Leading edge slat with optimized structure

Abstract

A leading edge slat of a wing element of an aircraft. The aircraft defining a mark including a main fuselage axis x and a spanwise axis y. The wing procuring a lift along an axis z. The wing element having a skin forming the leading edge slat, a spar linked to the skin and a stiffening structure linked on the leading edge side to the spar and to the skin. The stiffening structure being formed from a formed sheet metal having a plurality of bosses distributed according to the length of the leading edge. The bosses extending between the spar and the inner face of the skin.

Claims

1. A leading edge slat of a wing element of an aircraft, said aircraft defining a mark comprising a main fuselage axis x and a spanwise axis y, the wing element procuring a lift along an axis z, the wing element comprising a skin forming the leading edge slat, a spar comprising a core extending in a y-z plane and soles on either side of the core, the spar being linked to the skin by the soles and a stiffening structure linked on a leading edge side to the spar and to the skin, the stiffening structure being formed from a formed sheet metal comprising a plurality of bosses distributed according to a distribution pitch along a length of the leading edge slat, the plurality of bosses extending between the spar and an inner face of the skin, wherein the plurality of bosses is a succession of domes and hollows connected by flanges, each dome comprising a zone in contact with the skin and tangent to the skin, each hollow between two domes being in contact with the core of the the spar and tangent to the core of the spar and wherein any surface of any flank forms an angle less than 90° in relation to a surface of the core of the spar and to a surface of the skin with which the domes are in contact.

2. The leading edge slat according to claim 1, wherein the leading edge slat is a movable leading edge slat.

3. The leading edge slat according to claim 1, wherein the skin forming the slat and the spar are made of a composite material with continuous fibers in a polymer matrix, and wherein the stiffening structure is linked to the spar and to the skin by welding.

4. The leading edge slat according to claim 1, wherein the distribution pitch of the bosses varies over the length of the leading edge slat.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is disclosed hereinafter according to its preferred embodiments, which are in no way limiting, and in reference to FIGS. 1 to 3 wherein:

(2) FIG. 1 shows, according to a cross-section view, a diagrammatical example of a slat according to prior art;

(3) FIG. 2 shows according to a perspective and exploded view, an embodiment of a leading edge according to the invention; and

(4) FIG. 3 diagrammatically shows according to a cutting plane AA shown in FIG. 2, the response of the structure of FIG. 2 during an impact, with as a dotted line the shape of the elements before impact and as a solid line the deformation of these elements during the impact.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) FIG. 2, according to an embodiment, corresponding for example to the leading edge of a slat, the structure of a leading edge according to the invention, comprises a spar (210) with a section substantially in the shape of a U, and a skin (220), partially shown in FIG. 2, forming the leading edge. The skin extends from a single part or in several assembled portions, on the upper surface side and on the lower surface side.

(6) The spar (210) comprises a core (211) extending in the plane y-z according to this embodiment and soles (212) on either side of the core.

(7) The spar (210) and the skin (220) are linked by the soles (212) of the spar on the upper surface and lower surface sides by riveting or by welding according to the embodiments.

(8) According to the alternative embodiments the spar (210) and the skin (220) are formed from a metallic material, for example an aluminum alloy or are formed from a continuous reinforced composite in a thermosetting or thermoplastic polymer matrix.

(9) A stiffening structure (230) extends between the skin (220) and the spar (210) it is fastened on the one hand to the core (211) of the spar and on the other hand to the inner face of the skin.

(10) The stiffening structure (230) is a sheet metal comprising a plurality of bosses (231), distributed over the length, here the axis y, of the leading edge.

(11) Each boss (231) forms a dome that comprises, on the skin side, a zone (232) tangent to the inner surface of the skin, and to the hollows between two bosses, a zone (233) tangent to the surface of the core (211) of the spar.

(12) None of the flanks (236) of the domes (235) that constitute the bosses (231) are parallel to the normal to the core of the spar, in such a way that no surface of said domes (235) is parallel to the main component of the speed vector, directed substantially according to the X axis, of an object impacting the leading edge.

(13) According to this embodiment, the stiffening structure comprises 9 domes (235) distributed along a regular pitch along the axis y. It advantageously replaces 9 straight ribs between the spar and the leading edge skin.

(14) Alternatively, the pitch of the bosses is variable and preferably increases along an axis y by moving away from the root of the wing element in such a way as to adapt the stiffening to the rigidity of said wing element.

(15) According to an embodiment, the stiffening structure is formed from a formed sheet metal by of aluminum alloy. Such a form is obtained by hydroforming, superplastic forming or by incremental forming.

(16) By way of a non-limiting example, the sheet metal has a thickness of 1 mm and weighs about 500 grams, thus representing a gain of 1.3 kg in relation to a solution of prior art implementing 9 straight ribs of 200 grams each.

(17) According to another embodiment the stiffening structure (230) is formed from a composite material comprising a continuous reinforcement, for example in the form of carbon fibers, in a thermoplastic polymer matrix for example made from polyetheretherketone (PEEK).

(18) Using a thermoplastic polymer matrix provides superior resistance to the impact in comparison with a thermosetting matrix.

(19) According to this composite configuration, the stiffening structure (230) is advantageously assembled to the spar (210) and to the skin (220) by welding, with the latter also being of a composite structure.

(20) The welding is carried out using ultrasound or by bringing the assembly to be assembled to a suitable temperature in a tool. If one of the skin or the spar is comprised of a composite with a thermosetting matrix, a thermoplastic film that can bind with the polymer forming the matrix of this element is deposited beforehand on the surfaces that correspond to the assembly zones.

(21) According to an embodiment this film is deposited by an additive manufacturing method according to a method such as described in document EP 3 242 790.

(22) According to this embodiment of the stiffening structure made of composite material, the pitch of the bosses as well as the angles of their flanks (236) are chosen in such a way as to facilitate the passage of a fiber placement head for the realization thereof.

(23) FIG. 3, in case of impact on the structure object of the invention with a direction of impact (300) of which the main component is oriented along the X axis, the deformation of the skin (220) solicits the deformation of several bosses of the stiffening structure (230) thus distributing the energy of the impact in a substantial volume of material and the reaction force on a substantial surface of the spar (210) which is thus preserved.

(24) Due to the inclination of the flanks of the bosses, the more substantial the penetration of the impinger according to x is, the higher the number of bosses affected by the deformation is, which all the more so increases the dissipation capacities of the energy of the impact.

(25) The plastic deformation of the skin (220) and of the stiffening structure (230) when the latter are formed from a metallic material, or their degradation via delamination when they are formed from a composite material, thresholds the force transmitted to the spar over a large distance of displacement of the impinger, practically until the latter reaches the spar.

(26) The description hereinabove shows that the leading edge structure according to the invention allows for: a gain in mass, better resistance to the impact and a stiffening that better preserves the deformation compatibility between the leading edge and the wing element when this leading edge is movable.

(27) In addition, the structure objet of the invention opens the possibility of realizing a leading edge according to a composite construction able to respond to the impact resistance requirements.