Vumat-composite material

[pani3882]

Dear Dr. Jorgen Bergstrom

I have been working on a material model for composite, which i am trying to link with abaqus using vumat.

When i try linking the FORTRAN and the input file,i am getting the following error:

***ERROR: Bad Material definition: zero or negative initial dilatational
modulus caused by bad material data. Please check your material
input and any initial conditions if necessary.

The problem description is as follows: a cube of 40 mm is held at one end and at the other end a displacement is defined. The material orientation is defined.

Though there is no dynamic loading, i have defined the step to be dynamic as has been done in you example problems of neo-hookean material model.

I do not know how to go about the above error, as with the same material parameters, the program works well in matlab.

Can you please guide me in this regard ?

Thank You
Bye

[Jorgen]

It sounds like the volumetric response from your VUMAT is incorrect. I would add a few print statements in the source code to make sure it behaves as you expected.

-Jorgen