Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-11-26
2003-12-23
Staicovici, Stefan (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S074000, C156S245000, C264S221000, C264S257000, C264S258000, C264S317000, C264S324000, C249S061000, C425S176000
Reexamination Certificate
active
06666941
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method of manufacturing a composite-material product, such as a container, a tubular product, a wing or another structure, reinforced by, for example, reinforcing fibers. More particularly, the present invention relates to a method of manufacturing a ribbed structure made of fiber-reinforced plastic or the like by using a mold, for example, a core, the removal of which from the structure has been difficult and which is made of a biodegradable material.
BACKGROUND
When a composite-material product reinforced by carbon-fiber-reinforced plastic (hereinafter called “CFRP”) or glass-fiber-reinforced plastic (hereinafter called “GFRP”), for example, a hollow structure having an undercut, is manufactured, a method structured as shown in
FIG. 30
has been employed.
That is, a metal and split mandrel
401
composed of a shell
401
a
and a core
401
b
having shapes corresponding to a shape attempted to be molded is prepared. Then, CFRP or GFRP is laminated on the outer surface of the shell
401
a
of the split mandrel
401
so that a reinforcing-fiber-reinforced resin layer
402
is formed. The reinforcing-fiber-reinforced resin layer
402
is hardened with heat or at room temperatures. Then, the shell
401
a
and core
401
b
of the split mandrel
401
are mechanically decomposed (separated) so as to be removed from the inside portion of the reinforcing-fiber-reinforced resin layer
402
. As a result, a hollow structure
403
is molded.
If the shape of the hollow structure attempted to be molded by the metal and split mandrel is too complicated to easily be removed by mechanical decomposition after the molding process has been completed, the following method is employed. That is, the mandrel is made of a metal material having a low melting point. Moreover, the CFRP or GFRP is laminated on the outer surface of the mandrel as described above to form the fiber-reinforced resin layer. Then, the fiber-reinforced resin layer is hardened at room temperatures, and then the mandrel is heated at appropriate temperatures so as to be melted and removed.
Another method is known with which the mandrel is made of a material which can be melted with a chemical. Another method is known with which the mandrel is made of collapsible plaster which is crushed so as to be removed after the molding process has been completed. The above-mentioned manufacturing methods have been employed to mold a product, such as a duct
404
including a warped portion
404
a
and a branch portion
404
b,
as shown in FIG.
31
(
a
). Also the foregoing methods have been employed to mold, for example, a tubular member
405
having bent portions
405
a
at two ends thereof, as shown in FIG.
31
(
b
).
However, the split mandrel cannot easily be manufactured and thus the manufacturing cost is enlarged. If a complicated shape is attempted to be formed, the separation and removal which are performed after the molding process has been completed cannot easily be performed as well as the difficulty in manufacturing the same. In this case, excessively large force is added to the molded product and, therefore, the molded product is deformed or broken.
Any one of the above-mentioned method of removing the mandrel by heating and melting the same, the method of removing the mandrel by melting the same by using a chemical and the method of removing the mandrel by crushing the collapsible plaster require a large number of steps. Thus, all of the foregoing methods suffer from unsatisfactory productivity. When a molded product having a complicated shape is attempted to be manufactured, the mandrel cannot completely be removed. When the core is manufactured by aluminum, the solvent of the chemical is sodium hydroxide. However, a great cost is required to perform disposal of sodium hydroxide after the core has been dissolved. What is worse, environmental pollution is undesirably caused to take place.
In recent years, weight reduction and increase in the strength have been required. Therefore, prepreg has energetically been developed which contains thermosetting resin, such as epoxy resin or unsaturated polyester, serving as a matrix thereof and a reinforcing material, such as carbon fibers, aramide fibers or glass fibers, added thereto. Therefore, the needs for a variety of products containing the prepreg have considerably been grown. In addition, the needs for a composite-material product such that thermoplastic resin, such as nylon or polyether-ether ketone (PEEK), is used as the matrix have been grown.
Since the prepreg of the foregoing type is a material having excellent characteristics which enable light weight and strong structure to be manufactured, it can be considered that a composite material is an advantageous material to make various elements for use in an extreme condition in, for example, an aerospace industrial field. Since the foregoing structures usually have complicated shapes, complicated processes are required to manufacture the foregoing structures.
When the thermosetting resin or the thermoplastic resin is employed as the matrix of the core of the honeycomb for use in the composite-material structure and long carbon-fiber-reinforced plastic (hereinafter called “CFRP”) or the glass-fiber-reinforced plastic (hereinafter called “GFRP”) is employed as the reinforcing fiber, the prepreg must be laminated in a trapezoidal mold having asperities so as to be hardened by an autoclave or a pressing machine.
A fact is known that a structure that the long fiber CFRP or GFRP employed as the reinforcing fiber of the core material enables a strong and rigid honeycomb plate to be manufactured. However, there arises a problem in that long time and great effort are required to inject the material and to perform a laminating process when a waveform plate is molded to manufacture the core member. Further, since the honeycomb structure such as the honeycomb plate has normally a directional property, etc., it has been difficult to design and manufacture the three-dimensional honeycomb structure. However, the honeycomb plate suffers from unsatisfactory strength against a load added in a direction perpendicular to the longitudinal plate.
When an airplane or a wing structure such as wings or fan's blades are manufactured by using the known honeycomb structures, the main body of the wing
411
is constituted by honeycomb cores
412
having lower densities, that is, a large cell size (the length of one side of a hexagon is long), as shown in FIG.
32
. In this case, the weight of the wing
411
can be reduced. If the outer surface of the wing
411
is attempted to be smoothed or if the resistance against collision with an object is attempted to be somewhat enlarged, it is preferable that honeycomb cores
413
each having a high density, that is, a small cell size (the length of one side of a hexagon is short) is employed.
Therefore, a two-layer structure has been employed which is composed of the honeycomb cores
412
having the large cell size and the honeycomb cores
413
having the small cell size which are laminated through the prepreg
414
. However, the manufacturing process requires long time and great effort and a complicated three-dimensional curved surface cannot easily be manufactured. Therefore, the above-mentioned structure cannot practically be employed. Although the honeycomb can be preformed at high temperatures, a large heat-resisting mold is required to preform the honeycomb. Thus, the manufacturing cost is enlarged.
When a three-dimensional curved surface is manufactured by using the honeycomb, a core material
415
must be cut to form a rectangular block into the three-dimensional curved surface, as shown in FIG.
33
(
a
). As an alternative to this, a honeycomb core material
416
for forming a three-dimensional curved surface must be employed, as shown in FIG.
33
(
b
). In either case, the manufacturing cost cannot be reduced. Therefore, another requirement is imposed to manufacture a complicated structure of the foregoing type by using the composite material at a
Sakura Rubber Co. Ltd.
Staicovici Stefan
Volpe and Koenig P.C.
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