Influence of Shear Loads on Crush of Honeycomb Materials

We conduct static experiments to investigate the influence of shear stress on the crush behavior of honeycomb materials. The aluminum honeycomb materials selected in this investigation are orthotropic due to their manufacturing processes. A test fixture and honeycomb specimens are designed such that combined compressive and shear loads along the strongest material symmetry axis can be controlled and applied accurately. The experimental results indicate that both the peak and crush strengths under combined compressive and shear loads are lower than those under pure compressive loads. A yield function is suggested for honeycomb materials under the combined loads based on a phenomenological plasticity theory. The microscopic crush mechanism under the combined loads is also investigated. A microscopic crush model based on the experimental observations is developed. The crush model includes the rupture of aluminum cell walls so that the kinematic requirement can be satisfied. The results of the crush model indicate that as the shear stress increases, the crush strength decreases. The increase of shear stress also causes the wavelength of the fold to increases first and then decrease. In addition, the shear displacement of the fold increases as the shear stress increases. In general, the results of the microscopic model agree with those of the available experiments.