CH710405A1 - A method of manufacturing parts made of composite material. - Google Patents

Abstract

A method of manufacturing fiber reinforced thermoplastic composite parts comprises a step (100-200) of making a prepreg by positioning at least one thermoplastic plate in a template, said thermoplastic plates being pressed with one or more layers of fabric comprising long reinforcing woven fibers, at a pressure of between 0.5-3 MPa, in a heating press or any other suitable means, and at a temperature of between 300 and 610 Kelvin so as to embed the fibers of reinforcement in the thermoplastic material. The shaping (300) of the prepreg is done in a suitable mold, made of a material resistant to the treatment temperature of between 300 and 600 Kelvin, said mold being at least partially covered with a release layer whose surface is configured according to the desired surface state of the final piece (400) at said pressure treatment temperature of 0.1 to 1.5 MPa.

Description

The object of the present invention is to provide a manufacturing method for producing composite material components responding to the demands of the luxury market.

Less heavy than steel and very resistant, composite materials were first used for their performance, regardless of their high cost. Highly used materials in aeronautics, composites have over the years declined in very varied sectors. Emphasis was placed on reducing production time, which was very difficult to generalize as composite manufacturing processes are varied because there are almost as many as there are materials.

Other constraints have emerged depending on the field of application and this is particularly the case of the luxury industry which, in addition to obtaining very resistant parts, requires a very high quality aesthetics.

Many patent documents describe processes using composites for a wide variety of applications.

[0005] EP 2 143 354 B1 discloses a method of manufacturing a high heel for a shoe, the method being characterized in that the method comprises the following steps of shaping and / or treating a mixture of thermoplastic resin and pieces of carbon fibers in a mold to obtain an inner heel core. A second step is to wrap said inner core using at least one layer of material comprising the carbon fiber.

[0006] WO 2010 048 101 discloses systems and methods for manufacturing prepregs which have improved capacity for gas removal in prepregs and prepreg layers before and / or during at least a part of the consolidation process and hardening to form composite structures. In some embodiments, perforations of selected configurations may be introduced into the prepregs before, during or after the formation of layers. The perforations provide exit routes for the gases trapped in and between the prepregs and the prepreg layers perforated during the consolidating and curing process, reducing the residual porosity in the resulting composite. For example, composites whose residual porosities make up less than 10% by volume, based on the volume of the composite, can be obtained in this way.

[0007] The production of a composite component can not be made as a metal component. The characteristics of a composite component (matrix + fiber) will depend on the design of the product (material used, number of folds, weaving, type and size of fibers, etc.) but also the process of implementation (time, temperature, pressure, deformation, constraints, etc.) Composites often contain defects inherent to the processes used (porosity, fiber displacement, local residual stresses, dimensional variation, etc.). These local imperfections are mostly eliminatory for an object of high aesthetic quality.

The present invention aims to produce components of composite material responding to the demands of the luxury market such as watchmaking or accessories. The composites used for the luxury market must not only be decorative but their technical performance (rigidity, flexibility, strength, wear resistance, etc.) must allow use in severe conditions and in an unfavorable environment.

According to the invention, the process for manufacturing parts made of fiber reinforced thermoplastic composite material comprises the following steps: Providing at least one sheet of thermoplastic plastics material; Elaboration of a prepreg by positioning at least one thermoplastic sheet in a template, said thermoplastic sheets being pressed with one or more layers of fabric comprising long woven reinforcing fibers at a pressure of between 0.5-3 MPa, in a heating press or any other suitable means, and at a temperature of between 300 and 610 Kelvin so as to embed the reinforcing fibers in the thermoplastic material; Optionally, cutting prepreg to the shape and dimensions necessary for the manufacture of the part to be produced; and Prepreg forming in a suitable mold, made of a material resistant to the treatment temperature of between 300 and 600 Kelvin, said mold being at least partially covered with a non-stick layer whose surface is configured according to the surface state desired end piece, at said treatment temperature of between 300 and 600 Kelvin at a pressure of 0.1 to 1.5 MPa.

In one embodiment, said fabrics comprising long woven fibers are colored or have additive color adjustments. In a variant, these tissues may be without coloration.

In one embodiment, the sheets or said sheets are thermoplastic plates placed in thickness in a template by means of a heating press or any other suitable means at a temperature between 300 and 570 Kelvin and a pressure between 0.2 and 4 MPa. The thermoplastic sheets are in particular PMMA, PEN, PET, PC, PES, ABS, PP or EPP.

Alternatively, a fabric formed of thermoplastic son can be used for the preparation of prepreg. The fabric comprising reinforcing fibers is especially based on carbon fiber, fiberglass, aramid fiber, metal fiber or natural fiber.

The prepreg is optionally cut to the shape and dimensions necessary for the manufacture of the part to be produced, since the prepreg does not have the right dimensions.

The mold for shaping prepreg is made of a material resistant to the processing temperature such as brass, copper, steel or aluminum.

Optionally, an anti-counterfeiting control to identify that the finished product is from the process is included in the material during the prepreg manufacturing operation and / or during the final shaping operation.

In one embodiment, during the shaping prepreg, pre-machined elements may be included in the mold so as to be overmolded with the prepreg in the mold.

Preferably, during the prepreg formation, the temperature follows a controlled ramp by starting at an ambient temperature and then after the treatment time at the maximum temperature, returns to ambient temperature according to a controlled ramp, the maximum temperature being reached around two thirds of the total cycle time and maintained up to 90% of the cycle time.

Preferably, during the prepreg formation, the pressure increases by one or more steps to reach its maximum value around two-thirds of the total cycle time.

The characteristics of the invention will appear more clearly on reading a description of several embodiments given solely by way of examples, in no way limiting with reference to the schematic figures, in which: <tb> Fig. 1 <SEP> represents a diagram of the steps of the process for manufacturing composite parts; <tb> fig. 2 <SEP> represents the stages of the process production chain; <tb> fig. 3 <SEP> represents pressure and temperature curves as a function of time during the manufacture of composite parts; <tb> fig. 4 <SEP> represents curves illustrating the influence of time and temperature on porosity; and <tb> fig. <SEP> represents curves illustrating the influence of pressure and temperature on porosity.

In the example illustrated in FIG. 1, the process for manufacturing parts made of fiber reinforced thermoplastic composite material comprises the following steps: Providing one or more thermoplastic plastic plates (step 100); Elaboration of a prepreg by positioning at least one thermoplastic plate in a template, said thermoplastic plates being pressed with one or more layers of fabric comprising long woven reinforcing fibers at a pressure of between 0.5-3 MPa, in a heating press or any other suitable means, and at a temperature of between 300 and 610 Kelvin so as to embed the reinforcing fibers in the thermoplastic material (step 200); Optionally, cutting prepreg to the shape and dimensions necessary for the manufacture of the part to be produced; and Prepreg forming in a suitable mold, made of a material resistant to the treatment temperature of between 300 and 600 Kelvin, said mold being at least partially covered with a non-stick layer whose surface is configured according to the surface state desired end piece, at said treatment temperature of between 300 and 600 Kelvin under pressure of 0.1 to 1.5 MPa (step 300).

The thermoplastic sheets, such as PMMA or PET, are placed in a thickness in a template by means of a heating press or any other suitable means. The temperature and pressure are adapted to the material, for example, 480 ° K for PMMA at a working pressure of 0.5 to 1.5 MPa. These parameters make it possible to have a state of matter in the viscous domain and to obtain a sheet of the exact thickness desired. These parameters are adjusted to shape a sheet having the desired optical characteristics for the final piece. For example, the heating is done with a ramp of 1 to 5 degrees per minute depending on the material with a pressurization from 250-300 ° K. The cooling is accelerated until the return to a temperature below 300 ° K while maintaining the pressure. The cycle is very similar to that shown in fig. 3.

The plates may be made by the method described above or be provided by other means.

The plates thus obtained are taken up in a new template and pressed in a heating press or any other suitable means with one or more layers of fabrics comprising the long fibers woven according to the desired design. These tissues can be with or without coloration, or include additive coloring.

In another embodiment, instead of plates, it is also used a fabric formed of thermoplastic son. This fabric may be in the same form as the fiber fabric subsequently used, under a different weave, or be directly blended with the reinforcing fiber fabric (comele). When using these alternatives, the process temperature, as well as the pressure, must be adapted to the material and form used to ensure good bonding and impregnation of the prepreg. The base fabric defines the characteristics of the prepreg obtained (multilayer reinforcement-matrix, integration reinforcement-matrix in monolayer, etc.)

Figure 2 shows the steps of the production line of the process.

The method according to the present invention allows to develop a monolayer or multilayer prepreg and the parameters linking the implementation conditions and the desired characteristics depending on the materials used to obtain the final pieces. This operation takes place, for example for PMMA, at a temperature of between 320 and 610 Kelvin. This rise in temperature makes it possible to work in an area where the material is more fluid. The pressure is about 1 MPa and is adapted to the exact composition of the prepreg. The fluent thermoplastic material between the fibers makes it possible to obtain a prepreg plate comprising long fibers. These fibers can be of various kinds, for example carbon, glass, aramid, linen, hemp, etc. and are perfectly embedded in a thermoplastic matrix. The optical effect can be modulated and the result can vary from matt to gloss depending on the choice of the thermoplastic base material. The temperature and the pressure, during the manufacture of the prepreg, are determined on the one hand by the type of fabrics comprising the long fibers, according to the type of weaving, the thickness, and the desired effect and on the other hand, by the chemical, mechanical or thermal characteristics of the thermoplastic. As illustrated in FIG. 3, the cycle starts at ambient temperature, rises to the desired temperature according to a controlled ramp and adapted according to the materials used, then, after the treatment time at the maximum temperature, returns to ambient temperature according to a controlled ramp.

During this prepreg manufacturing operation, an anti-counterfeit witness may be included in the material. This witness makes it possible to verify that the finished product is indeed resulting from this process and is not an imitation of this one made in other matters.

Optionally, the prepreg is then cut to the size necessary for the manufacture of the part to be produced. The cutting can be done by mechanical means, such as a cutting tool, a milling operation or stamping. The cutting can be done by tool-less means such as a laser, or a high-pressure water jet.

The shaping of the prepreg is done in a suitable mold, made of a material resistant to the processing temperature, such as aluminum, the mold being at least partially covered with a release layer and the surfaces being treated according to the desired surface condition on the final piece.

Optionally, pre-machined elements can be integrated in the mold so as to be overmolded.

A structure design can be integrated into the mold by modifying the surface condition on the mold parts in contact with the composite.

The temperature during this treatment is about 460 to 560 ° K, according to the prepreg used, at a pressure ranging from 0.1 to 1.5 MPa. The pressure is adjusted during the heating cycle according to the exact shape of the part and the desired tolerances to obtain the desired surface quality in the end. For this shaping step, the pressure in the mold is constant or may vary depending on the materials composing the prepreg. The exact cycle of temperature and pressure as a function of time is controlled during the process and is specific to each mix or type of material.

The shaping is made by deformation and hardening of a prepreg by thermal process, thermoforming type.

The cooling cycle is also precisely controlled according to the desired quality at the output of treatment.

During this final formatting operation, an anti-counterfeit witness, additional or complementary to the previous, may be included in the material. This cookie can also replace the cookie implemented in the prepreg. This witness makes it possible to verify that the finished product is indeed resulting from this process and is not an imitation of this one made in other matters.

By controlling the implementation parameters, the optical quality (brightness, transparency, opacity, ...) of the object can be changed.

The process implemented according to the present invention can produce parts meeting high aesthetic criteria (flatness, surface condition, fineness, structure, design, etc.) and meeting the specifications defined for the final product. .

The color of the product can be made by lacquering or varnishing the fiber fabric, by lacquering or varnishing the prepreg or using a colored thermoplastic in the mass. The coloration is made in the plate during the first shaping, intermediate treatment during the manufacture of prepreg or intermediate treatment during the final shaping.

The parameters of the color setting are adjusted according to the basic material, the material and the shape of the fibers, the desired effect or the design.

The process according to the present invention can produce very high quality parts required especially in the luxury sector.

These very high quality composite material parts can be used for example in the watch industry, or for writing instruments, lighters, accessories such as key rings, usb keys, loops, leather goods, or cufflinks.

These composite parts of high optical and aesthetic quality can have a decorative appearance such as plain woven, twill woven, satin woven or other weaving, or even be braided, or have a free deposition.

All shapes of parts can be made by the method described according to the present invention as flat parts, volume, convex, concave, round, cubic, left.

Claims (12)

A method of manufacturing fiber reinforced thermoplastic composite parts, the method comprising the steps of: - Providing at least one sheet of thermoplastic plastic material; - Preparation of a prepreg by positioning at least one sheet of thermoplastic in a template, said thermoplastic sheets being pressed with one or more layers of tissue comprising long fibers woven reinforcement at a pressure of between 0.5-3 MPa and at a temperature of between 300 and 610 Kelvin so as to embed the reinforcing fibers in the thermoplastic material; Optionally, cutting the prepreg to the shape and dimensions necessary for the production of the part to be produced; and - Shaping the prepreg in a suitable mold, made of a material resistant to the treatment temperature of between 300 and 600 Kelvin, said mold being at least partially covered with a release layer whose surface is configured according to the state of desired surface of the final piece, at said treatment temperature of between 300 and 600 Kelvin under pressure of 0.1 to 1.5 MPa. 2. A method of manufacturing composite parts according to claim 1, wherein said woven fabrics having long woven fibers are colored. 3. A method of manufacturing composite parts according to one of claims 1 or 2, wherein the sheets or said sheets of thermoplastic are thermoplastic plates set in thickness in a template at a temperature between 300 and 570 Kelvin and a pressure between 0.2 to 4 MPa. 4. A method of manufacturing composite parts according to one of claims 1 or 2, wherein the sheet or said sheet of thermoplastic is formed of a fabric formed of thermoplastic son or a fabric formed of thermoplastic son comélangés with reinforcing wires. 5. A method of manufacturing composite parts according to one of the preceding claims, wherein the prepreg is cut to the shape and dimensions necessary for the manufacture of the part to be produced. 6. A method of manufacturing composite parts according to one of the preceding claims, wherein the mold for shaping the prepreg is made of a material resistant to the processing temperature such as in particular brass, copper, steel or aluminum. 7. A method of manufacturing composite parts according to one of the preceding claims, wherein an anti-counterfeit control to identify that the finished product is from the process is included in the material during the manufacturing operation of the prepreg and / or during the final formatting operation. 8. A method of manufacturing composite parts according to one of the preceding claims, wherein during the prepreg shaping pre-machined elements are included in the mold so as to be overmolded with the prepreg in the mold. 9. A method of manufacturing composite parts according to one of the preceding claims, wherein during the prepreg formation, the temperature follows a controlled ramp starting at an ambient temperature and after the treatment time at the maximum temperature, returns to ambient temperature in a controlled ramp, the maximum temperature being reached around two-thirds of the total cycle time and maintained up to 90% of the cycle time. 10. A method of manufacturing composite parts according to one of the preceding claims, wherein during the formation of prépreg, the pressure increases by one or more levels to reach its maximum value around two thirds of the total cycle time. . 11. A method of manufacturing composite parts according to one of the preceding claims wherein the residual porosity is reduced to less than 5% by adjusting the parameters time and temperature, pressure and temperature, or time pressure and temperature. 12. A method of manufacturing composite parts according to one of the preceding claims, wherein the thermoplastic sheets are in particular PMMA, PEN, PET, PC, PES, ABS, PP or PPE and the fabric comprising reinforcing fibers. is based on carbon fiber, fiberglass, aramid fiber, metal fiber or natural fiber.