Composite beam with integrated rupture initiator and aircraft fuselage including such beams
View Patent ↗Composite beam with integrated rupture initiator and aircraft fuselage including such beams. A composite beam ( 18 ) comprises a web ( 20 ) with a sinusoidal-shaped section and a bottom flange ( 22 ). The web ( 20 ) comprises a stack of at least one central layer of single-directional carbon fibers oriented along the depth of the beam, and aramide fiber and carbon fiber fabrics. The lower part of the beam ( 18 ) is designed so that rupture is initiated in it if the aircraft in which the beam is installed crashes. This is achieved by gluing the bottom flange ( 22 ) on the sides of the web ( 20 ), the bottom edge of each layer of single-directional carbon fibers is setback from the corresponding edges of the fabrics and saw-tooth cut-outs are formed in this bottom edge
1. Composite beam to which a compression force can be applied in the direction of its depth, causing its rupture of the beam, the beam comprising a web with an approximately sinusoidal-shaped section in a place perpendicular to the said direction and a flange connecting the web to a structure through which the compression force is applied, the web comprising a stack of at least one layer of single-directional fibres oriented along the said direction, and fabrics, the beam comprising rupture initiation means, the said means comprising cut-outs formed on one edge of each layer of single-directional fibres, adjacent to the flange, so that the layer is progressively loaded and degraded during application of the said compression force.
2. Composite beam according to claim 1 , in which the flange is added onto each side of the web by glue films, the said glue films also forming part of the rupture initiating means.
3. Composite beam according to claim 2 , in which the flange comprises two angles added onto each side of the web by the said glue films.
4. Composite beam according to claim 1 , in which the said edge of each layer of single directional fibres is located set back from the corresponding edges of the fabrics, the said rupture initiating means also comprising the said set back.
5. Composite beam according to claim 1 , in which the cut-outs are in the shape of saw teeth.
6. Composite beam according to claim 5 , in which the vertex angle of the saw teeth is equal to about 30°.
7. Composite beam according to claim 5 , in which the saw teeth are uniformly distributed around the edge of each layer of single-directional fibres at a pitch that is a sub-multiple of the pitch of the sine curve formed in section by the web of the beam.
8. Composite beam according to claim 7 , in which the points of the saw teeth are then offset as much as possible from the centreline of the said sine curve.
9. Composite beam according to claim 5 , in which not more than about 20% of the saw tooth surface is located facing the flange.
10. Composite beam according to claim 1 , in which each layer of single-directional fibres is formed from carbon fibres.
11. Composite beam according to claim 10 , in which the layer(s) of single-directional carbon fibres form a central part of the web of the beam, the said central part being placed between two aramide fibre fabrics oriented at ±45° with respect to the direction of the depth of the beam, such that each layer is in contact with at least one of the fibre fabrics.
12. Composite beam according to claim 1 , in which the fabrics comprise aramide fibre fabrics oriented at ±45° with respect to the direction of the depth of the beam.
13. Composite beam according to claim 1 , in which the fabrics comprise carbon fibre fabrics oriented at ±45° with respect to the said direction.
14. Composite beam according to claim 13 , in which the carbon fibre fabrics are placed on the outside faces of the web of the beam.
15. Aircraft fuselage, comprising a framework to which an outer skin is fixed, the framework comprising stiffener frames in which an approximately straight lower part is connected to the outer skin by at least two beams made according to claim 1 .