Secondary instability development in the post-buckling regime in soft composites

In this paper, we report the numerical observations of a distinctive phenomenon – the development of secondary buckling in soft particulate composites. After experiencing the first microstructural buckling event and consequent microstructure transformations, the composite re-enters a stable state. However, the composite may undergo a secondary buckling upon exceeding a certain deformation level. This secondary buckling event gives rise to a plethora of distinct instability patterns and behaviors. We conduct the finite-amplitude post-buckling and Bloch Floquet analyses implemented in the post-buckling regime to characterize the development of the secondary buckling. These analyses also characterize the dependence of the critical strain and wavelength of the secondary buckling on the composite's initial microstructure parameters.