FR2620375A1 - Method of manufacturing linear composite materials of variable cross-section and materials obtained by this method - Google Patents

Abstract

Method of manufacturing composite elongate articles. According to the invention, a continuous or discontinuous liner 14, having a constant or variable cross-section, is inserted along the axis of a ply of filaments 13 which are impregnated with resin 11. The cohesion of the assembly is ensured by a braid 12 conforming to the variable contour, depending on the liner, with the speed of pulling and the speed of braiding being possibly controlled as a function of the external profile. Applications: continuous manufacture of nesting tubes (pipes), tension rods, or similar profiles (sections).

Description

PROCESS FOR PRODUCING LINEAR COMPOSITE MATERIALS
WITH VARIABLE SECTION AND MATERIALS OBTAINED ACCORDING TO THIS PROCESS
The subject of the present invention is a process for the continuous production of linear composite materials with variable cross-section as well as the materials, of the tube, rod, profile or similar type, obtained by this process.

Rigid or semi-rigid linear composite materials are known. They comprise a solid or hollow core, along the generatrices- from which extend parallel fibers completely surrounding the core and joined to these by a synthetic resin, for example of the polyester or epoxy type, the assembly being included in a protective cover. The longitudinal reinforcing fibers are currently glass or carbon fibers. The essential advantage of such composites is to have mechanical characteristics comparable to those of high quality steels for a weight approximately 4 times less than that of a steel rod of the same section.

Such composites are produced by different processes, one of which is known as "pultrusion". It consists of impregnating the longitudinal reinforcing fibers on the core or core and pulling the assembly through a heated die which causes cross-linking of the impregnation product, but, given the passage through the die, this process does not allow variable sections to be obtained.

Another method, called filament winding, or wrapping, consists in winding wires having a determined angle relative to a generator, on a rigid mandrel. This process allows variable sections to be obtained, provided that the wrapping slope is always in the same direction, but it does not allow continuous manufacturing and is always limited by a determined length of product.

In addition, it is quite difficult in this process to place the wires lengthwise, so as to obtain a large tensile or flexural modulus.

DE-OS-1 504 197 describes a process for the preparation of bars, profiles and tubes, from fibrous composite materials in which fibers are assembled continuously from a warping machine, then sent to a bucket can be heated and filled with a synthetic resin, the assembly being formed and regularized through dies. After impregnation and forming, the fibrous material is wrapped with a twisted fibrous material and the composite obtained passes through one or more curing ovens. But, as indicated above, the presence of a die precludes obtaining bodies with variable section.

The object of the present invention is to overcome the drawbacks of known devices and to allow the continuous production of tubes, rods, or the like, having variable sections.

Obtaining variable sections can be justified by construction needs, especially when it comes to reinforcing certain areas of the rod, but its essential purpose is to allow easy assembly end to end of tubes or rods, meeting which previously required the termination of the elements with caps or end pieces, an additional operation which reduces cost prices.

According to the present invention, the method of manufacturing tubes with variable cross-section, comprising a slender sleeve around which extend reinforcing fibers in parallel, the assembly being included in a cover, is characterized in that the reinforcing fibers, impregnated by an excess resin, are deposited around a variable section sleeve, the assembly being coated with a braided cover placed under tension and drawn through ovens polymerizing the resin.

The braiding of the outer cover carried out under tension causes migration or exudation of the resin, from the interior of the elongate body towards the outside thereof, so that the outer braid is itself completely coated. Braiding takes place naturally, regardless of the section of the sleeve. 1-1 can be controlled by a section variation detector so that the braiding pitch remains constant.

Other characteristics and advantages of the present invention will appear during the following description of two particular embodiments, given only by way of nonlimiting examples, with reference to the drawings which represent - FIG. 1, a view in partial section of a tube obtained by
the method according to the invention - Figure 2, a block diagram of the connection of two
lengths of tubes, allowing the realization of end caps
force recovery at each end - Figure 3, a partial sectional view of the profile obtained in
continuous, before it is cut for bonding
as shown in Figure 2 - Figures 4 and 5, another embodiment, the tubes
with conical tips - Figure 6, a block diagram of an installation
allowing the implementation of the method.

Figure 1 shows, in partial vertical section, a tube obtained by the method according to the invention. It is in the form of a hollow structure wrapped in a resin layer 11. Inside this resin layer, there is, from the outside to the inside, a braid 12 which holds and grips the fibers. longitudinal 13 of reinforcement, these fibers 13 constituted for example by glass fibers or carbon fibers, being joined by the resin 11 and bonded to the sleeve 14 or "liner", the liner being made of a light material of small thickness which does not require any particular mechanical resistance. The longitudinal wires 13 are regularly arranged all around the liner 14, and the braid 12 comes to clamp these longitudinal wires against the liner 14 and simultaneously causes the excess resin 11 to rise to the surface, so that without a die, a suitable surface finish is obtained, the external surface reproducing the configuration of the liner.

In the example shown in Figure 1, the liner 14 is constituted by a hollow tube which is advantageously of circular section. However, as indicated above, the advantage of the method according to the invention is that it makes it possible to obtain a composite with variable section. Figures 2 and 3 show such a composite which is manufactured continuously. This structure shows the structure described above, namely the liner 14, the reinforcing fibers 13, the braid 12 and the resin 11.

 As shown in Figure 3, it is possible, thanks to the braiding operation, to obtain a regular deformation of the fibers 13 which naturally follow the outer contour of the sleeve or liner 14. When the diameter of the liner increased, the braiding angle 15 varies, but this phenomenon can be overcome by slaving the speed of the braiding loom or of the tractor to the outside diameter of the liner which is easily optically controlled. Thus, despite the variation in diameter, and thanks to the braiding operation, a good impregnation of the fibers and the absence of air bubbles inside the product are obtained. There is also the advantage of a rise of the resin on the surface, which gives the exterior surface of the composite a regular appearance and free of reinforcing fibers.

A composite such as that shown in FIG. 3 can be cut at the outlet of the manufacturing machine, for example according to planes A and B in FIG. 3. The end cut along plane B then constitutes a female part 17 inside which a male part 16 can be introduced, as appears in FIG. 2. In the case of a removable structure, the male part is simply inserted into the female part. In the case of a permanent structure, the two parts are fixed by gluing. The problem of resumption of forces by bonding of a nozzle at each end is thus simply resolved.

Another example of application is shown in FIGS. 4 and 5. In this embodiment, a biconical part 18 is inserted inside the bundle of reinforcing fibers 13 which, in the example shown, constitutes the core of the cable, these fibers being, as previously, held by a braid which compresses them radially. The biconical part 18 causes a double conical deformation on which the braiding can optionally be modified in order to obtain a densification of the fibers of the braid 12. It is also possible to modify the value of the braiding angle 15 to obtain characteristics Particular mechanical in this location. If a cut is made in the bicone middle plane 18, a bar 19 (shown in FIG. 4) is obtained terminated by two conical ends 18 on which particularly resistant fixing ends can be adapted, and able to recover the tensile strength of the bar by jamming effect.

This application is extremely important in the field of bars made of composite materials having high mechanical strength characteristics, intended in particular for replacing metal rods when corrosion problems arise.

FIG. 6 represents an installation for implementing the method according to the invention. The wires 13 coming from a creel are chosen from the range of wires usually used in the composites industry (glass, carbon, "Kevlar" (registered trademark) etc ..., known for their characteristics of tensile strength.

At first, the wires or fibers 13 are brought inside a tank 2 filled with a thermosetting resin of the epoxy or polyester type for example, or possibly thermoplastic. It is the applied resin that will give the rod its rigidity in combination with the structure of the reinforcing threads. They are purposely impregnated with excess resin. At the outlet of the tank 2, the wires 13 pass through a spacer device 3 making it possible to define a zone 1 for introducing a liner or the like inside the bundle of wires 13. The bundle is then tightened and enters a loom to be braided 4 which braids a sheath 12 around the parallel wires, the arrangement of which is optionally modified by an inner core 5 ′ introduced by the introduction zone 1. At the exit of the braiding loom 4, there is one (or two) oven 6 intended to cause the crosslinking of the resin, and one or more scrapers 7 mounted in a flexible manner, so as to be able to follow the profile of the composite intended to remove, if necessary, the excess resin. A tractor 8 drives the system at a continuous speed or possibly controlled by the speed of the braiding machine. If necessary, the product is cut as indicated previously in 9.

In order to obtain a constant distribution of the fibers of the braid 12, provision is preferably made in zone 1 for an optical detector 5 of section connected to a control stage 10 which can act, separately or simultaneously on the speed of the braider 4, on the speed of the tractor 8, and on the knife 9, in order to make the operation of the assembly automatic.

It is thus possible to manufacture continuously, tubes of composite materials having the following advantages - controlled chemical inertia depending on the choice of material
constituting the inner sleeve or "liner" - obtaining a high modulus of traction and bending in
choosing high modulus reinforcing fibers 13 and
calculating the quantities required - absence of reinforcing fibers outside the product and
obtaining a good resin cover - good densification of the fibers by the braid pressure
during the crosslinking operation.

It goes without saying that many variants can be introduced in particular by substitution of technically equivalent means without departing from the scope of the invention.

Claims (5)

1. Method for manufacturing profiles, tubes or the like,  linear composite materials, with variable section,  comprising a slender sleeve around which extend  in addition reinforcing fibers, impregnated in  excess by a thermosetting resin, characterized in  that the reinforcing fibers (13) are deposited, after  impregnation, around a section sleeve (14, 18)  variable, continuous or discontinuous, entering the zone (1)  a spacer (3), the assembly being covered with a cover  braided (12) laid under tension, and pulled through at least  an oven (6) by a tractor (8). 2. The manufacturing method according to claim 1,  characterized in that the shape of the  sleeve (14) by an optical detector (5) connected to a  control stage (10) acting on the braider (4) and / or  on the tractor (8) or a cutting deck (9) in operation  section variations detected.  3. Method according to one of claims 1 or 2, characterized  in that the variations in section of the sleeve (14)  correspond to the formation of tips (17, 18) of  connection. 4. Profile obtained according to the method of claim 1,  characterized in that the hollow sleeve (14) has, at  determined intervals, cylindrical parts in  extra thickness compared to the normal diameter. 5. Profile obtained according to the method of claim 1,  characterized in that an insert (18) is inserted between  the reinforcing fibers (13) constituting the core of the  streamlined.