Acoustic attenuation panel for e.g. aircraft jet engine has structural layer perforated with non-circular holes aligned with perpendicular axes

摘要

A panel, comprising a layer of a cellular, e.g. honeycomb, structural material with a resistive layer on one side made from porous and structural perforated layers, and a total reflective layer on the other, has the perforated layer pierced with non-circular holes which have their greatest and smallest dimensions aligned with two perpendicular axes. A panel, comprising a layer of a cellular, e.g. honeycomb, structural material (1) with a resistive layer (2) on one side made from porous (2b) and structural perforated (2a) layers, and a total reflective layer (3) on the other, has the perforated layer pierced with non-circular holes (4) which have their greatest and smallest dimensions aligned with two perpendicular axes. The holes' smallest dimension is at least 0.5mm, and the greatest is at least 1.5 times greater; they can be rectangular, oblong or hexagonal in shape, with their greatest dimension in line with the direction of the main stresses, e.g. parallel to a jet engine's lengthwise axis. The perforated layer can be made from a metal such as aluminium or stainless steel, plastics with a high temperature resistance or fibre-reinforced composition materials with mineral or organic fibres, impregnated with a thermo-setting or thermoplastic resin and polymerised.