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Many natural materials demonstrate ideal design inspirations for the development of lightweight composite materials with excellent damage tolerance. One notable example is the layered architecture of nacre, which possesses toughness an order of magnitude higher than its constituent parts. Man-made nacre-like ceramic/polymer composites obtained through direct infiltration of polymer in ceramic scaffolds have been shown to produce improved mechanical properties over other composite architectures. Replacing the polymer phase with metal could provide higher damage tolerance but the infiltration of metal into complex ceramic scaffolds is difficult due to the surface tension of molten metal. To address this, bioinspired nacre-like micro-layered (µL) alumina scaffolds with different ceramic fractions from 18 to 85% were infiltrated with aluminium alloy 5083 via pressureless and squeeze casting infiltrations techniques. The scaffolds were created using a bi-directional freeze-casting and one-step densification method. As a result, the µL alumina/aluminium composites displayed significant extrinsic toughening mechanisms with both high strength and toughness. The mechanical performance was highly dependent on the interface, microstructure, and composition. The nacre-like composites with 18% alumina and AlN interface displayed a maximum resistance‐curve toughness up to around 70 MPa.m½ (35 MPa.m½ at the ASTM limit) and a flexural strength around 600 MPa.

In this manuscript, we elucidated, for the first time, the substructural mechanisms present in our recently developed bioinspired polyurethane-based pancreatic tissue models. Different protein coatings of the model, i.e., collagen and fibronectin were examined. More specifically, analysis took place by combined real-time synchrotron X-ray scattering techniques and confocal laser scanning microscopy, to quantify the structural alteration of uncoated-polyurethane (PU) and protein-coated PU as well as the time-resolved structural reorganisation occurring at the micro-, nano- and lattice length scales during in situ micromechanical testing. We demonstrate that a clear increase of stiffness at the lamellar level following the fibronectin-PU modification, which is linked to the changes in the mechanics of the lamellae and interlamellar cohesion. This multi-level analysis of structural-mechanical relations in this polyurethane-based pancreatic cancer tissue model opens an opportunity in designing mechanically robust cost-effective tissue models not only for fundamental research but also for treatment screening.

A cost-effective one-step densification process based on bi-directional freeze casting was investigated to produce nacre-like alumina/poly(methyl methacrylate) (PMMA) composites with a unique micro-layered (µL) architecture. This method has the advantage of shorter processing time, as it requires only sintering once instead of twice as in the fabrication of conventional brick-and-mortar (BM) composites via freeze casting. By tuning the processing parameters, composites with different ceramic content and layer thickness were obtained. The resultant mechanical properties of µL composites showed that ceramic content and wall thickness affected mechanical properties significantly. The µL composite with fine ceramic walls (8 µm) and relatively high ceramic fraction (72 vol.%) exhibited an exceptional combination of high flexural strength (178 MPa) and fracture toughness (12.5 MPa m1/2). The µL composites were also compared with the conventional BM composites. Although the fracture behaviour of both composites exhibited similar extrinsic toughening mechanisms, the µL composites with longer ceramic walls displayed superior mechanical properties in terms of strength and fracture toughness in comparison with the BM composites comprising short ceramic walls (i.e. bricks), due to the effectiveness of stress transfer of load-bearing ceramic phase within the composites.