EXPERIMENTS AND FULL-SCALE NUMERICAL SIMULATIONS OF INPLANE CRUSHING OF A HONEYCOMB

The in-plane mechanical behavior of honeycombs has been widely used as a two-dimensional model of the behavior of more complicated space fil ling foams. This paper deals with the mechanisms governing in-plane cr ushing of hexagonal aluminum honeycombs. Finite size honeycomb specime ns are crushed quasi-statically between parallel rigid surfaces. The f orce-displacement response is initially stiff and elastic but this is terminated by a limit load instability. Localized crushing involving n arrow zones of cells is initiated and subsequently crushing spreads th rough the material while the load remains relatively constant. When th e whole specimen is crushed the response stiffens again. It has been f ound that although the crushing patterns that develop during the load plateau vary from specimen to specimen (influenced by geometric imperf ections and by specimen size) the underlying cell collapse mechanism i s common to all specimens. As a result, the level of the stress platea u and its extent in strain are quite repeatable. The crushing process is simulated numerically by full-scale FE models in which the geometri c characteristics of the actual cells are used. The manufacturing of t he honeycomb involves cold expansion of specially bonded aluminum shee ts. This is simulated numerically in order to reproduce the material c hanges and residual stresses introduced to the aluminum by the process . The expanded honeycomb is then crushed as in the experiments. It is demonstrated that once the key geometric, material and processing para meters are incorporated in the models, the simulations reproduce the e xperimental results both qualitatively as well as quantitatively. (C) 1998 Acta Metallurgica Inc.