FR2783195A1 - Molded fiber-reinforced plastic article, especially an automobile bodywork or shell structural component with a foam core, is produced by compression molding a deformable reinforcement mat prior to impregnation - Google Patents

Abstract

Molded fiber-reinforced plastic article production, comprising compression molding of a deformable reinforcement mat (24) prior to impregnation, is new. Molded fiber-reinforced plastic article production, by pressure impregnating and covering a molded reinforcement layer (24, 24') with a liquid polymerizable material and then curing, comprises introducing the reinforcement layer (24, 24') into a mould (25a, b) in the form of a deformable mat which is then compression molded. Preferred Features: The reinforcement mat (24, 24') may be molded within the polymerizable material pressure injection mould. An article, comprising a plastic foam core (22) and two covering walls of glass fiber-reinforced resin, is produced by (a) molding and polymerizing the core in a first mould; (b) covering the core surface with a layer of thermosetting resin, e.g. polyester resin; (c) positioning the coated core between two glass fiber mats (24, 24') and placing in a second mould (25a, b); (d) molding the mat onto the core and cross-linking and curing the thermosetting resin within the second mould; (e) placing the covered core into a third mould; and (f) injecting and then curing a second thermosetting resin within the third mould. The contact surfaces of the third mould may be pre-coated with a gel coat. In an alternative process, the mat molding and resin injection operations are carried out in the same mould. The deformable mats may comprise a plastic foam layer sandwiched between glass fiber sheets.

Description

The invention relates to a method of manufacturing a shaped part in

  plastic material comprising at least one reinforcing layer constituted by fibers. The invention relates in particular to the manufacture of a part

  shaped with a foam core covered by reinforced walls

  cées. For the manufacture of future-oriented motor vehicles,

  simplified, we plan to make the entire hull or coach-

  rie, from very rigid plastic structural elements

  easy to assemble and presenting a surface appearance without

  must and can be used possibly without protective or appearance paint. Such structural elements, which may for example be in the form of panels, the surfaces of which have recessed portions and raised portions, may include a core of plastic foam giving very good acoustic insulation properties.

  and thermal to structural elements.

  Such insulating panels can also be used in the

  in the building sector, or in the construction of pleasure boats

  sance. The foam core is covered on two opposite sides by

  plastic walls reinforced with fibers.

  It is also possible to design vehicle body parts.

  automobiles or parts involved in the aerodynamics of vehicles which are constituted by a profiled wall of reinforced plastic

by fibers.

  These parts are generally made by a molding process

  with resin transfer or RTM process (from the English name Re-

sin Transfer Molding).

  In such a method, a reinforcing layer of the part essentially consisting of glass fibers is shaped to reproduce the shape of the part or of its external walls, then introduced into a mold.

  to be completely impregnated and covered with liquid resin under pressure

  if we. After solidification and hardening of the resin, the part is removed from the mold

  made up of at least one layer of glass fibers embedded in glass

  sine. Preforming the part or the walls of the part requires successively performing the following operations:

  - cutting of the reinforcement constituted by glass fibers and a thermal binder

  moplastic, - heating the reinforcement to melt the thermoplastic binder,

  - transfer of the hot reinforcement between two parts of a preform mold-

  mage, - closing of the preforming mold,

  - cooling of the preformed reinforcement to freeze the thermoplastic binder

  than. In the case of a part comprising a foam core coated with two external walls or skins, it is necessary to preform the two skins using two different preforming molds and then to cover the foam bread by stapling the preforms of the two skins on the nucleus

foam.

  The assembly consisting of the foam core coated with the preforms

  mes is introduced into a resin injection mold to achieve the impr

  generation of the preforms with liquid resin under pressure.

  Manufacturing operations are therefore complex, long and costly.

  teuses and require the use of several molds, especially in the case

  of the production of a part comprising a foam core.

  On the other hand, reinforcing layers of glass fibers are known.

  consisting of a deformable mat under low pressure, which can be applied

  qué manually on a core of a structure such as a shell of a

  before carrying out the impregnation of the reinforcing layer with a liquid resin. This manual process, which requires cutting operations and applying the reinforcing layer on the core, is however long to implement and cannot be used for industrial production of structural elements such as vehicle parts. automobiles or panels for the building or other types of construction requiring the

  manufacture of many parts.

  The object of the invention is to provide a method of manufacturing a plastic part comprising at least one reinforcing layer made up of fibers, consisting in shaping the reinforcing layer and impregnating it and cover it with a polymerizable material and then

  hardening of the polymerizable material under pressure, this

  can be implemented industrially, on self-propelled machines

  matics. For this purpose, the reinforcing layer is introduced into a mold, in the form of a deformable mat and the mat is formed, according to the form.

  of the part, by compression inside the mold.

  In particular, in the case of a part comprising a core in

  foam coated with two skins reinforced with glass fibers, two layers

  reinforcement pads intended to constitute the external skins of the piece may

  can be shaped simultaneously on the surfaces of the foam core, inside a preforming mold or inside the mold

  injection resin impregnation itself.

  In order to clearly understand the invention, we will now describe, by way of example, with reference to the attached figures, an embodiment according to the invention of a part comprising a foam core and two external skins covering the foam core reinforced by

glass fibers.

  FIGS. 1A, 1B, 1C, 1D and 1E are diagrammatic views illus-

  trant five successive stages of the manufacturing process of a com- ponent

  carrying a foam core, according to the prior art.

  Figure 2 is a schematic view of a preforming installation

  reinforcing layers for implementing the process according to the prior art

laughing.

  Figures 3A, 3B, 3C and 3D schematically show that

  three successive steps in a process for manufacturing a part comprising

  a foam core, according to the invention and according to a first embodiment of

  reading. FIGS. 4A and 4B schematically show two successive stages of a process for manufacturing a part comprising a core

  foam, according to the invention and according to a second embodiment.

  Referring to Figures 1A to 1E and 2, we will describe a process according to the prior art for manufacturing a part comprising a core of plastic foam and two walls reinforced with glass fibers. In FIG. 1A, two mold parts 1a and 1b are shown between

  which have formed a plastic foam core 2 made up of

  killing the central part of a structural element for a motor vehicle.

  Conventionally, after closing the mold in two parts 1a, 1b, a plastic material containing a foaming agent is injected into the mold cavity. After molding and hardening of the part, the mold is opened, as shown in FIG. A. As can be seen in FIG. 1B, the forming of two preforming elements 3a and 3b is then carried out. a reinforcement 4 to form a preform of a first skin covering the foam core. As shown in Figure 1C we also realize, between two

  mold parts 3'a and 3'b, forming a reinforcing layer 4 'to obtain

  a preform of a second skin of the part intended to be added

on the foam core 2.

  The reinforcing layers 4 and 4 ′ are formed in the form of mats

  of glass fibers comprising, in addition to glass fibers, a thermally

fiber bonding mastic.

  The preforms 4 and 4 'are heated to a melting point of the plastic before being introduced between the mold parts 3a, 3b or 3'a, 3'b. When closing the mold, by bringing the parts 3a and 3b and 3'a and 3'b together, as indicated by the arrows 5 and 5 'in the figures

  l B and 1 C, the reinforcement blanks 4 and 4 ', which are held by a clamping frame

  blank 6 or 6 'of a shape corresponding to the piece, are shaped by

  compression between the mold parts.

  The reinforcing layers 4 and 4 'preformed between the mold parts are cooled, so as to freeze the thermoplastic binder and to keep the shape given to the reinforcements. Two preforms 7 and 7 ′ are thus obtained which are

  used to make the covering of the foam core 2, as shown

  felt in Figure 1 D. The preforms 7 and 7 'are held around the foam bar 2, in their position shown in Figure 1 D, by stapling

on the foam core.

  In FIG. 2, a whole installation has been shown which allows

  both to perform the preforming of reinforcing layers constituted by

  layers of glass fibers in which a thermoplastic binder is incorporated.

  The glass fiber mats are unwound from supply rollers 8 and moved in the direction of advancement of the line (in the horizontal direction and from left to right) by a conveyor belt 9 and

drive rollers 10.

  The unrolled glass fiber mats are brought into an installation

  cutting unit comprising a saw 11 which cuts off the continuous glass fiber mats, so as to obtain blanks 12 which are

  supported by transfer carts 13.

  The transfer carriages 13 which move in the direction of advance-

  ment of the line bring the blanks one by one into a heating installation 14 comprising infrared lamps intended to heat the

blanks 12 on their two faces.

  The blanks 12 are then brought one by one into the grip of a press comprising a punch 3a and a die 3b. The blanks intended to constitute reinforcing layers of glass fibers are formed, as

  indicated above, between the two parts of the press, so that

  holds reinforcements covering the foam core.

  As can be seen in FIG. 1E, the foam core 2, which is covered by the preforms 7 and 7 ′, is introduced between two parts 15a, 15b

  of a mold whose cavity delimited between the two parts 15a and 15b pre-

  feels the shape of the part to be produced, i.e. practically the shape of the

  core covered with preforms 7 and 7 '.

  The mold is closed by bringing the parts 15a and 15b together.

  After closing the mold, the part 16 is kept in perfect position-

  fixed inside the mold, by pinching the lateral edges 17 and 17 'of the preforms 7 and 7' in superimposed position, between peripheral edges of desired shape of the parts 15a and 15b of the mold. Liquid resin is then introduced under pressure of a few bars

  inside the mold, via a feed opening 18, as shown

  felt by the arrow 19. The liquid resin under pressure achieves the impregnation

  glass fiber mats and the complete filling of the tank part

  quickly from the mold containing the preforms. After hardening of the resin, the foam core 2 of the part is covered with two skins constituted by

  glass fiber mats embedded in the resin.

  The different stages of the manufacturing process according to the prior art which has just been described, and in particular the preforming of the reinforcing layers and the covering of the foam core by the preforms, are relatively complex, long and therefore expensive and require the use of production lines with numerous successive installations and in

  especially at least three molding units.

  In FIGS. 3A to 3D on the one hand and 4A and 4B on the other hand, we have shown

  presented the different steps of a method according to the invention, according to a

  first embodiment and according to a second embodiment, res-

  pectively. In FIGS. 3A to 3D, the successive stages of a method of manufacturing parts have been represented, comprising a foam core of shape and structure identical to those of the part manufactured by the method of

prior art.

  Part 20 in the finished state is shown inside a mold

  resin injection, in Figure 3D.

  In FIG. 3A, the foam core 22 of the part is shown, the forming of which has been carried out inside a first mold in two parts 21a, 21b. This step in the process is identical to the step shown in the

  Figure 1A of the process according to the prior art.

  As can be seen in FIG. 3B, the foam core 22 formed between the parts 21a, 21b of the first mold and removed from the mold after hardening

  foamed plastic is covered with a layer of thermosetting resin

  curable such as a layer of polyester resin sprayed by a projection head 23. As can be seen in FIG. 3C, the foam core 22 is then

  placed between two parts 25a and 25b of a second mold or preform mold

  mage, between two reinforcing layers 24 and 24 'obtained by cutting out

  blanks, from a roll of a glass fiber mat.

  An easily deformable glass fiber mat of the type of mats used for the manual covering of parts cores such as boat hulls is used. These glass fiber mats comprise, in addition to layers of fibers, at least one layer of plastic foam

  intended to give a certain thickness to the fiber mat while ensuring it

very good formability.

  The parts 25a and 25b of the preforming mold, which are associated with

  hydraulic press elements comprising cylinders are brought together

  each other, so as to ensure the closing of the mold and a compression of the fiber mats 24 and 24 'on the outer surface of the core

foam 22.

  The mold parts 25a and 25b are maintained at a temperature

  of the order of 60 during preforming.

  When the mold is closed, the glass fiber mats 24 and 24 ′ are deformed in compression by the parts of the preforming mold 25a and 25b, in shapes corresponding to the shapes of the external surface of the foam core 22, so that the masts 24 and 24 'are maintained,

  with pressure, inside the preforming mold against the surfaces ex-

  dull core 22 covered with polyester resin.

  The temperature of the mold makes it possible to crosslink the

  thermosetting polyester sine and bonding of glass fiber mats

  24 and 24 'against the outer surface of the core.

  As can be seen in FIG. 3D, the core 22 covered with the masts

  of fibers 24 and 24 'is introduced into the cavity of a third mold comprising

  both two parts 26a and 26b which are pressed against each other to achieve

  closing the mold into which the covered core 22 has been introduced

  24 and 24 'glass fiber mats.

  A second resin, which can also be polyesin resin

  ter, is injected into the mold, through an injection opening 28, as shown diagrammatically by the arrow 29. The edge parts 27 and 27 ′ of the fiber mats 24 and 24 ′ are held by clamping between the two parts mold, so as to avoid any displacement of the fiber mats

during the injection of the resin.

  The second resin is injected into the mold so as to completely impregnate the fiber mats 24 and 24 'and to completely fill the part of the mold cavity which is not filled by the foam core 22 and the

24 and 24 'fiber mats.

  After crosslinking and hardening of the second resin in the

  mold, the part 20 can be removed from the mold.

  This part comprises, around the foam core 22, two walls in

  resin reinforced with glass fibers.

  So as to obtain a perfect surface appearance of the part 20 and

  a color similar to that given by a paint, we generally coat

  Lely the contact surfaces with the part of the parts of the molds 26a and 26b with a gel-coat on a thin thickness, so as to obtain a hardened layer on the part after injection of the second resin, having a

  thickness of the order of 400 to 500 μm. The gel coat layer, which is applied

  quée directly on a preformed surface, does not undergo deterioration.

  In case it is not necessary to cover the part with a

  gel-coat, we can use a manufacturing process of the part which is simpli-

  trusted, as shown in Figures 4A and 4B.

  The corresponding elements in FIGS. 3A to 3D on the one hand and 4A

  and 4B on the other hand have the same references.

  In FIG. 4A, a foam core 22 is shown after it has been formed between two parts 21a, 21b of a first mold. This operation is identical to the operation already described and shown in FIGS. 1A and 3A,

  in the case of the methods described above.

  The foam core 22 is placed, between two fiber mats 24 and 24 ', directly between the parts 26a and 26b of the resin injection mold

  which then constitutes the second mold.

  The 24 and 24 'glass fiber mats are easily deformed

  mables of a type analogous to that described in the context of the first mode of

realization of the invention.

  In particular, such fiber mats can be formed by

  reinforcements sold under the name Rovicore, by the company Chomarat.

  The mold is closed by bringing its parts 26a and 26b together, the foam core 22 interposed between the fiber mats of

  glass 24 and 24 'being placed in the mold cavity.

  The mold parts 26a and 26b ensure by compression the form

  mage of fiber mats 24 and 24 'inside the resin injection mold, against the foam core 22 not coated with resin and without having to

heat the mold.

  A thermosetting resin is injected, as above, through a resin inlet opening 28 inside the mold cavity. The resin permeates and covers all of the layers of fibers of the mats 24 and 24 '. The crosslinking and hardening of the resin is carried out inside the

  mold before removing the part from the mold.

  In the case of this embodiment of the invention, it would not be possible to obtain a layer of good quality gel coat, since this layer of thin gel coat would be torn, during

  shaping of the fiber mats in the mold, during its closing.

  The invention is of course applicable to the production of a part without foam core and comprising a single wall constituted by a fiber mat having the shape of the part impregnated and covered with resin. In this case, an easily formable fiber mat is directly introduced to

  inside a resin injection mold, between two mold pieces

  mitten between them a cavity whose shape corresponds to the shape of the part to be obtained. During the closing of the mold, the fiber mat is formed by compression between the two parts of the mold in a shape analogous to

  the shape of the room. The injection of a volume of resin equal to the vo-

  lume remaining from the mold cavity in which the fiber mat is placed

which has been preformed.

  After injection of the resin and crosslinking thereof inside the mold cavity, the part which is constituted by a simple resin wall reinforced with glass fibers can be removed from the mold.

  Of course, the method applies in the case of any piece in re-

  sine or more generally in any polymerizable plastic material,

created by glass fibers.

  The invention has applications in the manufacture of bodywork or structural parts for the automotive industry, of elements such as panels or doors for the building industry, or of any shaped part for the manufacture of boats. The invention may also have applications in other object manufacturing industries

  in common use, for example household appliances.

Claims (7)

  1.- Method of manufacturing a plastic shaped part   comprising at least one reinforcing layer consisting of fibers,   resistant to form the reinforcing layer (4, 4 ', 24, 24') and to impregnate it and to cover it with a liquid polymerizable material under pressure, then to ensure the hardening of the polymerizable material, characterized by the fact that the reinforcement layer (24, 24 ') is introduced into a mold (25a, 25b, 26a, 26b) in the form of a deformable mat (24, 24') and that the forming of the mat (24, 24 ') depending on the shape of the part, by compression inside the mold (25a, 25b, 26a, 26b).   2.- Method according to claim 1, characterized in that the mat is formed (24, 24 ') directly in a mold (26a, 26b)   injection of the polymerizable material under pressure.   3.- Method according to claim 1, for the manufacture of a shaped part comprising a core (22) of plastic foam and two   covering walls of the foam core (22) constituted by a   sine reinforced with glass fibers, in which we form and polymerize   makes the core (22) in a first mold (21a, 21b), characterized by the fact   that the outer surface of the core (22) is covered with a layer of   thermosetting sine such as a polyester resin, which the core (22) covered with thermosetting resin is introduced, between two easily deformable glass fiber mats (24, 24 '), inside a second mold (25a , b) preforming the glass fiber mats (24, 24 '), that the second mold is closed so as to form the fiber mats (24, 24')   on the outer surface of the foam core (22), which provides the reticula-   tion and hardening of the thermosetting resin in the preforming mold, so as to bond the glass fiber mats (24, 24 ') to the outer surface of the foam core (22), which the core is introduced foam (22) covered with fiber mats (24, 24 ') glued to its outer surface, in a third mold (26a, 26b), which is injected with a thermosetting resin in the liquid state under pressure into the mold ( 26a, 26b), so as to impregnate and cover the glass fiber mats (24, 24 ') with the second thermosetting resin, inside the cavity of the   mold and hardening of the second thermosetting resin   sand inside the mold (26a, 26b).   4.- Method according to claim 3, characterized in that the contact surfaces with the part (20) are coated with the third mold (26a, 26b) with a gel-coat, prior to the introduction of the core of foam (22) covered with fiber mats (24, 24 ') in the third mold (26a, 26b).  5.- Method according to claim 1 for the manufacture of a shaped part comprising a core (22) of plastic foam and two walls covering the outer surface of the core of plastic foam constituted by a thermosetting resin reinforced by glass fibers, in which the plastic foam core is molded in a first mold (21a, 21b), characterized in that the plastic foam core (22) is introduced inside a second mold (26a, 26b) between two easily deformable glass fiber mats (24, 24 '), which the second mold (26a, 26b) is closed so   forming the glass fiber mats (24, 24 ') on the surface ex-   of the foam core (22), inside the second mold, which is in-   ejects into the mold cavity, in the closed state, a thermosetting resin, so as to impregnate and cover the mats with glass fibers (24, 24 ′) and that the thermosetting resin is hardened with inside the second mold (26a, 26b).   6.- Method according to any one of claims 1 to 5, ca-   characterized by the fact that the deformable mast or masts consist of nap-   glass fiber pes between which is placed at least one layer of plastic foam.   7.- Use of a process according to any one of the claims   1 to 6, for the realization of a structural element of the hull or the   bodywork of a motor vehicle.