BEHAVIOR OF INTACT AND DAMAGED HONEYCOMBS - A FINITE-ELEMENT STUDY

The Young's moduli, the elastic buckling strength and the plastic coll apse strength of regular honeycombs with defects consisting of missing cells in the structure were analyzed using the finite element method. The behavior of intact honeycombs was first analyzed; the results of this numerical study are consistent with those of previous analyses. T he effect of single, isolated defects of varying sizes and the effect of the separation distance between two defects on the elastic and plas tic behaviors were then analyzed. Single, isolated defects reduce the modulus and strength. The elastic buckling strength of a honeycomb wit h a defect normalized by the intact strength, decreases directly with the ratio of the minimum net cross-sectional area normalized by the in tact cross-sectional area. The plastic collapse strength of a honeycom b with a defect normalized by the intact strength decreases less rapid ly than the ratio of the minimum net cross-sectional area normalized b y the intact cross-sectional area. Two closely spaced, sepal ate defec ts interact to reduce the elastic buckling strength of a honeycomb; at a separation distance of about ten cells separate defects act indepen dently. The separation distance between two defects has little effect on the Young's modulus or the plastic collapse strength of a honeycomb . The finite element analysis allows localization behavior to be studi ed: we find that the localization strain decreases with increasing t/l . (C) 1998 Elsevier Science Ltd. All rights reserved.