Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-02-03
2001-03-27
Lorin, Francis J. (Department: 1775)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S297000, C156S209000, C427S131000, C427S197000, C427S200000, C427S202000, C427S206000, C427S271000, C427S274000, C427S275000, C427S302000, C427S372200, C427S375000
Reexamination Certificate
active
06207003
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the fabrication of a panel structure, and, more particularly, to the fabrication of a panel structure having embedded layers with selected electrical or magnetic properties.
In a number of applications, it is necessary that a panel exhibit particular electrical and/or magnetic properties, as well as being structurally strong. An example is skin panels for use in low-observables military aircraft or other vehicles having multiple, spaced-apart layers embedded within the structural skin, with each of the layers having particular electrical properties. In other applications, embedded electrically conductive or magnetic layers are useful for de-icing, lightning-protection, radome, or sensor roles. The design of the spaced-apart active layers—their specific locations, thicknesses, morphologies, and properties—depends upon the application, and such designs are known in the art. The present invention is concerned with the fabrication of such structures, not their design.
In the past, such structures have been fabricated by several techniques. In one, conductive fibers are placed into sheets of a substrate material to form an active layer, taking care to orient the individual conductive elements in desired patterns, and the sheets are laminated together with structural sheets. This approach is tedious and expensive, and it is difficult to obtain the exact patterns of fibers required for some applications. In another approach, coatings are placed onto exposed surfaces of structures. This technique is not suitable for producing embedded conductive layers with carefully controlled properties and patterns. In another approach, conductive patterns are imprinted on thin plastic sheets, such as by silk screening onto polyethylene sheets, and the imprinted sheets are laminated together with base structure. The problem with this approach is that control of the properties of the conductive pattern is difficult, and the conductive pattern is necessarily quite thin. Such materials may also be made by patterning the surface layers or sides of honeycomb materials, an expensive undertaking which is also limited as to the thickness of the conductive pattern.
There is a need for an improved approach to the fabrication of structures with embedded layers having selected electrically conductive or magnetic properties. The present invention fulfills this need, and further provides related advantages.
SUMMARY OF THE INVENTION
The present invention provides a method for preparing a structure having embedded active layers with elements having preselected electrical or magnetic properties, and preselected patterns. The method allows precise control over the electrical or magnetic properties of each active element, and also precise control over the shape, thickness, positioning, and arrangement of each active element. The method is suitable for making multilayered structures, wherein each active layer is spaced apart by a structural layer, and wherein the active layers are the same or intentionally different in properties. This approach is suitable for large-scale production of structure at relatively low cost.
In accordance with the invention, a method of preparing a structure comprises the steps of furnishing a substrate material, patterning a set of recesses into a surface of the substrate material, preferably with a patterning tool, and filling the set of recesses with a mixture of an active phase and a matrix. The matrix of the active phase is thereafter cured, if appropriate. The sheet may then be laminated to a base structure.
In a preferred approach for continuously fabricating the material, a patterning tool in the form of a patterning wheel having a set of protrusions thereon is furnished. A substrate material is contacted to the patterning wheel, thereby producing a set of recesses in a surface of the substrate material, and the set of recesses is filed with a mixture of an active phase and a matrix. The substrate material is preferably a heated sheet of an organic resin substrate material in an initially solid form or continuously cast onto the patterning wheel, as by extrusion of a flowable substrate precursor. The patterning wheel has projections thereon corresponding in location and size to the pattern of recesses to be formed, producing the pattern of recesses in the surface of the substrate material. The projections may be made in any desired pattern and may be of any desired height, so as to define a corresponding pattern and depth of recesses on the sheet. The pattern of recesses is filled with a mixture of an active phase and a matrix, which at this point is flowable so as to fill the recesses, and any excess is removed. The active phase may be any type of active material, such as an electrically conductive material, a semiconducting material, or a magnetic material. If the matrix is curable, the sheet and the mixture are cured. The sheet, with its active material and matrix, is preferably laminated to a base structure, such as a composite sheet or a foam sheet, to form a structural element. In most instances, multiple alternating active layers and structural layers are laminated together.
The use of the patterning approach to prepare the active layers offers several important advantages. A single patterning tool, such as the preferred patterning wheel, is prepared for each type of active layer. The precise pattern and depth of the active elements is defined by the projections on the patterning wheel. The arrangement of active elements is reliably repeated over large areas of the extent of the substrate material using the patterning tool. A different patterning tool is prepared for each desired arrangement of active elements, allowing different arrangements to be used for each of several active layers in the structure, if desired. This patterning approach permits the depth of each active element—its thickness in the through-thickness dimension of the panel—to be much greater than possible using conventional imprinting or screening procedures, and to be accurately controlled. The thickness of each active element, together with the lateral width of each active element and the nature of the mixture filling the recess, determines the electrical properties of that element and, ultimately, the properties of the active layer.
The present approach is therefore economical to produce large areas of active-layer material and large amounts of structure incorporating the embedded active-layer material. The properties and pattern of the active-layer material, and thence the properties of the final structure, may be controlled more accurately than with other techniques. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.
REFERENCES:
patent: 2838416 (1958-06-01), Babiarz et al.
patent: 5522962 (1996-06-01), Koskenmaki et al.
Lang Lawrence A.
McClure Vance E.
Lorin Francis J.
Scaled Composites, Inc.
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