Coating processes – Immersion or partial immersion
Reexamination Certificate
2001-04-24
2003-07-01
Barr, Michael (Department: 1762)
Coating processes
Immersion or partial immersion
C427S294000, C427S385500, C264S101000, C264S136000, C264S137000, C264S313000
Reexamination Certificate
active
06586054
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to the manufacture of fiber-reinforced polymer composite articles. Specifically, the invention relates to an apparatus and method for the manufacture of fiber-reinforced polymer composite articles wherein the resin is selectively distributed and controlled during the impregnation stage of the fiber reinforced articles.
(2) Description of Related Art
Fiber reinforced polymer composite articles have been available and in use for some time. Interest in these materials is due in part to their lightweight, high stiffness and strength, and corrosion-resistant properties. The transportation industry, for instance, has shown interest in the manufacture and use of fiber reinforced polymer composite materials due to the potential for increased fuel savings and the potential to carry increased payloads due to the reduced weight offered by the use of these types of materials. The lightweight, corrosion-resistant nature of these composite articles has also attracted the interest of the construction/infrastructure sectors.
Unfortunately, one of the key barriers to use of fiber-reinforced polymer composite articles has been the cost of their manufacture. The cost of the manufacture is significantly due to the labor required to produce such articles as well as the material waste incidental to such manufacture. Use of fiber-reinforced resin structures is difficult to justify when an acceptable, metal-based alternative may be available, often at a fraction of the cost.
Vacuum assisted resin transfer molding technology (VARTM) has been employed in manufacturing fiber-reinforced polymer composite structures. Described simply, processes employing VARTM generally use (1) a preform (i.e., a mold containing reinforcing fibers therein or thereon) to be impregnated with a resin; (2) a fluid impervious, flexible sheet, liner or bag (generally referred to as vacuum bag); (3) a vacuum; and (4) resin. In a VARTM type process, the preform is prepared in the desired shape, having the desired reinforcing fiber content and geometry then covered with a fluid impervious flexible sheet, liner or bag in such a manner such as to form a seal around or on the preform (vacuum bag). The vacuum bag has a resin port through which resin may be introduced. Liquid resin is then introduced into the vacuum bag at one end of the preform. A vacuum is then applied to the interior of the vacuum bag at the opposite end of the preform from where the resin is being introduced so as draw the resin across the preform and to collapse the vacuum bag against the preform. Once the preform is fully infused, the resin-containing preform is then cured and the vacuum bag removed. Use of a vacuum assists in the flow of the liquid resin within the preform. A description of vacuum assisted or vacuum bag techniques used to form fiber reinforced plastic structures is set forth in U.S. Pat. No. 4,902,215; and the description set forth therein is incorporated herein by reference.
U.S. Pat. No. 4,902,215 (Seemann III), issued Feb. 20, 1990, describes and claims a VARTM process known in the art as SCRIMP (Seemanns Composite Resin Infusion Molding Process). In addition to employing a VARTM process as generally described above, SCRIMP further employs a resin distribution medium positioned between the fabric lay up and the fluid impervious, flexible outer sheet (i.e., vacuum bag). This distribution medium serves to enhance the uniform distribution of resin across the top and through the fiber lay up upon the application of a vacuum by keeping the upper surface of the lay up and the lower surface of the fluid impervious outer sheet apart. In order to enhance the separation of the completed resin impregnated fiber lay up from the mold surface and the vacuum bag, porous peel plies which do not adhere to the resin are provided between the distribution media and the fiber lay up. After the resin has cured, the vacuum inlet is cut off, and the fluid impervious outer sheet, the distribution medium and peel ply are peeled from the fiber reinforced plastic structure.
U.S. Pat. No. 5,052,906 (Seemann), issued Oct. 1, 1991, describes and claims a modification/improvement to the claimed invention of Seemann, III '215, described above. In order to facilitate resin flow, this patent describes the use of two resin distribution layers as opposed to one. One of said layers is placed/located on the mold surface per se, beneath the lower face of the fiber lay up, and the other on top of the fiber lay up, between the fiber lay up and the fluid impervious outer sheet. After the resin has been cured, the impervious outer sheet, the distribution mediums and peel plies are peeled from the resulting fiber reinforced structure (fiber reinforced lay up).
The VARTM processes described in these patents require the installation of distribution layer(s), peel ply, and, in some cases, a breather layer to ensure proper vacuum application during resin impregnation. These layers are used to provide a preferential flow path for the resin during the process and are disposable. Installation and removal of these materials can be time consuming and costly due to the specific labor involved. Furthermore, these layers become contaminated with resin as part of the impregnation process. Hence, these layers must be disposed of along with any residual resin that remains affixed to these consumable materials. It would be desirable to reduce the waste and labor associated with the manufacture of fiber reinforced resin structures using vacuum techniques.
U.S. Pat. No. 5,316,462 (Seemann), issued May 31, 1994, describes a VARTM process that does not employ a distribution medium of the type described above. Seemann '462 describes and claims a unitary vacuum bag for use in forming fiber reinforced composite articles wherein the vacuum bag integrates the features of resin distribution and vacuum draw. For instance, U.S. Pat. No. '462 describes that a multiplicity of cross channels may be formed on the inner surface of the vacuum bag to facilitate resin distribution. The vacuum bag taught may be cleaned and reused. The resulting fiber reinforced composite article would have embedded thereon an impression of these cross channels.
There remains a need to improve the VARTM type apparatus and processes. The present invention does not require the installation and removal of consumable resin distribution layers. Moreover, the present invention provides for superior resin flow paths using a novel means for establishing resin flow channels and provides for the resulting fiber reinforced composite article having a smooth surface thereon.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method for the manufacture of fiber-reinforced polymer composite articles using vacuum assisted resin transfer molding technology wherein some of the steps, labor and material waste associated with conventional, prior art VARTM manufacturing techniques are eliminated.
The process of the present invention has been termed FASTRAC, which refers to Fast Remotely Actuated Channeling. The FASTRAC process is a unique process that employs VARTM techniques in the general sense and operates without a traditional resin distribution medium. The FASTRAC process and apparatus employ a fluid impervious flexible outer sheet of the type referred to in the prior art in order to create a chamber around a fiber containing preform within which a vacuum can be applied via a primary vacuum line. This fluid impervious, flexible outer sheet is referred to herein as “primary vacuum bag.”The primary vacuum bag is used to seal a fiber containing preform to be impregnated with a resin to a mold (tool) surface. In the FASTRAC process and apparatus herein, the primary vacuum bag itself acts as the resin distribution medium via remote actuated channeling.
Once the primary vacuum bag has been installed, a resin channeling means (also referred to herein as FASTRAC layer) is placed on top of the primary vacuum bag that is in contact with the pref
Barr Michael
Clohan Paul S.
Randolph William
The United States of America as represented by the Secretary of
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