Compressive response of notched, woven fabric, face sheet honeycomb sandwich panels

Centre notched honeycomb sandwich panels with woven carbon-epoxy face sheets and Nomex(TM) cores, tested uniaxially in compression, have been analysed to estimate their strength and damage tolerance. A plain weave T-300 carbon fibre fabric was used for the face sheets in two stacking sequences: [45/0/90] and [0/90]. Observations of macroscopic damage behaviour were different in the two layups. Linear damage zones (LDZs), consisting of fibre microbuckles and extensive delamination, were typically observed in the [0/90] material. The [45/0/90] material exhibited a delamination/bulge zone (DBZ), which consisted of an out of plane curved deformation of the outer 45degrees ply accompanied by a delamination from the interior 0degrees plies. Modelling of these failure modes and comparison with experimental data showed that the only mode representative of damage tolerant behaviour is LDZ formation and propagation for both material systems, and that the delamination/bulge behaviour is a secondary phenomenon. A linear softening cohesive zone model predicts the notched compressive strength reasonably well. (C) 2002 IoM Communications Ltd.