The response of sandwich structures with composite face sheets and polymer foam cores to air-blast loading: Preliminary experiments

The response of composite sandwich structures to blast loading has received little attention from researchers when compared to the research performed on their metallic counterparts, despite the fact that composite sandwich panels are becoming more generally used in practice. This paper reports on a preliminary experimental investigation into the response of sandwich panels comprising E-glass fibre reinforced vinyl ester facesheets and closed cell PVC foam cores to localised blast loading. The loading is generated by detonating discs of plastic explosive in close proximity to the panel. Multiple failure modes were exhibited by the panels. A failure progression pattern was identified, with increasing impulse: front facesheet delamination, core compression, back facesheet delamination, fibre fracture, core fragmentation, plastic deformation and debonding of the back facesheet following by complete core penetration. No back facesheet rupture was observed, but this was anticipated as the next failure mode to occur at higher impulse levels. The panels with denser cores exhibited lower levels of damage. Theoretical estimates of midpoint displacement were calculated using an analytical beam model. Simple estimates of the delamination, core compression and fibre fracture energies were also made. The energy partition showed that delamination, core compression and fibre fracture were significant energy absorption modes, and that fibre fracture energies exceeded the core compression and delamination energies at higher impulses. This was particularly evident for the lower density core which provided lower resistance to front facesheet deflection.