Paper number 420


J. M. Mirazo M. G. Toribio and S. M. Spearing

Technology Laboratory for Advanced Composites
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, U. S. A.

Summary Honeycomb sandwich panels with woven graphite-epoxy face sheets and NomexTM cores were manufactured with through-thickness slits as an experimental model for severe impact damage. The facesheets consisted of plain weave plies in [03] and [45/02] stacking sequences. Both material configurations showed a pronounced notch size effect. However, the two configurations were visually observed to exhibit different subcritical damage behaviors. In the [03] material linear damage zones (consisting of fiber microbuckles or kink bands) propagated perpendicular to the loading direction, whereas in the [45/02] material the visible subcritical damage consisted of bulging of the outer (45) plies accompanied by interior delamination. Mechanics analyses of these two apparently distinct damage modes revealed that the linear damage zone is the dominant failure mode in both materials, and that the delamination buckling behavior is a secondary phenomenom.
Keywords honeycomb sandwich panel, damage tolerance, delamination, buckling, compression, linear damage zone.

Theme : Composite Structures ; Sandwiches

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