INPLANE CRUSHING OF A POLYCARBONATE HONEYCOMB

The in-plane compressive response and crushing of a polycarbonate hone ycomb with circular close-packed cells is studied through combined exp erimental and analytical efforts. Under displacement controlled quasi- static loading the response is characterized by a relatively sharp ris e to a load maximum Followed by a drop down to an extended load platea u which is then terminated by a sharp rise in load. In the initial ris ing part of the response, the deformation is essentially uniform throu ghout the specimen. Following the load maximum, the deformation locali zes in a narrow zone of cells. These cells collapse in a shear type mo de until contact between cell walls arrests their deformation and caus es spreading of the deformation to the neighboring rows of cells where the process is repeated. This propagation of the collapsed zone occur s at a relatively constant load and continues until all the rows of ce lls have collapsed. As a result of the rate dependence of the material , the initiation and propagation stresses increase as the rate of Crus hing of the honeycomb is increased. This process of crushing has been simulated numerically using appropriately nonlinear kinematics. An ela stic-powerlaw viscoplastic constitutive rule, calibrated to uniaxial e xperiments spanning strain rates of six decades, is used to model the behavior of the polycarbonate. In addition, the model is capable of tr eating contact between cell walls which result from crushing. Results from analyses involving a characteristic cell and from full scale simu lations of the experiments are presented which are shown to be in exce llent agreement with the experimental results. (C) Elsevier Science Lt d.