Exhaust with an acoustic attenuation system

1. An exhaust cone for an aeroengine extending from upstream to downstream along a longitudinal axis,

said cone comprising a structural core of composite material made up of an axisymmetric part having an upstream endpiece at its upstream end and a downstream endpiece at its downstream end,

said core providing the structural strength of the cone,

said cone further comprising an acoustic attenuation system made of composite material and fastened on the structural core;

wherein the acoustic attenuation system comprises

longitudinal partitions of composite material fastened to the upstream and downstream endpieces by connection means that are mechanical, and

transverse partitions of composite material fastened to the longitudinal partitions by connection means that are mechanical, said longitudinal and transverse partitions defining resonator boxes, and

wherein the ratio of a thickness of structural parts of the core and a thickness of components of the acoustic attenuation system lies in the range of 3 to 5.

2. An exhaust cone according to claim 1 , wherein the longitudinal partitions are fastened respectively to the upstream and downstream endpieces by connection means that are mechanical and reversible, and

in that the transverse partitions are fastened to the longitudinal partitions by connection means that are mechanical and reversible so as to form an assembly that can be dismantled.

3. An exhaust cone according to claim 1 , wherein the structural core is made of composite material comprising fiber reinforcement made of refractory fibers densified by a matrix that is at least partially made of ceramic.

4. An exhaust cone according to claim 3 , wherein the structural core is made of composite material comprising fiber reinforcement made of silicon carbide fibers densified by a silicon carbide matrix including one or more self-healing phases.

5. An exhaust cone according to claim 1 , wherein the longitudinal and transverse partitions present thickness lying in the range 0.7 mm to 1.5 mm.

6. An exhaust cone according to claim 1 , wherein the acoustic attenuation system further comprises a multiply-perforated skin of composite material fastened between the upstream endpiece and the downstream endpiece of the core, said multiply-perforated skin closing the top portions of the resonator boxes.

7. An exhaust cone according to claim 6 , wherein the multiply-perforated skin presents thickness lying in the range 0.7 mm to 1.5 mm.

8. An exhaust cone according to claim 1 , further including a terminal portion of composite material fastened to the downstream endpiece of the structural core.

9. An aeroengine afterbody including an exhaust cone according to claim 1 .