Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Infrared radiation
Reexamination Certificate
1999-04-16
2002-03-12
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Infrared radiation
C264S494000, C264S496000, C264S036180, C264S036220, C264S510000, C264S511000, C156S094000, C156S098000, C156S275500, C156S286000
Reexamination Certificate
active
06355203
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates mainly to the reconstitution or reconstruction of an object, especially of an object or component which is a composite or made of a composite material, which has a defect, to be treated or repaired, which affects at least its surface or even its entire thickness.
More specifically, the invention relates to the reconstitution or reconstruction or repair of objects as defined above by placing in or on the said defect, on the one hand, mechanically strong, continuous or staple fibres which are organized, for example in the form of a web or technical fabric, or are not organized, for example loose or in the form of a nonwoven, and, on the other hand, a polymeric material or resin (a single resin or a polymer alloy) which is thermoplastic or crosslinkable, especially thermocrosslinkable or thermosetting, this all forming, in the solid state, a matrix in which the said fibres are distributed or spread. By way of example, the fibres are glass, carbon or kevlar fibres, and the resin is an epoxy or polyester or phenolic or bismaleimide resin. These fibres may be put into the defect separately from the resin, in which case the said fibres are placed in the said defect, for example, in the form of superposed layers of fabric, and then the resin is injected into the mass of fabric in liquid form, or concomitantly, in which case a ready-to-use composite material is used, for example a prepreg material having a reinforcement consisting of the aforementioned fibres and a matrix of the resin, for example a partially crosslinked or uncrosslinked resin.
In both cases, the structure obtained on or in the defect is called monolith or monolithic, since it forms one piece in the solid state, without it being possible in practice to separate, for example by delamination, the aforementioned components, namely the fibres or layers on the one hand and the resin on the other.
For the purposes of the present description, and in the claims, unless otherwise indicated the term “composite” refers to a structure, an object or a material consisting in a uniform manner of the assembly of several elementary materials or components, namely and especially fibres and resins, bonded together, and together having properties, especially mechanical properties, that no component has just by itself.
In practice, throughout the present description, the term “resin” refers to polymeric materials, which may be qualified, as is customary, by the term of adhesive or glue, for example a structural adhesive, whether these be thermoplastic or thermosetting plastics.
According to document DE-A-4,019,744, and more particularly according to the embodiment in
FIG. 7
of that document, a process has been described for reconstituting or reconstructing an object, for example a composite object, having a defect which affects at least its surface. According to that process:
a—at least one added piece or material, the shape and dimensions of which are matched to those of the said defect, is placed in or on this defect, this piece or this material comprising mechanically strong, continuous or staple fibres which may or may not be organized; for example, a superposition of fabric layers, collecting the mechanically strong fibres in an organized manner, is placed in this defect.
b—a polymer material, or resin, is placed in or on this defect in order to obtain a plastic matrix in which these fibres are distributed; for example, this polymer material is brought into the defect in liquid form and under pressure, thus impregnating the aforementioned fibres and obtaining, after the polymer material has cured, a solid plastic matrix in which these fibres are distributed,
c—a gas-draining means, for draining the gases given off by the plastic matrix during step (d) below, and a gas-extraction cover are placed, in succession and one on top of the other, on the added piece that was impregnated with the plastic matrix, which together with the rest of the object being reconstructed or repaired form an enclosure which is sealed with respect to the external atmosphere and circumscribes the defect and the added piece; by way of example, the venting means consists of a gas-draining textile web,
d—while evacuating the sealed enclosure, the added piece is heated using a radiant source, the emission from which comprises infrared radiation, and placing this source with respect to the aforementioned defect so as to irradiate the cover for extracting the gases given off by the plastic matrix.
Document DE-A-4,019,744 has described the abovementioned process only for treating or repairing solid objects made of one and the same material, to the exclusion of any other object.
Moreover, at the present time, in order to repair a monolithic composite object, for example in the aeronautical industry, the process employed is carried out in the following manner, with reference to
FIG. 1
which is an exploded and diagrammatic view:
one or more pieces
2
, or a material, the shape and dimensions of which are matched to those of the defect
1
a
to be repaired or filled, are prepared, especially by cutting; this material or these pieces, either assembled or superimposed one with respect to another, are themselves made of a composite material in the sense in which they combine, in a bonded manner, a plastic matrix and mechanically strong, continuous or staple fibres which may or may not be organized, for example made of carbon, kevlar, glass, etc. . . ;
the piece or pieces
2
, or the material thus prepared, is or are added in or on the defect
1
a
in the treated object;
the following are placed in succession on the piece
2
and on the object
1
, on each side of the defect and one on top of another:
a perforated or unperforated film
9
, which does not adhere to the subsequently treated, for example crosslinked, added piece
2
;
a gas-draining textile web
3
for draining, via it peripheral border
3
a
, the gases which will be given off by the plastic matrix during its treatment, for example its crosslinking;
a film
8
impermeable to the plastic;
a cover-shaped flexible heating structure
10
having, in general, electrical heating elements embedded in an electrically insulating material, for example a silicone;
a layer
11
for thermal insulation with respect to the outside;
and a flexible gas-extraction cover
4
, forming, using suitable means
12
(for example seals), with the rest of the object
1
an enclosure
5
which is sealed with respect to the external atmosphere; this enclosure circumscribes not only the defect
1
a
and the added piece
2
, but also all the superimposed elements described above.
The extraction cover
4
is evacuated, for example using a pump
13
, and the flexible heating structure is connected to an electrical supply
14
.
Using suitable control means, especially temperature sensors, the plastic matrix is thermally treated, for example thermally crosslinked, in the case in which the said plastic matrix is a crosslinkable or thermosetting polymer. The heat treatment is closely controlled, especially depending on the nature of the plastic matrix and on the desired mechanical performance.
SUMMARY OF THE INVENTION
The present invention relates to the reconstitution or reconstruction of composite objects, of the sandwich type, i.e. object having a solid cellular layer, for example a material of the “honeycomb” type, made of various materials such as board impregnated with a phenolic resin, made of plastic, or made of metal, or made of a structural plastic foam. This cellular layer is bonded, in a structural manner, at least on one side to a monolithic layer, as defined above, that is to say combining, in a monobloc manner, a plastic matrix and mechanically strong fibres distributed in the said matrix.
At the present time, no satisfactory solution exists, or even any solution at all, for repairing or reconstructing sandwich-type composite objects, particularly when only one face of the said object is accessible.
In practice, in order to reconstruct or reconstitute such an object, for ex
Charmes Michel
Comoglio Bruno
Oliff & Berridg,e PLC
Silbaugh Jan H.
Staicovici Stefan
Sunkiss Aeronautique
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