WO2014099841A1

WO2014099841A1 - Expandable mandrel and method of making hollow composite structures

Info

Publication number: WO2014099841A1
Application number: PCT/US2013/075541
Authority: WO
Inventors: Nicholas Joseph Kray; Paul Stephen Manicke
Original assignee: General Electric Company
Priority date: 2012-12-17
Filing date: 2013-12-17
Publication date: 2014-06-26

Abstract

An expandable mandrel apparatus (100, 200, 300) for making a composite component includes: a plurality of blocks (110, 210, 310) of rigid material arranged to form a member elongated in a first direction and collectively defining a body outer surface (112, 212, 312) having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed; and an expander structure (144, 244, 344) disposed between the blocks (110, 210, 310), the expander structure (144, 244, 344) operable to expand the blocks (110, 210, 310) in at least one direction perpendicular to the first direction.

Description

EXPANDABLE MANDREL AND METHOD OF MAKING HOLLOW COMPOSITE

STRUCTURES

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to composite structures, and more particularly to tooling and methods for constructing hollow composite components.

[0002] The term "composite" refers generally to a material containing a reinforcement such as fibers or particles supported in a binder or matrix material. A typical composite component is constructed from a "layup" including a number of layers or plies embedded in a matrix. The material for the layup may be supplied as bulk resin and fibers, or commercially-available "prepreg" material comprising fibers unidirectionally aligned into a tape that is impregnated with a resin. The layup is cured via an autoclaving process or press molding to form a light weight, stiff, relatively homogeneous article. Examples of composite systems include polymer matrix composites ("PMCs") and ceramic-matrix composites ("CMCs").

[0003] Some composite parts include hollow interior cavities. Prior art processes for producing such hollow composites include pressurizing the layup from the outer surface over a rigid inner mandrel. Experience shows that this process can cause the composite plies to buckle. This is caused by the release of volatile compounds during the cure process and an overall bulk factor of the material system, which can be upward of 20%. Buckling of the plies results in a component that does not meet the design intent with respect to strength and durability.

[0004] Accordingly, there is a need for a means of constructing hollow composite components without buckling of the composite plies.

BRIEF DESCRIPTION OF THE INVENTION

[0005] This need is addressed by the present invention, which provides an apparatus and method for stretching the fibers in a composite during curing, rather than rather than compressing them, so that buckling will not occur. This stretching process may be accomplished by applying inner pressure to the hollow cavity using an expandable mandrel.

[0006] According to one aspect of the invention, an expandable mandrel apparatus for making a composite component includes: a plurality of blocks of rigid material arranged to form a member elongated in a first direction and collectively defining a body outer surface having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed; and an expander structure disposed between the blocks, the expander structure operable to expand the blocks in at least one direction perpendicular to the first direction.

[0007] According to another aspect of the invention, a first one of the blocks includes a tab received in a slot in a second one of the blocks.

[0008] According to another aspect of the invention, the expander structure comprises at least one inflatable tube comprising a resilient material.

[0009] According to another aspect of the invention, a resilient cover overlies at least a portion of a joint between first and second ones of the blocks.

[0010] According to another aspect of the invention, a resilient flexible sleeve surrounds all of the blocks.

[0011] According to another aspect of the invention, the elongated member is arcuate and the cross-sectional shape of the body outer surface includes opposed, spaced-apart forward and aft surfaces and opposed, spaced-apart upper and lower surfaces comprising a resilient material disposed at corners defined by adjacent ones of the surfaces.

[0012] According to another aspect of the invention, the expander structure includes inflatable corner tubes comprising a resilient material disposed at corners defined by adjacent ones of the surfaces.

[0013] According to another aspect of the invention, the blocks are formed from metal.

[0014] According to another aspect of the invention, a expandable mandrel apparatus for making a composite component includes: a body of rigid material elongated in a first direction and including a body outer surface having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed; a resilient, flexible sleeve surrounding the body; and an expander structure disposed between the body and the sleeve, the expander structure operable to expand the sleeve away from the body in at least one direction perpendicular to the first direction.

[0015] According to another aspect of the invention, a space between the body and the sleeve is configured to be coupled to a source of pressured gas. [0016] According to another aspect of the invention, the body is arcuate and the cross-sectional shape of the body outer surface includes opposed, spaced-apart forward and aft surfaces and opposed, spaced-apart upper and lower surfaces.

[0017] According to another aspect of the invention, the expander structure includes inflatable corner tubes comprising a resilient material disposed between the body and the sleeve, at corners defined by adjacent ones of the surfaces.

[0018] According to another aspect of the invention, the body is formed from metal.

[0019] According to another aspect of the invention, an expandable mandrel apparatus is provided for making a composite component, the mandrel comprising: a body of resilient material elongated in a first direction and including a body outer surface having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed, the body having a positive coefficient of thermal expansion; and a spar of rigid material disposed inside the body.

[0020] According to another aspect of the invention, the apparatus further comprises an expander structure disposed inside the body the expander structure operable to expand the body in at least one direction perpendicular to the first direction.

[0021] According to another aspect of the invention, the expander structure comprises a cavity formed in the body and configured to be coupled to a source of pressured gas.

[0022] According to another aspect of the invention, the body is arcuate and the cross-sectional shape of the body outer surface includes opposed, spaced-apart forward and aft surfaces and opposed, spaced-apart upper and lower surfaces; and the spar extends parallel to one of the surfaces.

[0023] According to another aspect of the invention, the body is formed from room- temperature -vulcanizing silicone.

[0024] According to another aspect of the invention, a method of making a composite component includes: placing a composite layup into an outer tool, the layup comprising a plurality of fibers embedded in an uncured matrix and shaped so as to define an interior space; placing an expandable mandrel including at least one rigid member into the interior space; expanding the mandrel so as to force the layup against the outer tool; and curing the composite layup. [0025] According to another aspect of the invention, the mandrel includes: a body comprising a plurality of blocks of rigid material; and an expander structure configured to expand the blocks in at least one direction.

[0026] According to another aspect of the invention, the expander structure includes at least one inflatable tube disposed between the blocks.

[0027] According to another aspect of the invention, the mandrel includes: a body comprising a resilient, flexible material having a positive coefficient of thermal expansion; and an expander structure configured to expand the body in at least one direction; and the curing is carried out at an elevated temperature so as to cause the body to expand outward against the layup.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:

[0029] FIG. 1 is a schematic front elevational view of a hollow composite component constructed in accordance with an aspect of the present invention;

[0030] FIG. 2 is a cross-sectional of view the component shown in FIG. 1;

[0031] FIG. 3 is a cross-sectional view of a layup which is a precursor to the component of FIG. 1 , shown in a tooling assembly;

[0032] FIG. 4 is a partially-cut-away front elevational view of the layup and tooling assembly of FIG. 3;

[0033] FIG. 5 is a schematic cross-sectional view of an expandable mandrel constructed according to an aspect of the present invention;

[0034] FIG. 6 is a schematic cross-sectional view of another expandable mandrel constructed according to an aspect of the present invention;

[0035] FIG. 7 is a schematic cross-sectional view of another expandable mandrel constructed according to an aspect of the present invention;

[0036] FIG. 8 is a schematic cross-sectional view of another expandable mandrel constructed according to an aspect of the present invention; [0037] FIG. 9 is a schematic cross-sectional view of another expandable mandrel constructed according to an aspect of the present invention; and

[0038] FIG. 10 is a schematic cross-sectional view of another expandable mandrel constructed according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views, FIGS. 1 and 2 illustrate an exemplary composite component C. In the illustrated example, the component C is a segment of a turbine shroud for a gas turbine engine, but the principles of the present invention are applicable to any composite component having a hollow interior space. The component C includes inner and outer walls Wl and W2, and forward and aft walls W3 and W4. The component is arc-shaped and extends in the tangential direction between end faces F. Collectively the walls W1-W4 define a hollow interior space or cavity "S". It is noted that directional terms such as "forward", "aft", "inner", "outer", "upper", "lower", etc., are used herein merely for convenience in description and do not imply that any particular orientation of the components described is required.

[0040] The component C is constructed from composite material. The term "composite" refers generally to a material containing a reinforcement such as fibers or particles supported in a binder or matrix material. In the illustrated example the composite includes a number of layers or plies embedded in a matrix and oriented substantially parallel to the walls W1-W4. A nonlimiting example of a suitable material is a carbonaceous (e.g. graphite) fiber embedded in a resin material such as epoxy. These are commercially available as fibers unidirectionally aligned into a tape that is impregnated with a resin. Such "prepreg" tape can be formed into a part shape, and cured to form a light weight, stiff, relatively homogeneous article. The principles of the present invention are equally applicable to ceramic-matrix composites ("CMCs").

[0041] As seen in FIGS. 3 and 4, a composite layup L, which contains fibers or plies in an uncured matrix and is a precursor to the component C, is placed into a tooling assembly comprising a rigid outer tool 10 having an interior cavity 12 which receives the uncured composite layup L and defines the outer surface of the component C, and a mandrel M having an outer surface 16 which bears against the layup L and defines the inner surface of the component C. The entire tooling assembly with the layup L inside is then placed in an autoclave or press and cured at elevated temperature, in accordance with known techniques, to cure the layup L and form the component C. [0042] The mandrel M shown in FIGS. 3 and 4 is generally representative of the exterior size and shape of the tooling component that is placed inside the layup L. In accordance with the present invention, the mandrel M may incorporate any one of several expandable configurations comprising one or more rigid elements, described in detail below. The expandable mandrel is inserted into the intended hollow part section and exerts an outward pressure onto the composite material during the curing process. This outward pressure is reacted by the rigid outer tool 10. The process of exerting an outward pressure enables the fibers of the layup L to be stretched and thereby prevent wrinkles and buckling of the fibers in the finished component C.

[0043] FIG. 5 illustrates an exemplary expandable mandrel 100 constructed according to one aspect of the present invention. The mandrel 100 is an elongated member having forward and aft ends 102 and 104, and upper and lower surfaces 106 and 108. The surfaces are blended with radiused curves. FIG. 5 is a cross-sectional view and it will be understood that by the term "elongated" it is meant that the mandrel 100 may have an arcuate shape as shown in FIG. 4, or could also be prismatic, with the illustrated cross-sectional shape extending along a straight-line axis. The exact shape depicted herein is merely for the purpose of explanation and it will be understood that the principles of the present invention may be applied to the manufacture of any hollow composite component.

[0044] The mandrel 100 includes a body with upper and lower forward blocks 110A and HOB, upper and lower middle blocks 1 IOC and HOD, and upper and lower aft blocks 110E and 110F. The blocks 11 OA- 11 OF may be constructed from any rigid material, such as steel or aluminum alloys. As used herein the term "rigid" refers generally to a material having a high modulus of elasticity, of the order of magnitude of a steel alloy, as opposed to a material such as rubber or a soft polymer. Each of the blocks 11 OA- 11 OF has an outer surface which defines a portion of a body surface 112 that is geometrically similar to the cross-sectional shape of the interior cavity S of the component C.

[0045] The blocks 110A-110F are mechanically interlocked so that they may slide apart from each other to expand while maintaining their relative orientation. In the illustrated example, the upper forward block 110A has a tapered axial tab 114 received in a tapered axial slot 116 of the upper middle block 1 IOC. The lower forward block HOB has a tapered axial tab 118 received in a tapered axial slot 120 of the lower middle block HOD. The upper forward block 110A also has a tapered radial tab 122 received in a tapered radial slot 124 of the lower forward block HOB.

[0046] The upper aft block 110E has a tapered axial tab 126 received in a tapered axial slot 128 of the upper middle block 1 IOC. The lower aft block 110F has a tapered axial tab 130 received in a tapered axial slot 132 of the lower middle block HOD. The upper aft block 110E also has a tapered radial tab 134 received in a tapered radial slot 136 of the lower aft block 110F. Finally, the lower middle block HOD has a radial tab 138 received in a radial slot 140 of the upper middle block HOD.

[0047] A forward channel 142 A is defined at the mutual intersection of the upper forward block 110A, the lower forward block HOB, the upper middle block 1 IOC, and the lower middle block HOD. An aft channel 142B is defined at the mutual intersection of the upper aft block 110E, the lower aft block 110F, the upper middle block 1 IOC, and the lower middle block HOD.

[0048] Inflatable forward and aft tubes 144A and 144B are disposed in the channels 142A and 142B, respectively. Means are provided for selectively pressurizing the tubes 144A and 144B. For example, one end of each tube may be connected to a source of pressurized air such as compressed shop air, and the other end of the tube may be closed off by an end wall or plug. The tubes 144 A and 144B may be connected to a single air circuit or may be individually inflatable. When the tubes 144A and 144B are not pressurized, the blocks 11 OA- 11 OF are collapsed into a rest position. (The gaps between the blocks 11 OA- 11 OF are exaggerated for illustrative purposes). When the tubes 144A and 144B are pressurized, they expand and force the blocks 11 OA- 11 OF outward, expanding the mandrel outer surface 112 in both axial and radial directions, as indicated by the arrows labeled A and R in FIG. 5. In general, the mandrel 100 is dimensioned so that it may be conveniently inserted into the interior of the layup L prior to curing, and will expand enough to stretch the layup L to the desired degree during the curing process.

[0049] Expansion of the mandrel 100 will cause gaps between the blocks 11 OA- 11 OF to appear and/or to expand compared to a rest state. Optionally, a resilient, flexible sleeve 150 may be placed over the mandrel outer surface 112 to prevent indentations (also called "markoff) of the layup L caused by the presence of the gaps. The sleeve 150 may be made from an elastomeric material such as rubber or room-temperature-vulcanizing silicone ("RTV").

FIG. 6 illustrates another exemplary mandrel 200 constructed according to an aspect of the present invention. The mandrel 200 is an elongated member having forward and aft ends 202 and 204, and upper and lower surfaces 206 and 208. The surfaces are blended with radiused curves.

[0050] The mandrel 200 includes forward and aft blocks 21 OA and 210B, and upper and lower middle blocks 2 IOC and 210D. The blocks 210A-210D may be constructed from any rigid material, such as steel or aluminum alloys. Each of the blocks 210A-210D has an outer surface which defines a portion of a body surface 212 that is geometrically similar to the cross-sectional shape of the interior cavity S of the component C. Optionally, the blocks 210A-210D may be mechanically interlocked so that they may slide apart from each other to expand while maintaining their relative orientation, in the manner described above for the mandrel 100.

[0051] From front to rear, first, second, third, and fourth channels 242A-242D are defined at the mutual intersections of the blocks 210A-210D. Inflatable first, second, third, and fourth tubes 244A-244D are disposed in the channels 242A-242D, respectively. Means are provided for selectively pressurizing the tubes 244A-244D. For example, one end of each tube may be connected to a source of pressurized air such as compressed shop air, and the other end of the tube may be closed off by an end wall or plug. The tubes 244A-244D may be connected to a single air circuit, may be individually inflatable, or may be connected in groups as desired. When the tubes 244A-244D are not pressurized, the blocks 210A-210D are collapsed into a rest position. When the tubes 244A-244D are pressurized, they expand and force the blocks 210A- 210D outward, expanding the mandrel outer surface 212 in both axial and radial directions, as indicated by the arrows labeled A and R in FIG. 6.

[0052] Pressurization of the tubes 244A-244D may be controlled to tailor expansion of the blocks 210A-210D in either direction. For example, a first relatively lower pressure may be supplied to tubes 244B and 244C, and a second, relatively higher pressure may be provided to tubes 244 A and 244D. This would tend to cause more expansion in the axial direction A than the radial direction R.

[0053] Expansion of the mandrel 200 will cause gaps to open between the blocks 210A-210D. Optionally, various means may be used to over these gaps and thereby prevent markoff of the layup L during the curing process. For example, FIG. 6 illustrates small covers 248 applied over each corner. These covers 248 take the form of rectangular strips and may be made from materials such as flexible tape, metal shim stock, or cut sections of thin wall tubing. Alternatively, a resilient, flexible sleeve (not shown), similar to the sleeve 150 described above, may be placed over the mandrel outer surface 212 to prevent markoff.

FIG. 7 illustrates another exemplary mandrel 300 constructed according to an aspect of the present invention, generally similar to the mandrel 200. The mandrel 300 is an elongated member having forward and aft ends 302 and 304, and upper and lower surfaces 306 and 308. The surfaces are blended with radiused curves. [0054] The mandrel 300 includes forward and aft blocks 31 OA and 31 OB, and upper and lower middle blocks 3 IOC and 310D. The blocks 310A-310D may be constructed from any rigid material, such as steel or aluminum alloys. Each of the blocks 310A-310D has an outer surface which defines a portion of a body surface 312 that is geometrically similar to the cross-sectional shape of the interior cavity S of the component C. Optionally, the blocks 310A-310D may be mechanically interlocked so that they may slide apart from each other to expand while maintaining their relative orientation, in the manner described above for the mandrel 100.

[0055] From front to rear, first, second, third, and fourth channels 342A-342D are defined at the mutual intersections of the blocks 310A-310D. Inflatable first, second, third, and fourth tubes 344A-344D are disposed in the channels 342A-342D, respectively. Means are provided for selectively pressurizing the tubes 344A-344D. For example, one end of each tube may be connected to a source of pressurized air such as compressed shop air, and the other end of the tube may be closed off by an end wall or plug. The tubes 344A-344D may be connected to a single air circuit, may be individually inflatable, or may be grouped as desired.

[0056] Four corner channels 346 are defined at the distal corners of the cross-sectional shape of the mandrel 300. An inflatable corner tube 348 is disposed in each of the corner channels 346. Means are provided for selectively pressurizing the corner tubes 348 singly or in groups are provided in the same manner as for the tubes 344A-344D.

[0057] When the tubes 344A-344D and the corner tubes 348 are not pressurized, the blocks 310A-310D are collapsed into the rest position shown in FIG 3. When the tubes 344A-344D and the corner tubes 348 are pressurized, they expand and force the blocks 310A-310D outward, expanding the mandrel outer surface 312 in both axial and radial directions, as indicated by the arrows labeled A and R in FIG. 7. The provision of the corner tubes 348 helps to ensure uniform expansion of the blocks 310A-310D.

[0058] Optionally, a resilient, flexible sleeve 350, similar to the sleeve 150 described above, may be placed over the body surface 312 to prevent markoff.

[0059] FIG. 8 illustrates another exemplary mandrel 400 constructed according to an aspect of the present invention. The mandrel 400 is an elongated member and includes a body 401 having forward and aft ends 402 and 404, and upper and lower surfaces 406 and 408. The transitions between the surfaces are blended with radiused curves. In the particular example illustrated, the upper surface 406 includes a rear portion which extends in the axial direction, and a forward portion that extends at an acute angle to the rear portion. [0060] The body 401 may be constructed from any rigid material, such as steel or aluminum alloys. The body 401 defines a mandrel outer surface 412 which is geometrically similar to the cross-sectional shape of the interior cavity S of the component C.

[0061] A resilient, flexible sleeve 450 surrounds the mandrel outer surface 412. The sleeve 450 is bonded to the body 401 along the upper surface 406, for example using a known adhesive or thermal bonding, to provide a tight tolerance. The sleeve 450 may be made from an elastomeric material such as rubber or RTV. A cavity 452 is defined between the body 401 and the sleeve 450 and is coupled to a source of pressurized air (not shown).

[0062] When the cavity 452 is not pressurized, the sleeve 450 is collapsed against the body 401. When the cavity 452 is pressurized, it expands in both axial and radial directions, as indicated by the arrows labeled A and R in FIG. 8. The sleeve 450 is sized such that its exterior dimensions in the pressurized condition are equal to the dimensions of the interior space or cavity S of the component C.

[0063] The mandrel 400 may be configured specifically to maintain a tight dimensional tolerance of one or more walls W1-W4 of the component C (see FIG. 1). For example, the radius of curvature of the upper surface 406 of the body 401 may be selected to be equal to the radius of curvature of the corresponding outer wall W2 of the component C, minus the wall thickness of the sleeve 450.

[0064] FIG. 9 illustrates another exemplary mandrel 500, similar to the mandrel 400 described above. The mandrel 500 is an elongated member and includes a body 501 having forward and aft ends 502 and 504, and upper and lower surfaces 506 and 508. The surfaces are blended with radiused curves.

[0065] The body 501 may be constructed from any rigid material, such as steel or aluminum alloys. The body 501 defines a mandrel outer surface 512 which is geometrically similar to the cross-sectional shape of the interior cavity S of the component C.

[0066] A resilient, flexible sleeve 550 surrounds the mandrel outer surface 512. The sleeve 550 is bonded to the body 501 along the upper surface 506, for example using a known adhesive or thermal bonding. The body 501 and the sleeve 550 may be configured specifically to maintain a tight dimensional tolerance of one or more walls W1-W4 of the component C as described above for the mandrel 400. The sleeve 550 may be made from an elastomeric material such as rubber or RTV. A cavity 552 is defined between the body 501 and the sleeve 550 and in use is coupled to a source of pressurized air (not shown).

[0067] Four corner channels 546 are defined at the distal corners of the cross-sectional shape of the body 501. An inflatable corner tube 548 is disposed in each of the corner channels 546. Means are provided for selectively pressurizing the corner tubes 548 singly or in groups are provided in the same manner as for the cavity 552.

[0068] When the cavity 552 and the comer tubes 548 are not pressurized, the sleeve 550 is collapsed against the body 501. When the cavity 552 and the comer tubes 548 are pressurized, the mandrel 500 expands in both axial and radial directions, as indicated by the arrows labeled A and R in FIG. 9. The sleeve 550 is sized such that its exterior dimensions in the pressurized condition are equal to the dimensions of the interior space or cavity S of the component C. The provision of the comer tubes 548 helps to ensure uniform expansion of the sleeve 550.

[0069] FIG. 10 illustrates another exemplary mandrel 600 constructed according to the present invention. The mandrel 600 is an elongated member having forward and aft ends 602 and 604, and upper and lower surfaces 606 and 608. The transitions between the surfaces are blended with radiused curves. In the particular example illustrated, the upper surface 606 includes a rear portion which extends in the axial direction, and a forward portion that extends at an acute angle to the rear portion.

[0070] The mandrel 600 is primarily constructed from a resilient, elastomeric material, such as rubber or RTV. A spar 601 is disposed inside the mandrel 600 adjacent to and parallel to the upper surface 606. The spar 601 may be constructed from any rigid material, such as steel or aluminum alloys.

[0071] An inflatable channel 652 is formed in the mandrel 600, parallel to the lower surface 608. In use it is coupled to a source of pressurized air (not shown).

[0072] The material used for the mandrel 600 has a positive coefficient of thermal expansion (CTE). At the temperatures used for curing composites, for example about 1200° C (2500° F) the mandrel 600 expands in both axial and radial directions, as indicated by the arrows labeled A and R in FIG. 10. The provision of the spar 601 stiffens the portion of the mandrel 600 which abuts the outer wall W2 of the component C during the curing process and enhances dimensional precision. [0073] In addition to the thermal expansion of the mandrel 600, pressurization of the channel further expands the mandrel 600 in the radial direction R. The total amount of expansion required in axial and radial directions may be achieved through a combination of pressurization and thermal expansion.

[0074] The apparatus and method described above uses a combination of internal hard tooling pieces combined with expanding means. Any of the mandrels described herein can be configured to either expand in all directions (2-D) or in a single direction (1-D), as required for a particular composite component. The hard expandable mandrel can be combined with RTV to provide additional expansion via the RTV coefficient of thermal expansion (CTE). The expanding action of the mandrels described herein exert pressure on the interior surfaces of a composite layup to stretch the composite fibers to the hard outer tool thus reducing the tendency for buckled fibers.

[0075] It is noted that the inflatable tubes or bladders described above may be replaced by a mechanical expander (not shown) such as a combination of tapered pins or sleeves that are inserted from the free ends of the mandrel to in order to expand it.

[0076] Using the tooling and methods described herein, component quality will be greatly improved and component strength will not be affected by material knockdowns associated with poor laminate quality (i.e. porosity and buckled fibers). The process also provides a method of curing complex geometric hollow parts resulting in good quality laminate micro structure.

[0077] The foregoing has described tooling including an expandable mandrel and methods for its use. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention.

[0078] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0079] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. [0080] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

WHAT IS CLAIMED IS:

1. An expandable mandrel apparatus (100, 200, 300) for making a composite component, the apparatus comprising:

a plurality of blocks (110, 210, 310) of rigid material arranged to form a member elongated in a first direction and collectively defining a body outer surface (112, 212, 312) having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed; and

an expander structure (144, 244, 344) disposed between the blocks, the expander structure operable to expand the blocks in at least one direction perpendicular to the first direction.

2. The apparatus of claim 1 wherein a first one of the blocks (110) includes a tab (114, 118, 122, 126, 130, 134) received in a slot (116, 120, 124, 128, 132, 136) of a second one of the blocks (110).

3. The apparatus of claim 1 wherein the expander structure comprises at least one inflatable tube (144, 244, 344, 348) comprising a resilient material.

4. The apparatus of claim 1 further including a resilient cover (248) overlying at least a portion of a joint between first and second ones of the blocks.

5. The apparatus of claim 1 further including a resilient, flexible sleeve (150, 350) surrounding all of the blocks.

6. The apparatus of claim 1 wherein the elongated member is arcuate and the cross- sectional shape of the body outer surface includes opposed, spaced-apart forward and aft surfaces (102, 104, 202, 204, 302, 304) and opposed, spaced-apart upper and lower surfaces (106, 108, 206, 208, 306, 308) comprising a resilient material disposed at corners defined by adjacent ones of the surfaces.

7. The apparatus of claim 6 wherein the expander structure includes inflatable corner tubes (348) comprising a resilient material disposed at corners defined by adjacent ones of the surfaces

8. The apparatus of claim 1 wherein the blocks (110, 210, 310) are formed from metal.

9. An expandable mandrel apparatus (400, 500) for making a composite component, the apparatus comprising:

a body (401, 501) of rigid material elongated in a first direction and including a body outer surface (412, 512) having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed;

a resilient, flexible sleeve (450, 550) surrounding the body (401, 501); and

an expander structure (452, 552) disposed between the body (401, 501) and the sleeve (450, 550), the expander structure (452, 552) operable to expand the sleeve (450, 55) away from the body (401, 501) in at least one direction perpendicular to the first direction.

10. The apparatus of claim 9 wherein a space (452, 552) between the body (401, 501) and the sleeve (450, 550) is configured to be coupled to a source of pressured gas.

11. The apparatus of claim 9 wherein the body (401, 501) is arcuate and the cross- sectional shape of the body outer surface (412, 512) includes opposed, spaced-apart forward and aft surfaces (402, 404, 502, 504) and opposed, spaced-apart upper and lower surfaces (406, 408, 506, 508).

12. The apparatus of claim 11 wherein the sleeve (450, 550) is bonded to one of the surfaces of the body (401, 501).

13. The apparatus of claim 9 wherein the expander structure includes inflatable corner tubes (548) comprising a resilient material disposed between the body (401, 501) and the sleeve (450, 550), at corners defined by adjacent ones of the surfaces.

14. The apparatus of claim 9 wherein the body (401, 501) is formed from metal.

15. An expandable mandrel apparatus (600) for making a composite component, the mandrel comprising:

a body of resilient material elongated in a first direction and including a body outer surface having a cross-sectional shape geometrically similar to a predetermined interior cavity shape of a composite component to be formed, the body having a positive coefficient of thermal expansion; and a spar (601) of rigid material disposed inside the body.

16. The apparatus of claim 15 further comprising an expander structure (652) disposed inside the body the expander structure operable to expand the body in at least one direction perpendicular to the first direction.

17. The apparatus of claim 16 wherein the expander structure comprises a cavity (652) formed in the body and configured to be coupled to a source of pressured gas.

18. The apparatus of claim 15 wherein:

the body is arcuate and the cross-sectional shape of the body outer surface includes opposed, spaced-apart forward and aft surfaces (602, 604) and opposed, spaced-apart upper and lower surfaces (606, 608); and

the spar (601) extends parallel to one of the surfaces.

19. The apparatus of claim 15 wherein the body is formed from room-temperature- vulcanizing silicone.

20. A method of making a composite component (C), comprising:

placing a composite layup (L) into an outer tool (10), the layup (L) comprising a plurality of fibers embedded in an uncured matrix and shaped so as to define an interior space; placing an expandable mandrel (100, 200, 300, 400, 500, 600) including at least one rigid member into the interior space;

expanding the mandrel (100, 200, 300, 400, 500, 600) so as to force the layup (L) against the outer tool (10); and

curing the composite layup (L).

21. The method of claim 20 wherein the mandrel (100, 200, 300) includes: a body comprising a plurality of blocks (110, 210, 310) of rigid material; and an expander structure (144, 244, 344) configured to expand the blocks (110, 210, 310) in at least one direction.

22. The method of claim 21 wherein the expander structure includes at least one inflatable tube (144, 244, 344) disposed between the blocks (110, 210, 310).

23. The method of claim 20 wherein:

the mandrel (600) includes: a body comprising a resilient, flexible material having a positive coefficient of thermal expansion; and an expander structure (652) configured to expand the body in at least one direction; and

wherein the curing is carried out at an elevated temperature so as to cause the body to expand outward against the layup (L).