# US 8,771,443 B2 · Method of fabricating a composite laminate enabling structural monitoring using electromagnetic radiation

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- Number: US 8,771,443 B2
- Document ID: US8771443B2
- Status: Granted
- Kind: B2
- Application number: 13/344,182
- Filed: 2012-01-05
- Published: 2013-07-11
- Granted: 2014-07-08
- Earliest claimed: 2012-01-05
- Assignees: The Boeing Company
- Applicants: Mark J. Clemen, Jr.
- Inventors: Mark J. Clemen, Jr.
- Web page: https://patentgrep.com/patent/US8771443B2

## CPC

- B32B 37/18: involving the assembly of discrete sheets or panels only
- 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)}
- B32B 5/12: characterised by the relative arrangement of fibres or filaments of {different layers, e.g. the fibres or filaments being parallel or perpendicular to each other}
- B32B 7/023: Optical properties
- B32B 27/08: of synthetic resin
- B32B 27/12: next to a fibrous or filamentary layer
- B32B 27/38: comprising epoxy resins
- B32B 41/00: Arrangements for controlling or monitoring lamination processes; Safety arrangements
- G01N 22/02: Investigating the presence of flaws
- B32B 2262/108: Rockwool fibres
- B32B 2307/212: Electromagnetic interference shielding
- B32B 2307/418: Refractive
- B32B 2307/732: Dimensional properties
- B32B 2605/18: Aircraft
- Y10T 428/24058: including grain, strips, or filamentary elements in respective layers or components in angular relation
- Y10T 428/24124: Fibers
- Y10T 428/24942: including components having same physical characteristic in differing degree
- Y10T 428/2495: Thickness [relative or absolute]
- Y10T 428/31511: Of epoxy ether
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- 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)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Electromagnetic radiation scanning is used to monitor the integrity of a composite laminate structure. The laminate is designed to be optically resonant at the frequency of the radiation, allowing the inconsistencies in the laminate to be detected and mapped.

## Claims

### Claim 1

A method of fabricating a composite laminate enabling detection of inconsistencies in the composite laminate using electromagnetic radiation scanning, comprising:
laminating a stack of at least two resin layers;
selecting an approximate thickness of each of the at least two resin layers based on a preselected electromagnetic radiation frequency; and
selecting a resin for each of the at least two resin layers that results in the laminated stack being substantially resonant at the preselected electromagnetic radiation frequency.

### Claim 2 (depends on 1)

The method of claim 1, wherein selecting the approximate thickness of each of the at least two resin layers includes calculating the thickness of the layer using the formula:
t
i
=
λ
n
i
⁢
(
k
i
+
1
4
)
where ti is the thickness of the layer,
ni is an index of refraction of the layer,
λ is a wavelength of light corresponding to the preselected electromagnetic radiation frequency, and
ki is an integer greater than or equal to 0.

### Claim 3 (depends on 1)

The method of claim 1, wherein selecting the resin includes determining indices of refraction of the resin that cause each of the at least two resin layers to be anti-reflective.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
placing unidirectional reinforcement fibers between the at least two resin layers.

### Claim 5 (depends on 4)

The method of claim 4, further comprising:
arranging the unidirectional reinforcement fibers to minimize interaction between the unidirectional reinforcement fibers and electromagnetic radiation at the preselected electromagnetic radiation frequency such that the electromagnetic radiation is capable of penetrating an entire depth of the composite laminate.

### Claim 6 (depends on 4)

The method of claim 4, wherein:
the unidirectional reinforcement fibers comprise first unidirectional reinforcement fibers and second unidirectional reinforcement fibers, and further comprising:
arranging the first unidirectional reinforcement fibers and the second unidirectional reinforcement fibers such that an orientation of the first unidirectional reinforcement fibers is substantially perpendicular to an orientation of the second unidirectional reinforcement fibers.

### Claim 7 (depends on 4)

The method of claim 4, wherein the unidirectional reinforcement fibers comprise carbon fibers.

### Claim 8 (depends on 4)

The method of claim 4, further comprising:
arranging the unidirectional reinforcement fibers to minimize interaction between the unidirectional reinforcement fibers and electromagnetic radiation at a specific electromagnetic wavelength, polarization, and phase such that the electromagnetic radiation is capable of penetrating an entire depth of the composite laminate.

### Claim 9 (depends on 8)

The method of claim 8, wherein the electromagnetic radiation is circularly polarized.

### Claim 10 (depends on 1)

The method of claim 1, wherein the preselected electromagnetic radiation frequency is in the microwave region.

### Claim 11 (depends on 1)

The method of claim 1, wherein the at least two resin layers comprise fiber reinforced synthetic resin.

### Claim 12 (depends on 11)

The method of claim 11, wherein the fiber reinforced synthetic resin comprises carbon fiber reinforced epoxy.