Experimental and numerical investigation of the toughening mechanisms in bioinspired composites prepared by freeze casting

Strength and toughness have been generally deemed as two incompatible properties in many materials. However, balanced toughness and strength have been observed in biomaterials, whose hard and soft phases are arranged into unique and hierarchical architectures. Therefore, it is necessary to understand the underpinning toughening mechanisms and develop reliable procedures that can mimic these unique structures at different length scales. Here, alumina-Poly(methyl methacrylate) (PMMA) composites were prepared using freeze casting combined with interface modification (silanization treatment). High failure strain (~4.5%) is achieved in these composites. The overall toughness can be tailored through modifying the interfacial strength between alumina and PMMA. A weaker interface (~8 MPa) leads to a greater toughness (3.1 MPa m), which is even greater than the constituent phases, i.e., alumina (2.71 MPa m) and PMMA (1.1 MPa m). Using a cohesive zone model and extended finite element method (XFEM), the toughening mechanism has been investigated.