United States Patent [19]
`Murphy et a1.
`
`[54]
`[75]
`
`[73]
`
`[21]
`[221
`[511
`[52]
`
`[58]
`
`[56]
`
`Inventors:
`
`Assignee:
`
`WIDE CHORD FAN BLADE
`Guy C. Murphy, Fair?eld; Barrett J.
`Fuhrmann, Cincinnati, both of Ohio
`General Electric Company,
`Cincinnati, Ohio
`Appl. No.: 645,774
`Filed:
`Jan. 25, 1991
`
`Int. Cl.5 ........................ .. B63H 1/20; B63I-l l/26
`U.S. Cl. .......................... .. 416/204 A; 416/219 R;
`416/229 R; 416/241 A; 416/229 A; 416/248
`Field of Search ......... .. 416/204 R, 204 A, 219 R,
`416/229 R, 229 A, 241 R. 223 R. 224. 248. 241
`A: 29/8897, 889.71, 527.1, 527.4; 156/263. 267,
`309.6, 307.3
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3.600.103 8/1971 Gray et al. ........................ .. 416/224
`
`3.637.325 l/l972 Morley . . . . . . . . .
`
`. . . .. 416/230
`
`416/229 A
`3.649.425 3/1972 Alexander
`3.679.324 7/1972 Stargardter ....................... .. 416/229
`
`llllllIlllllllllllllllllllllllllllllllllllllllllllllllllllllllllllIllllllll
`USOO5141400A
`[11] Patent Number:
`5,141,400
`[45] Date of Patent:
`Aug. 25, 1992
`
`3.699623 10/1972 Kreider ............................ .. 29/1568
`4.029.838 6/1977 Chamis et a1. .
`4.416.949 11/1983 Gabellieri .......................... .. 428/461
`4.594.761 6/1986 Murphy et al. .................. .. 29/1568
`5.018.271 5/1991 Bailey et a].
`.. 416/219 R
`5,049,036 9/1991 Bailey et al. ................... .. 29/538971
`
`OTHER PUBLICATIONS
`Wide Chord Fan Club; 23~29, May. 1990.
`Primary Exam1‘ner—Th0mas E. Denion
`Aztorney, Agent, or Firm—Carmen Santa Maria; Jerome
`C. Squillaro
`ABSTRACT
`[57]
`A laminated airfoil for use in a high bypass engine. The
`airfoil preferably has a large tip chord and is comprised
`of alternating layers ofthin metallic foil and elastomeric
`layers. The exterior surfaces of the airfoil are comprised
`ofa thin, metallic foil. The airfoil also has a metal sheath
`secured to the leading edge. High strength metal mem
`bers extend through the dovetail root sections.
`
`31 Claims, 2 Drawing Sheets
`
`GE-1021.001
`
`

`
`US. Patent
`
`Aug. 25, 1992
`
`Sheet 1 of 2
`
`5,141,400
`
`FIG. 2
`
`GE-1021.002
`
`

`
`US. Patent
`
`Aug. 25, 1992
`
`Sheet 2 of 2
`
`5,141,400
`
`28
`minim“
`30 ""IIIIIIII [-50
`m“““ 28
`
`FIG. 3
`
`GE-1021.003
`
`

`
`1
`
`WIDE CHORD FAN BLADE
`
`5,141,400
`
`2
`These conditions caused severe delaminations in the
`blades and led to blade failure in relatively short times.
`Another composite fan blade program was discontin
`ued when the blades could not withstand small bird
`impacts (bird size of about 2.0-4.0 ounces) without
`delaminations under, the leading edge. Although the
`blade could pass FAA requirements at the time, main
`tainability of the blades was projected to be a problem
`because these delaminations were “invisible", that is
`undetectable by visual inspection, and could propagate.
`causing potentially serious blade failures. It was be
`lieved that engines would always see impacts in this size
`range that would not be detected, so that the incident
`would go unnoticed, even though internal damage
`would have occurred to the blade.
`Thus, there exists a need to provide a composite wide
`chord fan blade which can withstand typical impacts
`and operating conditions experienced by modern turbo
`fan engines. The composite blade should offer stiffness
`and light weight, which are important as engine size and
`thrust continue to increase. However. the composite fan
`blade must be capable of equivalent or better perfor
`mance at all operating conditions, including impact, of
`current metallic fan blades. Maintenance requirements
`should be comparable to current fan blades, and desir
`ably should be reduced.
`
`SUMMARY OF THE INVENTION
`The present invention is a damped, energy absorbing,
`laminated airfoil. The airfoil, of wide chord configura
`tion, has a tip portion, a dovetail root section, the dove
`tail root section having ?ank surfaces, a leading edge
`extending from the tip portion to the root section. and a
`trailing edge oppositely disposed to the leading edge
`and extending from the tip portion to the root section.
`The tip chord is larger than the conventional chords of
`current engines. being at least about 20 inches, and as
`large as 28 inches. The airfoil is comprised of alternat
`ing layers of thin metallic foil and elastomeric layers,
`thereby forming a laminated composite airfoil. The
`metallic foil forms the first and the last layers of the
`laminated structure, so that the outer surfaces of the
`airfoil are made from metallic foil. The alternating elas
`tomeric layers provide the means of bonding the metal
`lic foil layers, while providing inherent energy absorb
`ing characteristics to the structure. At least one hole or
`aperture, and preferably a plurality of holes or aper
`tures, are drilled into each dovetail ?ank surface extend
`ing at least partially through of the dovetail. A high
`strength metal member is then disposed through each of
`the dovetail root section apertures across the alternating
`layers and secured in place by adhesive bonding.
`thereby further securing the layers and providing addi
`tional strength. The adhesive bonding agent is prefera
`bly the same material used to secure the metallic foil
`layers together. A metal sheath is secured to the leading
`edge of the airfoil by adhesive bonding. In a preferred
`embodiment, the high strength metal member is a titani
`um-base pin, while the metallic foil in the airfoil is a
`titanium alloy foil or a stainless steel alloy foil having a
`uniform thickness of about 0.005 to about 0.015 inches.
`The leading edge sheath is a nickel alloy foil having a
`thickness of about 0.008 to about 0.012 inches on each of
`the edges and increasing to a thickness of about 0.040 to
`about 0.060 inches at the airfoil leading edge. Alterna
`tively, the leading edge sheath is a stainless steel alloy or
`
`BACKGROUND OF THE INVENTION
`Aircraft and aircraft engine design have always
`strived for reduced weight and greater efficiency.
`Other factors affecting aircraft and engine design in
`volve cost and size, including the maintenance of the
`aircraft and the engines. With increased emphasis in
`these areas, future aircraft are growing in size, requiring
`either more thrust from the engines or additional en
`gines. Reduced maintenance costs and initial costs can
`be achieved by enlarging the engines, increasing the
`thrust developed by the engines rather than by increas
`ing the number of engines on a particular aircraft. How
`ever, as the engines grow larger, weight reduction be
`comes paramount as all the engine components are
`required to grow.
`The next generation of commercial high thrust en
`gines will have fan diameters ranging in size from 106
`inches to 124 inches. The increased fan diameters will
`require longer blades. The longer blades will have
`wider chords for increased efficiency. The chord,
`which is the axial straight line dimension between the
`trailing edge and the leading edge of the airfoil, will
`grow with the increased blade size. Typical fan blades
`currently have tip chords of about 8 to 12 inches, while
`the wide chord fan blades for the larger engines will
`have tip chords in the range of about 20 to 28 inches.
`The wider chord blades offer the increased efficiency
`because they have greater stability margins and move
`the air more efficiently across the blade face due to their
`longer chords. The increased stability allows the blade
`to be manufactured without a mid-span shroud. which
`on current Titanium blades causes a decrease in blade
`efficiency. Increased blade efficiency is important in
`high bypass turbine engines because about 75‘)? to 80%
`of the air bypasses the core engine combustor and is
`used to provide direct thrust.
`The majority of the current fan blades in turbofan
`engines are solid titanium construction. Another fan
`blade construction utilizes titanium skin over a titanium
`honeycomb core. The manufacture of a solid titanium
`wide chord fan blade is prohibitive because of the initial
`cost of the materials and the ultimate weight of the
`blade upon completion. Thus, a solid fan blade for a
`larger engine would probably be more of a standard
`chorded blade with a mid span shroud.
`A proposed solution to the problem of weight and
`cost for blades in larger engines is an all-composite wide
`chord fan blade. A large engine having all-composite
`wide chord fan blades has a projected weight savings of
`about 800 pounds over- a large engine having standard
`chorded fan blades. The all-composite wide chord fan
`blade would also display a somewhat smaller, but nev
`ertheless substantial, weight savings over titanium
`skin/titanium honeycomb blades.
`'
`The concept of all-composite blades has been at
`tempted in the past. However, these blades have never
`been successfully implemented for several reasons. One
`early program developed erosion problems due to the
`poor erosion characteristics of the applied coating and
`to the lack of a metallic leading edge. The coating could
`not withstand rain droplet impacts without sustaining
`damage. Once the exterior coating was damaged, expos
`ing the underlying laminated composite structure, the
`underlying composite structure was subjected to water
`damage from water ingestion and further impacts.
`
`15
`
`30
`
`35
`
`45
`
`55
`
`65
`
`GE-1021.004
`
`

`
`3
`a titanium alloy foil having a uniform thickness of about
`0.008 to about 0.015 inches.
`The laminated airfoil is formed by preshaping the
`metallic foil. This may be conveniently done by super
`plastic forming. which is accomplished under stress at
`elevated temperature. The preshaped metallic foil hav
`ing a thickness of from 0005-0015 inches is then
`trimmed to a predetermined size by conventional cut
`ting or trimming techniques. The metallic foil and a heat
`?owable elastomeric ?lm are then assembled into an
`assembly of alternating layers of each material and
`placed into a die. The die has a cavity which accepts the
`foil assembly and may also accept a metal leading edge
`sheath. The die cavity is further designed so that the
`?nal part produced will be a net shape or near net shape
`airfoil. The assembly, when placed into the die cavity,
`has a metallic foil ?rst layer and last layer, so that the
`outer surfaces of ?nal part are metal. After placing the
`assembly into the die, sufficient heat and pressure are
`applied to the ply assembly to cause the elastomeric ?lm
`to flow by conventionally die pressing the assembly.
`This operation causes the elastomeric ?lm to simulta
`neously bond to the alternating metal layers and to cure.
`After removal of the cured airfoil from the die, subse- _
`quent ?nishing operations. such as drilling of dovetail
`root flank holes and insertion of high strength metal
`members coated with adhesive, ?nal machining of the
`dovetail root section. ?nal trimming, if necessary, and
`attachment of a leading edge sheaths, if not accom
`plished during die pressing. may be performed.
`The present invention permits the use of alternating
`plies of materials to form airfoils, such as fan blades. and
`in particularly. wide chord fan blades. as well as com~
`pressor vanes The advantages of airfoils formed in this
`manner is that they are lighter in weight than conven‘
`tional airfoils, but retain strength and toughness re
`quired for such demanding applications. The reduced
`weight becomes more important in jet engine design as
`engines become larger and more powerful, requiring
`ever larger fans and vanes.
`Other features and advantages of the present inven
`tion will be apparent from the following more detailed
`description of the preferred embodiment, taken in con
`junction with the accompanying drawings which illus
`trate. by way of example, the principles of the inven
`tion.
`
`30
`
`35
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The subject matter which is regarded as the invention
`is particularly pointed out and distinctly claimed in the
`concluding portion of the speci?cation. The invention
`itself. however, both as to its organization and its
`method of practice, together with further objects and
`advantages thereof. may best be understood by refer
`ence to the following description taken in conjunction
`with the accompanying drawings, in which:
`FIG. 1 is a perspective view of a fan blade airfoil
`having a dovetail root section and a metal sheath lead—
`ing edge.
`FIG. 2 is a cross section of an elastomeric layer in
`which a polyurethane ?lm is coated on each side with
`an adhesive layer or alternatively, a combined elasto
`meric adhesive.
`‘
`FIG. 3 is a partial cross-section of a laminated blade
`having alternating layers of metallic foil. elastomeric
`material and polymeric composite ply.
`
`50
`
`55
`
`65
`
`5,141,400
`
`4
`FIG. 4 is a perspective view of a fan blade airfoil
`having a dovetail root. a metal tip cap. a metal leading
`edge and an abrasive tip applied to the metal tip cap.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Pursuant to the present invention. a laminated airfoil
`having alternating layers of a metallic foil and light
`weight ?lm, with the metallic foil forming the ?rst layer
`and the last layer so that the outer surfaces of the airfoil
`are metal is provided.
`The present invention also encompasses methods for
`forming laminated airfoils from metallic foils and ener
`gy-absorbing elastomeric ?lms or polymeric composite
`materials and combinations thereof. The energy-absorb
`ing elastomeric ?lms provide impact resistance and
`vibration damping to the composite blades, which is an
`important feature in preventing blade damage due to
`foreign object ingestion and fatigue.
`Referring now to FIG. 1, a perspective view of the
`laminated airfoil in the form of the wide chord fan blade
`10 is shown. The fan blade has a tip portion 12, dovetail
`root section 14, a leading edge 16 extending from the tip
`portion 12 to the root section 14. a trailing edge 18
`oppositely disposed to the leading edge 16 and extend
`ing from the tip portion 12 to the root section 14. The
`fan blade has a metal sheath 20 attached to the leading
`edge 16. apertures 22 extending through the flank sur
`faces 24 of the dovetail root section 14 and a high
`strength metal member 26 disposed through each dove
`tail root section aperture 22. The metal sheath 20 at
`tached to the leading edge helps provide the fan blade
`with additional impact resistance. erosion resistance and
`improved resistance of the composite structure to de
`lamination. The high strength metal member 26 im
`proves delamination resistance and provides a wear
`resistant surface for the dovetail, which has some re
`stricted movement in the dovetail slot ofthe rotor or fan
`disk. The metal member 26 also improves the compres
`sive strength of the dovetail ?ank by becoming the
`primary load bearing portion of the composite fan
`blade. This feature of the metal member is signi?cant
`since forces in the dovetail region are high during en
`gine operation. The stresses in the fan blade due to
`rotation have components radially outward as well as
`axial. These stresses are suf?cient to cause a fan blade
`without a stress-bearing metal member to flow out
`wardly and deform, resulting in potential blade separa
`tion from the disk or delamination of the composite.
`The fan blade is composed of alternating layers of me
`tallic foil 28 and energy-absorbing elastomeric layers 30
`forming the laminated composite fan blade 10 of FIG. 1.
`The metallic foil 28 forms the ?rst and last layers of the
`alternating layers so that the outside surface of the fan
`blade 10 is metal.
`The metallic foil may be any metallic foil suitable for
`use in aircraft engine applications. It is preferred that
`the metallic foil be selected from a group consisting of
`titanium alloys, nickel-base superalloys or stainless
`steels. It is preferred that the metallic foil be produced
`by superplastic forming. Superplastic forming is well
`known in the art. The Superplastic forming method
`subjects certain metals which exhibit Superplastic be
`havior to a low strain rate at high temperatures. Under
`these conditions. the metals can undergo unusually
`large amounts of plastic deformation, so that thin metal
`lic ?lms may be formed.
`
`GE-1021.005
`
`

`
`5
`.
`In a most preferred embodiment. the metal alloy of
`the airfoil is a titanium alloy foil produced by superplas
`tic forming. A Ti-6Al-4V titanium alloy is selected
`because of its high strength-to weight ratio. This metal
`may advantageously be superplastically formed as is
`well-known to those skilled in the art at temperatures of
`about 1600“ by using a pressurized inertgas to form the
`material to the desired shape and thickness against a
`mandrel using standard superplastic forming tech
`niques. The ?nal desired thickness is about 0.005—0.0l5
`inches.
`The energy-absorbing elastomeric layer 30 may be a
`modi?ed adhesive ?lm, an adhesive ?lm having a ther
`moplastic carrier, or a polyurethane ?lm coated with an
`adhesive layer A further distinguishing characteristic of
`the elastomeric layer, in addition to being energy
`absorbing, is its ability to bond with the metallic foil.
`When the elastomeric layer 30 is a modi?ed adhesive
`?lm. preferred elastomers are epoxy resins having low
`flow characteristics such as FM-300I obtainable from
`American Cyanamid.
`When the elastomeric layer 30 is an adhesive ?lm
`having a thermoplastic layer carrier, preferred elasto
`mers are HXT-440, or a bis-maleirnide such as I-IXT-44l
`both obtainable from American Cyanamid.
`When the elastomeric layer is a polyurethane ?lm
`coated with an adhesive layer. the total thickness of the
`polyurethane-adhesive coated ?lm is approximately
`0003-0015 inches. Referring now to FIG. 2, a cross
`section of a polyurethane ?lm 36 coated on each side
`with an adhesive layer 32 forming elastomeric layer 30
`is shown. A polyurethane ?lm having adhesive layers
`and of the required thickness may be obtained from the
`3-M Company.
`The laminated airfoil 10 is formed by taking the me
`tallic foil. and if necessary, pre-shaping the metallic foil
`into a predetermined shape. The metallic foil is then
`accurately trimmed to a predetermined size using stan
`dard trimming techniques. The metallic foil 28 and the
`heat-?owable energy-absorbing elastomeric layer 30 are
`then assembled into a die assembly in alternating layers.
`The die assembly is a conventional mold tool assembly
`in which the cavity of the die has the shape of the de
`sired end product, in this case a laminated airfoil. The
`metallic foil 28 and the heat flowable elastomeric layer
`45
`30 are alternately layered into the die cavity, with the
`metallic foil forming the ?rst layer and the last layer in
`the die cavity. so that the outer surfaces ofthe airfoil are
`metallic. Optionally, a leading edge sheath made from a
`metallic material, preferably a titanium alloy such as
`Ti-6Al-4V, may be assembled into the die assembly.
`This die assembly is then pressed while applying suf?
`cient heat and pressure to flow the elastomeric layer
`thereby simultaneously bonding the elastomeric layer to
`the foil and the optional leading edge sheath and curing
`the ply assembly into a cured airfoil having net shape or
`near net shape.
`'
`In a preferred embodiment, titanium alloy foil, such
`as Ti-6Al-4V in accordance with AMS-49ll having a
`nominal composition in weight percent of about 5.5 to
`60
`6.75% Al, 3.5 to 4.5% V, 0.30% Fe Max., 0.20% 0
`Max., 0.08% C Max., 0.05%'N Max., 0.015% H Max.,
`0.005% Y Max. and the balance Ti and incidental impu
`rities. with no more than 0.5% incidental impurities and
`an elastomeric layer 30 of polyurethane ?lm 36 and
`coated on either side with about 0.0025 inches of an
`adhesive ?lm 32 such as AFl63-2 obtainable from 3-M
`Company are placed in a die assembly in the manner
`
`40
`
`5,141,400
`
`6
`described above and heated at a temperature of about
`230°—260° F. and to a pressure of about 50-l50 psi for
`about two hours at temperature to form the near net
`shape airfoil.
`The airfoil is then removed from the die assembly and
`trimmed if necessary. As depicted in FIG. 1, apertures
`22 are drilled in the dovetail root flank surfaces 24 and
`adhesive-coated high strength metal members 26 are
`inserted into the apertures. These members provide
`additional strength to the airfoil. The additional
`strength is required in order for the dovetail to carry the
`compressive loads typically found in this portion of the
`blade. A metal sheath 20, preferably made from the
`same alloy as the metallic foil in the blade. in the pre
`ferred embodiment titanium alloy Ti-6Al-4V, is then
`applied to the leading edge 16 of the blade with an
`adhesive. preferably the same adhesive or material as
`used in the elastomeric layer. Optionally, the adhesive
`coated metal sheath may be applied to the airfoil leading
`edge after assembly of the laminated airfoil preform
`assembly, but prior to insertion of the assembly into the
`die assembly. thus permitting the leading edge to be
`co-cured with the airfoil.
`In a preferred embodiment of the present invention,
`the high strength metal members 26 disposed in each
`dovetail root section aperture 22 are titanium alloy pins.
`preferably Ti-6Al-4V. These pins are coated with an
`adhesive usually of the same type used in the elasto
`meric layer. These adhesives must be bondable to the
`metal of the pin and to the composite layers comprising
`the root section aperture 22.
`In an alternate embodiment of the present invention.
`an airfoil of the type previously described is made by
`alternating layers of a metallic foil 28 and a polymeric
`composite layer thereby forming a laminated composite
`airfoil. In this embodiment, the polymeric composite
`layer is utilized in the same manner as the previously
`described elastomeric layer 30. The metallic foil once
`again forms the ?rst and last layer assembled into the die
`so that the outer surfaces of the airfoil are metal. Tita
`nium alloy pins coated with an adhesive capable of
`bonding to the alloy and the laminated-composite are
`disposed in each dovetail root section aperture 22. Fur
`thermore. the minimum cure temperature capability of
`the adhesive must be approximately the same as the
`cure temperature of the laminated composite. Finally.
`the adhesive must be chemically compatible with the
`laminated composite comprising the blade. Adhesives
`which may be used include AF191 or AFl63-2 obtain
`able from 3-M Company, FM238 obtainable from
`American Cyanamid or PL777 obtainable from B. F.
`Goodrich. After application of the adhesive, the pins
`are assembled through the dovetail root apertures.
`In a preferred embodiment, the polymeric composite
`layer is a ?ber embedded in a ?owable resin based ma
`trix forming a lamina. Any polymeric composite layer
`having a high strength-to-weight ratio and having a
`resin capable of bonding to metal is acceptable. In a
`most preferred embodiment of the present invention,
`the reinforcement is a 12 K ?lament tow of an interme
`diate modulus carbon ?ber having an individual ?ber
`cross-sectional thickness of about 5 microns. The ?ow
`able resin based matrix is selected from the group con
`sisting of epoxy, BMI, and polycyanate. Preferred are
`F3900 or 8551-7 which are toughened epoxies. Thin
`layers of uncured polymeric composite material having
`thicknesses of about 0.005-0006 inches are commer
`cially available and may be obtained from Hexcel Corp.
`
`GE-1021.006
`
`

`
`t... 0
`
`7
`under the name of F3900/lM-7 or from Hercules Corp.
`under the name of 855l-7/lM-7. The preferred metallic
`foil is titanium alloy foil as previously described and the
`high strength metal members inserted into the dovetail
`root ?ank apertures are titanium alloy pins.
`The method of forming a laminated airfoil using a
`polymeric composite layer rather thanan elastomeric
`layer is similar to the method previously described.
`After accurately‘ preshaping and trimming both the
`metallic foil and the uncured polymeric composite plies
`to a predetermined size. the metallic foils and polymeric
`composite plies are alternately assembled into a ply
`assembly in alternating layers with the metallic foil
`forming the ?rst and last layers in the assembly so that
`the outer surfaces of the airfoil ply assembly are metal.
`This ply assembly is then inserted into the die cavity
`and compacted using sufficient heat and pressure to
`cause the polymeric composite matrix to flow, thereby
`simultaneously bonding the matrix 0 the polymeric
`composite to the metallic foil and curing the ply assem
`bly into a ?nished or semi-?nished airfoil. Optionally. a
`metal leading edge may be assembled to the ply assem
`bly prior to insertion ofthe assembly into the die cavity.
`In this case. the cured airfoil will include a metal lead
`ing edge.
`The cured airfoil is ?nished by drilling dovetail root
`aperture holes into the dovetail root ?ank surface and
`inserting adhesive-coated metal members through the
`apertures to provide additional strength. This operation
`is followed by ?nal machining of the dovetail ?ank and
`by trimming operations. if necessary. A metal sheath 20.
`usually of the same material as the metallic foil used in
`the ply assembly. is applied to the leading edge 16 ofthe
`blade using an adhesive, if this item was not cured with
`the airfoil assembly in the die. A typical adhesive is
`AF-l63-2 which is an epoxy-based adhesive obtainable
`from the 3-M Company.
`In the preferred embodiment using titanium alloy
`metallic foil. such as Ti-6Al-4V. and an uncured poly
`meric composite ply. such as F3900/IM-7, the ply as
`sembly is placed in the die cavity and heated to a tem
`perature of about 325°-375° F. at a pressure of about
`100-200 psi for about 2 hours at temperature.
`In still another embodiment of the present invention,
`as depicted in partial cross-section in FIG. 3, the lami
`nated airfoil as previously described is made from alter
`nating layers of metallic foil 28, polymeric composite
`ply 50 and an energy-absorbing elastomeric layer 30 to
`form a laminated composite airfoil assembly. In this
`embodiment, the elastomeric layer 30 is interposed be
`tween each layer of metallic foil 28 and polymeric com
`posite ply 50 to join the metallic foil 28 to the polymeric
`composite ply 50. Once again, the metallic foil 28 forms
`the ?rst and last layers of the ply assembly so that the
`outer surface of the airfoil is metal.
`The polymeric composite ply 50 comprises an inter
`mediate modulus carbon ?ber in a resin-based matrix of
`the type previously discussed, such as a F3900/IM-7 or
`855l-7/IM-7. The elastomeric layer in the preferred
`embodiment is a modi?ed adhesive ?lm such as FM
`3001 or an epoxy adhesive film having a thermoplastic
`carrier. such as EXT-440, or a bis-maleimide adhesive
`?lm with thermoplastic carrier such as HXT-441. The
`metallic foil is selected from the group consisting of
`titanium or titanium alloys, nickel base superalloys and
`stainless steels and may be produced by superplastic
`forming. However, the preferred metallic foil is tita
`nium alloy foil, Ti-6Al-4V, produced by superplastic
`
`5,141,400
`8
`forming. The method of forming the laminated airfoil
`using polymeric composite ply. metallic foil and an
`elastomeric adhesive is similar to the previously de
`scribed methods of forming airfoils. The metallic foil 28
`and the polymeric composite plies 50 are preshaped and
`accurately trimmed to a predetermined size. The metal»
`lic foil 28 and the polymeric composite plies 50 are then
`alternately layered into a laminated assembly, with elas
`tomeric adhesive interposed between each piece of
`metallic foil 28 and polymeric composite plies 50. The
`metallic foil forms the ?rst and last layers of the assem
`bly. The laminated assembly is then placed in a die
`cavity. Optionally. the metal sheath leading edge 20
`may be assembled into the die with the laminated assem
`ly in the manner previously discussed. The laminated
`assembly is then pressed in the die while applying suf?
`cient heat and pressure to cause the elastomeric adhe
`sive to ?ow thereby simultaneously bonding the poly
`meric composite matrix having embedded ?bers to the
`metallic foil. The heat and pressure also cure the poly
`meric composite matrix. The cured airfoil is then re
`moved from the die.
`If necessary. the cured airfoil may be trimmed. Aper
`tures 22 are drilled in the dovetail root flanks 14 and
`adhesive-coated titanium alloy pins are inserted into the
`apertures. A metal sheath, made from the same alloy as
`the metallic foil may be attached to the leading edge 16
`of the airfoil using an epoxy adhesive, if the metal lead
`ing edge is not applied to the laminated airfoil assembly
`as part of the curing operation in the die.
`In the preferred embodiment of this alternate assem
`bly, the ply assembly is heated to a temperature of about
`250°~350° F. and to a pressure of about 100—2OO psi for
`about 2 hours. The laminated airfoil of the present in
`vention is most useful as a wide chord fan blade in a
`turbine engine. The laminated airfoil of the present
`invention may also find use as a vane for the compressor
`section of a turbine engine.
`Any of the composite airfoils ofthe present invention
`may be provided with an optional tip cap 60, as shown
`in FIG. 4. The tip cap 60 may be a standard formed cap
`made oftitanium. titanium alloy or stainless steel. When
`a tip cap is provided. however, it is preferably of the
`same metal as that used in the blade assembly. Thus, in
`the preferred embodiment. the tip cap is superplastically
`formed Ti-6Al-4V. As is well-known in the turbine
`engine blade arts. any abrasive layer such as layer 62 in
`FIG. 4 may be applied to tip cap 60 to improve the
`abrasive wear characteristics of the blade as contact
`with the engine occurs during engine operation.
`In light of the foregoing discussion, it will be appar
`ent to those skilled in the art that the present invention
`is not limited to the embodiments. methods and compo
`sitions herein described. Numerous modi?cations,
`changes, substitutions and equivalents will now become
`apparent to those skilled in the art. all of which fall
`within the scope contemplated by the invention.
`What is claimed is:
`1. An energy absorbing, laminated airfoil having a tip
`portion, a dovetail root section, a leading edge extend
`ing from the tip portion to the root section, and a trail
`ing edge oppositely disposed to the leading edge and
`extending from the tip portion to the root section, com
`prising:
`alternating layers of a metallic foil and an elastomeric
`layer forming a laminated composite airfoil. the
`metallic foil forming the ?rst and last layers,;
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`GE-1021.007
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`the dovetail root section having ?ank surfaces with at
`least one aperture extending from each ?ank sur
`face through a portion of the dovetail root section;
`a high strength metal member disposed through each
`dovetail root section aperture: and
`a metal sheath attached to the leading edge.
`2. The laminated airfoil of claim 1 wherein the metal
`lic foil is selected from the group consisting of titanium
`alloys. nickel base superalloys and stainless steels.
`3. The laminated airfoil of claim 2 wherein the metal
`lic foil is a titanium alloy foil produced by superplastic
`forming.
`'
`4. The laminated airfoil of claim 1 wherein the elasto
`meric layer is selected from the group consisting of an
`adhesive ?lm having a thermoplastic carrier. a modi?ed
`adhesive ?lm and a polyurethane film coated with an
`adhesive layer.
`5. The laminated airfoil of claim 4 wherein the ?lm of
`the adhesive ?lm having a thermoplastic carrier is se
`lected from the group consisting of HXT-440, or HXT
`441.
`6. The laminated airfoil of claim 4 wherein the ?lm of
`the modified adhesive ?lm is FM-300l.
`7. The laminated airfoil of claim 4 wherein the adhe
`sive layer ofthe polyurethane ?lm coated with an adhe
`sive layer is AFl63-2.
`8. The laminated airfoil of claim 1 wherein the high
`strength metal members are titanium-alloy pins.
`9. The laminated airfoil of claim 1 wherein the airfoil
`is a wide chord fan blade for a turbine engine.
`10. The laminated airfoil of claim 1 wherein the airfoil
`is a vane for a turbine engine.
`11. An energy absorbing. laminated airfoil having a
`tip portion, a dovetail root section. a leading edge ex—
`tending from the tip portion to the root section. and a
`trailing edge oppositely disposed to the leading edge
`and extending from the tip portion to the root section,
`comprising:
`alternating layers of a metallic foil and a polymeric
`composite layer forming a laminated composite
`airfoil, the metallic