Fabrication and mechanical testing of bioinspired composites

• Main Author: Schooling, Ryan Hilary
• Other Authors: Hortense Le Ferrand
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Fabrication of bioinspired composites
• Online Access: https://hdl.handle.net/10356/176398
• Institution: Nanyang Technological University

Biological ceramic-based composites are often found with complex microstructures, which gives them good mechanical properties like high strength and toughness despite its weak building blocks. However, current efforts to replicate these microstructures have yielded bioinspired composites without the same degree of structure complexity and overall performance. Magnetically assisted slip casting (MASC) is the most promising fabrication method available due to its ability to fabricate microstructures with different orientations between layers. This processing technique uses a rotating magnetic field to manipulate magnetized ceramic microplatelets, giving it the potential of replicating complex microstructures found in nature. In recent studies, the addition of interpenetrating polymer networks (IPN) during the MASC process yielded impressive mechanical properties. To further research on the impact of IPNs as the matrix in alumina composites, the various components of the IPN, which includes the acrylamide monomer (AM), N-isopropylacrylamide monomer (NIPAM), crosslinker (MBA), and polyvinylpyrrolidone (PVP) were tweaked to create 11 different IPN-based suspensions. The samples were fabricated using MASC then hydrated, where the swelling of the samples was measured. Lastly, compression testing was performed on the hydrated samples and the ultimate compressive strength (UCS), strain at failure, Young’s modulus and toughness of each sample type were analyzed. The results obtained were split and compiled into three series: Series 1 changes the amount of MBA (crosslinker), Series 2 changes the ratio between AM and NIPAM (soft component), while Series 3 changes the amount of PVP (hard component). After analyzing the results, Series 1 showed that strain at failure and swelling increased when decreasing the amount of crosslinker because there is more chain mobility, leading to better energy dissipation. The modulus showed a decreasing trend while other properties showed some signs of increasing trends with decreasing MBA. In Series 2, samples consisting of only AM show higher stiffness but lower toughness when compared to samples with no AM. However, no clear trend was observed at the other mol ratios of AM for all mechanical properties, leading to difficulties determining the effects of AM and NIPAM to the samples. Lastly, in Series 3, it was discovered that an optimum amount of PVP is needed to achieve the best combination of mechanical properties to overcome brittleness.