# US 5,705,795 A · Gap filling for thermoplastic welds

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,705,795 A
- Document ID: US5705795A
- Status: Granted
- Kind: A
- Application number: 08/467,509
- Filed: 1995-06-06
- Granted: 1998-01-06
- Earliest claimed: 1995-06-06
- Assignees: The Boeing Company
- Inventors: Robert C. Anderson; Stephen Christensen; Todd R. Peterson
- Web page: https://patentgrep.com/patent/US5705795A

## CPC

- B29C 65/3644: {being a ribbon, band or strip}
- B29C 65/364: {being a woven or non-woven fabric or being a mesh}
- B29C 65/368: {with a polymer coating}
- B29C 66/301: {Three-dimensional joints, i.e. the joined area being substantially non-flat (B29C66/5223, B29C66/5224, B29C66/5225 take precedence)}
- B29C 66/524: {Joining profiled elements}
- B29C 66/5326: {said single elements being substantially flat}
- B29C 66/721: {Fibre-reinforced materials (B29C66/729 takes precedence)}
- B29C 66/7212: {characterised by the composition of the fibres}
- B29C 66/73116: {of different melting point, i.e. the melting point of one of the parts to be joined being different from the melting point of the other part}
- B29C 66/73921: {characterised by the materials of both parts being thermoplastics}
- B29C 66/8221: {Scissor or lever mechanisms, i.e. involving a pivot point}
- B29C 66/8242: {Pneumatic or hydraulic drives (using fluid pressure directly acting on the parts to be joined B29C66/8266)}
- B29C 66/836: {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)}
- B29C 66/1122: {Single lap to lap joints, i.e. overlap joints (B29C66/45, B29C66/472, B29C66/52272 take precedence)}
- B29C 66/71: {characterised by the composition of the plastics material of the parts to be joined (welding bar compositions B29C65/125)}
- B29C 66/72141: {Fibres of continuous length}
- B29C 66/72143: {Fibres of discontinuous lengths}
- B29C 66/7394: {characterised by the material of at least one of the parts being a thermoset}
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)

## Abstract

Thermoplastic welding is an emerging technology targeted at significantly reducing the cast of manufacture of aerospace structure by eliminating fasteners and the touch labor associated with fasteners to prepare, install, and inspect the assemblies. Thermoplastic welds, however, suffer from significant residual tensile strain caused by differences in the coefficient of thermal expansion between the carbon fiber reinforced composite laminates and the unreinforced weld. Holding fiber reinforcement to the weld using a structural susceptor which is a laminate of alternating layers of thermoplastic resin and fiber reinforcement sandwiching a conventional metal susceptor alleviates this strain. The structural susceptor can be peeled in selected locations to fill the gap between the laminates, eliminating costly profilometry of the faying surfaces and the associated problem of resin depletion where machining occurred to match the faying surfaces. The peeled susceptor is complementary in contour to the gap it will fill.

## Claims

### Claim 1

A method for thermoplastic welding to join two fiber-reinforced composite laminates with a susceptor encased in a thermoplastic resin, comprising the steps of:
(a) positioning at least two laminates to define a bondline;
(b) positioning a susceptor along the bondline;
(c) adding fiber reinforcement and additional thermoplastic resin where necessary to fill gaps along the bondline between the laminates and the susceptor; to fill gap, thereby eliminating resin deficient regions otherwise occurring; and
(d) heating the susceptor to melt the resin and to form a thermoplastic weld between the laminates.

### Claim 2 (depends on 1)

A product obtained by the process of claim 1.

### Claim 3

A method for filling gaps along a bondline between faying surfaces of fiber-reinforced resin composite laminates prior to their joined with a thermoplastic weld, the weld containing a susceptor having metal sheet encased in fiber-reinforced, thermoplastic resin, the method comprising the steps of:
(a) adjusting the thickness, number of plies, or both of the fiber-reinforced, thermoplastic resin along the bondline to fill gaps between the laminates, and
(b) welding the laminates by heating the susceptor to melt the thermoplastic resin.

### Claim 4 (depends on 1)

A product obtained by the process of claim 1.

### Claim 5

A method for thermoplastic welding to join at least two prefabricated resin composite laminates using a susceptor along a bondline, the susceptor being capable of heating to a temperature at which a welding resin in the bondline melts, comprising the steps of:
(a) positioning the laminates to define the bondline;
(b) identifying the gap profile between the positioned laminates along the bondline;
(c) tailoring the susceptor by peeling at least one filler layer associated with a metal sheet in the susceptor so that the susceptor profile substantially complements the gap profile;
(d) positioning the tailored susceptor along the bondline;
(e) welding the laminates together along the bondline by inducing eddy currents in the metal sheet of the susceptor to heat the bondline to at least the melting temperature,
wherein the susceptor comprises a metal film embedded in a thermoplastic resin and a plurality of additional filler layers sandwiching the metal film, each filler layer including a thermoplastic resin film and a fiber reinforcement.

### Claim 6 (depends on 5)

A product obtained by the process of claim 5.

### Claim 7 (depends on 6)

The product of claim 6 being a wingskin welded to a spar.

### Claim 8 (depends on 7)

The product of claim 7 wherein the wingskin and spar are reinforced with carbon fiber and wherein the fiber reinforcement in the filler layer is fiberglass.