Optimum design via PANDA2 of composite sandwich panels with honeycomb or foam cores

Abstract

PANDA2 has been extended to handle panels with sandwich wall construction by inclusion of the following failure modes in addition to those previously accounted for: (1) face wrinkling, (2) face dimpling, (3) core shear crimping, (4) core transverse shear stress failure, (5) core crushing and tension failure, and (6) facesheet pull-off. Transverse shear deformation effects are included both for overall panel buckling and for local face sheet dimpling and face sheet wrinkling. The new PANDA2 code will optimize stiffened sandwich panels in which the stiffener segments as well as the panel skin may have sandwich wall constructions. The effects of panel buckling modal initial imperfections as well as initial face sheet waviness are accounted for during optimization cycles. The updated PANDA2 code will also handle optimization of a panel supported by an elastic Winkler foundation. Examples are presented for a uniformly axially compressed perfect and imperfect unstiffened panel without and with a uniform temperature gradient through the panel wall thickness. Initial face sheet waviness and initial overall buckling modal imperfections both have major influence on optimum designs of sandwich panels with honeycomb cores.