Axial crush of metallic honeycombs

Experimental results for six types of honeycomb cellular structures under quasi-static and impact loads applied in the axial direction are reported. The specimens under both loading conditions were all back-supported with a steel block and were loaded by blunt impacters whose cross-sectional areas were larger than those of the specimens. In the impact test, the velocity history during impact was recorded by the developed laser-Doppler anemometer (LDA), and was subsequently transformed into force and the displacement histories. Both the quasistatic and the impact results showed a load plateau carried by small oscillations when the specimens started to buckle progressively. However, an increase of up to 74% of the crush strength was observed when the specimens which were loaded dynamically were compared with those loaded under the quasi-static conditions, and the increase was found to be proportional to the initial striking velocity of the projectile. For preservation of better energy-absorbing capability per areal density, use of a honeycomb structure with a smaller cell size and core height, and made of a stronger material is suggested. On the other hand, the previously published theoretical model and the manufacturer data both underestimated the crush strength significantly. (C) 1997 Elsevier Science Ltd.