Corrugated skin composite sandwich panels

The effect of corrugating the skins of composite sandwich panels was investigated analytically, numerically and with physical tests. For panels under uniaxial in-plane loading, with thin skins and a relatively soft core, skin wrinkling tends to dominate as a failure mechanism. Such panels benefit significantly from skin corrugations, directed parallel to the loading, when compared with equal mass flat panels. Semi-circular corrugations proved to be highly preferable to sine-wave shaped corrugations due to localized buckling in the latter. Over forty fiberglass and foam core sandwich specimens with semi-circular corrugations were tested to failure, providing corroboration of the numerical and analytical results.;For panels having a more complicated loading, a procedure was developed for calculating homogenized orthotropic plate stiffnesses of a sandwich using a simple representative volume element of the sandwich geometry. With these effective stiffnesses, a corrugated panel could be Finite Element modeled using a simple mesh that does not include the detail of each corrugation. The effect on uniaxial and shear panel buckling was investigated, with improvements seen for certain combinations of corrugation geometry and material properties.;Both conventional (flat) and corrugated skin sandwich panels with the size 1.34 m x 1.59 m were subsequently designed and manufactured for a large hybrid ship hull specimen. This specimen had the geometric shape of an existing bridge girder for a magnetically levitated train, which was retrofitted and tested as a 1:8 scale model of a destroyer class ship. A three point bending fatigue testing fixture was developed, and the specimen was non-reversing fatigue tested for 325 thousand cycles. Cracks were found in the steel of the specimen when the cyclic load was raised above the design load, however no catastrophic damage occurred in the bonded joints or composite panels, despite the corrugated panels having 15% lighter weight than the conventional flat panels.;Based upon this work, a high-speed boat was designed which will serve as an instrumented, real-world test facility for the effects of hull-water impacts. The hull of this boat was given a hybrid steel/composite construction and was designed to be removable, so that future experimental hull configurations can be tested.