Bending Deformable Tension-Shear Model for Nacre-Like Composites

Abstract

The nacre-like structures widely exist in biomaterials and bioinspired composites, where the tension-shear load transfer is the common load carrying mode due to the discontinuous platelet. However, under bending deformation the local tension-shear load transfer is coupled with the global bending deformation which can’t be described by the widely-adopted theoretical models in nacre-like composites, like the tension-shear chain (TSC) model and deformable tension-shear (DTS) model. In this work, a bending deformable tension-shear model (BDTS) model was developed to capture the tension-shear load transfer under bending configuration. In order to obtain a closed-form solution of BDTS model, the bending deformation of equal curvature was first studied, based on which two failure modes were defined, i.e., intralayer failure (Mode G) and interlayer failure (Mode I). Then, the effective bending rigidity of nacre-like structure, defined as the ratio of the average moment to curvature, was obtained, indicating the influence of material and geometrical parameters can be unified to a dimensionless parameter L/l_t, where L is the length of platelet and l_t=√((E_h h_h h_s)⁄G_s ) is the characteristic length parameter of tension-shear load transfer (E_h and G_s are Young’s modulus of hard layer and shear modulus of soft layer, h_h and h_s are the thickness of hard and soft layers, respectively). Furthermore, a general beam theory of nacre-like structures was constructed by introducing the effective bending rigidity to the modified Timoshenko beam model, which can predict the deflection of nacre-like structures well. This work first explores the two coupled deformations of local tension-shear and global bending-shear in nacre-like composites, which may guide the design of nacre-like artificial nanocomposites toward various applications where bending deformation is inevitable.

Keywords: Bending DTS Model, Tension-shear load transfer, Nacre-like Structure, Effective bending rigidity