Coating processes – With stretching or tensioning – Running lengths
Patent
1996-11-07
1998-11-10
Bareford, Katherine A.
Coating processes
With stretching or tensioning
Running lengths
427429, 118244, 118264, B05D 312, B05C 1100
Patent
active
058340564
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/EP 95/01476, filed Apr. 19, 1995.
BACKGROUND OF THE INVENTION
Field of the Invention
Discussion of the Background
Such a process is known from EP 415 517 B1. This document describes a procedure with a one-sided impregnating direction, in which an elevated system pressure of the liquid matrix material is built up at right angles to the fibre bundle. The fibre bundle is drawn via a nozzle head and the matrix material is forced through at right angles to the bundle movement direction. In this process the tribological stressing of the fibre bundle is high and the quality of the material produced can be reduced by a plurality of individual filament breaks in the fibre bundle. The filaments in a fibre bundle are often in the form of accumulations, i.e. not uniformly distributed over the fibre bundle cross-sectional surface.
As a result of this non-uniform distribution the flowing matrix melt splits the fibre bundle and consequently the matrix flows through the gap and not through the fibre bundle to be impregnated. However, even without the splitting of the fibre bundle the matrix always attempts to follow the path of least resistance, i.e. it only penetrates the fibre bundle where the thickness of the latter is at a minimum. This means that points having a large number of superimposed filament layers are inadequately impregnated.
Problems during impregnation are the high viscosities of the matrix materials and the high break sensitivity of the individual filaments within the fibre bundle. The individual filaments are very close together and it is difficult to uniformly impregnate all round the filaments with the matrix material. It is also necessary to ensure that within the impregnated fibre bundle, also known as a tape, no air inclusions or inadequately wetted zones are formed, which greatly reduce the strength, stiffness and other mechanical characteristics of the fibre bundle.
SUMMARY OF THE INVENTION
The object of the invention is to provide a process of the aforementioned type, in which there is a particularly good impregnation of the fibre bundle or some other fibre preform (e.g. fibre mats) in the case of a high throughput and at the same time filament breaks can be largely prevented. In addition, an apparatus is to be provided for performing the process according to the invention.
According to the basic concept of the invention the fibre bundle is carried along on a support during the impregnating process. The fibre bundle is supported by the support and led past the impregnating device. Thus, there is no relative movement between the fibre bundle and fixed parts of the impregnating device. Thus, abrasion processes, a high tribological stressing of the fibre bundle and also the impregnating tool are avoided. As a result of the supporting action of the support, the fibre bundle is effectively relieved, even in the case of a high impregnating pressure. As a result of the use of a support filament breaks are largely avoided and consequently the quality of the impregnated fibre bundle is improved.
In an advantageous further development the fibre bundle is secured on the support by additional measures. This leads to a particularly good contact between the bearing surface and the fibre bundle, so that the fibre bundle is particularly well protected against compressive loading during the impregnating process. This can be achieved by simply tensioning the fibre bundle, e.g. by guiding said bundle over a braked roll.
Matrix material is supplied to the fibre bundle in the following way. With the aid of a pressure built up in the feed mechanism (extruder), in the liquid state the matrix material is forced through a permeable bearing surface and then further guided through the fibre bundle. It is also possible to have a matrix material supply from the other side, i.e. initially through the fibre bundle and then through the support, provided that no use is made of the described uniform through-flow principle. In both cases the support fulfils its supporting function
REFERENCES:
patent: 3157536 (1964-11-01), Caines
patent: 4968534 (1990-11-01), Bogardy
Bareford Katherine A.
Institut Fuer Verbundwerkstoffe GmbH
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