Unnotched Izod impact characterization of glass hollow particle/vinyl ester syntactic foams

Vinyl ester matrix syntactic foams filled with hollow glass microspheres are characterized for unnotched Izod impact properties. The study is aimed to analyze the effect of wall thickness and volume fraction of the hollow glass microsphere on the impact properties of syntactic foams. The impact strength of syntactic foams was observed to be lower in comparison to the neat vinyl ester resin. The volume fraction of the hollow glass microspheres was found to have a more pronounced effect on the impact strength than the wall thickness. The energy absorbed until failure decreased with increase in the hollow glass microsphere volume fraction. The observed values decreased by 50-72.2% depending on the hollow glass microsphere volume fraction and wall thickness. The failure feature of syntactic foams under the current testing condition is explained using finite element analysis. The failure initiates from the tensile region, propagates through the specimen and is deflected near the compression region. The microstructural failure features are examined using a scanning electron microscope and matrix cracking, hollow glass microsphere-matrix debonding, and crack deflection by hollow glass microspheres are observed to be the failure features. Since the cracks were deflected around the compression zone, all types of syntactic foams showed tensile failure features, which include prominent matrix fracture and lack of hollow glass microsphere crushing. The understanding of the variation of impact properties with respect to the hollow glass microsphere volume fraction and wall thickness can help in tailoring the properties of syntactic foams.