Patent Application
20110204541
The present invention is directed to the production of composite components made of fiber reinforced composite material, and is in particular directed to the production of composite components using fluid density and pressure, and preferably also fluid temperature. The present invention will be described with respect to its use in the production of boat hulls. It is however to be appreciated that the present invention is not limited to this application and that other applications are also envisaged.
It is now normal practice to use fiber reinforced composite material to produce large boat hulls because of its relative strength and lightness in weight. Commonly used methods to lay down the boat hull include spray lay-up and hand lay-up methods. The spray lay-up method uses a spray consisting of chopped reinforcing fiber and catalyzed resin which is applied to the surface of a mold. In the hand lay-up method, the fiber in the form of woven, knitted, stitched or bonded fabric is laid on the surface of the mold and resin is then subsequently impregnated into the fiber lay-up using hand operated rollers and brushes. In both methods, the resin is left to cure under standard atmospheric conditions.
As the resin is exposed to the atmosphere in the above described two methods, significant amounts of volatiles, and in particular styrene gas, is emitted from the resin, and the airborne volatile concentrations can be high enough to reach levels hazardous to health. As government health authorities introduce legislation to control such emissions, boat builders need to move to other methods which minimize such emissions.
One such method is known as vacuum bagging where a release film, breather film and finally a vacuum bagging film is located over a composite lay-up applied using the above-described hand lay-up method. The vacuum bagging film is then sealed along its edge and the air from under the film evacuated using a vacuum pump. This vacuum bagging method helps to better consolidate the composite lay-up and ensure better wetting of the fiber as well as helping to reduce the amount of volatiles emitted during curing.
In a further development of this vacuum bagging method, the vacuum bagging film is laid out over a dry composite lay-up, and catalyzed resin drawn into the lay-up using an infusion method while the air under the vacuum bag film is evacuated by the vacuum pump. A knitted non-structural fabric or resin distribution tubes can be laid over the composite lay-up to assist in resin distribution under the vacuum bagging skin through the lay-up. Such a method is for example described in U.S. Pat. Nos. 4,902,215 and 5,052,906.
While these vacuum bag based methods do help to reduce airborne volatile emissions, they are time consuming methods as great eare must be taken to apply the films and ensure that there are no air leaks through the vacuum bagging film. If insufficient care is taken to ensure that there are no air leaks and if the resin is not properly mixed, this could lead to incomplete infusion of resin, with areas of the lay-up being left un-wetted with resin. The resultant dry areas will render the boat hull unusable. Furthermore, the costs can be high because the vacuum bagging film as well as the release and breather films used in this method can usually only be used once and must subsequently be disposed of. Any other resin distribution components such as resin distribution lines will also need to be discarded.
All of the above methods are nevertheless only suited for one off or small scale production of boat hulls and are not suitable for the mass production of such hulls. Another composite production method, which has been used in particular for the production of high precision composite components for the aeronautical and automotive industries, is resin transfer molding (RTM). This production method requires the use of solid male and female mold dies, which when held together define a mold cavity. Reinforcing fiber and other material is carefully laid within the mold cavity, and resin is injected under high pressure into that cavity.
There are a number of problems associated with the use of RTM in the production of boat hulls.
In U.S. Pat. No. 5,971,742, an apparatus is described which replaces each of the solid mold dies with a rigid housing supporting a thin, semi-rigid fiberglass membrane providing the mold surface. The housing and membrane together define a fluid chamber filled with a non-compressible heat conductive fluid. Temperature control coils extend into each fluid chamber to control the temperature of the fluid within the chamber. While this arrangement helps to alleviate the first problem, the high temperatures generated by the curing resin still requires a cooling period for the production plant after each production sequence. Furthermore, the use of semi-rigid mold walls having minimal deflection will still leave the possibility of the fiber preform being trapped at points between the opposing mold walls leading to point contacts where resin is unable to flow through. The practical problems associated with trying to form integral upright fittings, with the difficulty in transferring resin into upright portions of a fiber preform still also remain.
Any discussion of documents, systems, acts or knowledge in this specification is included to explain the context of the invention. It is not to be taken as an admission that any of the material formed part of the prior art base or the common general knowledge in the relevant art in or any country on or before the priority date of the claims therein.
It is therefore an object of the present invention to provide a composite component production method that avoids at least one of the disadvantages of prior art production methods including the RTM production method described above.
With this in mind, according to one aspect of the present invention there is provided a method of producing a composite component using a mold assembly having a relatively rigid mold section, and an elastically deformable mold section, the method including:
The relatively rigid mold section may be a female mold section having female mold cavity. The elastically deformable mold section may be a male mold face. It is however envisaged that the relatively rigid mold section, while the elastically deformable mold section may be the female mold section.
The elastically deformable mold section can readily conform to the variation in thickness of the fiber reinforcing material which may be provided using overlapping layers of sheets of this material. This avoids the problem of pinch zones associated with RTM where an excess thickness of fiber reinforcing material in particular areas when the matched dies are held together can lead to the impeding of resin flow into these areas.
The relatively rigid mold section may be a female mold section with a female mold cavity, and the elastically deformable mold section may be a male mold section with a male mold face; the method including;
The term “fiber reinforcing material” is used herein to refer to dry reinforcing fiber bundles formed of pre-cut fiber material and woven layers of this material, or laminates incorporating foam or other cores and reinforcing fiber fabric that have not been pre-impregnated with resin.
The fluid within the inner volume applies a fluid column pressure over an inner surface of the inner volume of the male mold section. As the male mold section is formed of an elastically deformable material, the fluid column pressure applied to the male mold section acts to conform and deform the male mold face to the shape of the fiber reinforcing material laid over the underlying female mold cavity. Furthermore, fluid column pressure applied by the fluid interacts with the fluid column pressure applied by the resin that has been supplied to the mold chamber. In particular, the fluid column pressure will naturally seek to come into equilibrium with the column pressure of the resin within the mold chamber so that the applied pressures are balanced. This has the effect of ensuring that the resin is uniformly distributed within the mold chamber and completely wets the fiber reinforcing material.
The fluid density of the fluid used to fill the inner volume may be selected to be close in value to the fluid density of the resin being supplied to the mold chamber. This allows the resin to be distributed as a result of the “balanced density” effect between the liquid within the bladder and the resin drawn into the mold chamber between the female mold cavity and the male mold face. The principle of the balanced density is described in the Applicant's International Patent Application No. PCT/AUO2/00078, details of which are incorporated herein, by reference. This balanced density effect occurs as the fluid pressures on either side of an elastically deformable membrane seek to balance out so that the resin can be evenly distributed even in the situation where the mold cavity is inclined at an angle.
It is noted that the resin will typically have a higher density than water, which may typically be used to fill the inner volume. The density of the resin and water may however be adjusted by preheating the water to thereby heat and lower the density of the resin. In addition, the resin may be preheated for this purpose. It is also possible to use a fluid of higher density than water within the inner volume. High temperature capacity fluids such as glycol can alternatively be used. Another alternative to ensuring that there are balanced pressures on opposing sides of the male mold section is to increase the height of the fluid above the male mold section thereby increasing the fluid column pressure over the inner surface of the male mold section.
As the male mold section is formed of an elastically deformable material, preferably with some point reinforcing, the male mold face will be deformed in shape due to the interaction between the fluid and the resin to thereby urge the resin into the composite material as well as helping to distribute the resin through the lay-up into corners and other “difficult” areas. The use of an elastically deformable material for the male mold face together with balanced density and/or pressure plus vacuum also allows more complicated structures to be made. This includes producing boat hull shells with the bulkheads and stringers and any other web integrally molded with the hull shell. Furthermore, less precision is required to lay the reinforcing fiber material as the distribution of the resin is not limited by the tight tolerances of the flow paths in conventional RTM methods.
While the resin can be distributed purely as a result of the interaction of the fluid and resin pressures, the infusion of resin into the composite material may be facilitated by applying a vacuum within the mold chamber. To this end, the method according to the present invention may also include supply resin into the mold chamber while applying a vacuum to the mold chamber. The vacuum will assist in the removal of trapped air within the composite material as well as assisting to draw the resin into the mold chamber thereby wetting the composite material with the resin.
The fluid and resin pressures may be individually varied or may be varied relative to each other in a predetermined relationship. For example, the resin pressure may be initially high to flood the mold chamber with a relatively large volume of resin. This resin volume can be accommodated by the outward movement of the resiliently deformable mold section away from the fiber composite material. The fluid pressure may then be subsequently increased to distribute and drive out the excess resin as the resiliently deformable mold section is pressured back against the composite fiber material. This may lead to more rapid wetting of the fiber reinforcing material. It is also envisaged that the resin pressure and/or the fluid pressure may be pulsed to facilitate distribution of the resin.
In the case of high viscosity resin, the mold assembly and mold chamber may be heated. This facilitates wetting of the fiber reinforcing material because the heating of this resin helps to reduce its viscosity while being distributed through the mold chamber.
The method may also include applying balanced fluid pressures on opposing sides of the mold assembly. One of the advantages of this is that it leads to more uniform pressure across the composite component being produced leading to more uniform material characteristics through the finished component. A production system allowing this balanced pressure to be applied will be subsequently described.
According to another aspect of the present invention, there is provided a production system for producing a composite component including, a mold assembly including a relatively rigid mold section, an elastically deformable mold section, fluid pressure means for applying a fluid pressure due to density and/or pressure of a fluid on said elastically deformable mold section, and a resin supply means for supplying resin to a mold chamber defined between the mold sections when brought together.
The relatively rigid mold section may be provided by either a female mold section having a female mold cavity, or a male mold section having a male mold face. The elastically deformable mold section may be correspondingly provided by either said male mold section or said female mold section.
The resin supply means may be provided by at least one resin supply line in fluid communication with the mold chamber. The resin supply line may communicate with an opening in the male mold face or female mold cavity or may enter an opening provided between the outer periphery of the female and male mold sections.
At least one vacuum line may also be in fluid communication with the mold chamber when a vacuum is being used to evacuate the mold chamber of air. To this end, a sealing means may be provided between the female and male mold sections for providing an at least substantially air tight seal for the mold chamber. The vacuum line may communicate with an opening in the male mold face or the female mold cavity or may enter an opening provided between the outer periphery of the female and male mold sections.
The male mold section may be at least substantially made from rubber or other similarly elastic and deformable material. Preferably, the male mold section may be made of a material and or alternatively may have a surface of the male mold face which readily separates from the composite component when fully cured. This eliminates the need for any release film flow membrane, breather etc. to be provided within the mold chamber.
The surface of the male mold face adjacent the fiber composite material may be provided with a series of channels extending along its surface. Preferably these channels may extend in a mesh pattern across the entire surface of the male mold face. These channels provide a passage through which resin and air can pass to facilitate the evacuation of air and distribution of the resin through the fiber composite material. The male mold face may be of a sufficient deformability such that the channels will flatten when a high enough fluid pressure is applied to the opposing side of the male mold face. This facilitates the driving out of the resin into the fiber composite material.
According to a further aspect of the present invention, there is provided a production system for producing a composite component including:
The ring chamber may be defined by a peripheral relatively rigid ring flange surrounding and supporting the male mold section, the ring flange engaging the peripheral portion surrounding the female mold cavity. A seal means, for example a resilient sealing rib(s), may be provided between the ring flange and the ring portion to provide an at least substantially air tight seal for the ring chamber.
The pool of resin within the ring chamber serves two purposes. It firstly provides the source of resin for wetting the reinforcing material within the mold chamber. It also provides a liquid seal around the mold cavity that ensures that a vacuum can be applied to that mold chamber.
At least a peripheral portion of the reinforcing material may extend into the area of the ring chamber, and may act as a wick to allow the resin to permeate into the rest of the reinforcing material through capillary action.
A series of resin supply lines may supply resin to the ring chamber at points distributed along the ring chamber. Alternatively, a single resin supply line may extend parallel with the ring chamber, the supply line having a series of bleed lines spaced therealong from which resin can be discharged into the ring chamber.
The vacuum supply means may include a vacuum pump and at least one vacuum line. A first vacuum line may be in communication with the mold chamber. The first vacuum line may be connected to an opening provided within the male mold section to thereby apply a vacuum to the mold chamber. Preferably a second vacuum line is provided in communication with the ring chamber to thereby apply a vacuum to the ring chamber. A valve may control the vacuum being applied by both the first and second vacuum lines. In a first position of the valve, a vacuum may be applied by both vacuum lines such that there is little to no pressure differential across the resin accumulated within the ring chamber. This restricts the transfer of resin from the ring chamber into the mold chamber. In a second position, the first vacuum line is blocked/closed to stop the vacuum in the ring chamber then opened to the atmosphere so that only a vacuum is applied by the second vacuum line. This results in a sudden increase in the pressure differential across the resin held in the ring chamber thereby forcing a “wave” of the resin through into the mold chamber. The vacuum is again reapplied to the ring chamber by again opening the first vacuum line when the resin is almost exhausted from the ring chamber. This allows more resin to be supplied to the ring chamber. The apparatus thereby allows for periodic waves of resin to enter the mold chamber.
A pulse of high pressure gas may also or alternatively be periodically supplied to the ring chamber from a pressurized gas supply. The effect of this high pressure pulse is to force the resin within the ring chamber into the mold chamber with a “wave” of resin being thereby transferred into the mold chamber. This resin wave helps to more rapidly and more efficiently transfer and infuse the resin into the composite material to ensure complete wetting therethrough. A resin sensor may be respectively provided at a lower and higher portion of the ring chamber to check when the resin level therein has reached a low point beyond which the resin seal would be broken, and a high point where no further resin is required to be supplied. When the resin reaches that lower point, the pressure differential and/or any further high pressure gas supply the ring chamber is stopped and further resin can then be delivered to replenish the supply within the ring chamber.
Vibration means such as a surface mounted external mechanical vibrator may also be used to vibrate the mold assembly and ensure complete wetting of the composite material.
In the Applicant's U.S. Pat. No. 6,149,844 there is described an apparatus for producing composite components utilizing balanced pressure. The apparatus has two opposing pressure chambers, one chamber supporting a floating rigid mold, the other chamber having an elastically deformable mold face. A composite lay-up could be laid on the mold, and a vacuum bag is then located over the lay-up and evacuated to thereby compact the lay-up and withdraw most of the air from the lay-up. The pressure chambers are then brought together so that the resiliently deformable mold face would be located over the vacuum bag under which is located the composite lay-up. Fluid at elevated pressure and temperature is then circulated through each pressure chamber to ensure that a balanced pressure and a uniform temperature is applied to the composite lay-up. This leads to composite components being produced having higher material quality than would be the case with more conventional methods including RTM.
Balanced pressures may also be used according to the present invention. To this end, the female mold section may be supported in a floating arrangement on a first housing to form a first pressure chamber while the male mold section may be supported on a second housing to form a second pressure chamber. The apparatus according to the present invention does not require the use of a separate vacuum bag to evacuate the composite fiber material, and the male mold/skin section may directly contact the composite fiber material. Fluid circulation means may circulate fluid at elevated pressure through each pressure chamber during the production process. The fluid pressure may be substantially equal in both chambers to thereby provide the additional benefits of balanced pressure.
It is also envisaged that the fluid being circulated through each pressure chamber is also at an elevated temperature where high temperature curing resins are being used or where the resin needs to be heated to reduce its overall viscosity and therefore its fluid density. Fluid at a lower temperature can be subsequently circulated through the pressure chambers to facilitate cooling of the component as the resin cures.
The present invention has particular advantages over the prior art RTM production methods currently used to produce boat hulls. Firstly, it is not necessary to produce expensive and heavy mold dies. Indeed, the female mold section can be fabricated from relatively low cost material as it is not required to support any substantial pressure or weight. The bladder construction of the male mold section can be simply formed from resiliently deformable material such as rubber, for example natural latex rubber. As well as being relatively simple to form, the weight of the male mold section will be much lower than would be the case for a rigid mold die.
Furthermore, balanced pressure and vacuum is a far more effective means of distributing the resin evenly within the reinforcing fiber material. Because of this efficiency, the mold chamber can be more complex in shape and may for example include volumes for forming the bulkheads of the ship hull. Also, separate components such as connecting lugs can be located within and integrally embedded within the final composite component. This allows the boat hull to be constructed as a single integral unit leading to more uniform material properties through the boat hull with no areas of potential weakness. Also, as the various components of the boat hull can be formed at the same time, this leads to significant reductions in production times. Furthermore, by comparison to conventional RTM methods where special high flow resins and high quality fiber materials are required, the present invention can use a variety of different resins and fiber materials.
It will be convenient to further describe the invention with reference to the accompanying drawings which illustrate preferred embodiments of the present invention. Other arrangements are possible, and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.
In the drawings:
We initially note that corresponding features in different preferred embodiments of the present invention are generally provided with the same reference numeral for clarity reasons.
Referring initially to
According to the method of the present invention, fiber reinforcing material 15 is initially laid within the female mold cavity 7. The male mold section 5 is then located over the female mold section 3 and the inner volume 11 of the male mold section 5 is then filled with a fluid 12. This fluid 12 can conveniently be water, but the use of other fluids of higher density or higher temperature capacity such as glycol is also envisaged. A resin supply means 17 including a resin supply line 19 and a resin tank 21 theft supplies catalyzed and/or mixed liquid resin through the resin supply line 19 to an opening 25 provided in the lowermost point of the male mold face 9. The resin 23 is supplied to the mold chamber 8 defined by the narrow volume between the female mold face 7 and the male mold face 9. The resin 23 may be pumped from the resin tank 21 to the mold chamber 8, or the resin tank 21 can be held at a height above the level of the fluid 13 within the inner volume 11 to allow resin 23 to flow into the mold chamber 8. The pressure within the mold chamber 8 at the opening 25 is a function of the fluid column height above the lowermost point of the male mold section 5.
The resin 23 upon entering through the opening 25 is dispersed through the fiber material 15 because of the pressure differential at this point and the capillary attraction of the resin to the reinforcing fiber material 15 with the resin “wicking” along the fibers. As the resin 23 continues to flow into the mold chamber 8 and spreads and moves towards the sides and top of the fiber bundle 15, the fluid column pressure on the male mold section 5 will also progressively decrease to a minimum adjacent the fluid level 13. As this can slow the speed of progress of the resin 23 as it moves higher within the mold the fluid 12 can preferably have a higher density than the resin 23, or the fluid level 13 may be at a height significantly above the mold sections 3, 5 such that a sufficient fluid column pressure is applied over the male mold section 5 to disperse the resin 23 through the fiber bundle 15. It is also envisaged that either the resin 23 or the fluid 12 be preheated to thereby result in the lowering of the viscosity and therefore the density of the resin 23 to more easily infuse the part over a long period of time say 40 C. The resin selected can be catalyzed and/or mixed to only cure at a high temperature say 60 to 80 C. Therefore to cure the part the fluid temperature can then be increased rapidly to 80 C to cure the part.
The supplied resin 23 is thereby distributed over and infused into the fiber composite material or fiber bundle 15 as the pressure applied by the fluid 13 accommodated within the inner volume 11 interacts with and seeks to balance forces with the liquid catalyzed resin 23 within the mold chamber 8. This helps ensure that the resin 23 is distributed evenly through the composite bundle 15.
The mold assembly 1 including the female mold section and the male mold section 5 can also be heated prior to and during the production process. This allows the use of high viscosity resin 23 which needs to be heated to reduce its viscosity thereby facilitating the wetting of the fiber reinforcing material 15.
The male mold section 5 must be deformable to enable the fluid column pressures to act on the resin 23 as well as to ensure that the male mold face conforms to the fiber bundle 15 supported within the female mold cavity 7. Referring now to
To facilitate the infusion of resin 23 through the composite material 15, a vacuum can be provided within the mold chamber 8 to evacuate air from the fiber reinforcing material 15 as well as to draw the resin 23 into the mold chamber 8.
It may be advantageous to further assist the transfer of resin 23 from the ring chamber 39 to the mold chamber 8 by also applying periodic pulses of high pressure gas into the ring chamber 39 to assist to push the resin 23 through into the mold chamber 8. A pressure tank 40 is connected to the first resin 37a via a second valve 36b. The first valve 36a first disconnects the vacuum line from the vacuum pump 35 before the second valve 36b connects the pressure tank 40 to the vacuum line 37a. This enables a pressure pulse to be applied to the ring chamber 39 by using high pressure gas from the pressure tank 40. This pulse of high pressure gas continues until the level of resin 23 within the ring chamber 39 drops below the level of the resin sensor 41a. At that time the high pressure gas supply is stopped and the ring chamber allowed to re-fill with resin 23 until the resin reaches the level of the second resin sensor 41b. The use of high pressure gas also helps to transfer resin 23 via the resin wave 46 passing into the mold chamber 8. This further facilitates the transfer of resin 23 increasing the speed at which the composite material 15 can be completely wetted by the resin 23.
The infusion of resin into the composite material 15 can also be facilitated by vibrating the mold assembly. A rotational vibrator 53 may therefore be secured to a portion of the mold assembly for this purpose. This vibrator 53 can for example be attached to the female mold section 3.
The example embodiment shown in
As previously noted,
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005903569 | Jul 2005 | AU | national |
This is a continuation of application Ser. No. 11/994,062, filed Apr. 17, 2008, the contents of which are expressly incorporated herein by reference, and this application is related to and claims the benefit under 35 U.S.C. §119 and 35 U.S.C. §365 of International Application No. PCT/AU2006/000945, filed Jul. 5, 2006.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11994062 | Apr 2008 | US |
| Child | 13094167 | US |
