A Comparison of Uniaxial Compressive Response and Inelastic Deformation Mechanisms in Freeze Cast Alumina-Epoxy Composites Without and With Rigid Confinement

Cellular ceramics have an array of improved mechanical properties that make them incredibly desired for different applications such as armor systems, aircraft structures, automobiles bumpers, and biomedical implants. It is also desirable that porous architecture could be shaped into bulk complicated shapes and easy to scale-up with low manufacturing cost. Despite several efficient techniques to fabricate cellular ceramics, some limitations are preventing us from meeting the high demand of the after mentioned applications. For that, freeze casting, also called ice-templating, is technique of solidifying an aqueous ceramic suspension under the effect of unidirectional temperature gradient. In this study, Ice-templated porous specimens of different suspension percent (20 and 30 vol.%) were processed from the ultra-fine Al2O3 particles (d50 = 300 nm APA-0.5 Sasol, Tuscan, AZ). Porous ceramic specimens (20P and 30P), epoxy and composites (20C and 30C) were tested under uniaxial compression without and with rigid lateral confinement. It was found that for the porous materials, the confinement was effective and mainly dominant in 30P materials, whereas for 20P no effect was observed. For composites, 20C and 30C exhibited an increase in strength with rigid confinement, but the effect was more dominant in 30C than in 20C. For epoxy, the effect of confinement was relatively moderate. Furthermore, the compression test was stopped at the peak of the test, and the retrieved partially deformed specimens were investigated to study the dominant inelastic deformation mechanisms for both ceramic contents (20 and 30 vol.%) using a scanning electron microscope (SEM). The images revealed that for 20C, using the lateral rigid confinement, the severity and intensity of material damages were significantly reduced. For 30C materials, it can be stated that the inelastic deformation mechanisms which caused the failure in freeze cast composites were almost the same without and with confinement. However, the intensity of the developed kink bands was less in the presence of lateral confinement. Also, more kink bands with higher inclination were observed inside the material on the interior surface after removing 1 mm, so it can be stated that kink bands were generated internally first and propagated to the exterior surface