EP0424216A1 - Composite material, its fabricating process and use of the material - Google Patents

Abstract

Composite material of substantial thickness, characterised in that it consists of a single set of strands which are woven in three dimensions, the said set being resin-coated. <IMAGE>

Description

The present invention relates to a composite material, its production method and use of said material.

The composite material is a heterogeneous substance generally comprising fibers, threads, free or assembled in layers, embedded in a resin.

These composite materials are generally in the form of large, fairly rigid thick plates. They are more and more used in industry, especially in the industry of construction of equipment, capital goods, transport, etc. to make bodywork, floors, etc.

These plates are transformed, according to traditional techniques by contact or vacuum molding, by injection and according to a more recent technique, by stamping.

Generally, a production process consists in assembling in layers or strata textile fabrics of fibers or reinforcing threads with high mechanical characteristics such as: glass, silica, silicon carbide, carbon, ceramic, aramids, high modulus polyethylene, etc., and to drown them in a resin matrix. More precisely, a base of resin and release agent is poured into a mold the size of a plate; above, a first layer of fabric is laid, made of reinforcing fiber threads for example, which is covered with resin; above, a second layer of fabric is placed in high-resistance reinforcing threads, which are also covered with resin; so on we stack several layers, for example five or six that are covered with resin, and we finish the stack with a last layer of resin and a release agent. This assembly is then subjected to a compression action intended to eliminate the maximum of air and to make the resin penetrate into the layers of fabrics, then a heat treatment which crosslinks or polymerizes the resin in order to obtain a rigid composite and the most homogeneous whole possible. These composite materials can comprise up to more than forty layers each with a thickness of the order of 0.1 to 0.2 millimeters: the most common have from one to fifteen layers and are of average total thickness between 3 and 5 mm after compression and ready to use. Their weight is around 200 grams / m2 for a 0.1 mm thick layer of glass. The material obtained is a composite product with high resistance, in particular to impact, traction, compression.

• 1- il est coûteux : le matériel nécessaire à sa mécanisation est très coûteux, et généralement les opérations sont manuelles, ce qui suppose une main-d'oeuvre importante; d'autre part il est long : les étapes de réalisation sont nombreuses;
• 2- le matériau obtenu présente une faible résistance au cisaillement : on observe du délaminage. Le phénomène s'explique par le fait que les couches de tissus renferment des bulles d'air qui ne sont pas chassées par la résine. Ces bulles forment autant de petits matelas d'air qui réduisent le contact couche-résine et l'adhérence entre les couches.
• 3- l'homogénéité recherchée par le traitement thermique, (imprégnation, polymérisation) est difficile à obtenir en une durée raisonnable, du fait de l'épaisseur du matériau ce qui accentue le délaminage.

However, such a method has many drawbacks:

• 1- it is expensive: the equipment necessary for its mechanization is very expensive, and generally the operations are manual, which supposes a significant manpower; on the other hand it is long: the stages of realization are numerous;
• 2- the material obtained has a low shear strength: delamination is observed. The phenomenon is explained by the fact that the layers of tissue contain air bubbles which are not expelled by the resin. These bubbles form as many small air mattresses which reduce the layer-resin contact and the adhesion between the layers.
• 3- the homogeneity sought by the heat treatment (impregnation, polymerization) is difficult to obtain in a reasonable time, due to the thickness of the material which accentuates delamination.

On the other hand and in a very general way, a fabric is a textile structure formed by an assembly of so-called warp threads assembled in so-called weft threads. This structure extends in a plane, the thickness of which is limited to that of the wire or wires used, dimension negligible in relation to the surface of the fabric. One of the usual characteristics of fabrics is their non-deformability in the plane, which can be a quality or a defect depending on the use made of them. It is well known that the deformation of a fabric to give it a shape produces folds, the fabric not being capable of deforming elastically due to its structure. Confection is then the art of assembling pieces of fabric so as to hold forms, whether in the clothing industry or any other industry. This is why, when making composite materials, assembling the layers of fabrics also consists in arranging strips of fabrics so as to promote the production of shapes, without producing folds.

The aim of the present invention is to produce a composite material according to a process which resolves all the difficulties exposed: mechanization, speed of production, high deformability, resistance to delamination, homogeneity, costs.

The subject of the invention is a composite material of substantial thickness, characterized in that it consists of a single set of reinforcing threads associated with a thermosplastic resin, woven in three dimensions.

It also relates to the use of a weaving loom provided with several chains of reinforcing threads in order to produce a composite coating of substantial thickness.

In order to better understand the invention, there is shown in the accompanying drawing a non-limiting example of material according to the invention.

As can be seen in the drawing, the fabric 1 comprises several series of 2 warp threads 2 extending parallel to each other. In the example, the fabric comprises 5 series of warp threads 2a to 2f. Each chain is horizontal, the series overlap vertically, forming a thick sheet, which extends in the three dimensions. The weft threads 3 are passed alternately through these warp threads and, depending on the choice, alternate between the thread of the first level 2a and the thread of the second 2b, or of the third 2c etc.

The weaving can be modulated according to the effect which one wants to give to the fabric.

Such a process gives a thick fabric, homogeneous in its thickness since it is made in one piece. On the other hand, the fact of weaving in three dimensions gives this fabric great deformability, by internal deformation.

In a first alternative embodiment, the wires are previously associated with the resin, that is to say that they comprise both reinforcing fibers and their matrix or resin. This "entrainment" is obtained either by intimate mixing in the yarn, of reinforcing fibers and of resin presented in the form of fibers, or by coating of reinforcing yarns with a sheath of resin.

In a second variant, weaving is carried out with threads comprising only reinforcing fibers, free of resin. The son-resin association, or "enresinement" is here a coating of the fabric; it is produced after passing through the loom by application with a brush, spraying, injection, or any other known technique.

The first variant is advantageous in that it gives, in a single operation, a flexible material which can be immediately wound up, or cut into panels, and constitutes a finished product ready to be used.

The coating obtained must then undergo a heat treatment followed or not by compaction intended to melt the resin, to give this coating the desired shape and then to give it great rigidity.

As an example of an embodiment, a three-dimensional fabric was produced with composite yarns of 60% glass, 40% PEEK, and the heat treatment and stamping gives armor plates.

The invention provides, among other things, the following considerable advantages:
- the three-dimensional assembly is perfectly homogeneous;
- deep weaving removes successive layers, there can no longer be delamination;
- After heat treatment, the presence of air bubbles between the woven threads does not have an unfavorable influence on the resistance characteristics: this operation can then be considerably simplified.
- The material can be more or less compressed which makes it very easy to make imprints which remain flexible;
- the material is very light; compared to traditional materials of comparable thickness. We can estimate a weight gain of around 20%.

Claims (5)

1. A method of manufacturing a composite material of substantial thickness consisting of a single set of three-dimensional woven threads, characterized in that the threads are prior to weaving associated with a thermoplastic resin. 2. Manufacturing method according to claim 1 characterized in that the son are associated with the resin by an intimate mixture in the son, reinforcing fibers and resin. 3. The manufacturing method according to claim 1 characterized in that each wire is coated with a resin sheath. 4. composite material of substantial thickness obtained by the process according to any one of the preceding claims 5. Use of the material according to claim 4 for the production of capital goods materials, in particular bodies.

Images