Fabrication and testing of bioinspired microstructured alumina composites with sacrificial interpenetrating polymer bonds

• Main Authors: Sapasakulvanit, Slocha, Chan, Xin Ying, Le Ferrand, Hortense
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2023
• Subjects: Engineering::Materials::Composite materials; Bioinspired Microstructure; Reinforced Composite
• Online Access: https://hdl.handle.net/10356/168484
• Institution: Nanyang Technological University

Bioinspired composites exhibit well-defined microstructures, where anisotropic ceramic particles are assembled and bound by an organic matrix. However, it is difficult to fabricate these composites where both the ceramic particles and organic matrix work together to unlock toughening mechanisms, such as shear dissipation, particle rotation and interlocking, etc., that lead to stiff, strong, and tough composites. Here, we produce composites inspired by seashells, made of alumina microplatelets assembled in complex microstructures and that are physically bonded by a small amount of interpenetrated polymer network (IPN) made of polyacrylamide (PAM) and polyN-isopropylacrylamide (PNIPAM). The fabrication employs magnetically assisted slip casting (MASC) to orient the microplatelets as desired, and in situ gelation of the IPN, followed by drying. The process was successful after carefully tuning the slip casting and gelation kinetics. Samples with horizontal, vertical, and alternating vertical and horizontal microplatelets orientations were then tested under compression. It was found that the IPN threads bonding the microplatelets acted as sacrificial bonds dissipating energy during the compression. Paired with the alternating microstructure, the IPN significantly enhanced the compressive toughness of the composites by 205% as compared to the composites with horizontal or vertical orientation only, with less than 35% reduction on the stiffness. This study demonstrates that microstructure control and design combined with a flexible and tough matrix can effectively enhance the properties of bioinspired ceramic polymer composites.