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HyperCrash composite nose cone

Altair Forum User

Hi,

I've been working on the crash simulation of a Formula Student CFRP nose cone for weeks, and the failure model is not working properly. After consulting with other Formula Student teams it is well known that in a racecar competing in Formula Student, a nose cone made of ~8-12 layers of carbon fiber should be enough to absorb 7350 J energy (300 kg object with 7 m/s speed). After trying out several options and material laws (of course we defined the material laws in laboratory through tests), and even a high number of layers, the elements in the nose cone either fail too easily and don't absorb the energy, either bend instead of rapturing and still don't absorb the energy.

Please help me what could be the problem with the material laws or the properties or the failure criteria. I have a 3 week deadline (2014.12.07.) as this is the topic of my thesis...

I uploaded 2 versions and videos about results:

https://onedrive.live.com/redir?resid=BC379CD7CAF9E179!13704&authkey=!AALFJynPe-uO-vs&ithint=file%2crar

Thank You very much,

Aecyd

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Altair Forum User

Thanks for sharing the files.

we will look into this and will get back to you as soon as possible.

Altair Forum User

Hi Aecyd,

I can see there is energy exchange (IE and KE) the nose (component 100) or am I missing something?

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Altair Forum User

Hi,

Yes, you see that correctly. However, after running the whole simulation you can see the total amount of absorbed energy is far less that 7350J.

In the meantime I realized that Hashin failure criteria is not a good choice for UD fabric (it is not intended to be used with UD), that is why the UD plies didn't absorb any significant energy. After using only woven fabric the energy absorption increases, but it still needs >20 layers of high quality carbon fiber to absorb the energy, which is way to more than the real life tests show (I don't have the files with me to upload right now). And of course it's not an option for me to eliminate UD fabric from my model.

Aecyd

Altair Forum User

Hi Aecyd,

can you check with LAW 25 (TSAI-Wu-CRASURV Criteria)?

Altair Forum User

Hi,

Yes I've tried it, in my 'v35' model I attached there is LAW 25 material with CRASURV criteria.

Aecyd