Method for repair of a stiffened panel of isogrid type and stiffened panel of isogrid type thus repaired

A method for repair of a damaged stiffened panel of isogrid type, wherein the repair method comprises a step of removal of material with the aim of removing at least one damaged rib and also steps of fitting at least one structural reinforcement connecting at least two nodes positioned about the damaged zone and of at least one wall reinforcement connecting the wall of the stiffened panel and the structural reinforcement.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No. 1904871 filed on May 10, 2019, the entire disclosures of which are incorporated herein by way of reference.

FIELD OF THE INVENTION

The present application relates to a method for repair of a stiffened panel of isogrid type and also to a stiffened panel of isogrid type thus repaired.

BACKGROUND OF THE INVENTION

A stiffened panel comprises a wall and also a network of ribs and nodes perpendicular to the wall and arranged relative to one another in such a manner as to form cells. In the case of a stiffened panel of isogrid type, all the cells have a contour in the form of a triangle.

Such a panel may be damaged in the region of the ribs and/or of the wall and/or of the nodes. One solution for repairing such a panel consists in replacing it in its entirety. This solution is relatively costly.

SUMMARY OF THE INVENTION

The present invention aims to remedy all or some of the prior-art drawbacks.

To that end, a subject of the invention is a method for repair of a stiffened panel of isogrid type, comprising a wall, a network of ribs and of nodes arranged in such a manner as to form cells, each having a triangular contour, the stiffened panel having at least one damaged zone. According to the invention, the repair method comprises a step of removal of material with the aim of removing at least one damaged rib from the damaged zone and also steps of fitting at least one structural reinforcement, connecting at least two nodes positioned around the damaged zone, and of at least one wall reinforcement connecting the wall of the stiffened panel and the structural reinforcement.

The structural and wall reinforcements make it possible to compensate for the removal of the damaged parts removed from the stiffened panel by conferring on it a mechanical strength that is substantially equivalent to that which it had initially.

According to another feature, the step of removal of material comprises removing all the damaged ribs from the damaged zone.

According to another feature, the recess forms a large cell corresponding to six adjacent cells of the stiffened panel, and the step of removal of material comprises making an orifice in the wall.

According to another feature, the structural reinforcement is fitted and connected to the nodes surrounding the damaged zone then each wall reinforcement is fitted and connected to the wall and also to the structural reinforcement.

According to another feature, the wall reinforcement is fitted and connected at least to the wall then the structural reinforcement is fitted and connected to the nodes surrounding the damaged zone and also to the wall reinforcement.

A further subject of the invention is a stiffened panel repaired using the repair method according to one of the preceding features, characterized in that the repaired stiffened panel comprises at least one structural reinforcement connected to at least two nodes positioned about the damaged zone and also at least one wall reinforcement connecting the wall of the stiffened panel and the structural reinforcement.

According to another feature, the structural reinforcement comprises at least two heads pressed against terminal faces of the nodes surrounding the damaged zone and connected to the nodes by link elements.

According to another feature, the structural reinforcement has a T transverse section and comprises a body in the form of a band of material, positioned in a plane parallel to the wall bearing against the terminal faces of the first and second nodes arranged on either side of the damaged zone, and also a core integral with the body positioned in a plane perpendicular to the wall between the body and the wall.

According to another feature, the stiffened panel comprises first and second wall reinforcements arranged on either side of the structural reinforcement.

According to another feature, each of the first and second wall reinforcements has an L transverse section and comprises a first wing pressed on and connected to the core of the structural reinforcement by at least a first link element and also a second wing pressed on and connected to the wall by at least a second link element.

According to another feature, the wall reinforcement comprises at least one reinforcement plate pressed on and connected to the wall by link elements.

According to another feature, the wall reinforcement comprises first and second reinforcement plates arranged on either side of the wall, and also a third reinforcement plate intercalated between the first and second reinforcement plates and positioned in the region of an orifice provided in the region of the wall.

According to another feature, the structural reinforcement comprises a plate comprising a first face configured such as to be pressed against the wall reinforcement and a second face opposite the first face, a node projecting and centered relative to the second face of the plate and also a plurality of ribs projecting relative to the second face of the plate and regularly distributed about the node, each rib comprising a first end connected to the node and a second end having a head connected to one of the peripheral nodes located about the damaged zone.

According to another feature, the wall reinforcement comprises a structure of isogrid type comprising a hexagonal wall having a contour approximately equal to that of a recess made in the stiffened panel, a first face configured such as to be pressed against the wall and a second face opposite the first face, a central node positioned on the second face of the wall and a network of radial and peripheral ribs positioned on the second face delimiting six triangular cells about the central node.

According to another feature, the structural reinforcement comprises a central body configured such as to be pressed on and connected to the central node of the wall reinforcement and also six branches distributed regularly about the central body, each branch comprising a first end connected to the central body and a second end having a head connected to one of the peripheral nodes located about the recess.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to an embodiment that can be seen inFIG. 1, a stiffened panel10comprises a wall12and also a network of ribs14and of nodes16perpendicular to the wall12and arranged in such a manner as to form cells18. In the case of a stiffened panel10of isogrid type, each cell18is delimited by three ribs14connecting three nodes16and has a contour in the form of a triangle. The stiffened panel10comprises a first face10.1corresponding to the face of the wall12opposite the ribs14and a second face10.2corresponding to the edges20of the ribs14opposite the wall12and also to the terminal faces22of the nodes16.

InFIG. 2, the stiffened panel10has a damaged rib14. This rib14separates first and second cells18.1,18.2and connects first and second nodes16.1,16.2. The first cell18.1comprises a first base24.1that corresponds to a part of the wall12and also three ribs14,14.1′,14.1″. The second cell18.2comprises a second base24.2that corresponds to a part of the wall12and also three ribs14,14.2′,14.2″.

According to a first operating method, the method for repair of the stiffened panel10comprises a first step of removal of material with the aim of removing the damaged rib14. After this removal of material, the first and second nodes16.1,16.2have first and second edges26,28and the wall12has a third edge30in place of the damaged rib14, as illustrated inFIG. 3.

The first and second nodes16.1,16.2have first and second anchoring points32.1,32.2such as, for example, tapped holes having axes perpendicular to the wall12. According to a first case, the anchoring points32.1,32.2are present in the region of each node16prior to the repair method. According to a second case, the anchoring points32.1,32.2are not present prior to the repair method and the latter comprises a step of producing the anchoring points32.1,32.2at least in the region of the first and second nodes16.1,16.2.

The method for repair of the stiffened panel also comprises a step of placing a structural reinforcement34connecting the first and second nodes16.1,16.2, as illustrated inFIG. 4. According to one embodiment, the structural reinforcement34is positioned against the second face10.2of the stiffened panel10, bearing against the terminal faces22of the first and second nodes16.1,16.2. The structural reinforcement34comprises, at a first end, a first head34.1in the form of a washer pressed against the terminal face of the first node16.1and connected to the latter by at least a first link element36.1, such as a screw screwed into the first anchoring point32.1of the first node16.1, and also, at a second end, a second head34.2in the form of a washer pressed against the terminal face of the second node16.2and connected to the latter by at least a second link element36.2, such as a screw screwed into the second anchoring point32.2of the second node16.2.

Naturally, the invention is not limited to this embodiment in order to provide the link between the structural reinforcement34and the first and second nodes16.1,16.2. Thus, the structural reinforcement34may be adhesively bonded or welded to the first and second nodes16.1,16.2.

According to one embodiment, the structural reinforcement34has a T transverse section (visible inFIG. 7) and comprises a body38in the form of a band of material, positioned in a plane parallel to the wall12bearing against the terminal faces22of the first and second nodes16.1,16.2, and also a core40integral with the body38positioned in a plane perpendicular to the wall12between the body38and the wall12. As illustrated inFIG. 6, the core40is approximately rectangular and of such a size as to be closely spaced relative to or practically in contact with the first, second and third edges26,28and30produced upon removal of the damaged rib14.

The repair method comprises a step of fitting at least one wall reinforcement42.1,42.2configured such as to connect the structural reinforcement34and the wall12.

According to one embodiment that can be seen inFIGS. 5 and 7, the stiffened panel10comprises a first wall reinforcement42.1positioned in the first cell18.1connecting the first base24.1and the core40of the structural reinforcement34and also a second wall reinforcement42.2positioned in the second cell18.2connecting the second base24.2and the core40of the structural reinforcement34. Thus, the first and second wall reinforcements42.1,42.2are arranged on either side of the structural reinforcement34.

Each of the first and second wall reinforcements42.1,42.2has an L transverse section and comprises a first wing44, pressed on and connected to the core40by at least a link element46, and also a second wing48pressed on and connected to the first or second base24.1,24.2by at least a link element50. According to one configuration, the second wing48of each wall reinforcement42.1,42.2is configured such as to cover practically all the first or second base24.1,24.2, as illustrated inFIG. 5.

Naturally, the invention is not limited to this configuration for the structural reinforcement30and the wall reinforcements42.1,42.2. Thus, the structural reinforcement34might not comprise a core40and the wall reinforcements42.1,42.2might be connected directly to the body38of the structural reinforcement30. Furthermore, the wall reinforcements may be connected to the wall12and/or to the structural reinforcement34by adhesive bonding, by welding or the like.

InFIG. 8, the stiffened panel10comprises a damage zone52in the region of the wall12that affects a node.

According to a second operating method, the method for repair of the stiffened panel10comprises a step of removal of material comprising removing a part of the wall12and the ribs connected to the affected node. After this step of removal of material, the stiffened panel10comprises a large cell54, corresponding to the six cells adjacent to the affected node that were initially separated by the removed ribs, and also an orifice56in the region of the wall12. In a particular exemplary embodiment illustrated inFIG. 9, the orifice56is centered in the large cell54. This large cell54comprises a base58corresponding to a part of the wall12and, at the periphery, six peripheral nodes16connected by six ribs14.

As for the first operating method, if the peripheral nodes16do not comprise anchoring points32′, these latter are produced during the repair method.

The repair method comprises a step of fitting at least one wall reinforcement60connected to the wall12by link elements62.

According to one embodiment, the wall reinforcement60comprises a reinforcement plate64pressed against the base58and connected thereto by the link elements62, such as rivets, for example. According to one configuration, the reinforcement plate64is configured such as to cover practically all the base58of the large cell54, as illustrated inFIG. 10.

According to another embodiment, the wall reinforcement60comprises first and second reinforcement plates64,64′ arranged on either side of the wall12, a first reinforcement plate64pressed against the base58of the large cell54and a second reinforcement plate64′ pressed against the first face10.1of the stiffened panel10, the first and second reinforcement plates64,64′ being connected to the wall12by the link elements62. The first reinforcement plate64is configured such as to cover practically all the base58of the large cell54. In parallel, the second reinforcement plate64′ extends beyond the large cell54, as illustrated inFIGS. 10, 11 and 13. The first and second reinforcement plates64,64′ have a hexagonal contour with rounded corners.

According to another embodiment that can be seen inFIG. 11, the wall reinforcement60comprises a third reinforcement plate64″, intercalated between the first and second reinforcement plates64,64′, positioned in the region of the orifice56of the wall12. This third reinforcement plate64″ has a thickness substantially equal to that of the wall12and a cross section substantially identical to that of the orifice56.

The reinforcement plate(s)64,64′,64″ may be connected to the wall12by the fitting of fasteners, adhesive bonding, welding or the like.

The repair method comprises a step of fitting a structural reinforcement34′ connected to all the peripheral nodes16positioned about the large cell54and also to the wall reinforcement(s)60.

According to one embodiment, the structural reinforcement34′ comprises a plate66comprising a first face66.1configured such as to be pressed against the wall reinforcement60and a second face66.2opposite the first face, a node68projecting and centered relative to a second face66.2of the plate66, a plurality of ribs70projecting relative to the second face66.2of the plate66and regularly distributed about the node68. Each rib70comprises a first end70.1connected to the node68and a second end70.2having a head72connected to one of the peripheral nodes16. According to one configuration, each head72has the form of a plate configured such as to be pressed against the terminal face22of one of the peripheral nodes16and to have a passage hole74.

The plate66, the node68, the ribs70and the heads72are produced as a single piece or by the assembly of components.

The structural reinforcement34′ is connected to each of the peripheral nodes16by virtue of link elements76such as, for example screws that traverse the passage holes74and screw into the anchoring points32′ of the peripheral nodes16. The structural reinforcement34′ is also connected to the wall reinforcement60by link elements78connecting the plate66of the structural reinforcement34′ and the wall reinforcement60. In a variant, the structural reinforcement34′ might be connected to the peripheral nodes16and/or to the wall reinforcement60by adhesive bonding, by welding or the like.

According to a third operating method, illustrated inFIGS. 14 to 18, the repair method comprises a step of removal of material and, optionally, a step of production of the anchoring points32′. These steps may be identical to those of the second operating method.

The repair method comprises a step of fitting at least one wall reinforcement80connected at least to the wall12by link elements82.

According to one embodiment, the wall reinforcement80comprises a structure81of isogrid type comprising a hexagonal wall84having a contour approximately equal to that of the large cell54and a first face84.1configured such as to be pressed against the base58of the large cell54, a central node86positioned on the second face84.2of the wall84and also a network of radial and peripheral ribs88,90positioned on the second face84.2delimiting six triangular cells92about the central node86.

The structure81of isogrid type comprises a first face81.1corresponding to the first face84.1of the hexagonal wall84and a second face81.2formed by the terminal face of the central node86and the edges of the radial and peripheral ribs88,90.

The central node86comprises an anchoring point93.

The hexagonal wall84, the central node86and the network of radial and peripheral ribs88,90are produced as a single piece or by the assembly of components. They are configured such that, when the structure81of isogrid type is inserted into the large cell54and the hexagonal wall84is pressed against the base58of the large cell54, the peripheral ribs90of the structure81of isogrid type are in contact with or closely spaced relative to the ribs14positioned at the periphery of the large cell54and such that the second face81.2of the structure81of isogrid type is coplanar relative to the second face10.2of the stiffened panel10, as illustrated inFIG. 17.

The wall reinforcement80is connected to the stiffened panel10by the link elements82positioned in the region of the hexagonal wall84and/or of the peripheral ribs90, as illustrated inFIGS. 17 and 18. In a variant, the wall reinforcement80might be connected to the wall12and/or to the ribs located at the periphery of the large cell54by adhesive bonding, by welding or the like.

The wall reinforcement80comprises a reinforcement plate94positioned in the region of the orifice56of the wall12, having a thickness substantially equal to that of the wall12and a cross section substantially identical to that of the orifice56. This reinforcement plate94is connected to the structure81of isogrid type by any appropriate means, such as by screwing, riveting or the like.

The repair method comprises a step of fitting a structural reinforcement34″ connected to all the peripheral nodes16positioned about the large cell54and also to the reinforcement wall80.

According to one embodiment, the structural reinforcement34″ comprises a central body96configured such as to be pressed on and connected to the central node86and also six branches98regularly distributed about the central body96. The central body96has a passage hole100.

Each branch98has a first end98.1connected to the central body96and a second end98.2having a head102connected to one of the peripheral nodes16. According to one configuration, each head102has the form of a plate configured such as to be pressed against the terminal face22of one of the peripheral nodes16and to have a passage hole104.

The central body96, the branches98and the heads102are made as a single piece.

The structural reinforcement34″ is connected to the peripheral nodes16positioned about the large cell54by link elements106, for example screws traversing the passage holes104and screwed into the anchoring points32′ of the peripheral nodes16. The structural reinforcement34″ is connected to the wall reinforcement80by a link element108, for example a screw traversing the passage hole100and screwed into the anchoring point93of the central node86of the wall reinforcement80. In a variant, the structural reinforcement34″ might be connected to the wall reinforcement80and/or to the peripheral nodes by adhesive bonding, by welding or the like.

Irrespective of the operating method, the repair method comprises a step of removal of material and also steps of fitting at least one structural reinforcement34,34′,34″, connecting at least two nodes positioned about the damaged zone, and at least one wall reinforcement42.1,42.2,60,80connecting the wall12of the stiffened panel10and the structural reinforcement34,34′,34″. The step of removal of material comprises removing at least a part of damaged rib in such a manner as to obtain a recess formed, as a minimum, by two cells. Generally, all the damaged ribs are removed and the recess has a symmetrical form such as, for example, the form of a large cell54corresponding to six cells of the stiffened panel.

At the end of the repair method, the repaired stiffened panel10comprises at least one structural reinforcement34,34′,34″ connected to at least two nodes positioned about the damaged zone and at least one wall reinforcement42.1,42.2,60,80connecting the wall12of the stiffened panel10and the structural reinforcement34,34′,34″.