Patent Application
20140265058
The present invention relates generally to the field of thin ply technology complexes. More particularly, the present invention relates to systems and methods for maneuvering flexible pre-impregnated composite sheets.
This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Various composites are known commercially for forming structures that must be strong yet lightweight. One such composite is a prepreg composite (“prepreg”). Prepregs are specially formulated resin matrix systems that are reinforced with filaments constructed of carbon, glass, aramid or the like. The filaments are embedded in a thermoset resin that cures at elevated temperature and pressure, undergoing a chemical reaction that transforms the prepreg into a solid structural material that is durable, temperature resistant, stiff, and lightweight.
Prepregs are generally comprised of a plurality of unidirectional or woven prepreg tapes. In a unidirectional prepreg tape, filaments are aligned parallel to each other and embedded in a thermoset resin. In a woven prepreg tape, filaments are woven and embedded in a thermoset resin. Both types of prepreg tapes are commercially available, for example, under the under the trademark HexPly by Hexcel.
To form a structure, one or more layers of prepreg tape are positioned to form a “complex” or “preform.” Once one or more complexes are positioned in a three-dimensional mold, it is cured using heat and pressure.
One known method for positioning complexes in a three-dimensional mold is by laying the prepreg tape in the mold by hand. Another known method is by using three-dimensional automated tape layer (“ATL”) machines that place the prepreg tape directly into a mold such as those available from Coriolis Composites or Ingersoll Machines Tools. Both methods, however, add significant expense to creating a prepreg composite structure. In particular, manually laying prepreg tape in molds is very labor intensive, which significantly increases the labor cost associated with creating a prepreg composite structure. Fully automated three-dimensional ATL machines significantly reduce the labor required to create a prepreg composite structure, but the high cost of the three-dimensional ATL machines increases the cost of creating a prepreg composite structure. Three-dimensional ATL machines may also be too expensive for some companies to acquire and, for those that can afford them, the high cost will likely mean that the machines are limited to commercially viable structures such as expensive, low-production structures or lower-cost, high-production structures.
Various embodiments of the present invention relate to systems and methods for constructing and maneuvering flexible pre-impregnated composite sheets. In general, embodiments of the system comprise a work surface, an automated tape layer (“ATL” or “tape layer”) machine for constructing a flexible pre-impregnated composite sheet comprised of at least one layer of prepreg tape on the work surface, a mold for forming rigid structures from the flexible pre-impregnated composite sheets, and a conveyor for maneuvering the flexible pre-impregnated composite sheets from the work surface to the mold.
In one embodiment, a method for maneuvering a flexible pre-impregnated composite sheet is disclosed. The method comprises positioning the flexible pre-impregnated composite sheet onto a work surface and operatively coupling a vacuum sheet to the flexible pre-impregnated composite sheet. The vacuum sheet is operatively coupled to a flexible conveyor sheet and the flexible conveyor sheet is positioned proximate to a mold such that the flexible pre-impregnated composite sheet is in contact with the mold. The vacuum sheet is decoupled from the flexible conveyor sheet and removed from the flexible pre-impregnated composite sheet.
In another embodiment, a method for forming a rigid composite structure is disclosed. The method comprises providing a flexible pre-impregnated composite sheet comprised of at least one layer of prepreg tape and a flexible conveyor sheet, the flexible conveyor sheet having a first lateral side, a second lateral side, and one or more connecting sides connecting the first lateral side and the second lateral side. The flexible pre-impregnated composite sheet is positioned onto and coupled to the flexible conveyor sheet. The flexible conveyor sheet is supported along at least a portion of the first and second connecting sides but not supported on the lateral sides. The flexible conveyor sheet is positioned proximate to a mold such that the flexible pre-impregnated composite sheet is in contact with the mold. Once in the mold, the flexible pre-impregnated composite sheet is cured until it becomes a rigid composite structure.
These and other advantages and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the several drawings described below.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.
Once the flexible pre-impregnated composite sheet 1 is disposed on the work surface 5 as illustrated in
Similar to the release strips 7, the breather strips 9 facilitate air flow between the vacuum sheet 11 and the flexible pre-impregnated composite sheet 1 during the debulking step described below. In an exemplary embodiment, the breather strips 9 are constructed of polyethylene, are slightly thicker than the release strips 7, and comprise a honeycomb geometry. The honeycomb geometry helps to facilitate airflow between the vacuum sheet 11 and the flexible pre-impregnated composite sheet 1 when the volume between the vacuum sheet 11 and the flexible pre-impregnated composite sheet 1 is subjected to a vacuum during the debulking step. The honeycomb geometry also facilitates airflow by resisting compression when the volume between the vacuum sheet 11 and the flexible pre-impregnated composite sheet 1 is subjected to a vacuum during the debulking step. Other materials and geometries may be suitable, so long as they are generally porous and incompressible to maintain an air passage between the vacuum sheet 11 and the flexible pre-impregnated composite sheet 1 during the debulking step.
After the release strips 7 and breather strips 9 are disposed on the flexible pre-impregnated composite sheet 1, a vacuum sheet 11 is disposed on the flexible pre-impregnated composite sheet 1 as illustrated in
After debulking the flexible pre-impregnated composite sheet 1 on the work surface 5, the flexible pre-impregnated composite sheet 1 may be coupled to the conveyor 13 for transferring to the mold 29. Before describing the process of transferring the flexible pre-impregnated composite sheet 1 from the work surface 5 to the mold 29, however, a description of an embodiment of the conveyor 13 is provided. In the embodiment illustrated in
With reference to
In yet another embodiment, the conveyor 13 comprises a heating device integrated or in thermal communication with the flexible conveyor sheet 17. For example, the heating device may be coupled to the upper or lower side of the flexible conveyor sheet 17. The heating device is configured to adjust the temperature of the flexible pre-impregnated composite sheet 1. In an exemplary embodiment, the heating device generates heat sufficient to increase the temperature of the flexible pre-impregnated composite sheet 1 from about 20 degrees Celsius to about 35 degrees Celsius. Adjusting the temperature of the flexible pre-impregnated composite sheet 1 manipulates the tackiness of the resin for purposes of uncoupling components from or coupling components to the flexible pre-impregnated composite sheet 1.
With reference to
While the foregoing describes how the vacuum sheet 11 is coupled to the flexible conveyor sheet 17, it is important to note that coupling the vacuum sheet 11 to the flexible conveyor sheet 17 serves to indirectly couple the flexible pre-impregnated composite sheet 1 to the flexible conveyor sheet 17. In particular, because the flexible pre-impregnated composite sheet 1 is tacky, the vacuum sheet 11 sticks to it. Accordingly, coupling the vacuum sheet 11 to the flexible conveyor sheet 17 indirectly couples the flexible pre-impregnated composite sheet 1 to the flexible conveyor sheet 17.
Once the flexible pre-impregnated composite sheet 1 is coupled to the flexible conveyor sheet 17 via the vacuum sheet 11, the flexible pre-impregnated composite sheet 1 is lifted from the work surface 5 and moved proximate to the mold 29 as illustrated in
As noted above, because the conveyor sheet 17 is flexible, the unsupported first and second lateral sides 23, 25 bend or sag under their own weight when lifted as illustrated in
One benefit of coupling the flexible pre-impregnated composite sheet 1 to the conveyor sheet 17 via the vacuum sheet 11 is that the flexible pre-impregnated composite sheet 1 may be debulked again once in the mold 29. In such an embodiment, an end of a vacuum hose (not shown) is inserted between the flexible pre-impregnated composite sheet 1 and the vacuum sheet 11 and, as illustrated in
Once debulking is complete, the vacuum sheet 11, release strips 7, and breather strips 9 are removed from the flexible pre-impregnated composite sheet 1 as illustrated in
Once the desired number of layers of flexible pre-impregnated composite sheet 1 are placed in the mold 29, the preform comprising the layers of flexible pre-impregnated composite sheet 1 may be cured by heat and pressure to transform the flexible preform into a rigid preform.
The foregoing description of embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the present invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the present invention. The embodiments were chosen and described in order to explain the principles of the present invention and its practical application to enable one skilled in the art to utilize the present invention in various embodiments, and with various modifications, as are suited to the particular use contemplated.
The construction and arrangements of the systems and methods for maneuvering flexible pre-impregnated composite sheets, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.
Various embodiments are described in the general context of method steps, which may be implemented in one embodiment by a program product including computer-executable instructions, such as program code, executed by computers in networked environments. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps.
Software and web implementations of the present invention could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various database searching steps, correlation steps, comparison steps and decision steps. It should also be noted that the words “component” and “module,” as used herein and in the claims, is intended to encompass implementations using one or more lines of software code, and/or hardware implementations, and/or equipment for receiving manual inputs.
