In the field of aerospace, structures must be designed with
low weight and high load bearing capacity. This type of structure is more
sensitive to dynamic problems associated with its natural frequencies. In
order to increase the structure's natural frequencies there is a need to
stiffen the structure. Usually, stiffening of the structure can be achieved by
complicated/expensive or heavy design.
The objective of this study is to examine the possibility
to increase the stiffness of sandwich plate structures, almost without
increasing their weight or complexity. The structures dealt with in this study
are tension stressed 3 layers sandwich plates, where tension is introduced into
their skins only.
This way, the natural frequencies will increase and
compensate for the decrease of the structure frequencies, particularly the
lower ones, which are expected due to discrete mass dispersing on the
This work presents an analysis dealing with the influence
of the change in sandwich structures stiffness, by applying tension to their
skins, on their dynamic characteristics, as reflected by their natural
frequencies. The analysis was performed using energy methods while considering
different discrete mass dispersing on the plates and exposing them to different
edge conditions and loads.
The results of the present study show that the natural
frequencies are influenced by the magnitude of applied tension that changes the
dynamic characteristics of the structure. This influence is highly perceived
when the edge conditions of the structure are of "soft" type. For
those edge conditions it is possible to achieve an increase of tens percents in
the natural frequencies while applying relatively reasonable tension stresses.