1. Introduction

ViscoElastic Materials (VEM) are intensively used to solve NVH issues. Damping pads and anti flutter products reduce the structure borne noise. Sealants and absorbing materials prevent the air terminal transmission. Adhesives are common solutions to assemble parts. Whereas VEM are well known, the finite element analysis of their dynamic behavior is not straightforward. Most of the time, the use of a finite element software requires to simplify VEM as elastic materials. This simplification is not always the obvious thing to do and may lead to consistent results.

This reference document addresses the finite element analysis of structures comprising VEM with frequency dependent dynamic properties. Conventional approaches are discussed and a method is proposed to overcome their limitations. The method computes frequency dependent modes using an iterative algorithm. The way how these modes can be used to improve the modal projection method is described. Implementation in*Code_Aster* is explained.