X‐Ray Microtomographic Characterization and Quantification of the Strain Rate Dependent Failure Mechanism in Cenosphere Epoxy Syntactic Foams

This work investigates the failure mechanism in cenosphere epoxy syntactic foams at the quasi‐static and dynamic strain rates. Split‐Hopkinson pressure bar experiments are controlled to stop dynamic deformation of the foams at various strain stages. The internal microstructure at each strain is characterized in the x‐ray microtomography and compared to the microstructure in the foams deformed quasi‐statically. The microscopic observations reveal that the failure process in syntactic foams at the low and high rates is dominated by the crushing of cenospheres and the cracking of the epoxy matrix. However, the mechanism of failure in the foam is significantly affected by the strain rate. Compared to quasi‐static compression, macro‐cracks form earlier in the matrix at dynamic rates and can propagate to split cenospheres. The volume of the damage as defined by the failure of both cenospheres and the matrix is calculated from the x‐ray microtomographic images. It is found that the damage can be quantitatively related to the strain and the strain rate using an empirical equation.