FR2684920A1 - METHOD AND DEVICE FOR MANUFACTURING A LOOP-LIKE ELEMENT IN FIBER REINFORCED COMPOSITE MATERIAL. - Google Patents

Abstract

To obtain, in a loop-shaped element of fiber-reinforced composite material produced by continuous winding on a winding form 2 of a reinforcing wire 18 impregnated with a matrix, a unidirectional orientation of the wire even when the wound product has a very small thickness, the tension of the reinforcement wire 18 is gradually reduced from a maximum value at the start of winding to a minimum value allowing perfect deposition of the wire as the winding in the winding space progresses . At the places where it is desired to obtain a rectilinear orientation of the fibers, the yarn is deposited practically without limitation in thickness.

Description

i Method and device for manufacturing a loop-shaped element in

  The invention relates to a process for manufacturing an element made of

  loop form of fiber-reinforced composite material, in particular

  bonding with a wide, thin loop, in prepreg, process according to which there is continuously wound, in the presence of a tensile stress, at least one reinforcing line impregnated with a matrix on a winding tool provided with a winding space adapted to the shape

  in cross section of the loop-shaped element The invention relates to

  also a winding device for the manufacture of elements

in the form of a loop.

  By document DE-27 36 124-C 3, it is known to manufacture

  a loop-shaped element of composite material reinforced by

  bres by winding by mechanical means, around a bo-

  hoeing, a reinforcing wire impregnated with a matrix, which wire, during the rotation of the winding tool, is pulled continuously with a preset tensile force in a winding space of the tool which is open radially outward and whose shape corresponds

  the cross-sectional shape of the ball-shaped element

  finished key Loop-wrapped loops are easy to make

  technically, but these elements have, in particular when their width is large, in the region of the curved parts of the winding space or of the loop, an irregular orientation of the turns located radially inside and, in the parts region

  rectilinear winding space, more or less strong placement-

  bulging towards the outside as the lar-

  product taste increases; off, to make the most of the

  superior characteristics of fiber-reinforced composite materials

  for elements in the form of a loop, perfect orientation is required-

  unidirectional wire, i.e. a parallel wire arrangement

  related to the winding space, concentric with respect to the center of curvature in the curved parts of the space or the loop and perfect

  linearly in the rectilinear parts of said winding space.

  As a result of orientation defects of this type, defects which can no longer be corrected after the fact, for example during the hardening process, the mechanical properties, in particular the dynamic fatigue strength of a loop-shaped element manufactured from this way are significantly lower than the maximum values that can be obtained with a loop-shaped element made of composite material

fiber reinforced.

  The objective of the present invention is to improve a process

  and a winding device of the type indicated in the introduction in a manner

  re to effectively eliminate the mentioned defects of orientation of the wire in the wound product, even when the wound product has a large radial width, and thus considerably increase the

  loop strength of fiber reinforced composite material.

  The problem is solved according to the invention by the fact that, at

  during the winding process, the voltage is gradually decreased

  reinforcement wire winding sion from a maximum value

  male at the start of winding as the winding progresses

  in the radial direction inside the winding space.

  According to the invention, when the winding is finished, the effective winding tension of the reinforcing wire is reduced

  prior to curing of the fiber reinforced composite material.

  According to a variant of the method according to the invention, the loop-shaped element is removed from the winding tool before hardening

fiber reinforced material.

  To produce a loop-shaped element open on one side, a part of the product is separated in accordance with the invention.

  rolled up, before hardening thereof.

  According to the invention, for manufacturing an element in

  form of loop comprising parts which interconnect, ma-

  the rectilinear curved parts of the loop, the reinforcement wire is deposited freely, without being supported laterally by the

  winding in the region of the straight parts ,.

  In accordance with the invention, the loop-shaped element is calibrated in thickness in the region of its rectilinear parts when the

winding is finished.

  According to a variant of the method according to the invention, at the end of the

  winding, the straight parts are deformed in the direction of the metric axis

  dian of the loop Optionally, we perform a compression-reaction

  tion of the loop-shaped element by calibrating it with precision

thickness and shape.

  The invention is based on the observation that the irre-

  regularity of the wire in the turns near the inner edge of the curved parts of the winding space is due to a displacement of the wire in the matrix bath which, for technical reasons, is kept in the viscous state during the winding phase , which displacement occurs after winding towards the center of curvature under

  the action of the normal forces which act perpendicular to the di-

  local rection of the traction forces of the superimposed wire turns and

  whose action is added By reducing according to the invention progressive-

  ment winding tension from a maximum value at the start of winding to a minimum value high enough to allow perfect placement of the last turns, it is achieved that, in each of the critical turns likely to move,

  on the one hand thanks to the relatively tight winding of the lower turns

  res which form a stabilized support preventing ra-

  dials and, on the other hand, thanks to the comparatively much lower tension of the following turns, the normal forces exerted by these

  and acting in the direction of a radial movement remain weak

  bles, with for consequence, for all the turns, an orientation of the wire adapted to the composite material and to the load to be supported by the loop, this even when the width of the strip is important, and thus after hardening of the loop in composite material reinforced

  by fibers mechanical properties, in particular a dynamic load

  than permissible, significantly improved in the winding device

  According to the invention, the progressive reduction of the thread tension is effected automatically using a regulation circuit which regulates the effective thread tension during the winding process in

  agreement with a setpoint which decreases as a function of the diameter

  winding of the wound product. Another important aspect of the invention is to obtain a unidirectional orientation of the wire in the rectilinear parts. In these parts, the normal force which results from the tensile stress and acts perpendicular to the local direction of the wire is very low and tends towards zero when the wire is straight, so that in this case, the wound product being limited laterally by the plates of the winding tool kept at a distance from each other which corresponds to

  the thickness of the loop, we obtain, especially in the case of very small

  buckle thicknesses, the curved arrangement of the wire in the direction of

  the exterior mentioned in the introduction to the wound product on the plate

  that of the unidirectional orientation According to the invention, the wire is deposited practically without limitation of thickness, the space of

  winding being increased with respect to the thickness of the loop, the

  these blocking which prevent an automatic linear arrangement of the

  wire being effectively eliminated and a straight line arrangement

  line of the wire in the width direction of the loop-shaped element being obtained by simple means Certainly the wall thickness is increased in the straight parts of the winding space, but

  this extra thickness can be easily removed at the end of the process.

  winding while maintaining the unidirectional orientation of the

  wire, in particular thanks to a thickness calibration operation.

  The winding device for the production of a loop-shaped element made of fiber-reinforced composite material comprises a form of winding on which at least one reinforcing wire is continuously wound under a tensile stress, the matrix of which is impregnated, the winding form being composed of a core and mold plates which are fixed on the side of said core and delimit

  a winding space open radially outwards, the pro-

  wire is adapted to the cross-sectional shape of the loop-shaped element, as well as a winding tension regulation circuit which progressively decreases the tension of the reinforcing wire during the winding process, automatically at as the winding progresses radially in the winding space. According to an improvement of the invention, the device comprises a means for driving in rotation the shape of the winding and

  a variable adjustable braking device for the wire The moment of traction

  the effective form of the winding is maintained at a predefined value.

  constant constant during the winding process by means of the

  regulation baking by adjusting the braking force accordingly

wire brake.

  According to a variant of the invention, the winding space widens

  git laterally in the region of the rectilinear parts, beyond

  the theoretical thickness of the loop-shaped element The widened parts

  gies of the winding space are progressively connected to the curved parts corresponding to the theoretical thickness of the element in

loop form.

  According to another characteristic of the invention, the winding core is provided, in the region of the rectilinear parts, with surfaces

curved inward.

  According to one embodiment of the invention, the plates

  coil shape mold each consist of an outer cheek

  rigid and of an inner shell, of small thickness, which delimits

  mites the winding space and can be removed together with the

  core and the product wound on it.

  It is recommended, to avoid unwanted tension of the wire in the finished loop-shaped element, especially in the loop parts wound with a high tensile force located in the region of the inner edge, to reduce the winding tension of the reinforcement wire at the end of the winding process, before solidification

  fiber-reinforced composite material Elimination of stresses

  tes is advantageously obtained by removing from the winding core

  the loop-shaped element before the composite material has hardened

  te and / or, when it is a question of manufacturing an element in the form of a loop open on one side, by separating a part of the loop from the wound product before hardening This results in both cases in a relaxation of the stresses in the reinforcing wire while retaining a

  unidirectional orientation of the wire.

  The winding method according to the invention is also suitable for the production of loop-shaped elements comprising concave parts bent inwards, as is the case for example in the region of the attachment of the rotor blades of helicopter In this case, the concave parts of the loop-shaped element are firstly wound in a straight line and, at the end of the winding process,

  deforms the straight parts towards the center line of the bou-

  key according to the desired geometry The winding core can be used for this forming operation, which reduces costs

  in tools For this purpose, the peripheral surfaces which delimit the es

  winding space in its lower part present, in the region

  rectilinear parts, a concave shape, curved in the direction of the

  in accordance with the desired shape of the loop and are arranged

  created on the molding surface for subsequent shaping of the parts

  loop ties This shape of the core promotes deposit at the same time

  wire in the region of the straight parts.

  In order to simplify the supply voltage regulation circuit

  bearing, this uses as the variable for adjusting the setpoint voltage either the number of revolutions of the winding tool, or a

  self-adjusting control which continuously varies the winding voltage

  reinforcement wire so that the shape of

  winding is driven with a pulling moment or a constant torque

  both regardless of the importance of the winding.

  In order not to disturb the placement of the wire in the parts of the winding space widened in the direction of the thickness of the

  loop, these parts have a progressive connection with the

  convex winding space ties that correspond to the thickness

  theoretical of the loop-shaped element.

  The plates of the winding form are made respec-

  two parts, namely a rigid outer cheek and a thin-walled mold shell which delimits the space of

inner side winding.

  When the winding phase is finished, the cheeks are removed, which are thus available for the manufacture of another loop-shaped element. The wound product, with the mold shells and the core, held by these elements, is preferably stored at heat-cooled state After removing the mold shells and

  core and, if necessary, after application by laminating tex-

  additional tiles, the product is worked, for example by reticu-

  adapted preliminary lation of the fiber-reinforced composite material and undergoes a compression-reaction with simultaneous forming-calibration, then is definitively hardened to form a laminated assembly with

  other similar loop-shaped elements.

  An exemplary embodiment of the invention is described below

  in connection with the drawings which represent in a very simple way

  folded: Figure 1, a winding device in perspective view,

  Figure 2, the winding shape in longitudinal section view

  the, the thickness ratios being greatly exaggerated for reasons of clarity, Figure 3, the element in the form of a loop before the start of the compression-reaction, Figure 4, the compression process using a plunger tool , Figure 5, the loop-shaped element after removal of the plunger tool. The winding device shown in Figures 1 and 2 comprises a form of winding 2 which is rotated around

  axis A-A (by a drive device not shown) The form-

  me consists of a central core 4 and two mold plates 6 which are fixed to said core with the possibility of disassembly The plates

  mold 6 consist respectively of an outer cheek 8 ri-

  gide and an inner mold shell 10 of thin thickness pre-

  pressing on the cheek and defining a winding space 12 sec.

  U-shaped open radially outwardly The winding device further comprises a wire feeding device, generally marked 14, with a traction control circuit comprising a

  adjustable variable wire brake 16, a sensor 20 which measures the stress

  effective tensile or winding in the reinforcing wire 18

  ment, a sensor 22 which counts the number of revolutions of the winding form 2 and, as a control member, an adjustment means 24 which acts on the wire brake 16 so that the effective tensile stress inside of the wire 18 gradually decreases from a maximum value at the start of winding to a minimum value suitable for the arrangement of the turns at the end of winding, as and

  as the number of revolutions of the molding form 2 increases

  The regulation circuit can also be arranged in such a way that the sensor 22 measures the driving torque applied to the winding form 2 and, using the adjusting means 24, maintains this at a predetermined constant value. during the winding process

  adjusting the wire brake 16 accordingly.

  The winding space 12 has an elongated shape and its free width, that is to say the distance separating the mold parts 10, in the arcuate parts of the winding space corresponds to

  the thickness d of the loop-shaped element 26 to be manufactured (FIG. 3).

  As shown in Figure 2, in the parts which interconnect the terminal areas in an arc and in which an arrangement

  straight line is sought, the winding space 12 widens symmetrically

  tracing in the direction of the thickness of the loop-shaped element until it reaches approximately twice the thickness d and furthermore the

  nucleus 4 presents, in the region of the enlarged parts of the bo-

  hoeing, a curved contour radially inward towards the straight line joining the terminal areas, as shown by the

  core outline drawn in dotted lines in FIG. 1; thus, the connecting wire

  forcing 18 is freely deposited practically without being limited by

  the winding space 12 in the enlarged parts of the winding space

  ge, the parts curved towards the inside of the core 4 being able to serve as a forming surface during a possible subsequent forming of the parts

  straight of the loop-shaped element.

  In order to guarantee trouble-free placement of the wire, the outer edge of the mold parts 10 is rounded and the widened parts of the winding space are connected to the end parts in an arc of a circle of the winding space by parts which are shrink in

  cone in the longitudinal direction of the winding space.

  When the winding shape 2 turns, the reinforcing wire

  18 prepreg of the matrix of the composite material reinforced by

  bres maintained in a viscous state during the winding phase is de-

  laid continuously in the winding space with a given voltage

  controlled by the voltage regulation circuit, the shape of the product bo-

  biné 28 in loop thus obtained being essentially determined by the

  surfaces which delimit the winding space 12 in the termi-

  nals in an arc As soon as the desired loop width b is reached

  shade, we remove the cheeks 8 which are thus available for a new

  winding process, while the coiled product 28 cools

  Lement with the mold parts 10 and the core 4 is stored, a loop part of the wound product 28 being separated to form an element

  open loop on one side.

  With the cooling of the matrix of the composite material, the core 4 and the mold parts 10 can be easily removed without

  that it is necessary to use any release agent.

  FIG. 3 shows a loop-shaped element 26 open on one side after demolding, the rectilinear parts 30 which follow the curved loop part 32 having an excess thickness compared to the theoretical thickness d due to the deposit without limitation thickness of the wire in the winding space; this extra thickness can be eliminated without difficulty during the compression phase which follows The element

  in the form of a loop 26, if appropriate associated with other pre-

  non-crosslinked impregnated, for example the laminated filling product 34 presented in FIG. 5, the fibers of which are crossed is placed in a

  forming tool 36 in two parts (Figure 4) including the chamber 38 cor-

  corresponds to the final geometry of the loop-shaped element 26 and is

  calibrated in shape and thickness therein under the action of pressure

  heat and until a given pre-crosslinking rate of the composite material is obtained, the rectilinear parts being able to be deformed radially inwards until they come into contact with each other, as shown in Figure 5 After compression-reaction,

  the loop-shaped element 20 partially crosslinked with the

  34 additional prepreg sheets have a thickness of

  aunt which can correspond to only one or only a few fibers and has a unique fiber orientation and it can be hardened into a composite material laminated with other similar loop-shaped elements to form a one-piece member made of composite material

forced by fibers.

he

Claims (10)

  1 Method of manufacturing an element in the form of a loop   fiber-reinforced composite material, in particular a wide loop   ge of thin prepreg, according to which there is continuously wound, in the presence of a tensile stress, at least one reinforcing wire impregnated with a matrix on a winding tool provided   a winding space adapted to the cross-sectional shape of the element   loop-shaped, characterized in that during the process   above winding, the winding tension of the reinforcing wire is gradually reduced from a maximum value at the start of   winding as the winding progresses in the direction   radial position inside the winding space.   2 Method according to claim 1, characterized in that, when the winding is finished, the effective winding tension of the reinforcing wire is reduced before hardening of the   fiber reinforced composite material.   3 Method according to claim 2, characterized in that the loop-shaped element is removed from the front winding tool   hardening of the fiber-reinforced material.   4 Method according to claim 2 or 3, characterized in that, to form an element in the form of a loop open on one side,   a part of the loop is separated from the wound product, before hardening.   Method according to any one of the preceding claims.   teeth for manufacturing a loop-shaped element, comprising parts which connect the curved parts to one another in a straight line   of the loop, characterized in that, in the region of the rec-   the reinforcing wire is laid freely, without being supported   laterally by the winding tool.   6 Method according to claim 5, characterized in that, after winding, the shaped element is calibrated in thickness   loop in the region of its rectilinear parts.   7 Method according to claim 5 or 6, characterized by the   makes that at the end of the winding, the straight parts are deformed di-   rection of the midline of the loop.   8 Method according to any one of the preceding claims.   teeth, characterized in that following the winding, one proceeds to   compression-reaction of the loop-shaped element by cali-   brant with precision in thickness and shape. 9 Winding device for the manufacture of an element in   loop form of fiber-reinforced composite material, in particular   bond with a loop, wide and thin, in prepreg,   as a form of winding on which we wind continuously under u-   no tensile stress, at least one reinforcing wire whose ma-   trice is impregnated, which form of winding consists of a core   and mold plates which are fixed on the side of said core and deli-   provide a winding space open radially outwards, the profile of which is adapted to the cross-sectional shape of the loop-shaped element, characterized by a voltage regulation circuit (16, 20, 22, 24) winding associated with the winding form (2), which gradually decreases the tension of the reinforcing wire (18) during the winding process, automatically as the winding progresses radially in the space of winding (12).   Winding device according to claim 9, comprising   both a means for rotating the winding form and an adjustable variable braking device for the wire, characterized in that the effective pulling moment of the winding form (2) is maintained at a predetermined constant value during the process   winding by means of the regulating circuit, setting accordingly   the braking force of the wire brake (16).   11 Winding device for the production of a loop-shaped element composed of curved loop parts and rectilinear parts connecting them, device comprising a winding form on which is wound continuously under a stress of   traction, at least one reinforcing wire whose matrix is impregnated   gné, which form of winding consists of a core and plates   mold which are fixed on the side of said core and delimit a space   this winding open radially outward whose profile is adapted to the cross-sectional shape of the loop-shaped element, characterized in that the winding space (12), in the region of the straight parts ( 30) widens laterally, beyond the theoretical thickness (d) of the loop-shaped element (26) 12 Winding device according to claim 11, character-   laughed at by the fact that the widened parts of the winding space shrink   gradually cord to the curved parts corresponding to   the theoretical thickness (d) of the loop-shaped element (26).   13 Winding device according to claim 11 or 12, characterized in that the winding core (4) is provided, in the   region of the rectilinear portions (30) of surfaces curved inwardly laughing.   14 Winding device according to any one of the res-   dications 9 to 13, characterized in that the mold plates (6) of   the form of winding (2) each consist of a cheek (8) external   rigid and an inner shell (10) of small thickness, which delimits the winding space (12) and can be removed at the same time   as the core (4) and the product (28) wound on it.