B. Zhu; O. Mohamad; A. Qambrani; H. Sun; N. Leung; H. Wan; N. Randall; D. Cox; B. Su; T. Sui
International Journal of Mechanical Sciences 304 (2025) 110709
The residual stresses, induced from complex fabricating processes of nacre-like bioinspired zirconia and polymethyl methacrylate (PMMA), play a dual role, enhancing or undermining fracture resistance. Leveraging the residual stress can optimise the material design and unleash the potential of material properties of the bioinspired composites. However, the interplay between localised ceramic phase distribution, residual stress, and cracking behaviour remains poorly understood due to limitations in conventional characterisation techniques. In this study, we present a novel correlative experimental approach that simultaneously resolves the local ceramic volume fraction, multiscale residual stress, and crack evolution mechanisms within layered zirconia/PMMA composites. By combining Plasma Focused Ion Beam and Digital Image Correlation (PFIB-DIC), in situ SEM nanoindentation and high-resolution microstructural quantification, we reveal how phase heterogeneity, ranging from 69 to 84 vol% zirconia, governs residual stress distribution across multiple phase layers and within individual phase. This integrated method enables us to establish a framework for estimating local residual stress states at crack tips and correlating them with fracture behaviours observed during in situ single-edge notch bending (SENB) tests. The results show that compressive residual stresses enhance fracture resistance by suppressing crack initiation and promoting deflection, while tensile stresses encourage energy dissipation through multi-crack formation but also accelerate failure. By linking microstructure, residual stress, and crack propagation, this work provides new mechanistic insights into toughening in bioinspired composites and lays the foundation for residual stress informed design of next-generation dental restorative materials.