Quasi-static and dynamic compression behaviour of epoxy-aluminium hybrid foams

Aluminium-epoxy hybrid foams are produced by coating of aluminium foam granules with epoxy adhesive containing a blowing agent and followed by foaming and curing of the polymer. Such hybrid foams can be used as fillings for hollow parts, as core material for sandwich structures or simply as monolithic foam blocks. They show high strengths and easy applicability even for the production of very large components. The aim of this work was to evaluate the effect of compositions and densities of the hybrid foams on the compression behaviour at different deformation rates. Different hybrid foams were produced using AlSi10 Foaminal foam granules of the same size but different densities and varying coating thicknesses of the epoxy Araldite AT1-1. Genitron OB was used as the polymer foaming agent. A significant effect of the coating thickness of the aluminium foam granule has been observed: whereas thin coating resulted in the development of a limited volume of epoxy foam, which did not fill the space in between the aluminium foam granules completely, thicker coatings provided a sufficient epoxy foam volume. The mechanical characteristics of the foams like compression strength and specific deformation energy absorption were determined using quasi-static and dynamic compression tests and related to the respective aluminium and polymer contents of the foams. Compression rates ranged from quasi-static to 10/s. All foam types showed pronounced stress plateaus during quasi-static as well as high-rate compression. Analysis of the compression stress-strain curves demonstrated a dominating influence of the polymer both for the quasi-static and the dynamic experiments.