Polymer Foams as Core Materials in Sandwich Laminates (Comparison with Honeycomb)

The mechanical properties of sandwich laminates with two different closed cell polymer foams (PEI and PMI) as core materials were examined compared with sandwich laminates with honeycomb as core material. The applied test methods were compression, tension, four-point bending and instrumented falling weight impact. To examine the influence of the adhesive bonding between the face sheet and the core material, the sandwich laminates were tested with and without adhesive bonding. For comparison purposes the processing procedure for all sandwich laminates was kept constant. Therefore all sandwich laminates were produced at the same time in the same autoclave. In comparison to a honeycomb core, sandwich laminates with foam as core material showed superior surface quality and impact energy absorption. The influence of the adhesive bonding between face sheet and core material was found to be very small under tensile loading conditions. From microscopical investigations of the bond line it was deduced that in the case of direct bonding, sufficient resin was able to flow during processing from the face laminate into the micropores at the foam core surface without adhesive.