<DOC>
<DOCNO>
720
</DOCNO>
<TITLE>
a note on the use of sandwich structures in severe acoustic
environments .
</TITLE>
<AUTHOR>
d. j. mead, d. c. ae.
</AUTHOR>
<BIBLIO>
d. j. mead, d.c.ae.
</BIBLIO>
<TEXT>
this paper reviews some of the experience to date of using sandwich type
structures in severe acoustic pressure environments .  the methods
used for testing sandwich structures for acoustic fatigue are described
and their limitations considered .  experimental and theoretical work
relating to the damping and mode-frequency relationships of certain
sandwich configurations is also reviewed .
special attention is given to the estimation of the stress in the bond
of a honeycomb sandwich panel subjected to sudden pressure
fluctuations .  a /uni-modal/ theory is presented, relating the meansquare
bond-stress to the random exciting pressure and panel dynamic
characteristics .  this theory indicates that tensile bond stresses
may be encountered of up to six times the local r.m.s. exciting
pressure .  these must be combined with bending and shear stresses
to obtain the principal stresses which precipitate bond fatigue
failures .
finally, an outline is given of some of the lines of future research
which should lead to the achieving of the maximum possible fatigue
resistance from sandwich configurations .
</TEXT>
</DOC>
