dimensions of aluminum honeycomb for impact attenuator

[PCR7]

hello all,please help me in the following topic how to calculate the cell size for an aluminium honeycomb structure and the dimensions for imapct attenuator?
thank u in advance

[Tom W]

Thats a pretty complicated question and one that you will struggle to find an answer to. The closest you will come to finding an answer without physical testing is to look through the for sale threads. In at least one of those a team selling spare honeycomb core quotes a crush pressure. You can use this to calculate dimensions required to provide a given crush force, a value you can extract from the rules. In practice honeycomb does not crush at an exactly constant pressure (in fact it is not even particularly close to it), you can use the quoted crush values to calculate dimensions and then conduct phsical testing to find the actual required length of the IA. If you end up buying material from another team they may be willing to supply you with the data that they use in their IA design.

For any other questions about IA's there have been some fairly comprehensive threads recently that can probably answer your questions.

[Richard B]

Contact some of the honeycomb manufacturers. Usually there is an engineer there who has experience with using honeycomb for energy absorption and they will be happy to guide you in the right direction. Some even will send you a worksheet with equations for you to calculate the sizes you want.

[Hub]

Hexcel have a nice pdf with all you need for your calculation.
http://www.hexcel.com/NR/rdonl...sorptionBrochure.pdf (http://www.hexcel.com/NR/rdonlyres/96FE250C-7BB1-4295-82C4-461A31CC97A0/0/HexWebHoneycombEnergyAbsorptionBrochure.pdf)

[Adambomb]

The spec sheet from Hexcel was something like 10% different from the values we got from crush testing, FWIW. It was fairly constant though, very similar in shape to the plot on that sheet. Also bear in mind that was a low-speed crush test, there is definitely a possibility that dynamic testing could also yield different results.

Best advice I have on this is to just remember that you have to do the testing anyway, why not just plan in advance to do 2 rounds of it? That's something you'll have to be prepared for in the relatively likely event that it doesn't behave just like the spec sheet, and just being close isn't close enough!