FR3027553A1 - METHOD FOR MANUFACTURING A SANDWICH COMPOSITE STRUCTURE TUBE - Google Patents

Abstract

The manufacturing method comprises a step of producing a tubular layer (20) made of a first material, a step of machining at least one groove (24), in particular a circumferential groove (24), in said tubular layer (20), and a step (220) of inserting a reinforcing material (28) into each groove (24).

Description

The present invention relates to a method for manufacturing a tubular element, and more particularly to a tubular element in sandwich composite structure.

Already known in the state of the art, especially from US 3,799,818, a method of manufacturing a tubular element extending along a longitudinal axis, comprising a step of producing a tubular layer made of a first material. The present invention is intended in particular to improve the stiffness and strength of a tubular element, while maintaining a relatively low mass. For this purpose, the invention particularly relates to a method of manufacturing a tubular element extending along a longitudinal axis, comprising a step of producing a tubular layer made of a first material, characterized in that it comprises: a step of machining at least one groove, in particular a circumferential groove, in said tubular layer, and a step of insertion of a reinforcing material into each groove. Said first material is for example an epoxy foam, which has a relatively low mass. The tubular element is reinforced by said reinforcing material, so that it has an optimized resistance. A manufacturing method according to the invention may comprise one or more of the following characteristics, taken alone or in any technically feasible combination. - The method comprises a prior step of providing a support member, made of a soluble material, especially water-soluble, and a step of machining this support member to give it a predetermined shape, corresponding to the shape of a inner surface of the tubular element to be manufactured. - The method comprises a step of wrapping the support member in a second material for forming an inner skin of the tubular member, and a step of polymerizing the second material. - The method comprises, prior to the wrapping step, a step (120) of applying a protective layer, in particular a Teflon® layer, on an outer surface of the support member. The second material is formed by a band of unidirectional carbon fibers rolled up into a first layer whose fibers are parallel to a first direction and then to a second layer whose fibers are parallel to a second direction, preferably perpendicular to the second direction; first. - The method comprises, prior to the polymerization step of the second material, a step of laying a tear-off fabric on the second material and, following the polymerization step of the second material, a step of removing the fabric tear. - The tubular layer of the first material is made over the second material. - The first material is an unexpanded epoxy foam, the foam being deposited in the liquid state on the second material, by controlling the thickness of the tubular layer by means of a planar applicator parallel to the longitudinal axis, the method comprising a step of expansion and polymerization of the foam, preceding the step of machining grooves. After the step of inserting the reinforcing material, the method comprises a step of enveloping the layer of first material in a third material, intended to form an outer skin of the tubular element, and a step of polymerization of the third material. The third material is formed by a band of unidirectional carbon fibers rolled up into a first layer whose fibers are parallel to a first direction and then to a second layer whose fibers are parallel to a second direction, preferably perpendicular to the second direction; first. - The method comprises, prior to the step of polymerization of the third material, a step of laying a tear-off fabric or a self-tightening smooth strip on the third material and, following the polymerization step of third material, a step of removing the tearing tissue or the smooth strip.

The invention also relates to a tubular element extending along a longitudinal axis, comprising a tubular layer made of a first material, characterized in that: - at least one groove, in particular a circumferential groove, is formed in said layer tubular, and - a reinforcing material is arranged in each groove. The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended figures in which: FIGS. 1 to 4 and 6 to 11 are side views of a tubular element during successive steps of a method of manufacturing this tubular element; FIG. 5 is a cross-sectional view of the tubular element of FIG. 4.

In the figures, there is shown a tubular element 10 during successive steps of a method of manufacturing this tubular element 10. The tubular element 10 is visible in the finished version in FIG. 11. The tubular element 10 has a general shape of revolution around a longitudinal axis. For example, the tubular element 10 has a generally cylindrical shape with circular cross section. The tubular element 10 has a sandwich composite structure. More particularly, it has in particular a core 20 formed of a first material, an inner skin 18 formed of a second material, and an outer skin 30 formed of a third material, for example identical to the second material. The method of manufacturing the tubular element 10 comprises a preliminary step 100 of providing a support member 12, as shown in FIG. 1. Advantageously, the support member 12 is made of a soluble material, c that is, capable of dissolving in a solvent. Preferably, the support member 12 is made of a water-soluble material capable of dissolving in water. The support member 12 has a general shape of revolution about a longitudinal axis X. This support member 12 is arranged on a rotary tool, and more particularly on a rotary rod 14 extending along the longitudinal axis X, and being movable in rotation about this axis X. The manufacturing method then comprises a step 110 of machining of the support member 12, shown in Figure 1. This machining step 110 is intended to give to the support member 12 a predetermined shape, corresponding to the desired shape for an inner surface of the tubular member 10 to be manufactured. Thus, in the example shown, the support member 12 is machined to have a cylindrical shape extending along the longitudinal axis X, circular cross section. The machining is performed by means of a milling tool 16 of conventional type, for example movable along three linear axes.

As shown in FIG. 1, the machining is performed by moving the milling tool 16 in translation in the direction of the longitudinal axis X while driving the support member 12 in rotation about the longitudinal axis X. Advantageously, the manufacturing method then comprises a step 120 of applying a protective layer on an outer surface of the machined support member 12. This protective layer is for example a Teflon® layer. This protective layer is intended to prevent direct contact between the second material forming the inner skin of the tubular member 10 and the water-soluble material forming the support member 12. Alternatively, the protective layer is formed by a protection product deposited by spraying on the outer surface of the machined support member 12. This variant is preferred when the geometry of this outer surface is complex and makes it difficult to apply adhesive Teflon® strips. This protective product is, for example, water-soluble, and can thus be removed together with the support member 12. As shown in FIGS. 2 and 3, the process then comprises a step 130 for wrapping the organ support member 12 in said second material, to form the inner skin 18 of the tubular member 10. The second material is for example formed by a unidirectional carbon fiber strip. As shown in Figure 2, said carbon fiber web is first wound into a first layer 18A, whose fibers are parallel to a first direction. Then, as shown in FIG. 3, the fiber strip is wound into a second layer 18B, over the first layer 18A, the fibers of the second layer 18B being parallel to a second direction, preferably perpendicular to said second layer 18B. first direction.

The fact of winding the fiber web in two layers reinforces said inner skin 18, in particular so that it has no point of weakness. Preferably, the method then comprises a step 140 of placing a tearing tissue on the inner skin 18. This laying step 140 is followed by a step 150 of polymerization of the second material forming the inner skin 18. The method then comprises a step 160 for removing the tear-off fabric, following the polymerization step 150. The laying and then the removal of the tear-off fabric makes it possible, in a manner known per se, to reinforce the inner skin 18, and to form an optimized attachment surface on this inner skin 18.

The method then comprises a step 180 for producing a tubular layer 20, shown in FIGS. 4 and 5, said tubular layer being intended to form the core of the composite tubular element 10. The tubular layer 20 is deposited by above the inner skin 18, to which it adheres in an optimized manner thanks to the attachment surface formed on the inner skin 18.

Said first material forming the tubular layer 20 is an unexpanded epoxy foam. This foam is deposited in the liquid state on the inner skin 18, by controlling the thickness of the tubular layer 20 thus formed by means of a flat applicator 22 parallel to the longitudinal axis X.

The epoxy foam is deposited continuously along the longitudinal axis X, while the rotating tool 14 rotates about its axis X, so that the foam is distributed around the inner skin 18. More particularly, the epoxy foam is poured between the inner skin 18 and the applicator 22, which advances in translation along the longitudinal axis X. The distribution and the thickness of the foam are thus controlled by the planar applicator 22. The process then comprises a step 190 of expansion and polymerization of the foam. During this step 190, the rotation of the rotating tool 14 is advantageously maintained. This rotation makes it possible, in combination with the fact that the foam has a good thixotropic property, to maintain the foam in position in the form of the layer 20 during its expansion and polymerization. It will be noted that the core 20 thus formed by this polymerized epoxy foam does not have points of weakness. Following step 190 of polymerization of the foam, the process advantageously comprises a step 200 of pre-surfacing of the foam. This pre-surfacing is for example carried out by means of the milling tool 16, in the same way as during the machining step 110. The preceded then comprises a step 210 of machining at least one groove 24, in particular a circumferential groove, in the tubular layer 20, as shown in FIG. 6. This machining is carried out by means of a milling tool 26. Each circumferential groove 24 is machined to a predetermined thickness of the layer For example, in the example shown, each circumferential groove 24 extends to the inner skin 18. As shown in FIG. then comprises a step 220 for inserting a reinforcing material 28 into each circumferential groove 24. The reinforcing material 28 is, for example epoxy resin loaded in order to lighten its mass while retaining good properties of r resistance to compression.

The method then comprises a step 230 for polymerizing the reinforcement material 28. The method then comprises a step 240 of surfacing the layer 20 and the reinforcing material 28, as shown in FIG.

This surfacing is for example carried out by means of the milling tool 16, in the same way as during the pre-surfacing step 200. As shown in FIGS. 9 and 10, the method then comprises a step 250 of wrapping the tubular layer 20 in said third material intended to form the outer skin 30 of the tubular element 10.

This third material is for example formed by a band of unidirectional carbon fibers, similar to that forming the second material. The carbon fiber strip is first wound into a first layer 30A, the fibers of which are parallel to a first direction, as shown in FIG. 9. The carbon fiber strip is then rolled into a second layer 30B, over the first layer 30A, the fibers of the second layer 30B being parallel to a second direction, preferably perpendicular to the first, as shown in Figure 10. Wrapping the fiber web into two layers makes it possible to reinforce said outer skin 30, in particular so that it has no point of weakness.

In the same way as for the inner skin 18, the method then comprises a step 260 for laying a tear-off fabric, or alternatively a self-tightening smooth band, on the outer skin 30, followed by a step 270 of polymerizing the third material 30, and then a step 280 of removing the tearing tissue or said smooth strip. It should be noted that a smooth strip makes it possible to obtain a smooth final surface, whereas a tear-off fabric makes it possible to obtain a gripping surface intended to receive coating or paint. The method then comprises, optionally, a machining step 290, especially drilling and cutting in the tubular element 10, as shown in Figure 11. This machining step 290 is performed in a conventional manner.

The method then comprises a step 300 of demolding the tubular element 10, by dissolving the support member 12, for example with water when the support member 12 is of water-soluble material. The use of a machinable and water-soluble support member 12 makes it possible to manufacture various shapes, in particular possibly complex shapes for the tubular element 10.

Finally, the method advantageously comprises a step 310 for baking the tubular element 10, for example at 40 ° C for six hours, in order to provide the epoxy foam, forming the layer 20, its final mechanical stability. It should be noted that the entire manufacturing process is cold, only the six-hour cycle at 40 ° of step 310 possibly being necessary (to provide the epoxy foam its final mechanical stability, as indicated below. above) which limits the means necessary to achieve the process and its cost of implementation. It is clear that the invention makes it possible to obtain a lightened structure having optimized mass and strength.

Note that the invention is not limited to the embodiment described, but could have various variants without departing from the scope of the claims.

Claims (12)

REVENDICATIONS1. A method of manufacturing a tubular element (10) extending along a longitudinal axis (X), comprising a step (180) for producing a tubular layer (20) made of a first material, characterized in that it comprises: - a step (210) for machining at least one groove (24), in particular a circumferential groove (24), in said tubular layer (20), and - an insertion step (220) a reinforcing material (28) in each groove (24). 2. Manufacturing method according to claim 1, comprising a prior step (100) of providing a support member (12), made of a soluble material, especially water-soluble, and a step (110) of machining of this organ of support (12) to give it a predetermined shape, corresponding to the shape of an inner surface of the tubular element (10) to be manufactured. 3. Manufacturing method according to claim 2, comprising a step (130) for enveloping the support member (12) in a second material, intended to form an inner skin (18) of the tubular element (10). , and a step (150) of polymerizing the second material. 4. Manufacturing method according to claim 3, comprising, prior to the wrapping step (130), a step (120) for applying a protective layer, in particular a Teflon® layer, on an outer surface. of the support member (12). 5. Manufacturing process according to claim 3 or 4, wherein the second material is formed by a unidirectional carbon fiber strip, wound into a first layer (18A) whose fibers are parallel to a first direction, then in a second layer (18B) whose fibers are parallel to a second direction, preferably perpendicular to the first. 6. Manufacturing process according to any one of claims 3 to 5, comprising, prior to the step (150) of polymerization of the second material, a step (140) of laying a tear-off fabric on the second material and, following the step (150) of polymerizing the second material, a step (160) of removing the tearing tissue. 7. The manufacturing method according to any one of claims 3 to 6, wherein the tubular layer (20) of the first material is made over the second material. 8. The manufacturing method according to any one of the preceding claims, wherein the first material is an unexpanded epoxy foam, the foam being deposited in the liquid state on the second material, by controlling the thickness of the tubular layer at means of a planar applicator (22) parallel to the longitudinal axis (X), the method comprising a step (190) of foam expansion and polymerization, preceding the grooving machining step (210) ( 24). 9. Manufacturing method according to any one of the preceding claims, comprising, following the step (220) of insertion of the reinforcing material, a step (250) of enveloping the layer (20) of first material in a third material, for forming an outer skin (30) of the tubular member (10), and a step (270) of polymerizing the third material. The manufacturing method according to claim 9, wherein the third material is formed by a unidirectional carbon fiber strip, wound into a first layer (30A) whose fibers are parallel in a first direction and then in a second layer ( 30B) whose fibers are parallel to a second direction, preferably perpendicular to the first direction. 11. The manufacturing method according to claim 9 or 10, comprising, prior to the step (270) of polymerization of the third material, a step (260) for laying a tear-off fabric or a self-adhesive smooth strip. clamping on the third material and, following the step (270) of polymerizing the third material, a step (280) of removing the tearing tissue or the smooth strip. Tubular element (10) extending along a longitudinal axis (X), comprising a tubular layer (20) made of a first material, characterized in that: - at least one groove (24), in particular a circumferential groove, is formed in said tubular layer (20), and - a reinforcing material (28) is arranged in each groove (24).