JPH0242658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an article,
More particularly, the invention relates to a method for manufacturing an article having a fiber-reinforced plastic bonded to a metal body. More specifically, but not exclusively, the present invention relates to an improved method for producing airfoil.

There are many ways to form or manufacture various structures from fiber reinforced plastics (FRP). Articles made of FRP have cost advantages over similar articles made entirely of metal, since fewer parts are required and therefore manufacturing labor can be reduced. It is possible to manufacture articles with fewer parts because casting FRP provides greater flexibility in using parts with complex shapes. However, in the case of structures that incorporate metal parts,
A secondary bonding process is required to improve the strength of the joint between FRP and the metal body, and
Direct casting and pasting of FRP is restricted. Although various primers have been developed to coat metal parts, bonds formed with laminating resins are generally insufficient for some types of structural bonds.

For example, U.S. Pat. A blade is disclosed. More specifically, the blade root structure disclosed in the above-mentioned patent includes alternating layers of aluminum reinforcement plates and glass fiber cloth impregnated with plastic. A suitable primer is provided between each metal plate and each layer of glass fiber cloth to prevent oxidation of the metal plate and to improve the adhesion between the metal plate and the plastic-impregnated fiberglass cloth. . Such primers are typically in the form of a coating having a thickness of 25.4 to 50.8 microns or less. Alternating layers of metal plates and fiberglass cloth are arranged on the spar member and then adhered to each other by a vacuum injection process in which liquid plastic impregnates the fiberglass cloth and fills the mold. The structure produced by such a method has sufficient strength and integrity (resistance to the shear stresses imposed by the bolts connecting the helicopter blade to the central hub) for its intended function. However, the bond between the metal plate and the fiberglass cloth does not have the strength and integrity required in other applications.

For example, fixed-wing aircraft have been using FRP propeller blades for the past 20 years. These propeller blades typically include a preformed FRP shell that is permanently bonded to a central metal spar, with the space between the shell and the spar completely filled with foam. . Between the shell containing glass fibers and the metal wing spar, for example
Some type of adhesive, such as a thermosetting, non-volatile modified epoxy resin such as AF111 manufactured by Mining & Manufacturing Company, is applied as a film on the wing spar before bonding the fiberglass shell to the wing spar. This provided sufficient structural integrity. Adhesives such as those described above can provide bond strengths that are significantly superior to those possible with the primers used in the aforementioned U.S. Pat. No. 3,321,019, and are therefore A spar-shell bond in the structure of the application can be formed. However, it will be appreciated that the method described above takes a long time to manufacture the blade. That is, in the above method, first a cast-molded FRP shell is formed,
A secondary bonding step is then required to join the shell and spar together.

Accordingly, a primary object of the present invention is to provide an improved method for manufacturing various fiber reinforced airfoils such as propeller blades. Such objectives include reducing manufacturing effort while maintaining or improving the uniformity or reproducibility of the product's structural characteristics and dimensions.

The present invention provides an improved method for manufacturing articles made of fiber-reinforced plastics bonded to metal bodies. Adhesive on the surface of the metal body,
It is coated with a thermosetting, non-volatile modified epoxy resin liquid adhesive which has excellent adhesive properties, especially after early curing. The thickness of the adhesive is 127 mm, which is necessary to compensate for dimensional errors in the metal body.
~1016μ and is formed into the desired shape in a mold. The adhesive is pre-cured and one or more layers of reinforcing fibers, such as glass fiber cloth, are applied to the adhesive-coated surface of the metal body. The fibers are impregnated with liquid plastic either beforehand or after the dressing process described above. The fiber-covered article is placed in a mold, and a liquid plastic, such as a polymeric composite (e.g., a thermosetting resin), is introduced into the mold, thereby impregnating the reinforcing fiber layer on the object with the liquid plastic. Preferably. After the step of impregnating the reinforcing fiber layer, the polymer composite (liquid plastic) is solidified in a mold and formed into an article according to the shape of the mold. By casting the glass fibers together with the adhesive-coated metal body in one step, a strong bond is formed between the glass fiber cloth and the metal body, and an otherwise secondary bond is created. The labor that would be required in the process can be substantially reduced.

In one preferred embodiment of the invention, the manufacturing method according to the invention is used to manufacture airfoils such as propeller blades. First, the blade subassembly is formed. This involves coating the metal spar with sufficient adhesive to compensate for its dimensional errors, then removably coating the inner circumferential surface of the subassembly mold with adhesive, and then moving the spar into the mold. the adhesive is partially solidified, the foam is introduced into the mold, and the foam is finally bonded to a portion of the spar to form the blade subassembly. It is formed by early curing of the adhesive. The blade subassembly thus formed is covered with reinforcing fibers, such as fiberglass cloth, and placed in a final mold into which a liquid plastic, such as a thermosetting resin, is injected and solidified, thereby Blade manufacturing is completed. The resin-impregnated glass fibers are bonded by adhesive to the foam in some locations and to the metal spars in other locations. Additionally, a protective metal sheath with an early-cured adhesive applied to the inner circumferential surface may be placed on the outer surface of the fiberglass cloth prior to the resin impregnation step, thereby providing an integral part of the produced blade. It may be incorporated into the blade as a component.

The invention will now be described in detail with reference to preferred embodiments and with reference to the accompanying drawings.

FIG. 1 of the accompanying drawings is a cross-sectional view of an airfoil, such as a propeller blade 10, manufactured according to a method according to the prior art. propeller blade 10
Outer shell 1 made of fiber-reinforced plastic
2, the outer shell is bonded with an adhesive 14 to an aluminum wing spar 16 extending substantially in the center of the outer shell to obtain an air-oil accuracy that is less than or equal to the combined tolerance of the wing spar, outer shell, and adhesive thickness. It is joined together. Outashiel 12
After the blade spar 16 and the blade spar 16 are joined together, the space between the outer shell 12 adjacent to the blade spar 16 is filled with a lightweight filler material such as a rigid urethane foam. A protective metal sheath 18 is then attached to the leading edge of the blade 10 and adhered with adhesive 19.

The outer shell 12 was formed by vacuum bag forming on a convex shell mold or mandrel in which the glass fibers were impregnated with a thermoset resin which was then solidified. The outer shell 12 is generally formed as a unitary structure having sufficient grooves along its leading edge to facilitate the introduction of the wing spar 16. Further, the trailing edge of the outer shell generally has a groove formed over its entire length, and is bonded with adhesive 15 after inserting a wing spar 16 having a film-like adhesive 14 on its surface. Adhesive 14 is then solidified by heat and pressure to provide the desired bond. By injecting a foaming liquid into the space defined by the outer shell 12 and the wing spar 16 and solidifying it with heat, the foamed material 17 formed in the space is well retained. , a bond coating mixture consisting of an epoxy resin, a polyamide solidifying agent, and toluene is used to coat the surfaces defining the space. Therefore, a considerable amount of time is required to prepare and complete the joining of the wing spar 16 and sheath 18, and to complete the blade.

In contrast to relatively complex prior art methods of manufacturing blades, in the method of manufacturing according to the present invention, the blade 30 is formed by an in situ molding process, as shown in FIG. The effort required to manufacture the blade is therefore reduced.
Blade 30 is structurally similar to conventional blade 10 and includes a fiber-reinforced plastic outer shell 32 bonded to an aluminum spar 36 that is bonded to a specific adhesive 34 in contact with the spar and outer shell. Bonded by layers. Further, the space between the outer shell 32 and the wing spar 36 in front and behind the wing spar is filled with a lightweight filler such as a rigid urethane foam 37. A protective nickel sheath 38 is also bonded to the leading edge portion of the outer shell 32 by a suitable adhesive 39. However, in the manufacturing method according to the present invention, the manufacturing of the blade 30 is considerably simplified compared to the blade 10 according to the prior art, and the accuracy of the dimensional tolerance and the reproducibility of the dimensional tolerance for each blade are improved to some extent. There is.

FIG. 3 shows that an outer shell 32 made of fiber-reinforced plastic is attached to an aluminum wing spar 3 by an adhesive 34.
FIG. 6 is an illustrative partial cross-sectional view showing an enlarged state in which the device is joined to the device shown in FIG. The selection of adhesive 34 used to carry out the manufacturing method according to the invention is a matter of relative importance, and in the preferred embodiment,
Thermosetting and non-volatile modified epoxy resin liquid adhesive, especially Minnesota, USA
EC− by Mining & Manufacturing Company
An adhesive sold under the trademark 2214R is used. Such adhesives, and similarly modified epoxy resin adhesives, when prematurely cured, provide a particularly strong bond between the metal substrate (aluminum spar 36) and the FRP resin (outer shell 32). This adhesive 34 is applied in situ.
The adhesive 34 is first applied to the aluminum spar 36 and pre-cured, and then reinforcing fibers, such as glass fiber cloth, are placed over the adhesive-applied surface of the aluminum spar, e.g. It facilitates carrying out a molding process in which a liquid plastic is impregnated with a liquid plastic, such as a curable epoxy resin, and then the liquid plastic is allowed to solidify while contained within a mold having the desired article shape.

A particular method of manufacturing an airfoil or propeller blade 30 will now be described in detail with reference to the accompanying FIGS. 4-9, which successively illustrate various aspects of the blade manufacturing method according to the invention. FIG. 4 shows a conventional elongated aluminum wing spar 36 having a root section 50 and a tip section 52. This spar 36 is the primary reinforcing member for the blade 30. Substantially the entire surface of the wing spar 36 except for its root portion 50 is coated with adhesive 34 . Adhesive 34 is diluted with methyl ethyl ketone in a conventional manner and applied by spraying onto the spar to a thickness of about 76.2 to 127 microns. The adhesive 34 is then allowed to solidify for about 45 minutes at a temperature of about 121 DEG C., then wiped with methyl ethyl ketone and its surface ground by sandblasting. Add 3 more adhesives until the thickness is approximately 254-305μ.
Coating No. 4 is sprayed onto the previously applied adhesive coating. Finally, a paste adhesive 34 is applied to the adhesive already applied to the upper and lower surfaces of the wing spar 36, so that the adhesive adheres to the wing spar and fills the micro-recesses in its surface. Further, it is finished to the final size until it reaches a dimension that at least continuously contacts the upper inner circumferential surface and the lower inner circumferential surface of the first mold. The thickness of the adhesive 34 on the top and bottom surfaces of the spar 36 ranges from about 127 to 1016 microns or more.

The other half of the blade subassembly mold
Similarly coated with 254-305μ of adhesive 34.
One half of such a mold is designated 60 in FIG.
Illustrated in. The cavity of the mold half 60 is first coated with a conventional mold release agent such as Kanstik LM and then coated with Arcon 5003. The adhesive 34 diluted with methyl ethyl ketone as described above is then applied by spraying onto the mold release agent applied to the mold cavity over substantially the entire blade area except the root portion 50.

The adhesive coated wing spar 36 of FIG. 4 is placed in a mold half 60 also coated with adhesive, and then another mold half is placed thereon. Adhesive 34 is then partially solidified by heating to 99°C for approximately 30 minutes. The mold cavity of the blade subassembly mold 60 has an adhesive 34 attached to the upper and lower surfaces of the wing spar 36.
The blade is substantially wider than the spars 36 forward and aft of the blade, thereby creating a space in those areas for receiving the urethane foam 37. ing. After injecting nitrogen into the mold, a two-component semi-prepolymer is mixed in appropriate proportions to form a rigid urethane foam 37, which then fills the space not occupied by the spar 36. The liquid is introduced into the sealed mold 60 by injection from the bottom thereof. Finally, the adhesive 34 is applied onto the urethane foam 37 and the wing spar 36, and is also removably applied onto the mold 60.
It is cured by heating at a temperature of 121°C for 45-60 minutes. The mold 60 is then cooled and a spar/foam blade subassembly 70 as shown in FIG.
taken out from

Blade subassembly 70 is only slightly smaller than final blade 30 and is coated with pre-cured adhesive 34 over substantially its entire outer surface except for the root section 50. The adhesive on the foam material 37 is transferred from the inner surface of the mold 60, and the adhesive on the upper and lower surfaces of the wing spar 36 is applied directly to these surfaces. Such a coating of pre-cured adhesive 34 has a thickness of at least 127 to 254 microns and has a thickness of at least 127 to 254 microns
In order to fill and smooth minute irregularities such as scratches and grooves formed on the surface of 6, it may have a thickness of 1016μ or more, which results in relatively high quality and high precision. A blade subassembly 70 is provided having a surface. The adhesive 34 thus serves to size the subassembly 70, thereby ensuring that the dimensions of the subassembly are reproduced. Furthermore, this adhesive 34
The coating protects the spar 36 and foam 37 to some extent from handling damage during subsequent steps in the manufacturing process.

The pre-cured adhesive 34 coating is then cleaned by wiping with methyl ethyl ketone and sandblasted in preparation for subsequent bonding. The root portion 50 of the subassembly 70 is then fitted with a suitable fixture (not shown) for disposing the reinforcing fibers.
installed inside.

FIG. 7 shows a blade subassembly 70 coated with one or more reinforcing fiber layers. In the illustrated embodiment, for example United
Sold by Merchants Company
Four to seven layers of non-woven fiberglass cloth 71, such as Style 1581, are aligned with the axis of the blade, i.e.
It is wrapped very tightly around the blade subassembly at a 35 degree angle and is held in place by stitching at the location indicated at 72. Glass fiber cloth 71 is foam material 37
and extends inwardly toward the root section 50 and engages the adhesive 34 on the wing spar 36 so as to completely enclose the foam 37 . The glass fiber cloth 71 is made of aramid, graphite,
It will be appreciated that other high strength reinforcing fibers such as boron and the like may be substituted. A protective nickel sheath 38 is then crimped over the leading edge of the fiberglass-coated subassembly 70 near the tip 52. In this case, the sheath 38 is temporarily held in place by some flexible engagement with the fiberglass sheath. The surface of the sheath 38 that engages the glass fibers is precoated with an adhesive 39 that is substantially the same as the adhesive 34 and pre-cured in substantially the same manner as the adhesive 34. . A heating wire 76 may be placed at the leading edge of a fiberglass cloth 71 wrapped in an area near the root portion 50 of the blade subassembly 70, in which case the heating wire 76 may be temporarily attached by attaching it with cotton thread. May be retained.

In FIG. 8, the fiberglass cloth-covered blade subassembly 70 of FIG. will be placed in In the first stage of the final casting process, the opposing halves of the final mold 80 are not in the fully open position but in a slightly opened position, for example, about 0.5 mm.
They are held slightly spaced apart by two or more thick spacers 82 . A compressible O-ring 84 is located between the two halves of the final mold 80.
is placed, and this O-ring is secured to a suitable clamp 86.
etc., the three halves of the final mold are fitted with spacers 82.
When pressed against the mold cavity, it acts to sealably close the mold cavity in a well-known manner.
A vacuum port 88 formed in the upper half 80 is connected to a vacuum source, not shown, and the required liquid plastic is then introduced into the mold cavity via an inlet port 89. In this case liquid plastics, polymerizable synthetic materials such as thermoset epoxy resins such as APCO 434 sold by Applied Plastics Company are preferred.

It is generally difficult to obtain the high glass/resin ratios required for various airfoils such as propeller blades, especially when the number of glass fiber layers is large. However, in the method according to the present invention,
By providing the spacer 82 between the two halves, complete wetting of all layers of the glass fiber 71 can be done quickly and easily even when using a high viscosity resin that cannot normally be used. Can be done.

In FIG. 9, when the resin injection is completed, the mold spacer 82 is removed and the mold 80 is completely closed. Excess resin is forced out of the mold cavity via vacuum port 88 and inlet port 89. At this stage of the final casting process, when the mold 80 is completely closed, the mold cavity defines the shape to form the desired final product, the blade 30, with great precision and over a long period of time. . The resin is heated in mold 80 to a temperature of about 121 DEG C. for about 45 to 60 minutes to polymerize and thereby solidify the resin. This solidification of the resin around the glass fibers forms a glass fiber reinforced outer shell 32 and creates a particularly strong bond between the pre-cured adhesive 34 and the wing spar 36. . A similar joint is formed between outer shell 32 and foam 37 with the aid of adhesive 34 in that area. Furthermore, the sheath-like body 38 is firmly adhered to the outer shell 32 by the adhesive 39. The mold 80 is then cooled, after which the blade 30 is removed from the mold in a substantially fully formed state. Generally, the amount of resin that spills out around the centerline of the mold is minimal, so it can be easily removed.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various modifications and omissions may be made within the scope of the present invention. will be clear to those skilled in the art. For example, impregnating reinforcing fibers with liquid plastic may be accomplished by methods other than injecting the liquid plastic into a mold. For example, the fiberglass fabric may be pre-impregnated with epoxy resin and partially cured before being placed on the substrate or subassembly, and the epoxy resin may be pre-impregnated with the epoxy resin while the fiberglass fabric is placed on the subassembly. may be brushed onto a fiberglass cloth and then allowed to harden in a mold. However, in the case of these methods, the reduction in manufacturing cost achieved by the above-mentioned preferred method can only be achieved to a certain extent.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a propeller blade manufactured by a prior art method. FIG. 2 is a schematic cross-sectional view similar to FIG. 1 showing a propeller blade manufactured by the method according to the invention. FIG. 3 is an illustrative enlarged partial sectional view showing a portion of the blade shown in FIG. 2 on an enlarged scale. Fourth
The figure is an illustrative perspective view showing the spars of the blades coated with adhesive. FIG. 5 is an illustrative perspective view of one half of a mold coated with adhesive for manufacturing a blade subassembly. 6th
The figure is an illustrative perspective view showing the blade subassembly. FIG. 7 is an illustrative perspective view of the fiber reinforced blade subassembly prior to final shaping. FIG. 8 is a schematic cross-sectional view of the blade subassembly shown in FIG. 7 along with the final mold during the first stage of the final casting process. 9th
The figure is an illustrative cross-sectional view similar to FIG. 8 showing the blade at the second stage of the final casting process. 10...Blade, 12...Outer Ciel, 1
4... Adhesive, 16... Wing spar, 17... Urethane foam (foaming material), 18... Sheath-shaped body, 30...
Blade, 32... Outer shell, 34... Adhesive, 36... Wing spar, 37... Urethane foam (foaming material), 38... Sheath-shaped body, 39... Adhesive, 5
0...Root part, 52...Tip part, 60...Half body, 70...Blade subassembly, 71...
Glass fiber cloth, 76... heating wire, 80... final mold, 82... spacer, 84... O ring,
86... Clamp, 88... Vacuum port, 89...
...Inlet port.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a rotor blade having a metal spar bonded to a fiber-reinforced plastic material, comprising: coating the outer surface of the spar with a curable adhesive; forming a transferable coating of a curable adhesive on an inner surface of a mold; disposing a wing spar coated with the coating in the first mold; defining a spatial region spaced apart from and between at least a portion of the wing spar to which the coating is applied; and introducing a curable lightweight filler into the spatial region formed in the first mold. , the curable adhesive and the curable lightweight filler are early cured in the first mold, and the outer surface contains the filler bonded to the wing spar by an adhesive and is early cured on the outer surface. forming an airfoil subassembly having a coating made of an adhesive; and wrapping the entire airfoil subassembly with a covering made of a fiber reinforced material having a predetermined fiber length; placing the thus covered Aerofoil subassembly in a second mold having a predetermined final shape of the Aerofoil, coating the fiber reinforcement in the second mold with a polymer composite, or A method for manufacturing a rotor blade, comprising: impregnating with a polymer composite material; and curing the polymer composite material in the second mold, thereby forming an airfoil having a predetermined shape. . 2. The manufacturing method according to claim 1, wherein the second mold includes a pair of mold halves that can be moved between an open position and a closed position, and when in the closed position, The Aerofoil subassembly is configured to define a mold cavity that accurately corresponds to the Aerofoil of a predetermined shape, and is covered by the fiber reinforcement within the second mold through each of the steps. is formed, the step of introducing a polymer composite into the second mold includes maintaining the second mold in a slightly open position, and the step of introducing the polymer composite into the second mold includes maintaining the second mold in a slightly open position; A mold cavity having an airfoil subassembly covered by a compressible sealing device is sealed by a compressible sealing device such that when the second mold is in a slightly open position, the required amount of polymer composite material is released. A method of manufacturing, characterized in that it is introduced into the mold cavity, the halves are closed and the polymer composite is cured. 3. The manufacturing method according to claim 1, wherein the outer surface of the wing spar and the inner surface of the mold are coated with the same adhesive, and the adhesive is a non-volatile thermosetting adhesive. The epoxy liquid is a modified epoxy liquid, wherein the filler is a rigid urethane foam, the fiber reinforcement is made of glass fiber, and the polymer composite is a thermosetting epoxy resin. Production method. 4. In the manufacturing method as set forth in claim 1, the two outer surface portions on both sides of the wing spar are spaced apart by at least 127 μm from the inner surface of the first mold, and the outer surface of the wing spar A manufacturing method characterized in that the adhesive coating formed on the side surface is formed to have a sufficient thickness to contact the inner surface of the first mold. 5. The manufacturing method as set forth in claim 4, wherein each of the outer surface of the spar and the inner surface of the first mold includes an adhesive layer having a thickness of at least 127 μm on the spar. is formed and coated with an adhesive so that an adhesive layer of at least 254 μm is formed on the inner surface of the first mold, thereby forming the airfoil sub-layer formed after the early curing step. A method of manufacturing, characterized in that the adhesive coating on the outer surface of the assembly is at least 127 μm thick. 6. In the manufacturing method as set forth in claim 5, the wing spar is provided with an inner first adhesive coating having a thickness of 76.2 to 127 μm, and the first adhesive coating is cured. , further comprising applying a second adhesive coating as an outer coating on the first adhesive coating, thereby forming an outer adhesive layer having a thickness of at least 254 μm. 7. In the manufacturing method according to claim 1, the adhesive coating on the outer surface of the wing spar and the adhesive coating on the inner surface of the first mold are made of the same adhesive, The method of manufacturing is characterized in that the adhesive coating formed on the inner surface of the first mold comprises a non-volatile, thermosetting modified epoxy liquid adhesive. 8. The manufacturing method according to claim 7, wherein the adhesive film is formed by a spray method. 9. A manufacturing method according to claim 3, characterized in that the glass fiber reinforcement is a multilayer glass fiber cloth. 10. The manufacturing method according to claim 3, wherein the spar includes a root end and a tip end, and the urethane foam extends over most of the spar, The glass fiber reinforcement is formed by a glass fiber cloth, the glass fiber cloth wrapping the entirety of the urethane foam, extending beyond the urethane foam toward the end of the wing spar, and extending along the root. A method of manufacturing comprising contacting an adhesive coating on the spar near an end, thereby isolating the urethane foam from its surroundings.