FR2614045A1 - FABRIC BASED ON GLASS FIBERS AND POLYESTER, AND ARTICLES COMPRISING SUCH A FABRIC - Google Patents

Abstract

FIBER-BASED FABRIC, ESPECIALLY SUITABLE FOR THE MANUFACTURE OF COMPOSITE ARTICLES FOR USE AS EXTERIOR STRUCTURES, CHARACTERIZED IN INCLUDING A MIXTURE OF: (A) ABOUT 45 TO 75 BY WEIGHT TEXTURED GLASS FIBER; B) APPROXIMATELY 25 TO 55 BY WEIGHT OF POLYESTER FIBER.

Description

The invention belongs to the field of so-called technical tissues, that is to say

  say tissues whose applications

  are essentially industrial. The invention has more

  Particularly for object a fiber-based fabric suitable for the manufacture of composite articles usable as external structures. The invention thus relates to the fabrics as well as the articles comprising said fabrics, such as those obtained by impregnating these fabrics with a resin, optionally in combination with other constituents, thereby producing structures having very diverse fields of application. , especially in the aerospace industry. At present, there is growing concern to find new lightweight and resistant materials, even under very severe conditions of use. These technical problems are particularly critical for the manufacture of aircraft exterior structures, such as fairings, cowlings, doors and the like. It is known that the external structures of an aircraft are subject to very large temperature variations. These reach in

  effect -55 C at altitude and sometimes go up to 700C on the ground.

  Overcrowd the repeated freezing and thawing of water, ab-

  sorbed by a composite article serving as an external structure

  micro-fissures, which in turn promote the recovery of water and ultimately lead to

serious damage.

  We have therefore endeavored to find composite materials for the manufacture of such external parts, which are capable of withstanding such temperatures, while

  possessing sufficient mechanical characteristics

  linked to the lowest possible unit mass. In the

  prior art, we first used composi-

  glass / epoxy resin, but they are currently preferred aramid / epoxy composites, whose density is less

  high and whose resistance to impact is generally

  périeure. By way of illustration, the density of a glass / epoxy composite comprising 50% of resin is approximately 1.87

  while the density of an aramid / epoxy composite,

  the same resin content is close to 1.32. Professionals-

  The properties of aramid-based composites are therefore at least higher in terms of unit mass and mechanical properties. However, the use of aramid fibers induces a strong tendency to recovery

  humidity, which can reach 4% of the mass of the

  site. This property is quite disadvantageous for the construction of the exterior structures of aircraft, because,

  as mentioned above, any external absorption

  cessation of water can cause serious damage, due to

  external temperature constraints.

  There is therefore a definite need to ensure

  longevity and safety of external structures, especially

  Aircraft, to develop materials free from such drawbacks, but nevertheless possessing properties at least equal with respect to the unit mass and the general mechanical properties. Thus, glass / epoxy composites are too heavy, while aramid / epoxy composites in addition to their sensitivity to water,

  still have poor characteristics in compres-

  if we. The present invention aims to provide a

  solution to this problem by providing a tissue based on

  particularly suitable for the manufacture of

  composites that can be used as external structures

  coatings, characterized in that it comprises a mixture of: a) about 45 to 75% by weight of textured glass fibers;

  (b) approximately 25 to 55% by weight of polyes-

  b. Such a fabric is well suited, by impregnation with usual resins, advantageously epoxy resins,

  for the production of articles, such as

  aircraft, which must withstand severe climatic conditions of use. The fabric according to

  the invention allows an excellent impregnation by the residence.

  to result in laminated composite structures in which the woven support consists of a number of plies or layers of the fabric according to the invention. The

  articles thus obtained are perfectly suitable as structural

  composite outer layers because they possess all the advantageous properties which are necessary for said

  structures, namely: surface appearance, mass,

  impact resistance, stiffness, compressive strength,

  in the fixing areas, the price, and especially a

  good resistance to moisture. The description which follows

  luster all the advantageous features of the ar-

tics according to the invention.

  The first constituent of the fabric according to the invention consists of textured glass fibers. Expression

  "texture" in the sense of the present description refers to a

  glass of which the alignment of each filament is

  random. In the technique of obtaining green fibers,

  we are also talking about frayed glass fibers. This type of fiber is known to those skilled in the art and can be obtained in a known manner by various treatments. The textured glass fibers used in the fabric according to the invention are continuous or discontinuous. We prefer in

  the continuous fibers that provide the best

mechanical results.

  In the application provided by the invention, the

  Textured glass bres have many advantages over non-textured glass fibers:

  - the textured glass fibers make it possible

  hold items with a better surface finish,

  because they have a net resin absorption capacity

  higher than untextured or smooth glass fibers; also the textured glass fibers, provide a better fiber / resin interface because they achieve a greater contact area with the resin; fabrics and articles based on textured glass fibers have a lower basis weight, because of the swollen structure of said fibers;

  The textured glass fibers have a

  random partition of the filaments, which is favorable for the compensation of dilations within tissues and articles

  according to the invention in which said fibers are

  flexed with the polyester fibers; on the contrary, the

  non-textured glass fibers mixed with polyester fibers can cause deformation during molding

finished products.

  - the drapability (or deformability) of the tissues

  textured fiberglass base is easier.

  Textured glass fibers have a weight per

  unit of length which may vary in fairly wide limits

  in particular from 11 to 126 tex (a tex representing the number of grams per kilometer of fiber). We got

  good results with glass fibers of about 68 tex.

  The second constituent of the fabric according to the invention consists of polyester fibers. Such fibers are well suited for the manufacture of composite articles usable as external structures because they have a low density (of the order of 1.1), good moisture behavior, good elongation at break and a low price. Polyester terephthalate type polyester fibers of non-fire or high tenacity quality, such as those commercially available under the names "Tergal (Rhone-Poulenc), Dacron", are most commonly used.

  (Du Pont de Nemours) or Diolen (Bayer). In general, the

  usable polyester fibers have titles from 200 to 1500

about decitex.

  As will be shown by concrete examples, the fabric according to the invention can be designed to

  have the same mass per unit area as the tissues

  aramid fibers which are the most commonly used

  have a mass of the order of 170 g / m2.

  The relative proportions of the two constituents of

  according to the invention are chosen according to the

  particular problems to be solved. It is indeed necessary

  to adopt a compromise in view of the imperatives to be respected.

  as regards the unitary mass and the price in particular. Therefore, the amount of textured glass fibers which is in general from about 45 to about 75% by weight, based on the total weight of the fabric, is preferably from about 45 to about% by weight. Correspondingly, the amount of polyester fiber which is generally between 25 and 55% by weight relative to the total weight of the fabric is

  preferably between 45 and 55% by weight.

  Good results have been obtained with a tissue constituting

  of a mixture of textured glass yarn and yarn

  polyester in equal weight amounts, ie 50% by weight.

  According to a complementary feature, the fabric according to the invention may also comprise a certain proportion, up to 30% by weight of the total weight of aramid or carbon fibers or of metal fibers, such as aluminum fibers, these conferring good additional properties of protection against

  external electrical phenomena (lightning).

  As previously mentioned, the fabric according to

  the invention is particularly suitable for impregnating

  resin, especially an epoxy resin. The impregnation rate can be high and in general it is 30 to

  %, in particular 35 to 50% relative to the total weight.

  The high absorption capacity of the resin by the fabric

  is favorable for obtaining a good surface.

  The fabric according to the invention can be directly

  used as a woven support for sandwich structures or

  exterior nolithic. The realization of such structures is known to those skilled in the art. The sandwich structures of

  honeycomb type can increase the inertia of the com-

  posite. Laminates comprising several layers of resin-impregnated fabrics can also be used, which

  corresponds to monolithic structures.

  The invention will now be illustrated without being

  not limited by the examples that follow.

EXENT 1

  In this example, it was first demonstrated that a composite formed of textured glass fibers impregnated with epoxy resin, had a very good mechanical behavior, very comparable to that of a continuous fiber composite / epoxy fiber resin equivalent, or 60% by weight. The comparison was also made on an aramid / epoxy resin composite. The aramid fibers were those marketed under the designation "Keviar" type K181

  or K285, having a basis weight of 170 gr / m2.

  In each case, the epoxy resin used was BROCHIER SA's M14 resin, adhesive and self-extinguishing

Class 120 C.

  For the tests, test pieces of 3

  mm thick obtained from a laminate with 40%

  impregnation epoxy and comprising, as the case may be, 10

or 12 layers of fabric.

  The results obtained by the usual standard tests are shown in Table I.

2 6 1 4 0 4 5

TABLE I

  Composite Composite Composite textured glass continuous glass aramid / resin / resin / epoxy epoxy epoxy Resistance to bending (r [Pa] 420 500 300 Flexural modulus (PPa) 23.000 24.500 23.000

Resistance to

  curds (PIPa) 53 47 30 Compressive Strength (I'Pa) 380 400 230 The respective strengths of the fibers were: textured glass fibers: 68 tex continuous glass fibers: 68 tex aramid fibers: 1140 denier

EXEI: PLE 2

  In this example, a mixture according to the invention was used:% by weight of textured glass fibers

% by weight of polyester fibers.

  A fabric having a nominal basis weight of 170 g / m 2 was woven from this mixture. The textured glass fibers were of the ET9 type, heading 68 tex. The polyester fibers were of the Diolen 550 type having a

  title of 96 tex. For the realization of the chalne, we used

  a mixture of textured glass fibers and polyester fibers at 28% by weight for the former and 22% by weight for the seconds. The same for the realization

  of the weft, we used the same textu-

  of polyester and with a residual mass distribution

28% and 22%.

  The thickness "Palmer" is of the order of 0.20mnm.

  The above fabric was impregnated with an M14 type epoxy resin at a rate of 50% by weight. Specimens 3 mm thick were made from a composite laminate comprising such woven support and their mechanical properties were measured. The results of the tests

are shown in Table II.

TABLE II

  Flexural strength (vMDa) 330 Flexural modulus (4Pa) 12,000 Shear strength (vPa) 44 Compressive strength (vPa) 280 The textured glass / polyester hybrid composite at 50% by mass has equivalent properties to those of a fiber-based composite

  aramid of the type tested in Example 1.

  Equivalent results were obtained by varying the proportions of polyester fibers in the fabric

  mixed according to the invention, between 25 and 55% by mass approximately.

  The preceding examples show that the man of the

  can choose the proportions of fiberglass tex-

  and polyester fibers according to the characteristics

  desired ticks of fabrics and impregnated articles

comprising such fabrics.

  Such fabrics are ideal for the manufacture of composite articles that can be used as outer sandwich or monolithic structures, especially

for aircraft.

Claims (10)

RESUME ICAT IONS   1. Fiber-based fabric, particularly suitable for   composite for use in the manufacture of composite articles for use as external structures, characterized in that it comprises a mixture of: a) about 45 to 75% by weight of textured glass fibers;   (b) approximately 25 to 55% by weight of polyes-   b. 2. Fabric according to claim 1, characterized in   that the glass fibers (a) are continuous.   3. Fabric according to one of claims 1 or 2,   characterized in that the glass fibers (a) have a weight per unit length of from 11 to 126 tex, in particular about 68 tex.   4. Fabric according to any one of the claims   1 to 3, characterized in that the polyester fibers (b) are of the polyterephthalate type, of non-fire quality or high tenacity having titers, in particular, from 200 to 1500 decitex about.   Fabric according to any one of the claims   1 to 4, characterized in that the amount of the textured glass fibers (a) is 45 to 55% by weight and, correspondingly, the amount of polyester fibers (b) is   from 55 to 45% by weight relative to the total weight of the fabric.   6. Fabric according to any one of the claims   1 to 5, characterized in that it also contains a   up to 30% by weight of the total weight of aramid or carbon fibers or metal fibers, such as   the aluminum fibers, which confer good   additional properties of protection against phenomena external electric (lightning).   7. Article characterized in that it includes a   fabric according to any one of claims 1 to 6 and a impregnating resin.   8. Article according to claim 7, characterized   in that the impregnating resin is an epoxy resin.   9. Article according to one of claims 7 or 8,   characterized in that the level of impregnating resin is 30 to 60%, in particular 35 to 50% of the total weight of the article.   10. Application of the article in accordance with   conque of claims 7 to 9, cormmne outer structure, especially for aircraft.