Definition Methods Mechanical Characteristics of Sound Absorption Structures

Abstract

Design techniques of Sound Absorption Structures (SAS) used in aviation engines coincide, on the whole, with the techniques of designing honeycomb parts, sandwich structures that are of wide application. However, SAS have their own distinctive features. First of all, perforating of skins decreases parts’ stiffness. SAS can have different forms (three- or five-layer SAS) and differ in honeycomb height, and can also be made of different materials. The whole of that is told on effective mechanical characteristics of SAS – stiffness in a skin plane, bending stiffness, strength of joints between separate members, and others. At present, the most sound-absorbing parts are not load-bearing structures and their mechanical damages or failures are not critical. At the same time, SAS, even those made from relatively light composites, are of heavy weight, especially in turbofans, that decreases engine perfor- mance. The abovementioned requires the development of techniques for the adequate estimation of SAS mechanical characteristics. The tendency to obtain SAS properties required for designing at lower expenses results in the necessity of their analytical prediction. In connection with this, the given work presents the analytical technique for defining SAS mechanical characteristics. The techniques of averaging are used for determining the characteristics of perforated skins and honeycomb assemblies.