Controlling failure regimes in Brick-and-Mortar structures

Abstract

Brick-and-Mortar structures have a highly tunable mechanical response, offering the possibility to achieve exceptional combinations of properties such as strength and toughness. These properties markedly depend on the failure mechanism. However, the effect of geometric and material parameters on failure is not fully understood. In this work we report the existence of a ‘two-peak’ and a ‘peak-plateau-peak’ failure regime, differing in the ability of the structure to distribute damage in the layers prior to failure. A transition from the ‘two-peak’ to ‘peak-plateau-peak’ regime is observed in 3D-printed Brick-and-Mortar structures by increasing the aspect ratio (brick width over height) in the lower “layer failure” aspect ratio range. Further control of the two regimes is investigated with the help of a semi-analytical model of finite-sized structures. Theoretical predictions suggest that the failure regime can be controlled by tuning the relative shear and normal layer materials. This is confirmed experimentally by testing Brick-and-Mortar structures made with different materials for the shear and normal layers. Our work demonstrates that the transition from the ‘two-peak’ to the ‘peak-plateau-peak’ failure regime significantly increases the toughness, without compromising strength or stiffness of the structure, highlighting the importance of controlling these regimes.