Modeling Fiber Microbuckling in the Bending of Soft Composites Using Nonlinear Homogenization

A new approach to model the microbuckling of fiber-reinforced soft composites under bending is presented, which takes into account large deformations of the matrix and nonlinear kinematics. It leverages recent advances from the field of nonlinear homogenization of fiber composites to model the response of the matrix under the three-dimensional loading observed during buckling. The model then calculates the strain energy of the system as a function of several parameters, such as the position of the neutral axis or the microbuckling wavelength, whose values are obtained through energy minimization. The moment-curvature relationship predicted by the model agrees with experimental results, particularly in the postbuckling regime. The predictions also capture the buckling wavelength, as well as the fact that microbuckling extends into the tension side for thin laminates, an experimental observation that contradicts kinematic assumptions in previous modeling efforts. A parametric study considering possible variations in the composite laminate shows strong trends for parameters, such as thickness and volume fraction.