Effect of freezing conditions on the microstructure and compressive response of alumina/epoxy nacre-type composites

Abstract

An attempt is made to fabricate nacre-type alumina/epoxy (cerepoxy) composites using ice-templated alumina scaffolds. A polydimethylsiloxane (PDMS) wedge with varying angles (0◦, 5◦, 10◦, and 20◦) is used to modulate the temperature gradients during the freezing. While a 2D nucleation is observed in uni-directional freezing (0◦ wedge angle), bi-directional freezing in non-zero wedge angles shows 1D nucleation. The lamellae thickness and interlamellar spacing increase with the increase in PDMS wedge angle. Moreover, the density of scaffolds varies along the freezing direction, with denser microstructure recorded at the bottom location (closer to the cold finger). The quasi-static and high strain rate compression testing reveals the anisotropy in the compressive mechanical properties of cerepoxy samples. The compressive strength and energy-absorbing capacity increase at higher loading rates. Finally, the present study establishes the structure-property relationship and shows that bidirectional freezing is an efficient route to design and fabricate cerepoxy composites having nacre-type microstructure