Low velocity impact of composites

[kyuzokyuzo]

Hi,

I was hoping someone might be able to help with some questions about composite toughness.

I am trying to find an FRP composite with comparable impact toughness and yield strength to 7075 T6 Aluminium. I'm having trouble finding any means of direct comparison. I've read that Kic is not a good measure of low-velocity impact toughness for composites as it varies a lot with impact velocity.

Other properties that I thought might be useful are Izod or Charpy energies. Does anyone know where I can find values for these? I have found data for the Izod and Charpy of many plastics but data for Aluminium seems harder to come by.

I found a paper ( http://nvl.nist.gov/pub/nistpubs/jres/104/6/j46sie.pdf ) about Izod and charpy from which its possible to calculate the charpy of 7075-T6, but this gave a value of around 60 kJ/m^2 and I'd like to check this.

What is the best way to compare impact toughness for a low-velocity application? For composites it seems there is no 'accepted' way that really represents a fundamental material property. Tests so far are all specific to the test setup, impact shape/mass/velocity/hardness etc.

Would it be best to just take Kic and Charpy/Izod results and use them as a rough means of gauging performance. Is there a better way that doesn't involve computation?

 

[Achy47]

Hello,

Thank you for your questions about composite toughness. It can be challenging to find direct comparisons between FRP composites and metals like 7075 T6 Aluminium, as they have different material properties and behave differently under impact.

As you mentioned, Kic is not a reliable measure of low-velocity impact toughness for composites. Instead, I would suggest looking at the Charpy or Izod energies, as these are commonly used for impact testing of materials. The Charpy and Izod tests measure the energy absorbed by a material during impact, and their results can give a good indication of a material's toughness and resistance to fracture.

I understand that finding data for Aluminium can be challenging, but there are some resources available that may help. The National Institute of Standards and Technology (NIST) has a database of material properties that includes Charpy and Izod values for various materials, including Aluminium. You can also try reaching out to material suppliers or manufacturers, as they may have data on specific materials and alloys.

It is important to keep in mind that the results of impact tests can vary depending on the test setup and conditions, as you mentioned. Therefore, it may be best to use a combination of different impact test results, such as Charpy or Izod energies and Kic values, to get a better understanding of a material's performance under impact.

I hope this helps and good luck with your research!