JPH02229024A - Method for controlling hardening of composite body - Google Patents

Abstract

PURPOSE: To exclude a volatile matter from air during laying-up if necessary by adapting a mold release agent to a mold and coating the lay-up placed on the mold with an air impermeable flexible film forming a seal preventing the outflow of an uncured resin to heat the same to a resin curing temp. CONSTITUTION: Before a lay-up 12 containing an uncured resin is placed on a mold 10, a usual mold release agent or a material 14 is placed on the mold. The lay-up 12 is a laminate containing a fiber reinforcing material embedded in a thermosetting resin or a perfectly stiffly kneaded product. An air permeable material 18 is directly placed on the mold 10 coated with the mold release material 14 so as to surround the lay-up 12 to achieve the removal of air. The lay-up 12 and the air permeable material 18 are sealed in a vacuum bag 20 sealed to the mold 10 by the sealing material 22 spreading around the vacuum bag to be directly placed between the vacuum bag and the mold. Further, a sealing material 26 is utilized in close vicinity to a connection pipe 24 in order to keep the certain seal capable of evacuating the vacuum bag 20.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION This invention relates to a method of forming a composite structure, and more particularly to a method of forming a composite structure.
The present invention relates to a method of forming composite structures utilizing non-breathable flexible films that provide uniform pressure distribution and help prevent resin flow from the layup during the curing cycle. .

It is known to utilize vacuum bag molding methods to provide the desired compressive force to the resin-impregnated layup during heat curing of the composite structure tube.

In order to obtain a good quality product, it is essential to remove all the air from the layamp formed as a composite structure, or, depending on the resin used, the gases generated from the resin due to polycondensation that occurs during heat curing. It is.

By the way, previous systems utilized to exclude air or volatiles did not accomplish their intended task and inevitably
A sump passageway was provided for excess resin to drain from the layup during the curing cycle.

Previous systems have used layers of various breathable materials, including glass cloth, porous mats, etc., in communication with both the layup and a vacuum source.

A decrease in the viscosity of the resin within the layup as a result of increased temperature during the curing cycle can result in destructive resin spillage, reduced strength, an unacceptable product, and the possibility of clogging the vacuum system. became.

Bleeding phenomenon of excess resin coloring during curing of the composite (b
leading) or squeezing phenomenon
One solution to the problem of ze-out is found in U.S. Pat.

There, a breathable material is used and air is removed from the layup during the early stages of the curing cycle, but resin has been shown to flow into the breathable material and block it. Despite one advance shown in the aforementioned patent, actual experiments have shown that even supplying a breathable material between the resin-impregnated layup and a vacuum source removes undesirable resin from the layup during the curing cycle. A leak occurred.

Other methods that have been utilized to control resin flow from layups include so-called ``stepped cures.''
During the staged curing operation, the layup was heated to very precise temperatures to ensure no excessive color bleeding or squeezing. The compaction process, typically using a pressure source external to the vacuum system, can reduce the bleeding phenomenon of excess resin coloring from the layup and/or during the layup. is started at very precise times during the curing cycle to avoid solidification of the resinous material.

Therefore, a new method of curing composites is needed that allows precise control of the proportion of resin and reinforcement in the layup by completely preventing the phenomenon of squeezing out the resin from the layup during the curing cycle. . Therefore, it was desired to establish a new system that can utilize highly elastic films that can be easily tailored into composite structures of specific shapes.

In addition, air during layup, volatile matter if necessary,
It is necessary to establish a new system for elimination. The present invention satisfies these needs and provides other related advantages.

[Summary of the invention]

The present invention relates to an improved method for economically manufacturing composite structures that can be formed into a variety of products in a variety of situations, and that provides precise control over the resin content of the reinforced composite structure. The method typically involves applying a mold release agent to the mold and then placing a layup containing uncured resin onto the mold. This layup is ultimately formed into a composite structure. The layup is covered with a non-breathable flexible film that forms a seal that prevents spillage of uncured resin and then maintains an even pressure distribution on the surface of the non-breathable flexible film facing the layup. The resin is cured to form a composite product by heating to curing temperature.

One preferred form of the invention is to coat a non-breathable flexible film with a breathable material that provides cushioning to help even out the distribution of externally applied pressure over its entire surface. be. The layup, non-breathable flexible film, and breathable material are enclosed in a bag sealed to the mold by a sealant extending around the bag and placed directly between the bag and the mold. During the curing operation, the breathable material is vented to the outside air to create a specific pressure that helps uniformly compress the layup.

This preferred method provides lining of the layup between the outer surface of the layup and the inner surface of the non-breathable flexible film that resists curing temperatures without bonding with the layup's resin. Further improvements can be made by using adhesive tapes that can be used to Such adhesive tape further helps to ensure that there is no bleeding of resin coloring from the layup during the curing cycle. Additionally, the adhesive tape can be used in combination with one or more abrasive materials to ensure that the layup is held in the desired orientation during the curing cycle. Layup using abrasive materials is advantageous as the layup typically changes excessively due to the reduction in viscosity of the resinous material that occurs during the curing cycle.

Another preferred form is to further coat the exposed surfaces of the layup with a mold release material after placing the layup on the mold. An inflatable bag having a non-breathable flexible outer surface is placed in close proximity to the release material covering the exposed surface of the layup. This inflatable bag effectively seals the layup to prevent spillage of uncured resin during the curing cycle. By pressurizing the inflatable bag, the layup can be pressure bathed during the curing cycle to increase the final strength of the composite structure. Additionally, when the inflatable bag is pressurized by the autoclave system, the bag can be effectively utilized to simultaneously heat the layup to resin curing temperatures.

If it is necessary to remove air from the layup, the present invention
It provides a convenient method for removing such air after placing the layup on the mold and before covering the layup with a non-breathable flexible film.

Additionally, the layup can eliminate excess air by placing a breathable material around the layup and directly onto the mold covered by the release material. The layup and breathable material are then encapsulated in a vacuum bag sealed to the mold by a sealant;
The breathable material is then connected to a vacuum source for a minimum of 10 minutes.

Similarly, layamps can be made into non-breathable materials by placing a breathable material around the layup and by inserting a layer of release material between the breathable material and the layup to prevent resin migration. Volatiles can be removed from the layup before coating with the flexible film. As with the air evacuation step, the layup and breathable material are enclosed in a vacuum bag and connected to a vacuum source. The layup is then heated to drive out volatiles, but not to reduce the viscosity of the resin within the layup to the point where it flows through the release material and bag into the venting material.

Other and advantageous aspects of the invention will be illustrated by the following detailed description, which explains the principles of the invention by way of example and in conjunction with the drawings.

[Detailed explanation of preferred specific examples]

DETAILED DESCRIPTION OF THE INVENTION As shown in the drawings, the present invention is directed to an improved method for controlling the curing of composites. First of all,
The improved method is to apply a mold release material to the mold, and then place the Ray'r tube containing the uncured resin on the mold together with the Ray amplifier that forms the composite structure after the curing cycle. Consists of.

If necessary, the layup is bagged and subjected to vacuum to remove air or volatiles. The layup is covered with a non-breathable flexible film that forms a seal that prevents the escape of uncured resin from the layup during the cure cycle. After coating with a non-breathable flexible film, pressure is applied on the surface of the non-breathable flexible film relative to the layup to give the necessary compaction to form a high strength composite structure. Heat the layup to resin curing temperature while maintaining uniform distribution.

One preferred form is to coat the non-breathable flexible film with a breathable material that provides a cushion that helps to even out the distribution of externally applied pressure over the entire surface of the non-breathable flexible film. It is to be. This breathable material, as well as a layup and non-breathable flexible film, is encapsulated within a bag that is stamped and sealed to the mold by a sealant spread around the bag and directly between the bag and the mold. placed in between. Breathable materials are in contact with the outside air,
The layup is then heated to the resin curing temperature while maintaining an even pressure distribution on the opposing bag surfaces. By connecting the breathable material with the outside air, a specific pressure is created, characterized by an externally applied pressure uniformly distributed over the surface of the layup.

In another preferred form, the exposed surfaces of the layup are coated with a mold release material after being placed on the layup mold. An inflatable bag with a non-breathable flexible outer surface is placed in close proximity to the release material in a way that effectively seals the layup to prevent uncured resin from escaping from the layup. be done. Upon heating the layup to the resin curing temperature, the inflatable bag is simultaneously pressurized to provide a uniform pressure distribution over the release material covering the exposed surface of the layup.

The improved method of this invention also contemplates effective control of the precise amount of resin cured during layup. This is accomplished by preventing resin from flowing out of the layup during the curing cycle as the resin's viscosity decreases and flows freely.

Furthermore, in order to achieve such results, the present invention
It utilizes a non-breathable, flexible film that typically has a non-uniform structural morphology and is useful for use in many composite product manufacturing processes. Furthermore, the present invention provides a convenient method for draining from within the layup as well as a method for removing volatiles if desired.

In accordance with the present invention, and as illustrated with respect to the first embodiment of FIGS. 1-5, a method of controlling the curing of a composite includes the use of a mold designated by reference number 10. and the composite structure is cured. Although the mold 10 shown in the accompanying drawings is flat, the composite structure is not flat and the mold can be made into any desired shape. Layup 1 containing uncured resin
2 onto the mold 10, a conventional mold release agent or material 14 is placed on the mold to facilitate removal of the composite structure at the end of the curing cycle.

The layup 12 can be a laminate, a sand inch or a fully kneaded product that includes a layer 16 of fiber reinforcement embedded in a thermoset resin. A laminate comprising a layer 16 of fiber reinforcement wrought into such a thermoset resin is shown in all the accompanying drawings.

For some types of layup 12, it is preferable to remove exhaust air from the layup after it is placed on mold 10. Such removal is accomplished by placing a breathable material 18 directly over the mold 10 coated with the mold release material 14 and around the layup 12, as shown in FIG. can do. The layup 12 and breathable material 18 have a sealant 2 spread around the vacuum bag.
2 vacuum bag 20 sealed against mold 10
and placed directly between the vacuum bag and the mold. This vacuum bag 20 is directly connected to a source (not shown) and has a connecting pipe 2 for placing the breathable material 18 thereon.
It has 4 consecutive openings. Furthermore, sealing material 2
6 is utilized in close proximity to the manifold 24 to maintain a positive seal that allows a vacuum to be created within the vacuum bag 20. Preferably, the vacuum maintained on the layup 12 through the breathable material 18 is maintained for at least 10 minutes to ensure complete evacuation of air. After the air in the layup 12 has been sufficiently evacuated, the material surrounding the vacuum bag 20 and the breathable material 18 is removed from the mold 10 and the layup in accordance with the operation of the invention described below.

When curing certain composite structures, it is preferable to remove volatiles from the layup 12 prior to beginning the curing cycle. After placing the layup 12 on the mold release material 14 proximate to the mold 10, as shown in FIG. Removal of volatiles is accomplished by placing a breathable material 18a around it. A layer of release material 28 is preferably inserted between the breathable material 18a and the layup 12 to prevent migration of resin from the layup. Next, sealant 2 is spread around the vacuum bag.
Layup 12 and breathable material 18a are enclosed within a vacuum bag 2Oa sealed to mold 10 by 2a and placed directly between the vacuum bag and the mold. As in the previously described process for evacuating air from layup 12, connecting tube 24a is provided to connect breathable material 18a to a vacuum source (not shown). The lay-up 12 is then drained of volatiles and is coated with release material 2.
The resin in the layup is heated to a temperature that does not reduce its viscosity until a large amount of the resin in the layup flows out through the air-permeable material 18a through the vacuum bag 20a. This temperature depends on the composition of the resin, but is usually 100° C. or lower. Furthermore, this vacuum is preferably maintained for at least 15 minutes. The air evacuation and volatile removal processes are very similar, as shown in Figures 1 and 2.
If necessary, they can easily be performed simultaneously.

After completely removing the volatiles from the layup 12, the material proximate the venting material n 18 a and the inserted mold release material 28 are removed from the mold 10 and the layup 12, and the composite of the present invention The method to control the hardening of
The implementation is as best shown in FIG. There, the layup 12 is covered with a non-breathable flexible film 30 that forms a seal around the layup 12 that prevents spillage of uncured resin during the curing cycle. Preferably, the non-breathable flexible film 30 extends around the layup 12 a distance of at least 50 mm to provide a complete seal. A non-breathable flexible film 30 with a breathable material 32 serving as a cushion that evens out the distribution of external pressure applied on the surface of the non-breathable flexible film.
Cover. As shown, the breathable material 32 has approximately the same dimensions as the non-breathable flexible film 30.

The breathable material 32 and the non-breathable flexible film 30 are
It is enclosed within a bag 34 that is sealed to the mold 10 by a sealing material 36 that extends around the bag and rests directly between the bag and the mold. A connecting tube 38 is sealed to the bag 34 by a sealing material 40 through which the breathable material 32 is connected to atmospheric pressure. By opening the breathable material 32, the bag 34
The pressure applied outside of the material serves to compress the breathable material, while it provides compression pressure to the layup 12 in such a way as to uniformly compress the layup in the desired manner during heating. It is. A lay-up that forms a composite structure under the influence of uniform pressure distribution by preventing squeezing out of the resin from the lay-up 12 and as a result by precisely controlling the actual resin content within the lay-up. Curing of gave a product of very high strength. Additionally, similar heating and pressurization of the layup during the curing cycle was advantageously and economically accomplished by simply inserting the layup, mold 10, and encapsulation device into an autoclave.

The method generally illustrated by the apparatus of FIG. 3 is to place adhesive tape 42 over the perimeter of layup 12 between the outer surface of the layup and the inner surface of non-breathable flexible film 30. Improved by adding Adhesive tape 42, which is added to the system of FIG. 3, is shown in FIG. Adhesive tape 42 must be of a composition that is capable of resisting curing temperatures without bonding to the resin of layup 12. Adhesive tape 42 preferably overlaps both layup 12 and mold 10 by a distance of at least 2 inches.

Although the drawings show a flat mold 10 and a flat layup 12, most of the composite structures are not flat. Therefore, the last layer 16 of the laminate forming the layup
are required and these layers act to reduce the viscosity of the resin during the curing cycle. Figure 5 shows
Abrasive material 2 is placed on top layer 16a and bottom layer 16b of fiber reinforcement material.
6, and taping the adhesive material to the mold with adhesive tape 42 in the same manner as already described in connection with FIG. Adhesive material 44 may be grass cloth, sandpaper, or other similar material that maintains the desired layup during the curing cycle. Adhesive tape 4
The function of 2 is similar to holding the adhesive material 44 in close proximity to the release material 14.

Of course, as shown in FIGS. 4 and 5, the function of adhesive material 44 and adhesive tape 42 is to bond to layup 12 at the desired location as well as to more completely seal the resin in the layamp. It is something that In this case, adhesive tape 42 should be placed around the entire perimeter of the layup, and adhesive material 44 can be placed only where needed around that perimeter.

In a second embodiment of the present rib, applying pressure to the layup in different ways as shown in FIG. 6 provides a uniform compressive force to the layup 12 and squeezes out the resin. A general principle is presented for curing composite structures while preventing In this second embodiment, the pressure applied to the layup 12 is provided by an autoclave or similar means using a pair of elastic or inflatable bags placed within the mold 10a.

The illustrated mold 10a includes similar upper plates 48 and lower plays 1-50 connected to mutually vertical walls 52. The right angle gap 54 is connected to a pair of bolts 56
and is located proximate the contact point of the wall 52 and the lower plate 50, and the soil plate 48 is connected directly to these walls by two bolts 58.

In placing the layup 12 proximate the mold IGa as described in connection with the first embodiment, the layup is placed proximate the elastic bag 46 and the mold release material 6
A layer of 0 is inserted between the elastic bag and the layup. The elastic bag is supported within the mold 10a by specific means 62 that hold it at the desired compression pressure when pressurized. Additionally, the pressurization of the inflatable bag 46 effectively seals the layup 12 to the mold 10a to prevent uncured resin from flowing out of the layup.

A portion 64 of the layup 12 is disposed between adjacent inflatable bags 46, and the middle portion of the layup is
It is advantageously compressed by the relative forces of the bags upon pressurization. In this way, the composite structure is effectively formed using the elastic bag 46 as an extended portion of the mold 10a. Since the inflatable bag 46 is pressurized by the method of heating the layup 12 and by a method independent thereof, the inflatable bag is pressurized by the autoclave system to provide the desired simultaneous pressurization and heating. It is preferable.

From the foregoing, this novel method of controlling curing of composites provides precise control of the amount of resin in the final composite structure. Although two specific embodiments of the invention have been described in detail, various modifications can be made without departing from the spirit and scope of the invention. Therefore, the present invention is not particularly limited except by the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a fragmentary schematic cross-sectional view of the layup and bag placement over the mold, showing the necessary bag placement to exclude air from the layup. FIG. 2 is a schematic diagram of a bag arrangement similar to FIG. 1;
Figure 3 shows how a layer of release material is inserted between the vacuum bag and the layup to prevent resin from escaping during the devolatilization step. FIG. 3 shows a schematic diagram of a typical apparatus utilized to control the curing of a composite to prevent resin squeezing phenomena during the curing cycle. FIG. 4 is a schematic diagram of a typical apparatus similar to FIG. 3, with the addition of adhesive tape around the layup to prevent resin squeezing. FIG. 5 is a schematic diagram of a typical device similar to FIG.
A pair of abrasive materials are shown slightly held around the layup by adhesive tape similar to that of FIG. and FIG. 6 is a schematic diagram of a typical apparatus utilized to control the curing of composites with an inflatable bag that compresses the layup during the curing cycle while preventing resin squeeze-out phenomena. shows.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a composite structure, comprising: supplying a mold release material to a mold; and forming a composite structure from uncured resin and reinforcing fibers without loss of resin. placing an impregnated layup film on the mold, coating the exposed surface of the layup with a release material, proximate to the release material coating the exposed surface of the layup, and An inflatable bag having a flexible, flowable, non-breathable outer layer portion in direct contact is placed between the portion of the inflatable bag and a mold extending around the layup to completely seal the layup. Forms a continuous seal, prevents uncured resin from escaping from the sealed layup during curing, and heats the sealed layup to the resin curing temperature while simultaneously The outer surface of the part is cured to form a composite structure by applying pressure and being laid up by a pressurized inflatable bag to uniformly distribute the release material covering the exposed surface. said method, comprising: supplying a pressure as high as possible. 2. The mold surrounds the layup, and the pressurization of the inflatable bag is a way to prevent cured resin from flowing out of the layup during the curing stage, compressing it from the center of the mold toward the outside. The method of claim 1, characterized in that: 3. At least a portion of the layup is disposed between adjacent inflatable bags compressing that portion of the layup such that adjacent bags are pressurized, and the compression of the layup A method according to claim 1, characterized in that it is achieved without spillage. 4. The method of claim 1, wherein the inflatable bag is pressurized by an autoclave system that simultaneously heats the layup to resin curing temperature. 5. The method of claim 1, wherein the breathable material is open to atmospheric pressure. 6. A method according to claim 1, characterized in that the layup is a laminate, a sandwich or an entirely kneaded product comprising a layer of fiber reinforcement embedded in a thermoset resin. 7. Includes another step of providing an adhesive tape capable of resisting curing temperatures without bonding to the resin of the layup, on the outer surface of the layup and on the inner surface of the flowable, non-breathable flexible portion. 2. The method of claim 1, wherein the tape is applied to wrap around the lay-up during the process. 8. A method according to claim 1, characterized in that the layup is a laminate, a sandwich or an entirely kneaded product comprising a layer of fiber reinforcement embedded in a thermoset resin. . 9. At least a portion of the layup is disposed between adjacent inflatable bags compressing portions of the layup such that adjacent bags are pressurized to avoid significant spillage of uncured resin from the layup. 3. The method of claim 2, wherein the layup is compressed. 10. The method of claim 2, wherein the inflatable bag is pressurized by an autoclave system that simultaneously heats the layup to resin curing temperature.