# US 2014/0151925 A1 · Method for producing a closed-section portion of an aircraft provided with deformation sensors

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- Number: US 2014/0151925 A1
- Document ID: US20140151925A1
- Status: Published application
- Kind: A1
- Application number: 13/911,488
- Filed: 2013-06-06
- Published: 2014-06-05
- Earliest claimed: 2012-06-11
- Assignees: Alenia Aermacchi S.p.A.
- Applicants: Alenia Aermacchi S.P.A.
- Inventors: Sabato Inserra Imparato; Giuseppe Lauria; Sergio Recchia; Alberto Russolillo; Carlo Arnone; Vincenzo De Vita; Antonio Fiore
- Web page: https://patentgrep.com/patent/US20140151925A1

## CPC

- B29D 99/0014: {provided with ridges or ribs, e.g. joined ribs}
- B29C 65/5057: {positioned between the surfaces to be joined (B29C65/5035 takes precedence)}
- B29C 66/112: {Single lapped joints}
- B29C 66/1122: {Single lap to lap joints, i.e. overlap joints (B29C66/45, B29C66/472, B29C66/52272 take precedence)}
- B29C 66/131: {Single flanged joints, i.e. one of the parts to be joined being rigid and flanged in the joint area}
- B29C 66/524: {Joining profiled elements}
- B29C 66/5326: {said single elements being substantially flat}
- B29C 66/61: {Joining from or joining on the inside (for making tubes by bending sheets and joining from the inside B29C53/387)}
- B29C 66/636: {using a support which remains in the joined object}
- B29C 66/721: {Fibre-reinforced materials (B29C66/729 takes precedence)}
- 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)}
- B29C 65/4835: {Heat curing adhesives}
- B29C 66/7212: {characterised by the composition of the fibres}
- B29C 66/73112: {of different thermal expansion coefficient, i.e. the thermal expansion coefficient of one of the parts to be joined being different from the thermal expansion coefficient of the other part}
- B29C 66/73161: {Roughness or rugosity}
- B29L 2031/3076: {Aircrafts (blades, propellers B29L2031/08)}
- B64D 2045/0085: {Devices for aircraft health monitoring, e.g. monitoring flutter or vibration}
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- 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)
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT

## Abstract

A method for producing a closed-section portion of an aircraft wherein a strain gauge is glued on a first face of a flat tape that, in turn, is fastened on a face of a tool comprising a rigid elongated body covered by an extensible sack. The tool supporting the tape is arranged in a cavity of an aircraft structure. A vacuum is then created to obtain the expansion of the vacuum sack and perform the pressure gluing of the tape onto a wall of said cavity. The tool is subsequently extracted from the cavity. Upon conclusion of these operations, the tape is integrally fastened onto a wall of the cavity so that any deformation applied to this wall is transmitted to said strain gauge.

## Claims

### Claim 1

A method for producing a closed-section portion of an aircraft provided with deformation sensors comprising the steps of:
a) inserting inside a mould (2) equipped with a first part (2a) and a second part (2b):
at least a first sheet (3) of composite material,
at least a second sheet (4) of composite material facing the first sheet and spaced apart therefrom; and
interconnection elements (5) in a composite sheet material that extend between the first and the second sheets (3 and 4) of composite material to delimit an elongated cavity (7);
b) inserting a tool (10) (plug) inside the elongated cavity (7), said tool (10) comprising a rigid elongated body delimited by a number of flat faces (11) and having a cross-section corresponding to that of the cavity (7)—the entire length of said rigid body being covered by and enveloped in a tubular sack (12) made of a deformable material;
c) creating a vacuum in an autoclave inside which the mould is arranged to allow expansion of the sack (12), which presses against the walls of the cavity during a first heating cycle in which the sheets of composite material fuse with each other;
d) extracting the tool from the cavity (7) at the end of the first heating cycle after having re-established the original pressure—at the end of the first heating cycle said cavity is delimitated by rigid walls,
and characterized in that it further comprises the steps of:
e) preparing a flat tape (15) having dimensions (l1 by l2) that allow it to be deposited on a face (11a) of the tool (10) covered by a tubular sack (12) made of a deformable material;
f) permanently fastening a strain gauge (17) on said flat tape (15);
g) arranging said tape (15) on the tool with its first face (15a) carrying the strain gauge (17) facing the tool and the sack, and a second face (15b) facing the outside;
h) depositing an adhesive layer (23) on the second face (15b) of said tape (15);
i) inserting said tool (10) supporting said tape (15) in said cavity (7);
j) creating a vacuum and performing a second heating cycle to obtain the expansion of said vacuum sack (12), which performs the pressure gluing of said tape onto a wall of said cavity;
k) extracting said tool (10) from said cavity—at the end of said second heating cycle, said tape being integrally fixed on a wall of said cavity such that any deformations applied to said wall are transmitted to said strain gauge.

### Claim 2 (depends on 1)

The method according to claim 1, wherein said tape is made of fibreglass.

### Claim 3 (depends on 1)

The method according to claim 1 wherein said step f) comprises the step of gluing said strain gauge on said flat tape.

### Claim 4 (depends on 1)

The method according to claim 1, wherein a flat cable of flexible insulating material (25) , carrying a plurality of metal tracks (26) connectable to the terminals (17t) of said strain gauge (17), is arranged on the first face (15a) of the tape (15).

### Claim 5 (depends on 1)

The method according to claim 1, wherein said tape is secured on the tubular sack (12) of said covered tool (10) by means of double-sided adhesive tape.

### Claim 6 (depends on 1)

The method according to claim 1, wherein a decontamination and degreasing step is carried out on the area of the tape on which said strain gauge is arranged.

### Claim 7 (depends on 1)

The method according to claim 1, wherein a roughing step is carried out on the area of the tape on which said strain gauge is arranged.

### Claim 8 (depends on 1)

The method according to claim 1, wherein a control step is carried out in which the complete fastening of said strain gauge on said tape is checked.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the step of arranging a ventilation fabric and a separator film between said tape (15) and said tubular sack (12) is included.

### Claim 10 (depends on 1)

The method according to claim 1, wherein said tape (15) has a lower coefficient of expansion under load than that of the structure that delimits a wall of said cavity.