FR2480667A1 - Mould with two stage ram for consolidating composite mouldings - is used to produce flash free mouldings without disorientation of integral fibres - Google Patents

Abstract

A tool for moulding composite materials involving reinforcement such as pre-impregnated mat has a male tool (25) incorporating an ancillary plunger which can withdraw to accept the moulding matl, then force the matl. into a closed cavity. After the mould is opened, by retraction of the opposite half of the tool, the plunger can advance further, to disengage the moulding from the male tool. Applicable to compression moulding processes with a horizontal daylight, or to horizontal motion tools. Produces mouldings without inducing significant reorientation of the reinforcing fibres from their format in the preform. Mouldings produced by pseudo transfer or injection into a closed circuit cavity do not require subsequent 'deflashing'.

Description

Process for molding reinforced composite materials.

The present invention relates to an improvement in the conditions for molding reinforced composite products, in order to avoid harming the mechanical properties of the material by the molding process and to reduce or eliminate deburring operations.

The current process for molding reinforced composite products, for example polyesters reinforced with glass fibers in the form of prepreg products, consists of having telescopic tools with positive molds with vertical joints. The load placed in the open mold is crushed during the closing of the tooling. In the extreme position, the die may or may not come into contact with the punch by means of stops, but it results from such a process burrs on the periphery of the part, #due to the material which creeps into the game must be left between the die and the punch. We therefore see the disadvantage of such an arrangement which requires subsequent deburring operations. However, the molding material pre-impregnated in large areas and relatively thin, deposited in the form of a blank covering a significant proportion of the part surface, loses only a few of its mechanical properties during the limit path to which it is subjected during filling, which is an advantage.

In order to avoid the need for deburring, it has been proposed to mold these types of composite materials by injection.

In this case, the mold is closed beforehand on "flat seals" plans ensuring a certain seal. The die is first pressed against the punch. Through the injection channel, the part is filled without burrs. The disadvantage of such a process is that it loses the planar stratification of the prepregs used as filling material and gives the molded product properties close to those which would have been obtained by starting directly with a compound commonly known as a premix. or phoenix.

The same is true when transfer molding is carried out where, when the mold is open, the material to be molded is placed in a cavity of small diameter. The die is pressed against the punch then, by means of a piston, the impression is filled by passing the material through a nozzle of small diameter, as in the case of injection. This process avoids burrs but delivers a molded material in which the reinforcing fibers are arranged in all directions of space, as in the case of premixes molded by compression or injection.

The method according to the invention aims to allow the filling of an already closed mold as in the case of injection or transfer, to avoid the formation of burrs around the periphery of the parts, but without harming the planar stratification. reinforcing layers su perposed, as they were produced during the constitution of the prepreg.

For this purpose, there are molds designed in such a way that large loads (more than a third of the projected surface) can be placed flat on a central movable part of the punch.

The present invention will be described by way of nonlimiting examples with regard to Figures 1 to 4 attached, which respectively represent - Figure 1: a vertical press for the implementation
of the process according to the invention.

- lesfigures2â4: a horizontal press also usable in
variant of the invention, showing different phases
of the process.

Consider the vertical press in Figure 1.

The die 1 being open, a blank of material 2 of dimensions close to those which would have been provided in the case of a positive mold molding and adapted to the shape of the part to be obtained is prepared.
This material is deposited on the central part 3 of the mold arranged in such a way that it is movable inside the punch 4.

The die 1 is then pressed against the punch 4 and realizes
sealing on the periphery of the part, the central part 3
of the punch then being in the remote position. Then the material is
pushed against the die 1 by the movable part 3 pushed by the
cylinder 5, until the impression is filled.

This ensures, after polymerization, the molding of a part 6 does
with no burrs on the periphery, but may present
ter in 7 at the level of the adjustment of the part 3 in the punch 4.

We naturally arrange for this to correspond to the hidden side
of the part in its subsequent use.

According to a detail of the invention, the central part of the mold 3 can
be made of a material with inferior thermal conductivity
lower than that of parts 4 and 1 in order to avoid that the maintenance too
extended from material 2 in contact with part 3, pending the
closing the mold, does not risk causing a start of polymerization
molding material. For this purpose, one can for example provide a
metallic part such as 8 associated with another part 9 by
through a less conductive material 10. The passage of
calories from the heated part 9 to the mold surface 8 being
thus slowed down.

Such a molding design is compatible with the use of compression presses, provided that they are equipped with a double
effect. The effort to keep the tool closed is as
usually a function of the product of the surface projected by the
pressure prevailing within matter. This pressure provided by
the jack 5 corresponds to a significant thrust force since by
hypothesis, the surface of the blank is high and may exceed one third
of the projected area. This results in the need to have
more expensive presses than single acting presses or
according to a preferred mode, to provide a device for blocking the
mold in the closed position. In this design, the press opens and closes the mold and most of the power is only
summed only when the mold is blocked in the closed position, to push on the material by the Double effect horsehair.

Such an arrangement can be advantageously arranged in the case of a horizontal press such as that symbolized in FIGS.

2 to 4.

There are, in fact, in Figure 2 - the toggle system 21 located between a fixed plate 22 and
a movable plate 23., - the matrix 24 carried by the movable plate 23 and the punch 25
carried by another movable plate 26, - the movable central part 27 of the punch 25, - the jack 28 coupled at 29 to the part 27 and supported on the plate
fixed plate 30, - the columns 31 and 32 guiding the movable plates 23 and 26, - an opening 33 formed in the punch 25 allowing intro
molding the blank of material to be molded 34.

According to the molding process of Figure 2, by action on the knee pads 21 the mold is closed on its periphery by bringing the die 24 against the punch 25. The jack 28 maintains the central part 27, # in the rear position, releasing the light 33.

 The material 34 is then introduced by the light 33 then the jack 28 rises in pressure and the impression is completely filled when the central part arrives in the position of FIG. 3.

 The polymerization of the area 34 takes place and, when it is completed, the tooling is open (FIG. 4) and the piece is ejected by the action of a complementary displacement of the central part 27 relative to the punch 25.

In the present case, taken by way of example, of a thin bodywork whose visible side is the convex face, it will result from the chosen method the presence of burrs 35 at the points of junction of the parts 25 and 27, on the non-visible side. It could also be used for attachments, in order to ensure that, when the tool opens, the part does not remain attached to the side of the die 24.

Claims (5)

1. Mold for obtaining reinforced composite materials, characterized in that it consists of a die i and a punch 4, the central part 3 of which is movable relative to the latter and secured to a jack 5 which can actuate it independently of the movement of the punch, in particular when the die is already pressed against it. 2. Mold according to claim l, characterized in that the central part 3 of the punch 4 is made of u; material of thermal conductivity lower than that of the rest of the mold. 3. Mold according to claim l, characterized in that the wall of the punch 25 has an opening 33 allowing the introduction of the blank of material to be molded. 4. A method of molding reinforced composite materials characterized in that the matrix l is pressed against the punch 4 in a leaktight manner, after the blank of materials to be conformed has been introduced into the mold, the central part 3 of the punch still being in the remote position, the latter then being brought closer to the matrix so as to repel and conform the composite material, thus maintained during its polymerization, the opening of the mold then occurring, with ejection of the molded part. 5. Method for molding reinforced composite materials, characterized in that after closing the mold, the blank of material to be conformed is introduced into the molding cavity through a hole 33 formed in the wall of the punch 25, the central part 27 of this the latter being still in a distant position, then the latter approaches the matrix 24 by pushing and shaping the composite material, thus maintained during its polymerization, the opening of the mold then occurring, with ejection of the molded part.