Strength and toughness trade-off optimization of nacre-like ceramic composites

Abstract

Bio-inspired by abalone nacre, all ceramic brick-and-mortar composites with impressive mechanical properties have been recently manufactured. Albeit comprising only brittle constituents, extrinsic reinforcement mechanisms impart to these nacre-like ceramics high toughness and non-catastrophic crack propagation properties. While several models have been developed to understand the mechanical properties of natural and synthetic brick-and-mortar materials, they have always considered a ductile interface and focused mostly on intrinsic toughening mechanisms. Modeling so far has not captured the extrinsic toughening mechanisms responsible for the properties of nacre-like ceramics. Here we show that the Discrete Element Method (DEM) can account for reinforcement mechanisms such as microcracking and crack deflection, and quantitatively assess strength, initiation toughness and crack growth toughness. Two approaches are studied to enhance strength and toughness of nacre-like ceramics, either by reinforcing the interface globally (an increase of the interface strength) or locally (addition of nano-bridges). We combine the results to provide design guidelines for synthetic brick-and-mortar composites comprising only brittle constituents.

Determination of interface fracture properties by micro- and macro-scale experiments in nacre-like alumina

“…Nacre-like composite microstructure may be optimized in order to promote such fracture mechanisms and thus enhance the apparent macroscopic toughness increase. Numerical simulations at the building block scale may help understand the influence of key microstructural features and provide guidelines for the microstructure optimization, for instance by means of periodic cell modeling [10,11,12,13,14]. Begley et al [10] developed a micromechanical model taking into account elastic perfectly plastic interfaces.…”

“…A resulting design recommandation was, for instance, a high platelet volume fraction with platelets five time stronger than the interface. Discrete element modeling was recently used [13,14] to simulate fracture in brick-and-mortar structures. Abid et al [13] highlighted the importance to control the architecture in order to minimize statistical microstructure variations and concluded that interfaces with large fracture toughness to strength ratio are more likely to maximize energy dissipation.…”

“…Abid et al [13] highlighted the importance to control the architecture in order to minimize statistical microstructure variations and concluded that interfaces with large fracture toughness to strength ratio are more likely to maximize energy dissipation. Radi et al [14] investigated the influence of the interface strength on the macroscopic toughness and maximum stress and derived guidelines for their optimization.…”

DECM: A Discrete Element for Multiscale Modeling of Composite Materials Using the Cell Method

“…In the specific case of materials consisting of a matrix that cements aggregates not in direct contact, these constitutive relations establish interactions between the aggregates when they are within an interaction range greater than the distance between the centroids of the aggregates [18]. This allows the study of damage in homogeneous materials such as ceramics [20] and heterogeneous materials such as concrete [21][22][23], rock [24], or composites with a brick and mortar architecture (both natural [25,26] and man-made composites, such as brick masonry). The identification of adequate cohesion laws between particles in direct contact is of fundamental importance to obtain an accurate modeling of the continuity of matter [27].…”

DECM: A Discrete Element for Multiscale Modeling of Composite Materials Using the Cell Method

“…In the specific case of materials consisting of a matrix that cements aggregates not in direct contact, these constitutive relations establish interactions between the aggregates when they are within an interaction range greater than the distance between the centroids of the aggregates [13]. This allows the study of damage in homogeneous materials such as ceramics [15] and heterogeneous materials such as concrete [16][17][18], rock [19], or composites with a brick and mortar architecture (both natural [20,21] and man-made composites, such as brick masonry). The identification of adequate cohesion laws between particles in direct contact is of fundamental importance to obtain an accurate modeling of the continuity of matter [22].…”