US4015035A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of forming fiber-reinforced epoxy composite joints, and product thereof
Assignee: Lockheed Martin Corp
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Filing: 1974-12-09
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Granted: 1977-03-29
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Expires: 1994-12-09
Abstract
Abstract An improved manufacture including a fiber-reinforced epoxy composite joint, and the method for producing same, in which the fibers of each of the composite adherends pass through and are intermeshed across the joint bondline. A scarfed mating surface is prepared on the end of each of the adherend elements-to-be-joined, after which a chemical etching of the mating ends to obtain exposed lengths of filaments or fibers is provided. A sheet of unsupported adhesive material is inserted between the scarfed and etched mating surfaces prior to their layup, after which heat and pressure are applied for bonding the joint. The exposed fibers of each element cross the bondline to intermesh with those of the other element during the melting of the unsupported adhesive. This process increases the joint efficiency to 83% of the efficiency of a non-joined element.
Inventors
- 👤 Leiv H. Blad
- 👤 Robert F. Warkow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:01
CPC Classifications
B; B29; B29C; B29C65/00; B29C65/48; B29C65/50; B29C65/5057; B29C37/00; B29C37/0078; B29C37/0082; B29C66/00; B29C66/01; B29C66/02; B29C66/022; B29C66/0222; B29C66/026; B29C66/05; B29C66/10; B29C66/11; B29C66/116; B29C66/1162; B29C66/14; B29C66/303; B29C66/3032; B29C66/30321; B29C66/40; B29C66/41; B29C66/43; B29C66/70; B29C66/71; B29C66/72; B29C66/721; B29C66/7214; B29C66/72141; B29C66/73; B29C66/739; B29C66/7394; B29C66/73941; B29C65/4805; B29C65/481; B29C65/4815; B29C65/483; B29C65/4835; B29C65/82; B29C65/8207; B29C65/8215; B29C66/001; B29C66/0012; B29C66/0014; B29C66/00145; B29C66/0224; B29C66/02245; B29C66/114; B29C66/1142; B29C66/7212; B29C66/72143; B29C66/74; B29C66/742; B29C66/90; B29C66/91; B29C66/914; B29C66/9141; B29C66/919; B29C66/92; B29C66/929; B29C66/94; B29C66/949; B29K; B29K2063/00; B29K2105/00; B29K2105/06; B29K2105/08; B29K2105/10; B29K2105/101; B29K2277/00; B29K2307/00; B29K2307/02; B29K2309/00; B29K2309/08; H; H05; H05K; H05K1/00; H05K1/02; H05K1/03; H05K1/0313; H05K1/0353; H05K1/0366; H05K1/14; H05K1/142; H05K3/00; H05K3/0011; H05K3/0017; H05K3/36; Y; Y10; Y10T; Y10T428/00; Y10T428/19; Y10T428/192; Y10T428/195
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
128 words
In a method of producing an improved joint wherein at least one element thereof is an epoxy composite adherend internally reinforced with fibers oriented in a substantially parallel relation and having a prepared mating portion including a beveled surface, the improvement comprising the steps of removing by an etching process the epoxy matrix of the adherend at the beveled surface of the mating portion to expose lengths of its reinforcing fibers, and utilizing an unsupported adhesive material between the etched mating surface portion of such adherend and an element to be joined to said adherend, whereby subsequent bonding of such adherend, adhesive, and the joined element provides for the intermeshing and contiguity of the lengths of fibers between such joined adherend and element to produce an improved joint.
Claim 2
Dependent Claim
128 words
In a method of producing an improved joint wherein at least one element thereof is an epoxy composite adherend internally reinforced with fibers oriented in a substantially parallel relation and having a prepared mating portion including a beveled surface, the improvement comprising the steps of removing by an etching process the epoxy matrix of the adherend at the beveled surface of the mating portion to expose lengths of its reinforcing fibers, and utilizing an unsupported adhesive material between the etched mating surface portion of such adherend and an element to be joined to said adherend, whereby subsequent bonding of such adherend, adhesive, and the joined element provides for the intermeshing and contiguity of the lengths of fibers between such joined adherend and element to produce an improved joint.
Claim 3
Dependent Claim
12 words
The manufacture resulting from the practice of the method of claim 1.
Claim 4
Dependent Claim
16 words
The manufacture of claim 2 wherein the joined element also comprises a fiber-reinforced epoxy composite adherend.
Claim 5
Dependent Claim
33 words
The manufacture of claim 2 in which the reinforcing fibers of the adherend are selected from a class of substances comprising graphite, boron, glass, pitch blend, carbon, and high modulus organic fiber compositions.
Claim 6
Dependent Claim
88 words
In the practice of claim 1, the step of removing comprising masking the adherend whereby at least its mating surface portion is exposed introducing the mating surface portion into a chemical etching bath for a period of time whereby the desired length of fiber is exposed, withdrawing the adherend from the bath, stripping the adherend of its maskant, flushing the exposed lengths of fibers with an alkaline or acid neutralizer and water, and subjecting the adherend to a secondary cleaning step to remove any residual fluids or debris.
Claim 7
Dependent Claim
28 words
In the method of claim 5, the etching bath comprising a sulfuric acid sodium dichromate mixture, and the temperature of such bath being at least substantially 150° F.
Claim 8
Independent Claim
151 words
A method of producing an improved bonded joint between at least one fiber-reinforced epoxy composite adherend having a prepared mating portion as a first element and a second prepared element, such elements forming a manufacture upon being bonded, comprising the steps of: masking the adherend whereby at least such prepared mating portion is exposed, introducing the mating portion of the adherend to an etchant whereby the epoxy matrix of the adherend is dissolved to expose lengths of the fibers thereof, withdrawing the adherend from such etchant, stripping the maskant from the adherend, flushing the exposed lengths of the fibers with a neutralizer and water, subjecting the adherend to a secondary cleaning step to remove any residual fluids or debris, drying the adherend, laying up a joint formed by the elements, inserting an unsupported adhesive material between such elements during the laying up thereof, and bonding the elements to form the joint.
Claim 9
Independent Claim
151 words
A method of producing an improved bonded joint between at least one fiber-reinforced epoxy composite adherend having a prepared mating portion as a first element and a second prepared element, such elements forming a manufacture upon being bonded, comprising the steps of: masking the adherend whereby at least such prepared mating portion is exposed, introducing the mating portion of the adherend to an etchant whereby the epoxy matrix of the adherend is dissolved to expose lengths of the fibers thereof, withdrawing the adherend from such etchant, stripping the maskant from the adherend, flushing the exposed lengths of the fibers with a neutralizer and water, subjecting the adherend to a secondary cleaning step to remove any residual fluids or debris, drying the adherend, laying up a joint formed by the elements, inserting an unsupported adhesive material between such elements during the laying up thereof, and bonding the elements to form the joint.
Claim 10
Dependent Claim
9 words
The product made by the method of claim 7.
Claim 11
Dependent Claim
25 words
In the method of claim 7, the second prepared element comprising an adherend having similarly exposed lengths of fibers as those of the first element.
Claim 12
Dependent Claim
9 words
The manufacture made by the method of claim 9.
Claim 13
Dependent Claim
28 words
The method of claim 7 wherein the dissolving etchant is a sulfuric acid sodium dichromate mixture, and the temperature of the etchant is at least substantially 150° F.
Claim 14
Dependent Claim
25 words
The method of claim 11 wherein the period for exposing the mating portion of the adherend in the dissolving etchant is at least 12 hours.
Claim 15
Independent Claim
107 words
A method for producing a fiber-reinforced epoxy composite joint having improved strength characteristics comprising in combination the steps of: preparing the elements to be joined together by forming portions having complementary mating surfaces thereon, masking portions of such elements other than such mating surface portions, chemically etching such mating surface portions to expose lengths of fibers, stripping the maskant from such elements, neutralizing and cleaning the etched mating surface portions formed and lengths of fibers exposed, introducing an unsupported adhesive between the etched mating surface portions of the elements to be joined, laying up said elements and unsupported adhesive to form the joint, and bonding the joint.
Claim 16
Independent Claim
107 words
A method for producing a fiber-reinforced epoxy composite joint having improved strength characteristics comprising in combination the steps of: preparing the elements to be joined together by forming portions having complementary mating surfaces thereon, masking portions of such elements other than such mating surface portions, chemically etching such mating surface portions to expose lengths of fibers, stripping the maskant from such elements, neutralizing and cleaning the etched mating surface portions formed and lengths of fibers exposed, introducing an unsupported adhesive between the etched mating surface portions of the elements to be joined, laying up said elements and unsupported adhesive to form the joint, and bonding the joint.
Claim 17
Dependent Claim
10 words
The manufacture as made by the method of claim 13.
Claim 18
Dependent Claim
37 words
The method of claim 13 wherein said etching step comprises introducing the mating surface portions into a dissolving bath formed of a solution of sulfuric acid sodium dichromate mixture at a temperature of at least 150° F.
Claim 19
Dependent Claim
20 words
The method of claim 15 wherein the period of dissolving time in the bath is at least substantially 12 hours.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-03-28 | 1980-09-27 | 1981-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-28 | 1984-09-27 | 1985-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-28 | 1988-09-27 | 1989-03-29 | $7700.00 | Window Closed / Lapsed |