Hello,

I am curious about one query we face in our work. We use different Composite materials (we use type = Lamina). For some of the composite materials, we face convergence issues in the Stress Intensity Factors (as adviced in ABAQUS doc, we ignore contour 1 and 2, and use contours 3 to 5 only). 

Our Energy Release Rate (ERR) result is converging. But, the SIF (K-factors) does not. Could you please kindly advice on the likely reasons for this issue? 

We see from the ABAQUS doc that ABAQUS is estimating SIF from J-integral directly (for pure mode - elastic) or through Interaction integral methods (mixed mode scenarios). Our doubt is that the Interaction Integral method was developed for Isotropic materials. 

In literature, however, interaction integrals has since been extended to linear elastic orthotropic materials. But have these been implemented in ABAQUS and how accurate are the ABAQUS implementations for a Composite is a question. 

So, kindly please comment if ABAQUS has extended Interaction Integrals for Composites and if so, how accurate are these? 

Thank you and kind regards.