Structural-Acoustic Optimization of Sandwich Panels
With the introduction of more lightweight vehicle structures for railway cars, a
great deal of interest is focused on the question of airborne sound reduction, since
lightweight structures have a reputation of poor sound insulation properties.
Although the high damping of sandwich materials is often pointed out along with
the other bene ts of using such materials, the sound reduction capabilities are more
strongly in uenced by the geometry and elastic properties of the constituents than
by damping. As a result of this, a sandwich panel can be lightweight and designed
to carry high mechanical loads, but be really poor when it comes to attenuation of
This thesis deals with the design of sandwich panels with minimum weight under
simultaneous sti ness, strength, and acoustic constraints. The acoustic constraints
are de ned as a required sound reduction index for air-borne sound.
A relatively well documented area of sandwich research is the mechanical behavior
of sandwich plates under various loads. Nevertheless a part of the present work
is an evaluation of a test-setup which can be used to verify research work regarding
sti ness or failure modes of sandwich panels.
The material damping and elastic modulus of a certain type of solid foam core is
investigated in order to use the core density as a design parameter. Face materials are
usually not used as design parameters, since there is a limited selection of materials
to choose from, and the choice is often given by factors which are not a part of the
detailed design of the sandwich constituents.
The acoustic model of sandwich panels are coupled to a weight optimization
of sandwich structures. In this optimization, the sound reduction index of various
panels in the structure is used as constraints. It is shown that it is possible to use
acoustic models as constraints in the optimization of large sandwich structures.
The acoustic theories for sound reduction of sandwich panels and the weight optimization
under acoustic constraints are veri ed experimentally through full scale
tests. The sound reduction index of two sandwich panels, one of which was optimized
for minimum weight, are measured and the agreement between theory and
experiments is good.
The conclusion is that a lightweight load carrying sandwich structure with high
enough sound reduction index can be designed using optimization with mechanical
and acoustic constraints.
School:Kungliga Tekniska högskolan
Source Type:Doctoral Dissertation
Keywords:Optimization; acoustics; multidisciplinary; sandwich; composite; sound reduction index; railway vehicle
Date of Publication:01/01/2001