Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1990-06-27
1993-01-05
Bell, James J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
156290, 428195, 428283, 428323, 428327, 428355, 428413, 428902, 428240, B32B 2714
Patent
active
051769492
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to the field of textile reinforcements for composite materials.
It is now well known to manufacture composite materials of high strength, despite their low weight, by coupling a matrix, generally a heat-curable resin with a set of textile structures, such as tissues. There are various methods for obtaining such materials. Reinforcing tissues can be impregnated with the resin manually, to be subsequently subjected to a contact molding method. A method which is employed, industrially consists of placing the textile reinforcement in a mold into which the resin is introduced and, to facilitate the flow of the latter, creating a pressure gradient in the mold to permit an optimum resin transfer. Another widely employed method consists of compressing a stack of textile reinforcements in a mold into which resin has been introduced.
In yet another method, a resin film or sheet is transferred under the effect of heat and pressure onto a stack of tissues or a multidimensional textile structure with fiber orientation. A further method also consists of passing the reinforcement, after impregnation with a resin, through a heated die to produce continuous profiled articles by extrusion. All these processes for the manufacture of articles made of composite materials are well known to the specialist and therefore do not need to be described in greater detail.
In practice, the cutting, handling and assembling of a number of layers and the forming of dry, that is to say not preimpregnated, textile structures frequently present problems and limit the possibilities of automation of the operations for the manufacture of articles made of composite materials, especially according to the methods referred to above.
In particular, the placing of dry reinforcements on a mold of complex shapes is a problem which has not been properly resolved, most especially in the case of stacking of a number of layers and when attempts are made to conform to the precise fiber orientations and to produce variable thicknesses, in order to obtain high mechanical performances.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a solution to the technical problems just mentioned. This object is achieved by providing a textile reinforcement for forming a composite material, characterized in that, at least one of its faces comprises a powder applied thereto, in at least point-fashion, in an amount of 3 to 25 g/m.sup.2 and in particular of 5 to 10 g/m.sup.2, and the powder being torate of a pulverulent composition comprising a prepolymer and a hardener for the latter, the composition being chosen so as to be compatible with the matrix of the composite material to be manufactured.
The object of the invention is also achieved by a process consisting of applying to at least one face of the textile reinforcement from 3 to 25 g/m.sup.2, in particular composition comprising a prepolymer and a hardener for the latter, the hardener becoming active only at a temperature above that at which the powder softens to become tacky, and the composition being chosen so as to be compatible with the matrix of the composite material to be manufactured.
It is already known (see for example GB-A-908,217 and EP-A-0,275,722) to distribute fusible components onto a support tissue, for example in the form of nodules of resin which are applied and softened by heating on one face of the tissue and adhere thereto after cooling. These are, hot-melt products, which are intended to be bonded by heat in clothing applications. Means are proposed for preventing the hot-melt substance from passing through the support.
Such articles are completely foreign to the field of the present invention, which relates to textile reinforcements for composite materials, which may be advantageously preformed to correspond to the desired shape of the reinforcement. The pulverulent hot-melt composition must be compatible with the matrix of the composite material to be manufactured. It is of no importance that such a composition passe
REFERENCES:
patent: 4139613 (1979-02-01), Hefele
patent: 4410385 (1983-10-01), Murphy et al.
patent: 4741873 (1988-05-01), Fischer et al.
patent: 4874655 (1989-10-01), Groshens
Allagnat Pierre
Charles Jean-Paul
Delehaye Michel
Bell James J.
Brochier S.A.
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