METHOD FOR MANUFACTURING A FIBRE PREFORM

Abstract

A method for manufacturing a fiber preform including a number of plies greater than or equal to two, includes: a) heating a ply; b) depositing the ply on a preforming mold; c) forming the ply, the ply then forming an intermediate preform; d) heating a new ply; e) depositing the new heated ply on the intermediate preform; f) forming the new ply in order to form a new intermediate preform; g) where applicable, repeating steps d) to f) at least once, the intermediate preform being replaced in these steps by the new intermediate preform in order to produce the fiber preform with the number of plies.

Claims

1. A method for manufacturing a fibrous preform comprising a predetermined number of plies greater than or equal to two, comprising the following steps: a) heating at least one ply, b) depositing said at least one ply on a preforming mold, c) performing an operation of forming of said at least one ply, said at least one ply then forming an intermediate preform, d) heating at least one new ply, e) depositing said at least one heated new ply on the intermediate preform, f) performing an operation of forming of said at least one new ply so as to form a new intermediate preform, g) possibly repeating, at least once, the steps d) to f), the intermediate preform being replaced in these steps by the new intermediate preform, so as to produce the fibrous preform with said predetermined number of plies.

2. The method as claimed in claim 1, wherein the number of plies in the step a) and/or d) is precisely one.

3. The method as claimed in claim 1, wherein the number of plies in the step a) and/or d) is precisely two.

4. The method as claimed in claim 1, wherein the number of plies in the step a) and/or d) is greater than or equal to two, this number being strictly less than the predetermined number of plies of the fibrous preform.

5. The method as claimed in claim 1, wherein, in the step d), the intermediate preform is also heated.

6. The method as claimed in claim 1, wherein the heating step d) comprises the simultaneous heating of said at least one new ply and of the intermediate preform.

7. The method as claimed in claim 1, wherein, in the heating step d), said at least one new ply is heated to a temperature lying between 80° C. and 200° C., and the intermediate preform is heated such that the outer surface of the intermediate preform, which will be in contact with said at least one new ply, is heated to a temperature greater than the melting temperature of a binder of said at least one new ply, notably greater than or equal to 60° C., and less than the deconsolidation temperature of the intermediate preform.

8. The method as claimed in claim 1, wherein the heating steps a) and/or d) are preceded by a step consisting in arranging said at least one ply and/or new ply draped flat on top of the preforming mold and/or intermediate preform, these steps being preferably performed using a needle gripper.

9. The method as claimed in claim 1, wherein the heating steps a) and/or d) are performed by infrared heating.

10. The method as claimed in claim 1, wherein the forming step c) and/or f) is performed by rapid forming of said at least one ply or a new ply by creation of a vacuum using a deformable membrane.

11. The method as claimed in claim 1, wherein the forming step c) and/or f) is followed by a step of cooling of the intermediate preform or new intermediate preform or fibrous preform.

12. The method as claimed in claim 1, wherein the thickness of the fibrous preform with the predetermined number of plies lies between approximately 0.5 mm and 100 mm.

13. The method as claimed in claim 1, wherein said at least one ply and/or a new ply is a dry ply.

14. The method as claimed in claim 1, wherein said at least one ply and/or said new ply comprises fibers chosen from the group consisting of glass fibers, carbon fibers, aramid fibers, ceramic fibers, polyester fibers, plant fibers, notably flax fibers, preferably glass fibers, and a mix thereof.

15. The method as claimed in claim 1, wherein the predetermined number of plies of the fibrous preform is between 2 and 200.

16. A method for manufacturing a part made of composite material comprising the following steps: producing a fibrous preform by implementing the method as claimed in claim 1, impregnating a polymer into the fibrous preform so as to obtain the part made of composite material.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0057] The invention will be able to be better understood on reading the following detailed description of nonlimiting examples of implementation thereof, and on studying the attached drawing, in which:

[0058] FIG. 1 is a block diagram illustrating the different steps of an example of a method according to the invention,

[0059] FIG. 2 is a block diagram illustrating the different steps of another example of a method according to the invention,

[0060] FIGS. 3 to 6 schematically illustrate the implementation, in cross section, of different steps of the method according to the invention,

[0061] FIG. 7 is a schematic view in cross section of an example of fibrous preform obtained with the method according to the invention, and

[0062] FIGS. 8 and 9 are graphs of temperature as a function of time applied illustrating the implementation of the method according to the invention with different parameters.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0063] Hereinafter in the description, the elements that are identical or functions that are identical bear the same reference symbol. For the brevity of the present description, they are not described in light of each of the figures, only the differences between the embodiments being described.

[0064] FIG. 1 shows an example of a method for manufacturing a fibrous preform comprising a predetermined number of plies greater than or equal to two, comprising the following steps.

[0065] In the step a), at least one ply is heated, in this example by infrared heating.

[0066] In the step b), said at least one ply is deposited on a preforming mold.

[0067] In the step c), an operation of forming of said at least one ply is performed, said at least one ply then forming an intermediate preform.

[0068] In the step d), at least one new ply is heated, in this example by infrared heating. In this step also, according to this embodiment, the intermediate preform is simultaneously heated, also by infrared heating. In this example, the latter is heated to a temperature, for example of 60° C., which is less than the heating temperature of the new ply, which is, for example, 110° C.

[0069] In the step e), said at least one heated new ply is deposited on the intermediate preform.

[0070] In the step f), an operation of forming of said at least one new ply is performed so as to form a new intermediate preform.

[0071] Next, if the predetermined number of plies greater than or equal to two is reached, the fibrous preform is obtained in the step g). If the predetermined number of plies greater than or equal to two is not reached, the steps d) to f) are repeated by following the arrow h), the intermediate preform being replaced in these steps by the new intermediate preform, so as to obtain, in the step g), the fibrous preform with the predetermined number of plies reached.

[0072] After the step g), the fibrous preform can be impregnated with a liquid or pasty polymer, notably by injection, in order to obtain a part made of composite material.

[0073] In this example, each ply is a dry ply produced from NCF. It advantageously comprises glass fibers.

[0074] Still in this example, the number of plies in the step a) and d) is precisely one. Thus, according to this embodiment, the preform is produced ply by ply, by heating the ply before depositing it on the intermediate preform already produced previously. That makes it possible to save on heating time since the thickness to be heated in these steps a) and d) is small.

[0075] The forming in the steps c) and f) is implemented in this example by rapid forming of said at least one ply or of said at least one new ply by the creation of a vacuum using a deformable membrane.

[0076] FIG. 2 shows another example of implementation of the method for manufacturing a fibrous preform according to the invention.

[0077] Once again, there are the steps a), b), c), d), e), f) and g) described above with reference to FIG. 1.

[0078] The method also comprises, in this example, a step i) prior to the step a) consisting in arranging said at least one ply draped flat on top of the preforming mold, this step being, in this example, performed using a needle gripper. Similarly, the step d) is preceded by a step k) arranging said at least one new ply draped flat on top of the intermediate preform, this step being also performed using the needle gripper in this example.

[0079] Moreover, the forming step c) is followed by a step j) of cooling of the intermediate preform. Similarly, the forming step f) is followed by a step 1) of cooling of the new intermediate preform which can then, if necessary, coincide with the fibrous preform obtained in the step g) if the predetermined number of plies is reached.

[0080] In this example, the number of plies in the steps a) and d) is precisely two plies. There is no departure from the scope of the invention if the number of plies in these steps is greater than two and strictly less than the predetermined number of plies of the fibrous preform, or is different between the steps a) and d).

[0081] In FIG. 3, the implementation of the heating step d) of the method according to the invention is visualized. An intermediate preform 5 is arranged on a preforming mold M. Two plies 6 superposed on one another are arranged draped flat on top of the intermediate preform 5, using a needle gripper P. An infrared heating 1 is introduced in the direction of the arrow W between the intermediate preform 5 and the plies 6 so as to heat them simultaneously according to the opposing arrows X. The heating temperature can be different, being notably less for the intermediate preform 5. As a variant, it is the same for the plies 6 and for the intermediate preform 5.

[0082] FIG. 4 represents the implementation of the step e) of the manufacturing method according to the invention. The plies 6, after heating and removal from the infrared heating 1, are brought toward the previous preform 5 using the needle gripper P according to the arrow Y. Then, the needle gripper P is removed according to the arrow V after the plies 6 have been deposited on the previous preform 5.

[0083] Finally, FIGS. 5 and 6 respectively represent the start and the end of the forming step f) with a rapid forming of the plies 6 and creation of the vacuum (FIG. 6) using a deformable membrane N applied according to the arrow Z with a counter-mold M′ against the plies 6 so as to produce a new intermediate preform 5′ including the intermediate preform 5 and the plies 6. This new intermediate preform 5′, visible in FIG. 6, can be the fibrous preform 10 if the predetermined number of plies of this preform is reached.

[0084] FIGS. 3, 4, 5 and 6 respectively represent the implementation of the steps d), e) and f) but it is also possible to imagine implementation of the steps a), b) and c) if the intermediate preform 5 is removed. The ply or plies 6 are then equivalent to said at least one ply of the steps a), b) and c).

[0085] FIG. 7 schematically represents an example of fibrous preform 10 obtained using the method illustrated in FIG. 2, consisting of a superpositioning of plies 6.

[0086] A part made of composite material can be produced from this fibrous preform 10, by impregnating the latter, by injection or maceration for example, of a liquid or pasty polymer.

[0087] A test was performed by implementing the method according to the invention and, during this test, the variation of the temperature as a function of time was studied at precise points of the plies 6 and of the intermediate preform 5 using thermocouples tc2, tc3 arranged on the intermediate preform 5 and thermocouples tc4 and tc5 arranged on the plies 6, as can be seen in FIG. 3. The result of this study is illustrated in the graphs of FIGS. 8 and 9.

[0088] For the start of the test performed for which the graph can be seen in FIG. 8, the starting point was an intermediate preform 5 consisting of two plies 6, to which two new plies 6 were added. As can be seen in FIG. 3, the temperatures of the intermediate preform 5 are tracked by the thermocouples tc2 and tc3, tc2 being arranged on the bottom surface of the intermediate preform 5 while tc3 is arranged on the top surface of the intermediate preform 5 which will be in contact with one of the new plies 6. The temperatures of the plies 6 are tracked by the thermocouples tc4 and tc5, tc4 being arranged on the top ply and tc5 is arranged on the bottom ply which will be in contact with the intermediate preform 5. The rest of the test performed for which the graph can be seen in FIG. 9 corresponds to the rest of the implementation of the method, with the addition, on the new intermediate preform 5′, of two new plies 6. The thermocouples tc2, tc3, tc4 and tc5 are then respectively arranged on the new intermediate preform 5′ and on the new plies 6.

[0089] The melting temperature T.sub.L of the binder is, in this test, 60° C.

[0090] For the start of the test for which the result T(t) is illustrated in FIG. 8, the step d) is implemented by applying, for 120 s, the infrared heating with an infrared oven power of 50%. The temperature of the intermediate preform and of the plies increases. At the end of this heating, it is found that the temperature difference AT between the two plies 6 is 15° C. and that the temperature of the top surface of the intermediate preform 5 has reached 89° C.

[0091] Then, heating is stopped and the step e) of deposition of the new plies 6 is implemented, followed by the step f) of forming of these plies before the temperature of the top surface of the intermediate preform reaches the melting temperature T.sub.L of the binder, which is 60° C. in this example. It can thus be seen, in the graph of FIG. 8, that 25 s are available to perform these two steps, the top surface of the intermediate preform 5 taking this time to go from 89° C. to 60° C. Indeed, the different plies can be bonded together only above this temperature. Then comes the cooling step 1) which, in this example, takes 200 s, the different temperatures of the plies/preform continuing to lower, as can be seen, until the new plies reach the temperature of 60° C.

[0092] Then, the rest of the test is performed with the rest of the method with the new intermediate preform 5′, by adding two new plies 6. In a new step d), heating is applied for 120 s with an infrared oven power of 50%. The temperature of the new intermediate preform and of the new plies increases, as can be seen in FIG. 9. At the end of this heating, it is found that the temperature difference AT between the two new plies 6 is 15° C. and that the temperature of the top surface of the intermediate preform 5 has reached 95° C. It should be noted that the starting temperature was not 20° C. as at the outset, but 30° C., the cooling of the new intermediate preform not being complete.

[0093] Then, the heating is stopped and the step e) of deposition of the new plies 6 is implemented, followed by the step f) of forming of these plies before the temperature of the top surface of the intermediate preform reaches the melting temperature T.sub.L of the binder, which is still 60° C. in this example. It can also be seen, in the graph of FIG. 9, that 57 s are available for performing these two steps, the top surface of the intermediate preform 5 taking this time to go from 95° C. to 60° C. Then comes the cooling step 1) of 200 s, the temperatures continuing to lower until the new plies reach the temperature of 60° C.

[0094] It is found, in viewing these graphs, that it takes a relatively short time to heat the intermediate preform and the plies to be deposited. The method according to the invention thus makes it possible to preform two plies on an intermediate preform in 345 s compared to 30 min for four plies in the prior art, which is advantageous.

[0095] It is also found that it is more advantageous to have a temperature of the top surface of the intermediate preform or new intermediate preform which is higher at the end of the heating, as in the rest of the test, in FIG. 9, because that makes it possible to have more time to perform the steps e) and f). In this example, the starting temperature is higher, which explains why the temperature of the top surface reaches a higher value at the end of the heating. It is also possible to envisage increasing the heating power and/or the heating time to increase this time.

[0096] The mold M can also be heated in such a way as to maintain the temperature of the intermediate preform at a temperature at least equal to the melting temperature of the binder.