Novel syntactic foams made of ceramic hollow micro-spheres and starch – theory, structure and properties

Novel syntactic foams made of starch and ceramic hollow micro-spheres were developed. Foams of four different micro-sphere size groups were manufactured with either preor post-mould gelatinisation process. Compressive failure behaviour and mechanical properties were evaluated. Not much difference in failure behaviour or in mechanical properties between the two processes (preand post-mould gel) was found. Compressive failure of all syntactic foams was of shear on plane inclined 45° to compressive loading direction. Compressive strength and modulus of syntactic foams were found to be dependant mainly on binder content but mostly independent of micro-sphere size. Some conditions of relativity arising from properties of constituents leading to the rule of mixtures relationships for compressive strength and to understanding of compressive/transitional failure behaviour were developed. The developed relationships based on the rule of mixtures were partially verified.