Unit cell finite element model showing several axial (x) half-waves of the buckling pattern and showing deformations of the unit cell cross sections at 4 stations (Image No. 7 of 9)

There is large local strain (especially shearing strain) in the soft silicone matrix.

This and the next image are from:

Francisco Lopez Jimenez (University of Colorado Boulder) and Sergio Pellegrino (California Institute of Technology),

“Folding of thin-walled composite structures with a soft matrix”, AIAA/ASME Structures, Structural Dynamics and Materials Conference, May 2009

ABSTRACT: The paper presents detailed micromechanical finite element simulations of composite materials with soft materials undergoing large macroscopic bending deformation. The simulations allow the study of fibre microbuckling under bending, including the kinematics of the fibres, as well as the strains in the matrix. These simulations lead to a simple analytical model that allows a quite accurate estimation of the buckling wavelength. It also provides the moment-curvature relationship. Finally, the model is also able to predict the maximum strain in the fibres for a given curvature.

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