Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
  • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
  • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T50/00—Aeronautics or air transport
  • Y02T50/40—Weight reduction

Definitions

• the present invention relates to composite honeycomb sandwich structure, and particularly to resin impregnated fabric sheets forming outer skins adhered on opposed surfaces of a honeycomb core with an intermediate barrier to eliminate resin flow from the skins to the core.
• U.S. Patent 5,445,861 describes composite sandwich structure for sound absorption (acoustic insulation) and other applications.
• the sandwich structures have seven layers as follows:
• microcracking that originated in the migrated resin could propagate to the bond line and degrade mechanical performance. Such microcracking potential poses a catastrophic threat to the integrity of the panel and dictates that flow be eliminated or, at least, controlled.
• the added tiedown ply means mat three or more tiedown plys will be included in d e final preform of the panel.
• tiiere will also be tiedown plys on die outer surfaces of die panel and possibly between d e laminate and die adhesive barrier film.
• Each tiedown ply extends outwardly from the part beyond die net trim line of die finished product.
• die tiedown plies are secured individually and sequentially to die layup mandrel witii tape. Especially when using low density core it is important to fix the relation of the plies to one another and to the mandrel. Failure of die tape results in facesheet ply wrinkles or core crush.
• die present invention relates to an improvement in the manufacture of composite structure, especially composite honeycomb sandwich structure, where tiedown plys are used to secure the part during autoclave curing at elevated temperature and pressure.
• tiedown plys are used to secure the part during autoclave curing at elevated temperature and pressure.
• a lower temperature curing adhesive to cure and to connect the several plys together during the early stages of autoclave curing prior to applying pressure.
• Fig. 1 illustrates a typical composite honeycomb sandwich structure.
• Fig. 2 is a schematic, partial sectional view of die skin-core interface in sandwich structure having a scrim-supported barrier film to prevent resin flow from the skin to the core.
• the supported film adhesive and barrier film layers in the sandwich structure also function as corrosion barriers between the skin 102 and core 106 in the case where the core is metal, such as aluminum, and d e skin includes a galvanically dissimilar material, such as carbon fiber.
• Core crush 200 occurs in the chamfer region 155 when the barrier film 1 10 and core 106 slip relative to the facesheets 102 when autoclave pressure is applied and when the resin is melted. As shown in Fig. 5, the barrier films 100 and core 106 have moved toward the right to compress the core in the chamfer region 155 to produce die core crush 200. The skin 102 has sagged in the edgeband region 160 where d e core moved away.
• die improved honeycomb sandwich panel includes at least one tiedown ply 150 in contact with the core 106 along a chamfer 155.
• a chamfer i.e. an angled transition in the core, often at the edgeband 160
• Such a chamfer typically occurs around the periphery ofthe panel, but it might also occur intermediate of the panel at join lines or hard points where fasteners or pass-throughs might be necessary in the assembled structure.
• a single ply 150 of carbon fiber or fiberglass fabric witii a conventional 0/90 fiber orientation in the fabrication of bismaleimide panels having 5 or 8 Ib/ft ⁇ HRP core, like Hartz et al. describe.
• the tiedown ply 150 functions to prohibit or to limit slippage ofthe skin relative to the core so as to reduce core crush otherwise attributable to the slippage.
• the tiedown ply 150 anchors the core with the inherent roughness of the fabric when the preform is heated during the autoclave processing cycle and me matrix resin softens, melts, and, for high flow resins, essentially liquefies. Witii these panels, we can save between 2.5-4 lb/ft ⁇ of core because we can use lighter density honeycomb core without suffering core crush. For a fighter, this change can save as much as 25 lbs per vehicle.
• the tiedown ply 150 is a narrow, peripheral strip tiiat contacts the core 106 along at least a portion of the chamfer 155 for about 1 inch overlap with the core 106 and extends outward into the edgeband 160 beyond d e trimline 165 of the part.
• the tiedown ply 150 might be on either the flat side of the chamfer or the angled surface (which is how we show it in Fig. 6).
• the key factor is that the tiedown ply 150 contact die core beneath the adhesive and barrier film 110 which is used to bond d e laminate skin to the core.
• the tiedown ply 150 is cutaway everywhere in the body of die part otiier than a narrow peripheral area in the chamfer region, and forms a peripheral frame around d e edge of the panel. In this way, the tiedown ply 150 allows an adhesive interface between the core 106 and die skins 102 in the panel region.
• the tiedown plies 150 and 175 extend through die edgeband 160 beyond the net trim line 165 to anchoring points that we tape to the layup mandrel.
• a low curing (i.e. 121°C for BMI panels) film adhesive 180 between die tiedown plies just outside d e net trim line of the part.
• the film adhesive 180 eliminates movement of one ply relative to the others when we apply pressure during the autoclave curing cycle. Curing at a temperature of about 100 - 150°F below the curing temperature ofthe laminate resin, the tiedown adhesive cures before we need to increase d e autoclave pressure and die cured adhesive bonds the tiedown plys to one another.
• Using the adhering method eliminates relative movement of die plys and eliminates facesheet wrinkles and core crush that otherwise can occur.
• the tiedown method saves material, reduces cost, and saves weight, because it use die "picture frame” peripheral tiedown ply 150 (with the traditional, internal sheets omitted).
• the normal tiedown procedure entails plys on the outer surfaces ofthe skins and internally between the skin and underlying adhesive (Fig. 5).
• a traditional tiedown system will fail without the "picture frame” ply because the barrier film 110 permits the core to slip.
• the Corbett and Smith method will fail occasionally witiiout the adhering method of die present invention.
• chamfer we mean an angled, cut region (a ramp) of the honeycomb core tapering from full thickness to no thickness with a steady slope.
• a chamfer is used at the edge band of a composite honeycomb sandwich panel to provide a smooth transition between the structural body ofthe panel that has the embedded honeycomb and a connecting edge band lacking any honeycomb core.
• the method of d e present invention allows us to use much steeper chamfer angles than traditional practices often require if one is to avoid core crush without one tiedown ply. While we prefer a 20° chamfer, we believe that we could increase die angle to whatever angle suited the panel design requirements.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Laminated Bodies (AREA)
• Moulding By Coating Moulds (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)

Applications Claiming Priority (7)

Publications (1)

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Family Applications (1)

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• 1997
  • 1997-01-06 WO PCT/US1997/000075 patent/WO1997025198A1/en active Application Filing
  • 1997-01-06 AU AU18229/97A patent/AU1822997A/en not_active Abandoned
  • 1997-01-06 JP JP52529497A patent/JP3913275B2/ja not_active Expired - Lifetime
  • 1997-01-06 CN CN97192447A patent/CN1101751C/zh not_active Expired - Lifetime
  • 1997-01-06 EP EP97903737A patent/EP0883484A1/de not_active Withdrawn
• 2006
  • 2006-07-24 JP JP2006200715A patent/JP4407964B2/ja not_active Expired - Lifetime

Non-Patent Citations (1)

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