Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-05-24
2003-11-04
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S169000, C156S191000, C156S194000
Reexamination Certificate
active
06641693
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a process for producing components or structural parts, a structural part produced by the process, a thermal insulation cylinder, a protective tube, a heating element, a stay pipe, a hot-press die and a thermal insulation element.
In the context of this invention the term “developable structural parts” is understood to mean a three-dimensional structural part, the body of which can be developed by geometric transformation into one plane and in that way can be illustrated in a drawing. Such structural parts include, for example, tubes or cylinders which have a circular, oval or even angular, for example, rectangular or square, cross-section and are hollow.
The production of tubular structural parts from fibrous composites is known in principle. Such structural parts are produced, for example, by laminating a plurality of fabric layers impregnated with a resin, preferably a synthetic resin, which are so-called prepregs, on top of one another. The production of developable fibrous composites which are free of structural defects is difficult and is carried out in accordance with a complex multi-stage process. In order to obtain a product which is free of gaps and wrinkles, approximately two to four layers of fabric are generally laid or wound on top of one another. Subsequently, the body obtained in that way must be subjected to a treatment during which the resin contained therein cures. Before continuing the production process the surface of the cured body must generally be smoothed in order to eliminate irregularities thereon and to prepare it for the accommodation of further prepreg layers. Such intermediate curing is very often carried out in conjunction with shaping and compaction by the vacuum bag process which is known among experts, for which a specific device is necessary. In that case, an autoclave used for the vacuum bag process is additionally adjusted to the desired curing conditions. After such intermediate curing, which is also time-consuming, further fabric layers are then applied to the surface. That process sequence is maintained until achieving the desired wall thickness of the element, which is to be produced. When producing high quality fibrous composite elements, up to three or even more such winding processes have to be carried out with intermediate curing. That process is therefore very time-consuming and cost-intensive. Consequently, for cost reasons, structural parts produced in that way are only used where structural parts made from other materials behave very unfavorably or fail.
A tubular structural part that is known from U.S. Pat. No. 5,638,8705 is produced from a fabric composed of reinforcing fibers which extend in warp direction of the fabric, corresponding to axial direction of the tubular element, and of thermoplastic resin fibers which extend in weft direction of the fabric and interweave with the reinforcing fibers. An example of the structure of the structural part known from that patent includes a first and a second fabric layer between which an intermediate layer of uniformly oriented fibers is disposed. That layer of uniformly oriented fibers is produced from fiber bundles which have reinforcing fibers and thermoplastic resin fibers. The composite produced in that way is applied to a core (mandrel), is subsequently shaped with the application of pressure and heat, and a mould for the external shaping is applied around the composite from the outside.
The disadvantages of that process are, on one hand, the complex process and, on the other hand, the necessity of having to use an external shaping tool.
Winding techniques for producing tubular structural parts are also known. U.S. Pat. No. 5,047,104 describes solid or hollow profiles made from fibrous materials which are impregnated with liquid resin and then covered with non-impregnated fibers or monofilaments made from organic materials. Those organic materials are selected in such a way that shrinkage forces are still active before the reactive resin being used reaches a gel phase. A covering of the first-mentioned fiber materials by the winding fibers of only approximately 12% is sufficient. The organic fibers being applied shrink during a subsequent curing step and penetrate into the resin. Due to that procedure it is possible to produce cross-sections in the structural parts which are exactly circular, wherein no external shaping units have to be used. Such structural parts are suitable in particular as cables or wires for reinforcing concrete. They also exhibit a high degree of weather resistance.
European Patent Application 0 443 470 A2, corresponding to U.S. Pat. No. 5,135,596, describes a structural part made from fibrous composites with a tubular region and at least one plane flange. A winding with fiber strands crossing at an angle to the axis of the core is applied to a mandrel. Subsequently, the ends of the tubular region are widened conically through the use of an expanding element. The winding is wound on both sides of the tubular region in each case through the use of such an expanding element and a shaping tool is applied to the tubular region of the winding from the outside.
German Published, Non-Prosecuted Patent Application DE 40 21 547 A1 describes a process for producing fibrous composite elements, wherein fibers are wound around a support element so as to be practically free of pores. To that end fiber ribbons are used in which individual fibers are surrounded without the formation of a hollow space by matrix material. Covered individual fibers which are gap-free can also be wound with matrix material. During subsequent hot isostatic pressing, matrix material, fibers and support elements are connected by fluid formation. Due to the use of fiber ribbons which have a substantially rectangular cross-section, embedding of the fiber ribbon layer into the matrix material is achieved, with the displacement of the fibers when using the structural part being avoided. In addition, due to the rectangular cross-section of the fiber ribbon, covering which is free of intermediate spaces is possible.
UK Patent Application GB 2 127 771 A describes the production of irregularly shaped winding elements which are formed of a first layer that is made, for example, from longitudinally oriented fabric segments being formed of carbon fibers which are wound on a mandrel and are formed of a second layer of transversely wound continuous fibers. The winding elements are then impregnated with thermoplastic or thermoset materials and the resin is cured. A carbonization treatment can then optionally follow. According to a second variation, fabric layers are wound onto the core specifically so as to conform to the later shape of the winding element or the core, until the desired strength of the winding is achieved. The core is therefore substantially covered by the fabric which contains a large number of warp threads that are wound peripherally around the core and a large number of weft threads crossing the former, which are disposed orthogonally to the weft threads. Subsequently, as in the first variation, impregnation with resin takes place. Curing of the resin and optionally further processing steps then follow.
The essential feature in both variations is that the wound layers are applied in the dry state and are impregnated in a later processing step. A dry structure is therefore described in that publication in which the fabric or the fabric segments have to be fixed in order to prevent slipping.
U.S. Pat. No. 4,555,113 describes the production of a shaft, for example for golf clubs, in which a resin layer is applied to a mandrel and a fabric is applied on top. Two different types of carbon fiber ribbons are wound spirally over that formed body in winding directions which are opposed to one another, so that many points of intersection are obtained as a result of that winding technique. Subsequently, the surface of the winding element is covered by a ribbon of CELLOPHANE and the resin is cured. The ribbon of CELLOPHANE a
Guckert Werner
Rauch Siegfried
Aftergut Jeff H.
Greenberg Laurence A.
Mayback Gregory L.
SGL Carbon AG
Stemer Werner H.
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