WO1999033639A1

WO1999033639A1 - A method of forming preforms in the manufacture of fibre composites

Info

Publication number: WO1999033639A1
Application number: PCT/SE1998/001969
Authority: WO
Inventors: Kjell Eng
Original assignee: Eng-Tex Ab
Priority date: 1997-12-16
Filing date: 1998-10-30
Publication date: 1999-07-08
Also published as: SE9704679L; SE511108C2; AU9773498A; SE9704679D0

Abstract

The invention concerns a method of forming preforms to manufacture fibre composites, comprising monoaxial or biaxial laid-yarn fabrics, which are injected with a thermosetting plastic or a thermoplastic material or - if the fabric is made from a thermoplastic hybrid yarn - are heated. According to the novel method, the fabric material is applied on a core (5), which is an elongate body, in the form of ribbons (1, 2, 3, 4). These are advanced at an angle relative to the core (5) and are wound onto the latter in overlapping relationship, preferably by rotation of the core (5) about the longitudinal centre core axis while said core is simultaneously being advanced in its longitudinal direction.

Description

A METHOD OF FORMING PREFORMS IN THE MANUFACTURE OF

FIBRE COMPOSITES

The invention concerns a method of forming preforms in the manufacture of fibre composites, according to which method textile structures in the form of monoaxial or biaxial laid-yarn fabrics are used as reinforcement material. To form these fibre composites, the laid-yarn fabrics are draped on a core and are injected with a thermosetting plastic or a thermoplastic material, alternatively are heated, when the fabric is made from thermoplastic hybrid yarns. In moulding plastic bodies according to the conventional technique, multiaxial laid-yarn fabrics are used, said fabrics serving as reinforcement material in the finished plastic body, which then forms a fibre composite. The reinforcement material imparts to the body considerable strength properties, due to the excellent tensile strength that laid-yarn fabrics exhibit in all directions .

A drawback found in the multiaxial laid-yarn fabric is, however, its poor drapability, which restricts the dimensions of the projecting sections of the mould that is to be used, when the multiaxial laid-yarn fabric is placed inside or on the mould prior to the application of the plastics material.

Another disadvantage resides in the fact that the machinery for producing multiaxial laid-yarn fabric has a comparatively complex structure, and consequently it is expensive. For technical reasons, when using such machinery one is also reduced to manufacturing fabrics of a comparatively restricted maximum width. In order to overcome the above-mentioned disadvantages one has started to employ the method referred to in the introduction hereto, see SE 9700893-2, according to which method monoaxial rather than multiaxial laid-yarn fabrics are used. Monoaxial laid-yarn fabrics consist of mutually parallel wefts joined together into a fabric by wales extending crosswise relative to the wefts and at an oblique angle relative to two opposite fabric edges, and they may extend at right angles in either the transverse or the longitudinal direction. By advancing in superposed relationship several webs of such monoaxial laid-yarn fabrics, wherein the wefts extend at mutually different angles, it becomes possible to produce a multi-layer web which, after having been cut crosswise, forms a multilayer fabric. This fabric may subsequently be used to manufacture a plastics-fibre composite in a moulding process. In addition to exhibiting excellent tensile strength in all directions, such a multi-layer fabric has the advantage over the above-mentioned prior-art multiaxial laid-yarn fabric in that it possesses excellent drapability properties, which means that it shapes itself well to the configuration of moulds having comparatively sharply protruding parts, without risking to crack or form folds.

The invention provides a novel method, which is a further development of the method referred to above and which exhibits additional advantages over that prior-art method. The characterising features of the novel method are that the fabric material is applied on a core, which is an elongate body, in the form of bands or ribbons, said bands or ribbons being advanced at an angle relative to the core and to one another and being wound onto the core in overlapping relationship, by rotation of the core about its longitudinal centre axis and simultaneous advancement of said core in its longitudinal direction. The invention will be described in more detail in the following with reference to the accompanying drawings, wherein Fig 1 is a perspective view showing a core in the initial stage of winding-on thereonto of four ribbons, Fig 2 shows the structure resulting from completed winding-on of the ribbons

Fig 3 shows a variety of the winding-on shown in Fig

1, Fig 4 shows the structure resulting from completed winding-on of the ribbons onto the core according to Fig 3, and

Figs 5-7 show a number of laid-yarn fabrics having mutually different structures. Fig 1 shows one embodiment according to which four ribbons 1, 2, 3 and 4 of monoaxial laid-yarn fabrics are being wound onto a core 5. For the sake of clarity, the ribbons 1, 2, 3, 4 are shown somewhat schematically, i.e. the drawing figure shows only the extension of the threads 6, 7, 8 and 9, respectively of the ribbons. As illustrated, the threads 6 of ribbon 1 extend at an angle relative to the direction of advancement of the ribbon 1, the threads 7 of ribbon 2 likewise extend at an angle relative to the direction of advancement of its ribbon, and the threads 8 and 9 of ribbons 3 and 4, respectively, extend at right angles to the direction of advancement of those ribbons 3 and 4, respectively.

The core 5 is illustrated in the drawing figure as an elongate parallepepidon body having a rectangular cross-sectional shape but it could of course be configured differently, e.g. having a round or square cross- sectional shape. Preferably, the core 5 is made from cellular plastics but could equally well be made from wood or metal, e.g. aluminium. The core 5 is assumed to be rotational about its longitudinal centre axis in the direction of arrow 10, and also to be displaceable in its longitudinal direction upwards (or inwards) with respect to the drawing figure.

When the ribbons 1, 2, 3, 4 are being wound onto the core 5 in the manner appearing from Fig 1 and in that order, they will form on the core a multi-layer fabric having the structure shown in Fig 2. Thus, the threads 6 of ribbon 1 will place themselves closest to the core 5 so as to extend in the cross-core direction, the threads 7 of ribbon 2 will place themselves on top of the threads 6 so as to extend in the longitudinal direction of the core 5, the threads 8 of the ribbon 3 will place themselves on top of threads 7 so as to extend at an oblique angle across the latter, and threads 9 of ribbon 4 will place themselves on top of threads 8 so as to extend essentially at right angles to the direction of extension of the latter. Thanks to this ribbon winding-on method, a multi-layer fabric is produced, which possesses excellent tensile strength in all directions as well as excellent drapability properties.

Fig. 3 illustrates an embodiment, which differs from the one shown in Fig 1 in the respect that ribbons 1 and 4 have changed places and in that the ribbons 2 and 3 are applied to the core 5 prior to ribbons 1 and 4. This small modification produces a different structure in the finished multi-layer fabric, as appears from Fig 4. Thus, in this latter case, the threads 7 of ribbon 2 will be the one located closest to the core 5 and will extend in the longitudinal direction of the core, the threads 8 of ribbon 3 will cross over the threads 7 of band/ribbon 2, the threads 9 of ribbon 4 will cross the threads 8 of ribbon 3 at right angles thereto, and the threads 6 of ribbon 1 will be placed on top of the threads 9 of band/ribbon 4 and extend at right angles to the longitudinal direction of the core.

By very simple means, the inventive method makes it possible to alter the structure as well as the thickness of the multi-layer fabric formed on the core 5. Such alterations may be effected for instance by altering the width of the ribbons 1, 2, 3, 4, by altering the thread count in the fabric, by altering the speed of advancement of the core in the longitudinal core direction, by altering the speed of rotation of the core 5, or by altering the winding angle of the ribbons 1, 2, 3, 4 onto the core 5. It is obviously also possible to alter the number of ribbons that are wound onto the core 5 at the same time. By using biaxial laid-yarn fabrics, the same multi-layer structure is obtainable but with a fewer number of ribbons.

One advantage of the method according to the invention over that described in SE 9700893-2, according to which latter method fabric webs are advanced in the same direction and are placed in superposed relationship in order to form a multi-layer fabric, is less material waste and also that the roving threads do not run in the direction of the entire core 5 but only have a length corresponding to the width of the ribbons. The result is increased drapability without detraction from the tensile strength of the multi-layer cloth. It is, however, preferably to wind-on the ribbons in a slightly overlapping relationship in order to pay regard to the mechanical qualities of the fibre material.

Figs 5, 6 and 7, finally, show various examples of combinations of differently structured laid-yarn fabrics in order to produce a multi-layer fabric of identical character. Thus, by sandwiching the fabric of Fig 5b between the fabrics of Figs 5a and 5c, the fabric of Fig 6b between the fabrics of Figs 6a and 6c, and the fabric of Fig 7c between the fabrics of Figs 7a and 7c, multilayer fabrics of identical structure are produced.

The method in accordance with the invention obviously may be varied in other ways than those mentioned herein, within the scope of the appended claims.

Claims

1. A method of forming preforms in the manufacture of fibre composites, according to which method textile structures in the form of monoaxial or biaxial laid-yarn fabrics are used as reinforcement material, which laid- yarn fabrics are applied on a core (5) and are injected with a thermosetting plastic or a thermoplastic material, alternatively are heated, when the fabric is made from thermoplastic hybrid yarns, to form said fibre composite, c h a r a c t e r i s e d by applying the fabric material on a core (5), which is an elongate body, in the form of ribbons (1, 2, 3,4), said ribbons being advanced at an angle relative to the core (5) and being wound onto the latter in overlapping relationship while said ribbons (1, 2, 3, 4) are being displaced relative to the core (5) in the longitudinal direction of the latter.

2. A method as claimed in claim 1, c h a r a c t e r i s e d by applying several ribbons (1, 2, 3, 4) having threads (6, 7, 8, 9) of mutually different orientation onto the core (5) at such angles relative to the latter that the threads (7) of one layer on the core

(5) extend in the longitudinal direction of the core (5) whereas the threads (6, 8, 9) of the other layers extend crosswise with respect to said longitudinal direction.

3. A method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the winding-on of the ribbons (1, 2, 3, 4) is effected by rotating the core (5) about the centre longitudinal core axis.

4. A method as claimed in any one of the preceding claims, c h a r a c t e r i s e d by winding the ribbons (1, 2, 3, 4) onto the core (5) during advancement of the latter in the longitudinal direction.