FR2584341A1 - Covering sheath for composite fibre structures - Google Patents

Abstract

Sheath consists of several intersecting yarn systems, which are produced by means of a yarn eye that moves to and fro in relation to a rotating mandrel on which the yarn systems are wound. The climbing angle of the reinforcing yarn is different in the forward and backward movement of the yarn eye and is selected in accordance with the required yarn density ratio and the angle of intersection of the two yarn systems.

Description

METHOD FOR MANUFACTURING SKIN COATED IN MATERIAL
FIBER REINFORCED COMPOSITE, ESPECIALLY FOR SANDWICH STRUCTURES.

 SANDWICHES.

 The invention relates to a method for producing a wound skin made of fiber-reinforced composite material comprising at least one fiber layer which is constituted by a first yarn system composed of unidirectional reinforcement yarns arranged in one direction and by at least one second yarn system intertwined with the first system in a crossed arrangement and composed of unidirectional reinforcing yarns arranged in a second direction, in which at least one endless yarn is continuously wound in several successive rounds of return and one eyelet on a winding mandrel rotating with respect to the eyelet with a helix angle determined by the ratio between the peripheral speed of the mandrel and the speed of advance of the eyelet, then removing from the mandrel the wound laminate thus formed to the uncured state.

 It is known to manufacture fiber-reinforced composite skins, for example covering skins for fiber-reinforced composite sandwich structures, by means of a continuous winding process using an eyelet which is driven by a reciprocating motion with respect to a rotating winding mandrel and depositing the reinforcing thread on the mandrel during a number equally large, or at most different from one, back and forth. The fiber-reinforced composite skin thus formed consists of two intertwined intersecting yarn systems whose crossing angle is twice as large as the helix angle chosen for the winding of the reinforcement yarn, and presents in the sense of both wire systems, fiber reinforcement coefficients are also high, that is to say with the same strength and stability.

 Fiber-reinforced composite skins which consist of several yarn systems having respectively different yarn densities and crossed by yarn binding points, and which are used to obtain optimum fiber distribution with respect to weight and load in Composite construction elements reinforced with defined-direction fibers of main tensions and deformations, on the other hand, must be manufactured using much larger means and at a higher cost, for example by a weaving process in the form of fiber-reinforced and chain-reinforced composite fabrics, and this is compounded by the fact that these fabrics are only available in a few samples of weight per square meter and only in a few chain-to-weft ratios, and, more inconveniently, certain kinds of fibers, precisely necessary for an ultra-light construction, but subject to the ru In particular, the ultra-high modulus carbon fibers can not be converted into such fabrics.

 The object of the invention is, however, to develop a process for producing a fiber-reinforced composite laminate with which it is possible to obtain, in a simple and inexpensive manner, on each of the yarn systems, mutually intertwined with a crossing angle. determined, the laminate, a son density that can be chosen individually and without graduation, and shape virtually any kind of fiber, including also the aforementioned carbon fiber.

 This result is achieved according to the invention in that the two yarn systems are wound with a different yarn density by modifying the helix angle of the endless thread or yarns at each change of direction of the eyelet. , that for the go it is determined according to the crossing angle and the desired son density ratio of the two systems and that for the return it is set to a different value according to the crossing angle.

formules dans lesquelles
4V =angle d'hélice pour le système.de fils enroulé à
l'aller c < R= angle d'hélice pour le système de fils enroulé au
retour
ss =angle de croisement des deux systèmes de fils
x = rapport des densités de fils entre le système de fils
enroulé à l'aller et le système de fils enroulé au
retour, tandis que les rapports entre la vitesse d'avance et la vitesse périphérique ou vitesse de rotation du mandrin de bobinage est déterminé de façon que

formule dans laquelle VV R = vitesse d'avance de l'oeillet à l'aller et au retour Uv,R = vitesse périphérique du mandrin de bobinage à l'aller
et au retour
ss = angle de croisement des deux systèmes de fils et
x = rapport des densités de fils du système de fils
enroulé à l'aller et du système de fils enroulé au
retour.According to the invention, a prior adjustment of the helix angle, taking into account the crossing angle and the ratio of the wire densities and different for the outward and return, is obtained with a winding process a simple, inexpensive, thread-free continuous fiber-reinforced composite wound skin which, optimally for weight, meets the requirement of a higher fiber-reinforcing coefficient on one side in one of the mutually interwoven yarns with a predetermined crossing angle. As the eyelet usually performs a large number of back and forth until obtaining the desired densities of threads, their ratio tends to one, even if the eyelet travels a total of one go once more or less In a particularly preferred embodiment of the invention, the helix angles for the outward and return directions are very simply chosen in this case so that

formulas in which
4V = helix angle for wire system wound to
the going c <R = helix angle for the wire system wound at
return
ss = crossing angle of both wire systems
x = ratio of wire densities between the wire system
rolled up and the yarn system wound up to
return, while the ratios between the speed of advance and the peripheral speed or speed of rotation of the winding mandrel is determined so that

formula in which VV R = forward speed of the eyelet on the outward and returnward Uv, R = peripheral speed of the forward winding mandrel
and back
ss = crossing angle of both wire systems and
x = ratio of wire densities of the wire system
wound and the wound wire system at
return.

 The wound laminate is preferably cut by directing the cut according to the orientation of the wire in the wound skin, so that azimuthal deflection of the wire systems is achieved in the manner of a common rotation, that is, that is, for example, so that the yarn system having the highest coefficient of fiber reinforcement is oriented in the direction of the main tension of the wound skin. It is, of course, very possible to impregnate the wire systems of the wound laminate or wound skin with the resin matrix of the fiber-reinforced composite material only after completion of the winding process, but to further simplify however, it is preferable to impregnate the reinforcement yarn with resin before it passes through the eyelet. A particular advantage of the process can be obtained with regard to an extremely light construction, by making the wound skin an ultra-high modulus carbon wire. If the wound skin is to be established for very high loads and is therefore manufactured with a large weight per unit area, the wound skin is preferably wound in a pattern repeating over several layers so that the yarns reinforcement in the laminate are not only arranged tightly next to one another but also one above the other.

The invention will be better understood from the description of an embodiment taken as an example, but not limited to, and illustrated by the appended drawing, in which:
FIGS. 1a, b show a fiber reinforced composite laminate wound according to the state of the art and wound skin cut therein
FIG. 2 is a highly diagrammatic representation of a winding device explaining the winding method according to the invention;
Figure 3a shows a wound laminate made with the method according to the invention; and
Figures 3b, c, show two wound skins of composite material reinforced with fibers cut differently in the laminate wound according to Figure 3a and with different orientation of the fibers.

 According to FIG. 1a, for the manufacture of a wound laminate of fiber-reinforced composite material and consisting of two yarn systems 2,4 mutually intertwined with a crossing angle θ, a continuous reinforcement yarn is continuously wound into several successive returns and with a helix angle corresponding to the half crossover angle ss on a rotating cylindrical winding mandrel 6 and provided at its ends with polar caps 8, 10 for the change of direction of the pitch of the reinforcing wire, and until the desired weight per unit area is obtained, after which the wound laminate is cut in a predetermined direction by the orientation of the fiber in the wound skin 12 (Fig. In the wound skin 12 thus formed, the weight per unit area of the fiber reinforcement is distributed in equal proportions over the two yarn systems 2 and 4, i.e. both 2.4 systems have the same fiber density. In the example shown, the crossover angle ss = 90, the forward and return helix angle is therefore 45, and the AA, BB directions of the section are chosen so that 2.4 threads in the wound skin 12 have an orientation of 90 "/ 0".

 The winding method according to the invention is explained by means of the winding device which is illustrated in FIG. 2 and which comprises, in the usual way, a cylindrical winding mandrel 6 continuously rotating at a rotation speed n and provided with 8,10, a eyelet 14 moving in a reciprocating movement parallel to the axis of the mandrel 6 and an impregnating tank mounted in front of the eyelet and provided with a roller 18 on which the reinforcing wire 22 taken from a coil of wire 20 and for example constituted by an ultra-high modulus carbon wire is impregnated with the resin matrix of the fiber-reinforced composite material before being deposited with uniform traction tension on the mandrel 6 .

et formules dans lesquelles
x = rapport des densités de fils exigé entre le système
de fils 2 enroulé à l'aller et le système de fils 4
enroulé au retour,
m = nombre des allers de l'oeillet 14,
n = nombre des retours de l'oeillet 14.The reinforcing thread is here also wound on the winding mandrel 6 in several successive rounds of return of the eyelet 14 until the wound laminate constituted by the two son systems 2,4 mutually interlaced with the angle of crossing has reached a predetermined fiber weight per unit area. At the same time, however, this weight per unit area is distributed differently over the two wire systems 2.4 in a predetermined manner, i.e., each wire system 2.4 receives an individual preselected wire density. For this purpose the helix angle &alpha; V for the wire system 2 wound in the outgoing direction and the helix angle sv RS completing the helix angle 4 V to give the crossing angle ss, for the wire system 4 wound on the return, are chosen so that

and formulas in which
x = ratio of wire densities required between the system
of threads 2 wound on the go and the yarn system 4
rolled back,
m = number of rings of eyelet 14,
n = number of returns of the eyelet 14.

et et
Comme tan d = V
lr

où l'on a
VV,R =vitesse d'avance de l'oeillet 14 à l'aller et au
retour,
U et nV,R = vitesse périphérique et vitesse de rotation à
l'aller et au retour du mandrin de bobinage 6.Since m = n or Im - n 1 = 1 and m, n # O, we have

and and
Like tan d = V
lr

where we have
VV, R = speed of advance of eyelet 14 on the outward and
return,
U and nV, R = peripheral speed and rotational speed at
the return and return of the winding mandrel 6.

For the crossing angle ss = 90, we can further simplify as follows
tan &alpha; v 1
tanO (R =
in the same way

If, as shown, we want the fiber reinforcement coefficient of the yarn system 2 to be twice that of the yarn system 4, so that x = 2 for
ss = 90, it is necessary that o (V be set to 26.5650 and (= '39 V) to 63.4350, and in case of constant rotation speed of the cylindrical winding mandrel 6, that the speed of advance from the eyelet 14 to the return is four times larger than the one to go.

 The wound laminate (Fig. 3a) wound in this way to the desired weight of fiber reinforcement per unit area is then cut in accordance with the desired fiber orientation to form the wound skin 12, the cutting directions AA and BB according to FIG. 3a giving the skin 12 a + 450 fiber orientation for the two wire systems 2 and 4 (FIG. 3b), whereas a cutting direction parallel or perpendicular to the wire direction of the systems 2.4 gives the wound skin 12 illustrated in Figure 3c wherein the yarn system 4 having the lowest fiber density has an orientation of 900 and the fiber reinforcement coefficient yarn system doubles a zero orientation.

Claims (7)

A method of manufacturing a pre-impregnated wound skin of a fiber-reinforced composite material comprising at least one layer of fibers which is constituted by a first yarn system composed of unidirectional reinforcement yarns arranged in one direction and by at least one second system yarn interleaved with the first system in a crossed arrangement and composed of unidirectional reinforcement yarns arranged in a second direction, in which at least one endless yarn is continuously wound in several successive returns of an eyelet on a winding mandrel rotating relative to the eyelet with a helix angle determined by the ratio existing between the peripheral speed of the mandrel and the speed of advance of the eyelet, then removing from the mandrel the wound laminate thus formed in the non state hardened, characterized in that both wire systems are wound with a different wire density by changing the helix angle end of the threads at each change of direction of the eyelet, that for the go it is determined according to the angle of crossing and the ratio of desired density of son of the two systems and that for the return the rule has a different value depending on the crossing angle. 2. Method according to claim 1, characterized by the fact that in the case of an equal number of goings and returns and / or of superior of goings or returns of the eyelet, one chooses the angles of helix for the go and back so that

  formulas in which V = helix angle for the wire system wound to  the forward 9 R = helix angle for the wire system wound at  return  ss = crossing angle of both wire systems  x = ratio of wire densities between the wire system  rolled up and the yarn system wound up to  return. 3. Method according to claim 1 or 2, characterized in that in the case of an equal number of trips and returns and / or superior of goings or returns of the eyelet, the ratio between speed of forward / forward peripheral speed and forward speed / peripheral speed back, so that

 formula in which VV, R = advance speed of the eyelet in the outward and return direction UV = peripheral speed of the forward winding mandrel  and back  ss = crossing angle of both wire systems and  x = ratio of wire densities of the wound wire system  on the way out and the wire system wound up on the way back.  4. Method according to any one of the preceding claims, characterized in that the wound laminate is cut in a direction corresponding to the orientation of the wire in the wound skin. 5. Method according to any one of the preceding claims, characterized in that the reinforcement is impregnated with resin before it passes through the eyelet. 6. Method according to any one of the preceding claims, characterized in that as reinforcing wire, is wound a carbon wire ultra-high modulus. 7. Method according to any one of the preceding claims, characterized in that for greater weight per unit area of the wound skin, the wound laminate is wound in a winding pattern repeating on several layers.