Al2O3 - PMMA Composite Inspired by Abalone Nacre with Improved Mechanical Properties

Abstract

The brick-and-mortar architecture of abalone nacre offers exceptional durability, withstands high compression and displays superior fracture toughness due to its unique microstructure. However, emulating the similar microstructure in the bulk materials is extremely difficult. In this work, different fabrication techniques such as uniaxial pressing, wax-assisted gravity sedimentation, and forced sedimentation were investigated for the fabrication of the inorganic brick phase using Al2O3 platelets. Although microstructural analysis unveiled similar kind of distinct large-scale platelet alignments based on the different fabrication processes, the forced sedimentation method yielding the highest relative density of the ceramic brick phase as 58%. Subsequent infiltration of the ceramic scaffolds with PMMA (Polymethylmethacrylate) through in-situ polymerization using 1 wt% AIBN (Azobisisobutyronitrile) increased the composite density to an impressive 92 - 96%. The mechanical characterizations of the nacre mimetic alumina-PMMA composites were conducted via 3-point bending and single edge notched beam (SENB) tests. The composites revealed improved mechanical properties having maximum flexural strength and fracture toughness of 75 MPa and 4.2 MPa√m respectively. This study shows the effectiveness of the forced sedimentation followed by in-situ infiltration technique in producing bioinspired inorganic-organic composites having brick-and-mortar microstructure with superior mechanical performance.