FR2780419A1 - Knitted fabric for molding into vehicle bodywork or boat hull shapes - Google Patents

Abstract

The knitted fabric is produced with at least one glass fiber filament and at least one filament which is of a different material. The other filament material is suitable for working with glass, and gives the fabric permeability for impregnation and a spring resilient property. The other filament is of a textile material, which is stiffer than glass, in a dia, of 0.01-2.0 mm and pref. 0.1-1.0 mm. The knitted material is composed of <= 50 wt% of the non-glass filaments, and pref. 1-10 wt%. The fabric is knitted with filaments of glass together with homogenous filaments of thermoplastics or metal, or composite filaments such as metalized plastics. The non-glass filaments are knitted into the knitted fabric of glass fiber filaments, or they are added to the knitted glass fiber fabric. The non-glass filaments can be used to plate or clad the glass fiber filaments, for at least part of the knitted fabric. The non-glass filaments are knitted in rows, pref. as one row in two of knitted glass filaments. The fabric has a simple knitted pattern, with one row of glass filament stitches in a tuck float (10) and a row of the other material in a jersey stitch (12) at the rear, and the same stitched row formations (14,16) at the front. A reinforcement textile material covers at least one surface of the knitted fabric, or both surfaces. The knitted material is impregnated with a heat setting resin.

Description

The present invention relates to glass knits of a new type,

  complex textile structures incorporating such glass knitwear and composite materials produced from said glass knitwear and / or said

complex textile structures.

  The present invention relates more precisely to a textile structure based on a glass knitted fabric (called glass textile structure), a complex textile structure comprising said textile structure based on a glass knitted fabric (called complex textile structure) and a composite material made from

previous textile structures.

  Complex textile structures exist according to the prior art, in particular of the type comprising a core interposed between two mats or fabrics. Such textile structures, impregnated with thermosetting resin, generate composite materials (of which they constitute the reinforcement), used for the manufacture of rigid parts having complex shapes. This is the case, for example,

  vehicle bodies or boat hulls.

  To obtain said composite materials, the complex textile structure is firstly introduced, with a view to impregnating it with a thermosetting resin, into a mold, the forms of which it must perfectly match: this is the draping operation. The draping is carried out all the more easily as the textile structure is capable of deforming easily in order to conform to the shapes of the mold. Once the draping operation has been carried out, a countermold is brought against the mold and the assembly is closed. The thermosetting resin is then

  injected, by one or more central points or by a peripheral channel.

  To allow good flow of the resin, in order to obtain times of

  short molding cycles, the textile structure must be sufficiently ventilated, i.e.

  say sufficiently permeable to said resin.

  Another important property that the textile structure must have is a certain resilience in the direction of the thickness. By this is meant that said textile structure must be able to adapt to a wide range of air gaps, the air gap being defined as the distance between the mold and the counter mold. Said textile structure must, in fact, have spring properties, so that it can be easily compressed locally, in a narrow area of the air gap, while retaining its thickness to fully occupy the wider areas of the air gap, including the areas adjacent to said compressed area. In this way, said textile structure occupies at best different air gaps or an air gap of non-constant width, undoubtedly determining the thickness of the final composite material, thus giving said final composite material excellent resistance.

  mechanical throughout its thickness.

  Various types of complex textile structures have been proposed according to the prior art, in order to meet these specifications which can be summed up by both.

  terms below: permeability and resilience.

  The Applicant has already developed a complex textile structure which it markets under the Rovicore brand. This textile structure has been described in European patent application EP-A-395,548 and is suitable for the manufacture of

  composite materials as previously described.

  The Rovicore is a complex textile structure of the sandwich type, consisting of a synthetic nonwoven core, made of crimped monofilaments and comprising, on either side of the said core, mats or fabrics of glass threads called Roving fabrics. The assembly of these different elements is carried out by a

sewing / knitting process.

  Rovicore has good impact properties in the direction of its thickness and therefore adapts well to variations in air gap width. These resilience properties are due to the very structure of the nonwoven core which is an assembly of monofilaments of large diameter and crimped, therefore easily

compressible.

  Rovicore also allows good creep of the resin; this property depends essentially on the size and the title of the glass fibers used for the manufacture of the glass mats or fabrics, and on the density of the core which itself depends on the size and the quantity of the crimped monofilaments

used.

  Furthermore, international application WO-A-96/27039 describes a so-called reinforcing textile structure, comprising as a layer giving it volume, a glass fiber nonwoven or a knitted fabric produced only from glass fibers. Such a structure, with which is associated at least one reinforcing layer, advantageously also based on glass fibers, is also intended for the manufacture of composite materials by impregnation with a thermosetting resin. Such a textile structure, advantageously made entirely of glass fibers, has good mechanical resistance to fatigue and excellent fire resistance. However, the intrinsic properties of glass do not allow the volume-imparting layer to be obtained with satisfactory resilience. In fact, this textile structure has neither a thickness nor satisfactory spring properties so that it can be used in a wide range of air gaps or with a mold and a counter mold having large variations in air gap width. To compensate for this lack of thickness and this lack of spring effect, two

solutions are proposed.

  According to the first solution, it is proposed to increase the thickness of the layer conferring the volume, by simply increasing the quantity of material used for its manufacture, which however makes said layer heavier and harms

  therefore subsequently to the homogeneous creep of the resin within it.

  According to the second solution, it is proposed to use as a layer conferring the volume, a knitted structure having beads which come from the presence of ribbed stitches in the knitting pattern. The presence of said beads makes it possible to obtain a structure having a certain thickness, without considerably hampering the uniform impregnation of said structure knitted by the resin. A major drawback of such a structure lies, however, in the fact that the composite material produced from such a knitted fabric necessarily has a

  bumpy, uneven surface appearance. This restricts its use.

  In this context, the aim of the present invention has been to provide a textile structure having satisfactory resilience properties, allowing excellent creep of the resin within it, and which, moreover, is easily usable for producing high-performance composite materials. (by impregnating said structure with a thermosetting resin). The Applicant notably wanted to perfect its product marketed under the brand

  Rovicore, in reference to its fire resistance and its mechanical properties.

  This object has been achieved thanks to a textile structure based on a glass knit produced with at least one glass thread and which typically comprises at least one other thread, different from said (said) yarn (s). glass, which has adequate properties and which acts in sufficient quantity to aerate said knitted fabric

  glass and give it spring properties.

  According to the prior art, glass knits exist in different forms.

  These are knitted or discarded knitted fabrics whose architecture and interlacing of the constituent thread (s) evolve according to their elementary pattern (weave). The present invention can be applied in all these different contexts and involves another wire, different from said glass wire (s), or several other wires, all of the same nature and / or diameter, or even several other wires including at least two are of different types and / or diameters. Advantageously, according to the present invention, a single thread or several identical threads are used as other thread or other threads, in a glass knitted fabric based on a

  single glass yarn or identical glass yarns.

  It is thus possible, according to the invention, to vary the characteristics of a glass knit, using another thread or other threads having specific mechanical and / or chemical properties. Thus, the textile structures according to the present invention have different mechanical and / or physicochemical properties depending on the nature, the diameter, the quantity and the mode.

  intervention of the other (of the others) thread (s) introduced (s) in the glass knitting.

  The textile structure of the invention is mainly intended for the

  production of composite materials by resin impregnation.

  The textile structure of the invention, of the knitting type, is easily deformable, which allows easy draping. Furthermore, this deformability is advantageous in that it can have, depending on the nature of the wire or wires introduced, an irreversible character, due to the intrinsic characteristics of a wire blocking the deformations of said structure. This deformability also allows a shaping of said structure before its insertion into the mold and its impregnation with the resin (preforming). Said textile structure can, moreover, be easily repositioned in the mold, which greatly facilitates the process for manufacturing composite materials by impregnating resin and therefore

improves productivity.

  The intervention, in sufficient but generally limited quantity, of at least one other yarn, having adequate intrinsic properties, to aerate the structure of the knitted fabric, makes it possible to increase the thickness of said knitted fabric, without adding considerable material. Such an excessive addition of material would increase its density and subsequently harm the homogeneous creep of the resin. This type of problem was encountered in the textile structures described in international application WO-A-96/27039. The textile structure according to the present invention therefore has a certain thickness and, by virtue of its ventilated structure, allows creep

homogeneous resin.

  In addition, the presence of at least one such other yarn considerably improves the resilience properties of the textile structure, giving it

  properties stands out when compressed.

  The presence of at least one such other yarn, used in sufficient quantity therefore ensures that the textile glass structure (knitting) thus made heterogeneous, at the same time,

  satisfactory spring properties and sufficient ventilation of the mesh

  ci (thus allowing a homogeneous creep of the resin within it).

  The textile structures according to the present invention can therefore be used in a wide range of air gaps and / or with a mold and a countermold.

  with large variations in air gap width.

  Insofar as the textile structures of the invention are intended to be mainly used (but not exclusively) for the manufacture of composite materials by resin impregnation, the other or the other intervening yarns are obviously chosen according to said chemical nature of the

resin used.

  Advantageously, the other yarn (s) has (have) a textile rigidity greater than that of said glass yarn (s) present in the structure, in order to obtain the spring and ventilation expected. We can, for information, specify that the textile rigidity of the said other yarn (s) involved is

  advantageously from 3 to 4 times greater than that of said glass wire (s).

  This notion of textile stiffness is familiar to those skilled in the art. It directly translates the stiffness of a wire, its resistance to bending. She is

  notably appreciable on a Teledyne type of apparatus from GURLEY (USA).

  Preferably, the other wire (s) have a diameter of between

  0.01 mm and 2 mm and advantageously between 0.1 mm and 1 mm.

  Generally, the glass fabric structure of the invention contains less than 50% by weight of said (said) other (s) yarn (s). It is not entirely excluded to involve more than 50% by weight. However, in such a hypothesis, the basic glass knitting is modified so much that one can then consider having generated a product of another type. The Applicant has not fully identified to date, all the interest of products of this new type. In any event, they make

  an integral part of the present invention.

  More generally, the glass textile structure of the invention contains from 1% to 10% by weight of said (said) other (s) yarn (s). Within this range, with many types of wire, it is possible to obtain, more or less intensely, the expected effects. We note that it is by no means excluded to already obtain a certain positive effect with a minimum quantity of intervention (lower

  or equal to 1% by weight) of certain types of other yarn.

  The other thread or the other threads are advantageously chosen from homogeneous threads such as thermoplastic monofilaments and metallic threads or

  composite wires such as metalloplastic wires and coated glass wires.

  Mention may, for example, be made, as usable thermoplastic monofilaments, of polypropylene (PP), polyamide (PA) monofilaments or

polyethylene terephthalate (PET).

  The use of metallic wires, such as copper or brass wires, allows, in particular, the manufacture of composites having particular properties: thermal and electrical conductivity, magnetic properties and

  improved mechanical properties (possibility of preforming said composites).

  The term “metalloplastic wires” is understood to mean in particular wires of metal coated with plastic material and wires having a plastic structure comprising

metallic particles.

  According to a preferred variant, said glass knit comprises only one kind of other yarns different from the glass yarn (s) or a single other yarn different from the glass yarn (s). This other thread or these other threads are advantageously a polyethylene, polypropylene monofilament or a metallic thread. It will be recalled that the diameter of this other yarn must be chosen so that its intervention in said glass knitting effectively provides the textile structure of the present

  invention satisfactory ventilation and spring properties.

  It is therefore clear that the invention can be declined according to numerous variants and typically involve, within a glass knit, a single thread of another nature, several threads of said other nature or else

  several threads of this type, at least two of which are different.

  The other wire or the other wires can be integrated into the glass knitting of

different ways.

  In a first embodiment, the other thread or the other threads are an integral part of the structure of said glass knit, that is to say that they have been

  knitted (that they were involved in the manufacture of said glass knit).

  In a second embodiment, the other thread or the other threads have been added to the structure of said previously knitted glass knit. The wire can, for

  example, being stitched inside the glass knit.

  Said first embodiment can be declined according to several variants. According to a first variant, the other thread or threads can be vanized or wrapped in at least one constituent glass thread at least in part of the glass knitting and are then thus knitted together with said glass thread (s). In the context of this first variant, such another yarn can be knitted with the single or all

  glass yarns constituting knitting.

  According to a second variant, the other yarn (s) is (are) knitted alone and forms rows of the glass knitted fabric. According to this variant, certain rows of said glass knit are made with meshes formed by another thread or several other threads. All the rows formed by the other wire or the other wires can be made using wires of the same kind and / or diameter or

  wires, at least two of which are of different types and / or diameters.

  Said rows can be distributed randomly in the glass knitting.

  They can intervene individually or in blocks of at least two rows.

  The Applicant has observed that when the other yarn or other yarns form rows, the structure of the glass knit is particularly airy,

  which further improves the creep of the resin.

  The Applicant has also found that, when the other thread or the other threads (other than the glass thread) form a row in two of said glass knitted fabric, the latter has properties of resilience in the transverse direction and of

  particularly improved resin permeability.

  A mixed variant according to which the glass knitting comprises, at the same time, one or more other yarns vanized or gimped with said yarn (s) of glass and whole rows formed by one or more other yarns. is not excluded from the scope of the present invention; the other wire or other wires vanized with said glass wire (s) which may be of a different nature and / or diameter from said other wire (s) forming whole rows. Similarly, in the rows formed only by said (s) other (s) wire (s) within a knitted glass wire (s), this (these) (the ( s) said (s) other (s) wire (s)) little (come) t intervene vanized (s) or gimped (s), ie presenting

  a composite structure based on at least two other wires.

  Knits are, conventionally, made from an elementary pattern repeated endlessly. The elementary pattern defines the various meshes

  used in the various rows.

  According to a particular embodiment of the present invention, the glass knitting has an elementary pattern composed of a row of glass yarn knitted in stitches picked at the back, of a row of another yarn knitted in jersey with the rear, a row of knitted glass yarn in the plaited mesh at the front and a row of the said other knitted yarn in jersey at the front. The Applicant has found that such a pattern makes it possible, with the intervention of a single kind of other thread, to obtain a particularly increased thickness of the textile structure, without having to have a ribbed appearance, like the knits of the prior art. Such a textile structure also has good properties of

  resilience, is easily deformable and allows a homogeneous creep of the resin.

  Conventionally, the glass textile structure according to the present invention, as previously described, can be associated with at least one other textile substrate, to form a complex textile structure. Such a complex structure may, in particular, comprise at least one textile reinforcement covering at least one of the faces of said textile structure. Such a complex structure constitutes the second object of the present invention. Said textile reinforcement can be, for example, a Roving fabric, a mat or even a knitted fabric, advantageously based on glass fibers. However, it is not excluded to use textile reinforcements made of other materials, such as carbon or aramid fibers (fibers

Kevlar).

  Such complex textile structures can be broken down into several variants. According to a first variant, at least one textile reinforcement covers only one of the faces of said glass knitted fabric. Several textile reinforcements can therefore be

  juxtaposed to cover the whole of one face of said glass knitted fabric.

  Advantageously, only one intervenes for this purpose.

  According to another variant, a single textile reinforcement is, for example, folded in half; said glass knit being inserted into the fold of said textile reinforcement,

  so that its two faces are covered by said textile reinforcement.

  According to another, preferred variant, each of the faces of said glass knitted fabric is covered by a textile reinforcement. The two textile reinforcements thus intervening

are the same or different.

  Incidentally, it can be noted here that it is not entirely excluded to involve at least one textile reinforcement, on at least one side of the knitted glass fabric structure; the said reinforcement (s) covering only at least partially

one of said faces.

  The textile reinforcement (s) can be fixed, in a conventional manner, to the structure based on glass knitting, by the sewing / knitting process or by mechanical needling. The glass fabric structures and complex textile structures described above are intended, mainly, for the manufacture of composite materials. The textile structure comprising only a glass knit as defined above can be used, alone, for the manufacture of such composite materials. It generally occurs in the skeleton of a complex textile structure, in particular to constitute the soul of such a complex structure. Composites, comprising a textile structure or a complex textile structure of the invention, impregnated with a thermosetting resin

  constitute the last object of the present invention.

  Said invention is illustrated by Figures 1 and 2 attached.

  FIG. 1 represents an example of an elementary pattern, in a particular embodiment of a textile structure according to the present invention; FIG. 2 represents the preferred elementary pattern of a particular mode

  for producing a textile structure according to the present invention.

  In these two particular embodiments, only one type of other wire

  intervenes to form entire rows of a glass knit.

  The elementary motif of FIG. 1 is a so-called Milanese rib motif and conventionally consists of a row 10 knitted in glass yarn, in ribbed stitch 1 and 1, of a row 12 knitted in other yarn, in back jersey. , a row 14 knitted in glass yarn, in ribbed knit 1 and 1 and a row 16 knitted in

other thread, in front jersey knit.

  The presence of ribbing knits makes it possible to obtain a textile structure of a certain thickness. The ribbed stitches being spaced by a row in another thread, knitted in jersey front or back, allow to obtain in the end a

  structure, with a practically regular, thick and airy surface appearance.

  FIG. 2 represents a preferred elementary pattern, conferring on the textile structure itself, excellent resilience and

resin permeability.

  The preferred elementary pattern is composed of a row 20 knitted in glass yarn, picked from the back, a row 22 knitted in other yarn, in back jersey, a row 24 knitted in glass yarn , knitted before and

  of a row 26 knitted in another yarn, in front jersey mesh.

  The preferred elementary pattern provides a textile structure

  relatively thick and presenting a perfectly uniform and regular surface.

  The presence of the other more rigid wire in this elementary pattern makes it possible to obtain a structure having a multitude of small tunnels, kept open by the rigidity of the other wire, thus allowing excellent creep of the resin inside said textile structure and giving it a sufficient thickness without a ribbed appearance, good resilience and good deformability and

compressibility.

  Finally, it is proposed to illustrate the present invention by the example below.

  after. A glass knit is produced, according to the preferred elementary pattern,

shown in figure 2.

  The glass thread intervening in rows 20 and 24 is a glass thread which has a count of 200 tex. As another thread, there is involved, in rows 22 and 26, a polypropylene monofilament, which has a titer of 200 dtex. Said polypropylene monofilament represents, in the end, 8% by weight of the knitted fabric. Said

  knit has a thickness between 5 and 6 mm and a density of 390 g / m2.

  Said knit has, compared to a knit of the prior art, 100% glass yarn (same glass yarn, knitted according to the same elementary pattern) a

  significantly higher permeability and resilience.

Claims (13)

  1. Textile structure based on a glass knit produced with at least one glass yarn, characterized in that said glass knit comprises at least one other yarn, different from said glass yarn (s), which has adequate properties and which intervenes in sufficient quantity to aerate said glass knitted fabric and give it properties spring.   2. Textile structure according to claim 1, characterized in that said (s) other (s) yarn (s) has (s) a textile rigidity greater than that of said (said) glass wire (s).   3. Textile structure according to one of claims 1 and 2, characterized in that   the said other wire (s) has a diameter between 0.01 mm and 2 mm,   advantageously, between 0.1 mm and 1 mm.   4. textile structure according to any one of claims 1 to 3,   characterized in that it contains less than 50% by weight of said other (s)   yarn (s), and advantageously, from 1% to 10% by weight of said other said yarn (s).   5. Textile structure according to any one of claims 1 to 4,   characterized in that the said other yarn (s) is (are) chosen from: - homogeneous yarns such as thermoplastic monofilaments and metallic yarns; - composite wires such as metalloplastic wires and coated glass wires.   6. Textile structure according to any one of claims 1 to 5,   characterized in that said glass knit comprises a single other yarn or several other identical yarns, advantageously chosen from monofilaments   polyethylene, polypropylene and metal wires.   7. Textile structure according to any one of claims 1 to 6,   characterized in that the said other yarn (s) is (are) an integral part of the structure of said glass knitted fabric or is (are) added (s) to the structure of said knitted fabric of glass.   8. Textile structure according to any one of claims 1 to 7,   characterized in that the said other yarn (s) intervene (s) vanized (s) or wrapped (s) with at least one glass yarn constituting at least in part of said glass knitted fabric .   9. Textile structure according to any one of claims 1 to 8,   characterized in that the said other yarn (s) is (are) knitted (s) alone and form (s) rows of said glass knitted fabric, advantageously every other row of said glass knitting.   10. Textile structure according to claim 9, characterized in that said glass knit has an elementary pattern composed of a row of knitted glass yarn knitted from the back, of a row of another yarn knitted in jersey at the back, a row of knitted glass yarn picked at the front, a row of the said   another yarn knitted in jersey at the front.   11. Complex textile structure characterized in that it comprises at least one textile reinforcement covering at least one of the faces of a textile structure according to   any one of claims 1 to 10.   12. Complex textile structure according to claim 11, characterized in that it comprises a textile reinforcement covering each of the two faces of a   textile structure according to any one of claims 1 to 10.   13. Composite, characterized in that it comprises a textile structure according to   any one of claims 1 to 10 or a complex textile structure according to   one of claims 11 or 12; said textile structure or said textile structure   complex being impregnated with a thermosetting resin.