GB2150070A - Making articles of fiber-reinforced resin - Google Patents

Abstract

Composite objects comprising fibers bound by a synthetic resin are formed by applying thermoplastic resin 4 first to individual fibers 2. These fibers are assembled in a bundle 6 and fused by heating the resin. Then the bundle is wound in a mould 9. The composite material is left cooling progressively in the mould and thereafter the moulded object is removed. In a modified apparatus, Fig. 2 (not shown), the resin-coated fibers are stored on spools for subsequent re-heating prior to assembly into a bundle for winding in a mould. The metal object may be subjected to compression to improve its surface finish or to modify its shape. <IMAGE>

Description

SPECIFICATION Process for making articles of fiberreinforced resin The present invention is directed to the embodiment of composite articles constituted of fibers or filaments agglomerated by a synthetic resin. An example of such articles is given by the steering-wheels of vehicles.

Such steering-wheels are described for instance in the French patents 1.561.120 and 79.05080 and have the interest to secure a great safety for the driver in the event of crash. So in the steering-wheel whereof the embodiment is described in the patent 79.05080, the arms linking the hub to the circle are formed by agglomerated fibers, parallel to each other, which absorb the crash energy through their progressive deformation, so that the wounds possibly affecting the driver are strongly reduced.

However for the steering-wheel so described in the last patent, the binder flooding the fibers to achieve their agglomeration is a resin of the thermo-hardening type, so that the fibers must be integrated into the binder in the process of polymerization treatment under pressure at high temperature destined to harden the resin in which the said fibers have been first impregnated by soaking.

Such process has practically numerous disadvantages: -the liquid resin runs very easily along the threads, unless the firstly impregnated threads are stored in a cold room, what is an uneasy and costly trick.

-this way damages material and machines and so makes the maintenance difficult.

-the resin runs into all the joints of moulds and needs at withdrwing from the mould a very costly burring of the parts.

-a great number of moulds is necessary in this process for its utilization in industrial mass production.

-at each step it is necessary to coat the moulds with an agent for withdrawing from the mould or to lay down in the moulds thermoformed sheets.

-it is necessary to clean up carefully the moulds between each moulding for numerous burrs remain in all the planes of joint.

-the produced parts are irregular and of questionable geometry.

-the manufacture cycle is long and costly.

-the time of polymerization limits the rates.

-the needful investments are very heavy in order to obtain industrial rates that are compatible with the needs of the automobile industry.

The present invention allows to remedy all these disadvantages: It consists essentially in the embodiment of the said articles with the use of a resin of the thermoplastic type in order to agglomerate the fibers, applied through appropriated means on individual fibers that are then assembled at warm temperature and finally would directly in a mould where they are agglomerated by cooling progressively, leading thus directly to the finished object.

The application of the resin on individual fibers can be operated according to several variants.

In a first variant, continuous fibers are firstly heated and then coated with the resin, for instance by passing into a fluidified bath of resin powders, or by wrapping by extrusion of melted resin, or still by electrostatic deposit of resin powder.

In this variant, the fibers can be directly assembled at warm temperature in bundles then wound in the mould, where they are agglomerated with each other while cooling.

In a second variant, continuous fibers are coated with resin at cold temperature, for instance by passing into a solution or by aqueous scattering of the resin or employ of an adhesive, their heating allowing then together to eliminate the solvent or to reactivate the adhesive before or during the assemblage of the fibers.

In the two variants, though the product is obtained directly as soon as the mould is cooled, and can be used in the state, it is possible, if the superior compaction of the fibers on themselves is desired, and on the hub in the case of a steering-wheel, to set the previously obtained framework in a mould of compression at warm temperature, leading so to a finished product with very precise dimensions and without any deformation. In such operation, it is yet possible to set in the product metallic and plastic inserts, if it appears needful for instance to strengthen the arms in relation to the rim or to include needful parts for electric devices or others.

As fibers, natural or artificial, mineral or organic fibers, such as fibers of polyamides, polyethylene, polypropylene, polyacrylic resins or fibers of cotton, or boron, of carbon, of glass or metal such as aluminium and steel, or still mixtures of fibers of different nature. It is also interesting to use fibers comprising, on one hand a revetment with a first resin as a result of the electrostatic deposit of powder of this one on the fibers, and on the other hand a sheath of a second thermoplastic resin, identical or different, resulting from the extrusion of the same, in compliance with the French patent n0 83.10632 on 28 June 1983. As thermoplastic resin, one can use polyamides, polyethylenes, poly-propylenes, polystyrenes, modified or similar.

The interest of a process according to the invention in relation to the anterior processes, and notably the one described in the French patent 7905080, is to allow a manufacture that needs only a single filamentary winding mould and contingently, a compression mould so as to obtain a better state of surface or give to the part a peculiar shape, moreover both moulds being possibly joined together and the compression resulting from the closing of the mould. In addition the parts go out from the the moulds without burr, and there is no need to employ an agent for withdrawing from the mould and the parts produced are good without any action of touching up.

The following examples illustrate the operation of the process for its application to the manufacture of steering-wheels of cars, with reference to the drawing annexed, two modes of embodiment, the two figures of which illustrate schematically the successive steps of this process.

Example I.

On Fig. 1 are shown schematically in 1 the spools from which the individual fibers 2 are unwound and destined to be agglomerated to constitute the framework of the article. These fibers can contingently be pre-heated by a rolling-up HT 3, thereafter immersed into a bath 4 containing pulverulent resin fed in fluidified state by air blasting 5. The particules adhere to the fibers 2 travelling through the volume 4, by electrostatic attraction. At exit the fibers cross another zone of heating 5, where the said particules under the effect of the heat melt and constitute a binder achieving the agglomeration of the fiber in a flexible unitary bundle 6 that, after passing through an equalizing drawplate 7, is laid down by a robot 8 in a mould 9, in which it is cooled while taking the definitive form.

Practically in this example, the fibers 1 are glass fibers identified by the designation: "Roving R 28 of 320 tex". They have a diameter about 10y and pass through the bath at a speed reaching possibly 100m/min; the resin being of the polyamide type, the temperature of the rolling-ups 3 and 5 is 220 C.

Example 2.

Now, with reference to Fig. 1, it is seen that, in the second variant of the invention, the bundle leaving the bath is sent to an extruder 10, from which it goes out sheathed in a coat of thermoplstic resin, that may be the same as the one of the bath 4, or different. Therefrom the sheathed thread is drawn by a device 11 through a cooling zone 12, and finally stored in spool 13. This intermediate storage is necessary by the fact that the treated thread 4-10 comes from the roving spool 1' and crosses the whole of the system at a speed of about 1000 m/min. Then one starts from several spools 13a, 13b, 13..... of so sheathed thread that is assembled in bundle 14 and heated again in 15, so that, by reheating, the particles of resins covered by the sheath melt and form with the sheath the binder agglomerating the fibers.

This bundle is laid down and distributed by a robot head 8' in the mould 9', in which it is cooled while taking its definitive shape as in example 1. By ulterior closing under pressure of the mould 9 (or 9'), the state of surface of the article is improved, or its shape modified; for instance, at the periphery of the steeringwheel, light undulations improving the grasp are created. The assemblage in the mould can also be made without heating, the mould being later heated. The heating can be carried out by infrared rays, by non-oxidizing flame, by laser or any other means.

The mould used in this example is directed to the achievement of steering-wheels, the features of which are peculiarly precious, as stated at beginning, but the technics according to the invention are applied very generally to the embodiment of the composite articles with filamentary winding up presently obtained from thermo-hardening resins, notably the ones that cannot be carried out by rolling up on a mandrel. As for example, it can be mentioned in the automobile industry, the torsion bars, the propeller shafts, the suspensions, just as, in other industries, frameworks such as the ones for seats, door frames, frameworks of suitcases, tennis rackets, ski sticks and similar. This enumeration being obviously non limiting.

Claims (8)

1. Process for the manufacture of composite objects comprising fibers agglomerated by a synthetic resin, characterized in that, the resin being of the thermoplastic type, this resin is firstly applied to individual fibers, then these fibers are assembled in bundle by fusion in the resin, and the bundle is wound in the mould, while the composite material is left progressively cooling in the mould and then the obtained object is pull out.

2. Process according to the claim 1, characterized in that the resin is applied to the fibers by passing through a volume containing the resin under the form of particules in fluidified state, that are fixed on the continuously passing fibers by an electrostatic action.

3. Process according to 1 and 2, characterized in that the fibers are heated before their passing in the volume of fluidified resin particules, so that these particles melt at contact with fibers that are agglomerating at the exit of the said volume.

4. Process according to 1 and 2, characterized in that the fibers cross in cold state the volume of fluidified resin particles, then cross an extruder, from which they go out sheathed with identical or different resin, their reheating causing the fusion of both superposed resins, either before laying down in the mould, or after, by heating of the mould.

5. Process according to either of the claims 1 to 4, characterized in that the obtained object is submitted at the exit of the mould to an additional compression at warm temperature, achieving a more advanced compaction of the fibers on themselves, in the purpose of a better state of surface or of the modification of the obtained object.

6. Process according to 5, characterized in that, on occasion of this additional compression, are set in the object metallic or plastics inserts for its strenghtening or the fastening of electrical connections.

7. Application of the process according to either of the claims 1 to 6, to the embodiment of composite articles with filamentary winding up, and notably of the ones that cannot be obtained by rolling up on a mandrel, and notably rotating parts such as steering-wheels, torsion bars, propeller shafts, just as all the frameworks such as the ones of car doors, suitcases, seats and the articles such as tennis rackets, ski sticks and similar.

8. Process according to claim 1 substantially as described herein with reference to the accompanying drawings.