Natural materials such as bone and the nacre of some seashells are made of relatively weak building blocks and yet often exhibit remarkable combinations of stiffness, strength, and toughness. Such performances are due in large part to their brick and mortar architectures. Many efforts are devoted to translate these design principles into synthetic materials. However, much of the progress is based on trial-and-error approaches, which are time consuming and do not guarantee that an optimum is achieved. Modeling is an appealing alternative to guide the design and processing routes of such materials. However, the current analytical approaches cannot describe the extrinsic toughening mechanisms that takes place during crack propagation and are responsible for the remarkable properties of such materials. Here we show that the Discrete Element Method (DEM) can be used to predict the elastic and fracture behavior of brick and mortar materials and capture non-continuous phenomena such as multi-cracking. In contrast with most analytical shear-lag models, which only predict crack initiation, the model proposed here can also tackle crack propagation. DEM simulations are compared to analytical results with special attention to the shear transfer at the interface. The case of nacrelike alumina-a ceramic/ceramic brick and mortar composite with a brittle interface-is investigated to illustrate the potential of the method. We demonstrate in particular the importance of controlling the interface strength for further optimization of the mechanical properties. This method could be extended to predict and investigate the behavior of brick and mortar composites with a ductile interface, such as polymer/ceramic or metal/ceramic composites.

The development of damage-resistant structural materials that can withstand harsh environments is a major issue in materials science and engineering. Bioinspired brick-and-mortar designs have recently demonstrated a range of interesting mechanical properties in proof-of-concept studies. However, reproducibility and scalability issues associated with the actual processing routes have impeded further developments and industrialization of such materials. Here we demonstrate a simple approach based on uniaxial pressing and field assisted sintering of commercially available raw materials to process bioinspired ceramic/ceramic composites of larger thickness than previous approaches, with a sample thickness up to 1 cm. The ceramic composite retains the strength typical of dense alumina (430 ± 30 MPa) while keeping the excellent damage resistance demonstrated previously at the millimeter scale with a crack initiation toughness of 6.6 MPa.m 1/2 and fracture toughness up to 17.6 MPa.m 1/2. These results validate the potential of these all-ceramic composites, previously demonstrated at lab scale only, and could enable their optimization, scale-up, and industrialization.