the elements;

(c) heating the bond line to connect the elements about the strip to form a joint containing Z-pin reinforcement.

2. The method of claim 1 wherein the composite elements are thermoplastic and heating the strip forms a thermoplastic weld between the strip and the composite elements.

3. The method of claim 1 wherein the Z-direction pins have a Young'"'"'s modulus of elasticity of generally greater than 10⁷ and, optionally, include barbs to increase their holding strength.

4. The method of claim 3 wherein the strip is a plurality of plies of fiber-reinforced resin or a laminated resin-metal foil composite.

5. A method for forming a reinforced joint at a bond line in composite structure, comprising the steps of:

(a) positioning along the bond line between at least two composite elements a Z-pinned precured strip,

the strip having reinforcing pins general extending in the Z-direction, embedded in a cured resin, and projecting on opposed faces of the strip to define stubble,

the strip also having a susceptor heatable with an induction coil the positioning placing the Z-direction pins so that the Z-direction pins extend substantially perpendicular to or at an angle with the plane of the bond line;

(b) optionally, applying an adhesive on the interfaces between the strip and the elements;

(c) heating the bond line to connect the elements about the strip to form a joint containing Z-pin reinforcement.

6. The method of claim 5 wherein the step of heating includes magnetically inducing eddy currents in the susceptor.

7. The method of claim 5 wherein the susceptor includes a metal mesh.

8. The method of claim 5 wherein the resin is a polyimide.

9. The method of claim 5 wherein the stubble is about 1/16th inch high and, optionally, include barbs to improve their holding strength.

10. The method of claim 5 further comprising the step of:

covering the stubble with uncured resin pad ups to fill at least one gap between the composite elements and the strip.

11. The method of claim 5 wherein the composite elements are thermoplastic and heating the strip forms a thermoplastic weld between the strip and the composite elements.

12. The method of claim 5 wherein the strip is a laminated resin-metal foil composite.

13. The method of claim 5 wherein the strip is thin enough to remain flexible so that the strip can assume the contour of the bond line.

14. A method for forming a reinforced joint at a bond line in composite structure, comprising the steps of:

(a) positioning along the bond line between at least two composite elements a Z-pinned precured strip,

the strip having reinforcing pins generally extending in the Z-direction, embedded in a cured resin and projecting on opposed faces of the strip to define stubble, the strip being positioned so that the Z-direction pins extend substantially perpendicular to or at an angle with the plane of the bond line;

(b) covering the stubble with uncured resin pad ups to fill a gap between one of the composite elements and the strip;

(c) optionally, applying an adhesive on the interfaces between the strip and the elements; and

(d) heating the bond line to connect the elements about the strip to form a joint containing Z-pin reinforcement.