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GB2256611A - Manufacture of perforated composite structures - Google Patents

Manufacture of perforated composite structures Download PDF

Info

Publication number
GB2256611A
GB2256611A GB9112766A GB9112766A GB2256611A GB 2256611 A GB2256611 A GB 2256611A GB 9112766 A GB9112766 A GB 9112766A GB 9112766 A GB9112766 A GB 9112766A GB 2256611 A GB2256611 A GB 2256611A
Authority
GB
United Kingdom
Prior art keywords
sheet
flexible sheet
rods
projections
laying over
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9112766A
Other versions
GB2256611B (en
GB9112766D0 (en
Inventor
Martin Moss
Roger Duffy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems PLC
Original Assignee
British Aerospace PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Aerospace PLC filed Critical British Aerospace PLC
Priority to GB9112766A priority Critical patent/GB2256611B/en
Publication of GB9112766D0 publication Critical patent/GB9112766D0/en
Publication of GB2256611A publication Critical patent/GB2256611A/en
Application granted granted Critical
Publication of GB2256611B publication Critical patent/GB2256611B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00Ancillary operations in connection with laminating processes
    • B32B38/04Punching, slitting or perforating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B26HAND CUTTING TOOLS; CUTTING; SEVERING
    • B26FPERFORATING; PUNCHING; CUTTING-OUT; STAMPING-OUT; SEVERING BY MEANS OTHER THAN CUTTING
    • B26F1/00Perforating; Punching; Cutting-out; Stamping-out; Apparatus therefor
    • B26F1/24Perforating by needles or pins
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00Moulds or cores; Details thereof or accessories therefor
    • B29C33/0033Moulds or cores; Details thereof or accessories therefor constructed for making articles provided with holes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00Moulds or cores; Details thereof or accessories therefor
    • B29C33/56Coatings, e.g. enameled or galvanised; Releasing, lubricating or separating agents
    • B29C33/68Release sheets
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/42Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
    • B29C70/44Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/54Component parts, details or accessories; Auxiliary operations, e.g. feeding or storage of prepregs or SMC after impregnation or during ageing
    • B29C70/545Perforating, cutting or machining during or after moulding
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29DPRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D24/00Producing articles with hollow walls
    • B29D24/002Producing articles with hollow walls formed with structures, e.g. cores placed between two plates or sheets, e.g. partially filled
    • B29D24/005Producing articles with hollow walls formed with structures, e.g. cores placed between two plates or sheets, e.g. partially filled the structure having joined ribs, e.g. honeycomb
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/10Isostatic pressing, i.e. using non-rigid pressure-exerting members against rigid parts or dies
    • B29C43/12Isostatic pressing, i.e. using non-rigid pressure-exerting members against rigid parts or dies using bags surrounding the moulding material or using membranes contacting the moulding material

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Forests & Forestry (AREA)
  • Laminated Bodies (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Abstract

A curved composite structure suitable for use in noise suppression panelling is fabricated by laying over a curved former (4) a series of rods (5) incorporating a row of pins (6), laying over the rods (5) a perforated, flexible sheet (7) so that the pins (6) protrude through the perforations, and laying over the flexible sheet (7) a prepreg carbon fibre sheet (8) so that this sheet (8) is perforated by the pins. The resulting assembly is then cured. After curing the prepreg sheet is peeled away from the tooling (4, 5, 6, 7) which can be re-used. The method allows easy removal of cured sheets (8) from the tooling without damage to either sheet (8) or pins (6). <IMAGE>

Description

Manufacture of Perforated Composite Structures This invention relates to a fibre-reinforced composite structure suitable for use in noise suppression panelling.
It is known for turbofan aeroengines to contain noise suppression panelling in regions such as the thrust reverser, inlet cowl and translating cowl assembly.
Referring to Fig 1, each panel consists of a honeycomb core 1 having a solid backsheet 2 and a perforated facesheet 3.
One known method of fabrication of the perforated facesheets involves punching or drilling the perforations in sheets of metal or pre-cured carbon fibre composites. When composites are used, however, it has been found that a punching or drilling technique damages the fibres to such an extent that delamination often occurs. In such cases where delamination is severe, the facesheet has to be discarded.
A second known method of fabrication of the perforated facesheets is described in GB1352198 and involves forming the perforations during the curing process. For example, a pre-impregnated fibre sheet is laid over a mould which comprises a base plate fitted with an array of rigid upstanding projections. The projections are allowed to pierce the fibre sheet which is subsequently cured in situ.
However, it was found that if the baseplate had a curvature for facilitating the manufacture of a curved facesheet, then removal of the cured facesheet from the baseplate and projections was extremely difficult because the contour of the facesheet tended to lock the projections in place.
Consequently a large number of projections were torn from the baseplate and remained in the facesheet, thus blocking the perforations.
To overcome this disadvantage, a second method was proposed wherein the baseplate and projections were formed (as a unitary structure) of flexible material, in particular, of a plastics material.
The inventors have found, however, that projections made from plastics cannot be made sharp enough to adequately pierce the fibre sheet.
The present invention aims to provide a method of producing either a flat or a curved perforated composite sheet by a process which involves manufacturing the perforations during the curing process and in which said method has none of the aforementioned disadvantages.
A further object of the invention is to provide a method for producing flat or curved sound-absorbing panelling in which said panelling incorporates a perforated composite sheet.
According to a first aspect of the invention, there is provided a method of manufacturing a perforated composite sheet including the steps of: laying over a former a series of spaced apart rigid rods, each rod incorporating a row of rigid, pointed, upstanding projections; laying over said series of rods a flexible sheet incorporating perforations so that said projections protrude through the perforations in the flexible sheet; laying over the flexible sheet a fibre-reinforced resin sheet so that the projections perforate the resin sheet; subjecting the resulting assembly to heat and pressure so that the resin is cured within the resin sheet; and peeling off the rods and flexible sheet from the cured resin sheet.
According to a second aspect of the invention, there is provided a method of manufacturing noise suppression panelling including the steps of: laying over a former a series of spaced-apart rigid rods, each rod incorporating a row of rigid, pointed, upstanding projections; laying over the series of rods a flexible sheet incorporating perforations so that the projections protrude through the perforations in the flexible sheet; laying over the flexible sheet a fibre reinforced resin sheet so that the projections perforate the resin sheet; laying over the resin sheet a sound-absorbing honeycomb structure; laying over the honeycombed structure a fibre-reinforced resin skin; subjecting the resulting assembly to heat and pressure so that the resin is cured; and peeling off the rods and flexible sheet from the cured resin sheet.
Owing to the rigidity of the projections and the flexibility of the flexible sheet, the cured resin sheet can be removed easily, without damage to any of the projections, even when a curved former is employed.
Preferably, the projections are made from metal so that a sharp point can be incorporated therewith.
The rods may be made from metal also e.g. brass, or carbon fibre composite material. They could incorporate more than one row of projections.
The flexible sheet can be made from spring steel or carbon fibre composite for example.
The perforations could be punched or drilled in the flexible sheet.
The former can be made from any suitable stable material and can be flat or curved. Examples of suitable materials will be well known to those familiar with composite tooling.
Some embodiments of the invention will now be described by way of example only with reference to the drawings of which: Figure 1 is a partly cut-away perspective view of noise suppression panelling; Figure 2 is a perspective view of apparatus suitable for performing a method of manufacturing a composite structure in accordance with the invention; Figure 3 is a sectional view of some of the components shown in Figure 2; and Figure 4 is a sectional view of apparatus suitable for performing a method of manufacturing a noise suppression panel in accordance with the invention.
Referring to Figure 2, the apparatus illustrated comprises a curved former 4 which supports a series of spaced-apart metal bars 5. Each bar 5 is provided with a row of sharply-pointed metal pins 6. Positioned over the bars 5 is a flexible sheet 7 made of spring steel. The flexible sheet 7 is provided with perforations through which the metal pins 6 pass. The flexible sheet 7 follows the contour of the former 4, being held in place by its own weight.
The apparatus is used to manufacture a curved, perforated structure as follows. Firstly, the upper surface of the flexible sheet 7 is coated with a release agent.
Next, a pre-impregnated, carbon fibre resin sheet 8 is laid over the flexible sheet 7 and pressed down so that the pins 6 perforate the resin sheet 8 and so that the resin sheet 8 follows the contour of the flexible sheet 7 and former 4.
The resulting assembly is placed in a vacuum bag and then in a autoclave until the resin has cured. The cured, perforated resin sheet 8 and flexible sheet 7 are then peeled apart (see Figure 3), the space between bars 5 allowing the required degree of flexibility. The former 4, pinned bars 5 and flexible sheet 7 can be used again to make further perforated structures.
Manufacture of noise suppression panelling will now be described with reference to Figure 4. The apparatus required for this method is the same as has been described with reference to Figure 2, viz a curved former 4 carrying spaced apart pinned bars 5 and a flexible perforated sheet 7.
in use, a coating of release agent is applied to the upper surface of the flexible sheet 7. Next, a pre-impregnated carbon fibre resin sheet 8 is laid over the flexible sheet 7 so that the pins 6 pierce the resin sheet 8. The upper surface of the resin sheet is coated with a film adhesive 9. Then a sound-absorbing pre-formed honeycomb core structure 10 is placed over the resin sheet 8 and held in place by the pins 6. The pins 6 are made sufficiently short so that they do not protrude beyond the upper surface of the honeycomb structure 10. A further adhesive film 11 is applied to the upper surface of the honeycomb structure 10 and finally a second pre-impregnated carbon fibre resin sheet 12 is pressed onto the adhesive film 11.
Again, the entire assembly is vacuum bagged and placed in an autoclave until the resins have cured.
The resulting curved noise-suppression panel composed of a perforated face sheet, honeycomb core and back sheet is then easily peeled away from the flexible sheet 7 and pins 6.
Using this method it has been found that 100% of the perforations are unblocked by resin or adhesive. This is because the pins 6 remain protruding into the honeycomb core 10 throughout the curing process.
In this method the second resin sheet 12 could initially be uncured or precured.
It has also been found that a higher skin to core bond peel strength is achievable compared with noise suppression panelling fabricated by other methods. This is because when bonding a perforated carbon fibre composite skin to honeycomb core it is usually necessary to reticulate a layer of film adhesive to the top of the cell wall for which the film adhesive must be carrierless. However, when bonding the perforated skin to core whilst positioned on the pins it is possible to use a film adhesive with a carrier which guarantees a more uniform distribution of adhesive thickness.

Claims (12)

1. A method of manufacturing a perforated composite sheet including the steps of: laying over a former a series of spaced apart rigid rods, each rod incorporating a row of rigid, pointed, upstanding projections; laying over said series of rods a flexible sheet incorporating perforations so that said projections protrude through the perforations in the flexible sheet; laying over the flexible sheet a fibre-reinforced resin sheet so that the projections perforate the resin sheet; subjecting the resulting assembly to heat and pressure so that the resin is cured within the resin sheet; and peeling off the rods and flexible sheet from the cured resin sheet.
2. A method of manufacturing noise suppression panelling including the steps of: laying over a former a series of spaced-apart rigid rods, each rod incorporating a row of rigid, pointed, upstanding projections; laying over the series of rods a flexible sheet incorporating perforations so that the projections protrude through the perforations in the flexible sheet; laying over the flexible sheet a fibre reinforced resin sheet so that the projections perforate the resin sheet; laying over the resin sheet a sound-absorbing honeycomb structure; laying over the honeycombed structure a fibre-reinforced resin skin; subjecting the resulting assembly to heat and pressure so that the resin is cured; and peeling off the rods and flexible sheet from the cured resin sheet.
3. A method according to claim 1 or claim 2 in which each rod incorporates more than one row of rigid, pointed, upstanding projections.
4. A method according to any preceding claim in which the rigid, pointed, upstanding projections are made from metal.
5. A method according to any preceding claim in which the rods are made from metal.
6. A method according to any of claims 1 to 4 in which the rods are made from carbon fibre composite material.
7. A method according to any preceding claim in which the flexible sheet is made from spring steel.
8. A method according to any of claims 1 to 6 in which the flexible sheet is made from carbon fibre composite material.
9. A method according to any of claims 2 to 8 in which the fibre-reinforced resin skin is uncured before the assembly is subjected to heat and pressure.
10. A method according to any of claims 2 to 8 in which the fibre-reinforced resin skin is precured before the assembly is subjected to heat and pressure.
11. A method of manufacturing a perforated composite sheet substantially as hereinbefore described with reference to Figs. 2 and 3 of the drawings.
12. A method of manufacturing noise suppression panelling substantially as hereinbefore described with reference to Fig. 4 of the drawings.
GB9112766A 1991-06-13 1991-06-13 Manufacture of perforated composite structures Expired - Fee Related GB2256611B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9112766A GB2256611B (en) 1991-06-13 1991-06-13 Manufacture of perforated composite structures

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9112766A GB2256611B (en) 1991-06-13 1991-06-13 Manufacture of perforated composite structures

Publications (3)

Publication Number Publication Date
GB9112766D0 GB9112766D0 (en) 1991-07-31
GB2256611A true GB2256611A (en) 1992-12-16
GB2256611B GB2256611B (en) 1995-05-31

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0665097A2 (en) * 1994-01-13 1995-08-02 British Aerospace Public Limited Company Method and apparatus for molding structural panels with a corrugated core
GB2323056A (en) * 1997-03-14 1998-09-16 Gkn Westland Helicopters Ltd Method of forming a composite panel provided with a plurality of holes
FR2763881A1 (en) * 1997-05-30 1998-12-04 Peguform France Piercing of composite fibre panel damage during hole formation for fastenings
EP0894613A1 (en) * 1997-07-30 1999-02-03 The Boeing Company Method for forming a composite acoustic panel
EP1401658A1 (en) * 2001-04-06 2004-03-31 Marion Composites, A division of Advanced Technical Products, Inc. Method of manufacturing a hollow section, grid stiffened panel
EP1985278A2 (en) * 1997-12-10 2008-10-29 Playtex Products, Inc. Method and apparatus for manufacture of vent disc for baby bottle
WO2009109863A3 (en) * 2008-03-07 2010-05-20 Giuseppe Meli Device and method for the production of cellular materials
GB2478312A (en) * 2010-03-02 2011-09-07 Gkn Aerospace Services Ltd Manufacturing composite acoustic panels
GB2486120A (en) * 2010-03-02 2012-06-06 Gkn Aerospace Services Ltd Manufacturing composite acoustic panels
WO2017093710A1 (en) * 2015-11-30 2017-06-08 Short Brothers Plc Methods, precursors and abrasive blasting masks for manufacturing noise attenuating devices
EP3616864A1 (en) * 2018-08-29 2020-03-04 The Boeing Company Method and system for forming holes within an uncured composite sheet, and method for forming a composite structure
US11001017B2 (en) * 2017-07-11 2021-05-11 Faurecia Automotive Industrie Manufacturing method of a component of automotive vehicle equipment and associated component of equipment

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106042052B (en) * 2016-07-01 2018-04-20 无锡格菲电子薄膜科技有限公司 A kind of array card punch and Electric radiant Heating Film for film surface punching is vented the method for fast mfg of array hole

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1352198A (en) * 1970-07-02 1974-05-08 Gen Electric Manufacture of perforated reinforced plastics members
GB2025302A (en) * 1978-07-15 1980-01-23 Rolls Royce Perforating Sheets

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1352198A (en) * 1970-07-02 1974-05-08 Gen Electric Manufacture of perforated reinforced plastics members
GB2025302A (en) * 1978-07-15 1980-01-23 Rolls Royce Perforating Sheets

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0665097A2 (en) * 1994-01-13 1995-08-02 British Aerospace Public Limited Company Method and apparatus for molding structural panels with a corrugated core
EP0665097A3 (en) * 1994-01-13 1996-02-07 British Aerospace Method and apparatus for molding structural panels with a corrugated core.
GB2323056A (en) * 1997-03-14 1998-09-16 Gkn Westland Helicopters Ltd Method of forming a composite panel provided with a plurality of holes
FR2763881A1 (en) * 1997-05-30 1998-12-04 Peguform France Piercing of composite fibre panel damage during hole formation for fastenings
EP0894613A1 (en) * 1997-07-30 1999-02-03 The Boeing Company Method for forming a composite acoustic panel
EP1985278A2 (en) * 1997-12-10 2008-10-29 Playtex Products, Inc. Method and apparatus for manufacture of vent disc for baby bottle
EP1985278A3 (en) * 1997-12-10 2009-03-25 Playtex Products, Inc. Method and apparatus for manufacture of vent disc for baby bottle
EP1401658A1 (en) * 2001-04-06 2004-03-31 Marion Composites, A division of Advanced Technical Products, Inc. Method of manufacturing a hollow section, grid stiffened panel
EP1401658A4 (en) * 2001-04-06 2008-01-23 Gen Dynamics Armament & Tech Method of manufacturing a hollow section, grid stiffened panel
US20130171409A1 (en) * 2008-03-07 2013-07-04 Giuseppe Meli Device for the production of cellular materials
US8343404B2 (en) 2008-03-07 2013-01-01 Giuseppe Meli Method for the production of cellular materials
WO2009109863A3 (en) * 2008-03-07 2010-05-20 Giuseppe Meli Device and method for the production of cellular materials
US9273631B2 (en) 2010-03-02 2016-03-01 Gkn Aerospace Services Limited Seamless acoustic liner
GB2486120B (en) * 2010-03-02 2012-10-31 Gkn Aerospace Services Ltd Seamless acoustic liner
GB2478312B (en) * 2010-03-02 2012-08-22 Gkn Aerospace Services Ltd Seamless acoustic liner
GB2486120A (en) * 2010-03-02 2012-06-06 Gkn Aerospace Services Ltd Manufacturing composite acoustic panels
GB2478312A (en) * 2010-03-02 2011-09-07 Gkn Aerospace Services Ltd Manufacturing composite acoustic panels
WO2017093710A1 (en) * 2015-11-30 2017-06-08 Short Brothers Plc Methods, precursors and abrasive blasting masks for manufacturing noise attenuating devices
CN108290637A (en) * 2015-11-30 2018-07-17 肖特兄弟公司 Method, precursor and sandblasting mask for manufacturing sound attenuation
CN108290637B (en) * 2015-11-30 2022-03-01 肖特兄弟公司 Method for manufacturing noise attenuation device, precursor and blasting mask
US11001017B2 (en) * 2017-07-11 2021-05-11 Faurecia Automotive Industrie Manufacturing method of a component of automotive vehicle equipment and associated component of equipment
EP3616864A1 (en) * 2018-08-29 2020-03-04 The Boeing Company Method and system for forming holes within an uncured composite sheet, and method for forming a composite structure
US10953612B2 (en) 2018-08-29 2021-03-23 The Boeing Company Method and system for forming holes within an uncured composite sheet, and method for forming a composite structure

Also Published As

Publication number Publication date
GB2256611B (en) 1995-05-31
GB9112766D0 (en) 1991-07-31

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 20060613