Composite stresses - Von Mises stresses

Staedtlerp

Hi all,

in this days I'm focusing on the study of composite materials using hypermesh. I founded the skateboard tutorial and I followed to start understanding the way to move in a composite FEM analysis. I find something that I can't figure out when I perform the calculation (Optistruct solver) and I visualize the stress contours (I selected CSTRAIN and CSTRESS in control cards).

On result type I choose Composite Stresses and I see below Von Mises stresses /emoticons/default_blink.png' title=':blink:' />  The question is that I don't understand why Von Mises stress is a result stress considering the fact that Composite Materials have other failure criteria hence other equivalent stresses (Tsai-Wu, Tsai-Hill, Hoffmann..).

 

Thank you in advance.

Altair Forum User

Hi,

 

Here we will look at only the allowable ply stress. Hence, we use Von Mises criteria.

 

Thank you 

Altair Forum User

Hi @Staedtlerp

 

With Composite stress, you look for stress in each ply (not on the entire laminate). The other stress is homogenized one over the entire laminate. In composites, it's important to understand stress at each ply.

 

Both are fundamentally different, 

Staedtlerp

Hi,

thank you so much.

So, summarizing, The Tzai-Hill (Hoffmann, Tsai-wu) criterion is used to get the equivalent stress in the entire laminate, but in each ply we use Von Mises stresses. Right?

Furthermore, in Hyperview how can I switch from one ply to another to get the stress contours?? 

 

 

Thank You

Altair Forum User

Hi,

 

use the Layers option as shown below.

Thank you

Altair Forum User

Altair Forum User said:

So, summarizing, The Tzai-Hill (Hoffmann, Tsai-wu) criterion is used to get the equivalent stress in the entire laminate, but in each ply we use Von Mises stresses. Right?

 

It's the other way. 

Staedtlerp

@Premanand Suryavanshi

thank a lot for the screenshot /emoticons/default_biggrin.png' srcset='/emoticons/biggrin@2x.png 2x' title=':D' width='20' />

 

@Prakash Pagadala

Sorry Prakash but I don't undestand. What does It means 'It's the other way'? Is it the opposite, Tsai-Hill is used for each ply and Von Mises for the entire laminate??

 

Thank You