Abstract: The aramid honeycomb node cracking occurred in high temperature and high pressure when the honeycomb sandwich was processed by secondary bonding. The typical sandwich samples were produced and the honeycomb node cracking was observed and detected by ultrasonic C-scan and X-ray. In order to analyze and study the mechanism of the honeycomb node cracking, the article induced the forces analysis of the core grid, and the stress suffered on the node was computed by the theoretical arithmetic and finite element simulation respectively. The results indicated that the node cracking started from the seam of the node under the dual action of the compression stress and the core grid pressure difference, and the core grid pressure difference was the key factor which effected the node damage stress. In addition, the honeycomb node peel strength was tested and compared with the node damage stress. After the honeycomb joint cracking happened, the bending instability of the honeycomb core grid walls was initiated under compression stress easily. At last, some suggestions were given to avoid the honeycomb node cracking.

Key words: honeycomb node, node cracking, compression stress, the core grid pressure difference, composites